Updated on 2023/02/05

写真a

 
OHKUBO Masaki
 
Organization
Academic Assembly Institute of Medicine and Dentistry Health Sciences Professor
Faculty of Medicine School of Health Sciences Professor
Graduate School of Health Sciences Health Sciences Professor
Title
Professor
Other name(s)
Okubo Masaki
External link

Degree

  • Doctor (Ph. D) ( 1994.6   Niigata University )

  • 工学修士 ( 1988.3   新潟大学 )

Research Areas

  • Others / Others

Research History

  • Niigata University   Graduate School of Health Sciences Health Sciences   Professor

    2013.4

  • Niigata University   Faculty of Medicine School of Health Sciences   Professor

    2013.4

  • Niigata University   Graduate School of Health Sciences Health Sciences   Associate Professor

    2004.4 - 2013.3

  • Niigata University   Faculty of Medicine School of Health Sciences   Associate Professor (as old post name)

    1999.10 - 2004.3

  • Niigata University   Associate Professor (as old post name)

    1997.4 - 1999.9

  • Niigata University   Research Assistant

    1988.4 - 1997.3

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Professional Memberships

  • Japanese Society of Radiological Technology

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  • Japanese Society for Magnetic Resonance in Medicine

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Papers

  • [A Study of Longitudinal NPS Measurement in CT Images Based on the Central Cross-section Theorem]. Reviewed

    Akihiro Narita, Masaki Ohkubo, Yuki Ohsugi, Kenichi Sakai, Takahiro Fukaya, Yoshiyuki Noto

    Nihon Hoshasen Gijutsu Gakkai zasshi   78 ( 7 )   719 - 725   2022.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    PURPOSE: Various approaches in noise power spectrum (NPS) analysis are currently used for measuring a patient's longitudinal (z-direction) NPS from three-dimensional (3D) CT volume data. The purpose of this study was to clarify the relationship between those NPSs and 3D-NPS based on the central slice theorem. METHODS: We defined the 3D-NPS(fx, fy, fz) that was calculated by 3D Fourier transform (FT) from 3D noise data (3D-Noise(x, y, z), x-y scan plane). Here, fx, fy and fz are spatial frequencies corresponding to the axes of x, y and z, respectively. Based on the central slice theorem, we described three relationships as follows. (1) The fz-directional NPS calculated from the 3D-Noise(x=0, y=0, z) is equal to the profile obtained by projecting 3D-NPS(fx, fy, fz) in fx- and fy-directions. (2) The fz-directional NPS calculated from the profile obtained by projecting 3D-Noise(x=0, y, z) in the y-direction is equal to the profile at fy=0 in the data obtained by projecting 3D-NPS(fx, fy, fz) in the fx-direction. (3) The fz-directional NPS calculated from the profile obtained by projecting 3D-Noise(x, y, z) in x and y-directions is equal to the profile of 3D-NPS(fx=0, fy=0, fz). To verify them, we compared the NPSs measured from actual 3D noise data that were obtained using a cylindrical water phantom. RESULTS: In each relationship (1)-(3), the fz-directional NPS matched the profile obtained from the 3D-NPS(fx, fy, fz). CONCLUSION: Based on the central slice theorem, we clarified the relationships between fz-directional NPSs and 3D-NPS. We should understand them and then consider which method should be used for fz-directional NPS measurement.

    DOI: 10.6009/jjrt.2022-1267

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  • [An Easy-to-use Method for CT Image Simulation with Parameter Optimization Using a Water Phantom]. Reviewed

    Akihiro Narita, Kazuki Okamoto, Kengo Toyonaga, Masaki Ohkubo

    Nihon Hoshasen Gijutsu Gakkai zasshi   78 ( 7 )   732 - 740   2022.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    PURPOSE: We developed an easy-to-use method to generate computed tomography (CT) images that simulate the images obtained when using an actual scanner. METHODS: The developed method generates images by simulating the data acquisition and image reconstruction processes of a scanner from a linear attenuation coefficient map of an object numerically generated. This approach is similar to general image simulation methods. However, we introduced adjustable parameters for the CT data acquisition process, for example, parameters related to X-ray attenuation in the anode of the X-ray tube and the bowtie filter. These parameters were optimized in advance by minimizing the difference between the simulated and measured images of a water phantom. To verify the validity of the developed method, a simulated image was generated for a torso phantom and then compared with the measured image of the phantom obtained using the scanner. RESULTS: The simulated and measured images of the torso phantom were in good agreement. The spatial resolution and noise characteristics of these two images were also comparable, further indicating the accuracy of the developed method. CONCLUSION: In the existing methods, various information/data related to an actual scanner, including difficult-to-acquire ones, were essential for image simulation. In the developed method, instead of determining the difficult-to-acquire information/data, we introduced adjustable parameters. Therefore, the developed method was easier to use than the existing methods.

    DOI: 10.6009/jjrt.2022-1222

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  • [A Method for Evaluating the T2∗-weighting Effect in MRI]. Reviewed

    Yuta Yagi, Masaki Ohkubo, Hiroaki Saito, Tsutomu Kanazawa

    Nihon Hoshasen Gijutsu Gakkai zasshi   78 ( 4 )   357 - 363   2022.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    PURPOSE: To propose a method for evaluating the T2*-weighting effect in MRI. METHODS: Multiple solutions with different concentrations of a superparamagnetic iron oxide contrast agent were made and their signal intensities on T2*-weighted images were measured. The relationship between iron concentration and signal intensity was determined, and we simulated an iron concentration map representing a simplified model of a brain microbleed and converted the pixel values in the map to signal intensity based on the determined relationship, generating a simulated T2*-weighted image. An 'S-value' parameter was defined to evaluate the low-intensity regions in the simulated image. S-values were obtained using T2*-weighted sequences acquired with different echo time (TE) values on three MRI scanners (Philips 1.5 T, GE 3.0 T, and Siemens 3.0 T). Another parameter (A-value) defined by the American Society for Testing and Materials (ASTM-F2119) for assessing artifacts was applied to evaluate the weighting effect in the T2*-weighted image of a laboratory-made susceptibility-effect phantom. RESULTS: With all three scanners, the S-values increased as the TE increased, indicating enhancement of the T2*-weighting effect. For every TE, the S-values obtained for the Philips scanner were the largest, followed by those for the GE and Siemens scanners. The results of this comparative evaluation were similar to those obtained using A-values. CONCLUSION: Comparisons with the established A-value parameter showed our proposed method for the quantitative evaluation of the T2*-weighting effect using S-values to be valid. The proposed method has the advantage that the S-values do not depend on a specific susceptibility-effect phantom.

    DOI: 10.6009/jjrt.2022-1189

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  • A Study of 3D-NPS Analysis in CT Images Based on the Central Cross-section Theorem Reviewed

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Kenichi Sakai, Yoshiyuki Noto

    Nihon Hoshasen Gijutsu Gakkai Zasshi   78 ( 4 )   342 - 347   2022.4

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    DOI: 10.6009/jjrt.2022-1217

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  • GlyCEST: Magnetic Resonance Imaging of Glycine—Distribution in the Normal Murine Brain and Alterations in 5xFAD Mice Reviewed

    Ken Ohno, Masaki Ohkubo, Bingwen Zheng, Masaki Watanabe, Tsuyoshi Matsuda, Ingrid L. Kwee, Hironaka Igarashi

    Contrast Media & Molecular Imaging   2021   1 - 8   2021.12

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    Publishing type:Research paper (scientific journal)   Publisher:Hindawi Limited  

    The glycine level in the brain is known to be altered in neuropsychiatric disorders, such as schizophrenia and Alzheimer’s disease (AD). Several studies have reported the in vivo measurement of glycine concentrations in the brain using proton magnetic resonance spectroscopy (1H-MRS), but 1H-MRS is not capable of imaging the distribution of glycine concentration with high spatial resolution. Chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI) is a new technology that can detect specific molecules, including amino acids, in tissues. To validate the measurements of glycine concentrations in living tissues using CEST from glycine to water (GlyCEST), we extracted the brain tissues from mice and performed biochemical tests. In wild-type C57BL/6 mice, GlyCEST effects were found to be higher in the thalamus than in the cerebral cortex (<inline-formula>
    <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1">
    <mi>P</mi>
    <mo>&lt;</mo>
    <mn>0.0001</mn>
    </math>
    </inline-formula>, paired t-test), and this result was in good agreement with the biochemical results. In 5xFAD mice, an animal model of AD, GlyCEST measurements demonstrated that glycine concentrations in the cerebral cortex (<inline-formula>
    <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2">
    <mi>P</mi>
    <mo>&lt;</mo>
    <mn>0.05</mn>
    </math>
    </inline-formula>, unpaired t-test) and thalamus (<inline-formula>
    <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3">
    <mi>P</mi>
    <mo>&lt;</mo>
    <mn>0.0001</mn>
    </math>
    </inline-formula>, unpaired t-test), but not in the hippocampus, were decreased compared to those in wild-type mice. These findings suggest that we have successfully applied the CEST-MRI technique to map the distribution of glycine concentrations in the murine brain. The present method also captured the changes in cerebral glycine concentrations in mice with AD. Imaging the distribution of glycine concentrations in the brain can be useful in investigating and elucidating the pathological mechanisms of neuropsychiatric disorders.

    DOI: 10.1155/2021/8988762

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    Other Link: http://downloads.hindawi.com/journals/cmmi/2021/8988762.xml

  • グリシンCEST-MRイメージング法の開発とアルツハイマー病モデルマウスへの応用 Reviewed

    大野 健, 計良 妙, 大久保 真樹, 渡辺 将樹, 松田 豪, 五十嵐 博中

    脳循環代謝   33 ( 1 )   119 - 119   2021.11

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  • Method for determining slice sensitivity profile of iterative reconstruction CT images using low-contrast sphere phantom. Reviewed

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

    Radiological physics and technology   2021.9

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    A novel method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed using an iterative reconstruction (IR) algorithm is proposed herein. A phantom that included a low-contrast spherical object was scanned and consecutive cross-sectional images were reconstructed. The mean CT values in a region including the sphere were measured for all images and plotted as a function of slice position along the longitudinal [Formula: see text] direction to yield a mean CT value profile [Formula: see text]. Next, we numerically generated an object function corresponding to the sphere and obtained the mean CT value profile [Formula: see text]. Subsequently, the SSP was modeled as a product of the Gaussian and cosine functions. We convolved [Formula: see text] with the modeled SSP to obtain [Formula: see text]. The difference between [Formula: see text] and [Formula: see text] was evaluated using the root mean square error (RMSE), which was minimized via optimization of the SSP model parameters. To validate the methodology, we first used filtered back projection (FBP) images to compare the SSPs determined using the proposed and standard coin methods. Subsequently, the proposed method was applied to measure the SSPs of four types of IR algorithms in two scanners. The SSPs of the FBP images determined using the proposed and coin methods showed good agreement. Additionally, in the SSP measurements using the proposed method, [Formula: see text] agreed well with [Formula: see text] for every IR algorithm. The RMSEs for all measurements were less than 0.7 HU, indicating the accuracy of the SSPs. Thus, the proposed method is effective for obtaining valid SSPs.

    DOI: 10.1007/s12194-021-00636-0

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  • Technical Note: A simple method for measuring the slice sensitivity profile of iteratively reconstructed CT images using a non-slanted edge plane. Reviewed

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

    Medical physics   48 ( 3 )   1125 - 1130   2021.3

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    PURPOSE: A method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed with iterative reconstruction (IR) algorithms was reported by the AAPM Task Group 233 (TG233). In this method, the phantom plane edge is slightly slanted with respect to the scan plane to obtain a composite oversampled edge-spread function (ESF). However, it is expected that a fine-sampled ESF can be obtained directly from images reconstructed with a small slice increment without slanting the edge plane. This study aimed to investigate the validity of using a non-slanted edge plane. METHODS: In the proposed non-slanted edge method, the phantom was positioned so that the plane edge was perpendicular to the longitudinal z-axis, and images were reconstructed with a 1-mm slice thickness and 0.1-mm increment. The mean CT value was obtained in each slice and plotted as a function of slice position along the z-axis, thereby generating the ESF. The SSP was calculated from the ESF by differentiation. In the TG 233-recommended slanted edge method, the SSP was obtained by following the procedure described in the TG233 report. To validate the methodology, we first used filtered back projection (FBP) images to compare SSPs obtained using the non-slanted edge method, slanted edge method, and a standard method using a high-contrast thin object (coin). Next, for two types of IR algorithms, we compared the SSPs obtained using the non-slanted and slanted edge methods. RESULTS: For the FBP images, the SSP measured using the non-slanted edge method agreed well with SSPs measured using the coin and slanted edge methods. For the IR images, the SSPs measured using the non-slanted and slanted edge methods showed good agreement. CONCLUSIONS: The non-slanted edge method was demonstrated to be valid. The simplicity and practicality of the method allows routine and accurate determination of the SSP.

    DOI: 10.1002/mp.14668

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  • [Central Slice Theorem-based Relationship between 1D-NPS Obtained by the Slit Method and 2D-NPS for CT Images]. Reviewed

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

    Nihon Hoshasen Gijutsu Gakkai zasshi   77 ( 8 )   828 - 832   2021

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    PURPOSE: The method using a numerical slit (slit method) is used commonly to obtain the one-dimensional (1D) noise power spectrum (NPS) in computed tomography. However, the relationship between the 1D-NPS obtained by the slit method and the original two-dimensional (2D) NPS derived by the 2D Fourier transformation has not been elucidated clearly. The purpose of this study was to clarify their relationship based on the well-known central slice theorem (projection slice theorem) and validate it using computer simulation analysis. METHODS: With the application of the central slice theorem, we described that the 1D-NPS obtained by the slit method was equal to the central slice (profile) in the 2D-NPS when we set the slit length to the maximum (i.e. the matrix size of the noise image). To verify this, we generated computer-simulated noise images with the known 2D-NPS (true 2D-NPS). From those images, we obtained the 1D-NPS that was obtained by the slit method and compared it with the central slice in the true 2D-NPS. RESULTS: When we set the slit length to the maximum, the 1D-NPS obtained by the slit method showed good agreement with the central slice in the true 2D-NPS. CONCLUSION: We clarified the relationship between the 1D-NPS obtained by the slit method and the 2D-NPS using a theoretical approach and the computer simulation. We had to maximize the slit length to achieve the accurate measurement of the 1D-NPS using the slit method.

    DOI: 10.6009/jjrt.2021_JSRT_77.8.828

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  • [A Simple Method for Computationally Generating Metal Artifacts in CT Images for Treatment Planning: A Pilot Phantom Study]. Reviewed

    Daisuke Mugishima, Akihiro Narita, Masaki Ohkubo

    Nihon Hoshasen Gijutsu Gakkai zasshi   77 ( 5 )   445 - 453   2021

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    PURPOSE: In treatment planning for radiation therapy, the use of computed tomography (CT) images including metal artifacts causes a reduction in the dose calculation accuracy. In clinical practice, the artifacts are manually contoured and assigned an appropriate fixed CT number. To validate the procedure, images taken before and after metal insertion into a patient are required, which may be impractical. We propose a simple method for computationally generating metal artifacts in clinical images. METHODS: In the proposed method, a clinical image free of metal artifacts is used. To simulate metal inside a patient, CT numbers of a region in the image are replaced with a fixed extremely high value. A sinogram is created by the forward projection of the image. Data values of the sinogram in the metal region are converted into smaller values. From the sinogram, an image including artifacts is reconstructed with the filtered back projection. RESULTS: The simulated artifacts consisted of dark and bright bands and were observed to be similar to the actual metal artifacts. CT numbers in multiple small regions of interest in the image obtained by the proposed method showed a good agreement with those in the actual image. CONCLUSION: The proposed method was demonstrated to generate the metal artifacts additionally on the clinical images. The method would be potentially applicable to a validation study for the clinical procedure of manually contouring and assigning CT numbers to metal artifacts.

    DOI: 10.6009/jjrt.2021_JSRT_77.5.445

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  • A pitfall of using the circular-edge technique with image averaging for spatial resolution measurement in iteratively reconstructed CT images. Reviewed

    Akihiro Narita, Masaki Ohkubo

    Journal of applied clinical medical physics   21 ( 2 )   144 - 151   2020.2

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    The circular-edge technique using a low-contrast cylindrical object is commonly used to measure the modulation transfer functions (MTFs) in computed tomography (CT) images reconstructed with iterative reconstruction (IR) algorithms. This method generally entails averaging multiple images of the cylinder to reduce the image noise. We suspected that the cylinder edge shape depicted in the IR images might exhibit slight deformation with respect to the true shape because of the intrinsic nonlinearity of IR algorithms. Image averaging can reduce the image noise, but does not effectively improve the deformation of the edge shape; thereby causing errors in the MTF measurements. We address this issue and propose a method to correct the MTF. We scanned a phantom including cylindrical objects with a CT scanner (Ingenuity Elite, Philips Healthcare). We obtained cylinder images with iterative model reconstruction (IMR) algorithms. The images suggested that the depicted edge shape deforms and fluctuates depending on slice positions. Because of this deformation, image averaging can potentially cause additional blurring. We define the deformation function D that describes the additional blurring, and obtain D by analyzing multiple images. The MTF measured by the circular-edge method (referred to as MTF') can be thought of as the multiplication of the true MTF by the Fourier transformation (FT) of D. We thus obtain the corrected MTF (MTFcorrected ) by dividing MTF' by the FT of D. We validate our correction method by comparing the calculated images based on the convolution theorem using MTF' and MTFcorrected with the actual images obtained with the scanner. The calculated image using MTFcorrected is more similar to the actual image compared with the image calculated using MTF', particularly in edge regions. We describe a pitfall in MTF measurement using the circular-edge technique with image averaging, and suggest a method to correct it.

    DOI: 10.1002/acm2.12821

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  • Longitudinal GluCEST MRI Changes and Cerebral Blood Flow in 5xFAD Mice. Reviewed

    Hironaka Igarashi, Satoshi Ueki, Hiroki Kitaura, Tae Kera, Ken Ohno, Masaki Ohkubo, Mika Terumitsu-Tsujita, Akiyoshi Kakita, Ingrid L Kwee

    Contrast media & molecular imaging   2020   8831936 - 8831936   2020

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    Many of the focal neurological symptoms associated with Alzheimer's disease (AD) are due to synaptic loss. Glutamate chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) is a candidate method to assess synaptic dysfunction. We assessed chronological changes in GluCEST in a 5xFAD mouse model of AD, comparing Glucest effects and regional cerebral blood flow (CBF). GluCEST effects and CBF in 5xFAD mice aged 1-15 months and their littermates (WT) were measured. Neurite orientation dispersion and density imaging (NODDI) MRI reflecting dendritic/axonal density was also measured and compared with GluCEST in 7-month-old mice. While regional CBF's decrease began at 7 months, GluCEST-reduction effects preceded hypoperfusion of the temporal cortex and hippocampus. While longitudinal 5xFAD mouse measurements revealed a correlation between the regional GluCEST effects and CBF, a generalized linear mixed model revealed statistically different correlations in cortical and basal brain regions. Further, NODDI-derived neurite density correlated with GluCEST effects in the parietal cortex, but not in the hippocampus, thereby revealing regional differences in pathophysiological mechanisms. Finally, GluCEST's effects correlated with regional synaptophysin. These results demonstrate that GluCEST can reflect subtle synaptic changes and may be a potential imaging method for AD diagnosis as well as serve as a biomarker of AD progression.

    DOI: 10.1155/2020/8831936

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  • [Applications of 3D-PSF of CT Image to QA for Thoracic CT-CAD: Part 4. Application of 3D-PSF 2. Virtual Nodule Application to QA for Thoracic CT-CAD]. Reviewed

    Shinichi Wada, Masaki Ohkubo, Akihiro Narita, Kohei Murao, Toru Matsumoto, Shusuke Sone

    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics   39 ( 4 )   77 - 85   2019

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    DOI: 10.11323/jjmp.39.4_77

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  • [Applications of 3D-PSF of CT Image to QA for Thoracic CT-CAD: Part 2. Application of 3D-PSF and Verification of Measurement Accuracy of PSF]. Reviewed

    Shinichi Wada, Masaki Ohkubo, Akihiro Narita, Kohei Murao, Toru Matsumoto

    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics   39 ( 2 )   42 - 49   2019

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    DOI: 10.11323/jjmp.39.2_42

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  • [Applications of 3D-PSF of CT Image to QA for Thoracic CT-CAD: Part 3. Application of 3D-PSF 1. Conversion and Normalization of the Spatial Resolution of CT Image]. Reviewed

    Shinichi Wada, Masaki Ohkubo, Akihiro Narita, Kohei Murao, Toru Matsumoto

    Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics   39 ( 3 )   61 - 67   2019

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    DOI: 10.11323/jjmp.39.3_61

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  • Advances and Challenges in Assessing 2-Hydroxyglutarate in Gliomas by Magnetic Resonance Spectroscopy: A Short Review Reviewed

    Neuropsychiatry (London)   8 ( 6 )   1831 - 1838   2018.7

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  • Improved wedge method for the measurement of sub-millimeter slice thicknesses in magnetic resonance imaging Reviewed

    Tsutomu Kanazawa, Masaki Ohkubo, Tatsuya Kondo, Takayuki Miyazawa, Shoichi Inagawa

    Radiological Physics and Technology   10 ( 4 )   446 - 453   2017.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Tokyo  

    The standard method for measuring the slice thickness of magnetic resonance images uses the inclined surface of a wedge (wedge method)
    it is sensitive to small increases in noise because of the differentiation of the edge response function (ERF) required. The purpose of this study was to improve the wedge method by fitting a curve to the ERF. The curve-fit function was obtained by convolving an ideal ERF (a ramp function) with a Gaussian function to represent ERF blurring. Measurements of 5- and 3-mm slice thicknesses were performed on a 3T scanner using the conventional wedge method, the improved wedge method, and another standard method using an inclined slab (slab method). Subsequently, 0.5- and 0.25-mm slice thicknesses from multiple slices acquired using a three-dimensional sequence were measured using the improved wedge method. When measuring 5-mm slices, the differences in measurements obtained using the improved wedge method and the conventional slab and wedge methods were very small: &lt
    0.6% of the 5-mm slice thickness. The difference was ≤1.7% for 3-mm slices. For 0.5- and 0.25-mm slices, the mean values obtained using the improved wedge method were 0.543 ± 0.007 mm and 0.247 ± 0.015 mm, with a 1.2 and 5.9% coefficient of variation across slices, respectively. The improved wedge method is valid and potentially applicable to the measurement of sub-millimeter slice thicknesses.

    DOI: 10.1007/s12194-017-0417-2

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  • Generation of realistic virtual nodules based on three-dimensional spatial resolution in lung computed tomography: A pilot phantom study Reviewed

    Akihiro Narita, Masaki Ohkubo, Kohei Murao, Toru Matsumoto, Shinichi Wada

    MEDICAL PHYSICS   44 ( 10 )   5303 - 5313   2017.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY  

    Purpose: The aim of this feasibility study using phantoms was to propose a novel method for obtaining computer-generated realistic virtual nodules in lung computed tomography (CT).
    Methods: In the proposed methodology, pulmonary nodule images obtained with a CT scanner are deconvolved with the point spread function (PSF) in the scan plane and slice sensitivity profile (SSP) measured for the scanner; the resultant images are referred to as nodule-like object functions. Next, by convolving the nodule-like object function with the PSF and SSP of another (target) scanner, the virtual nodule can be generated so that it has the characteristics of the spatial resolution of the target scanner. To validate the methodology, the authors applied physical nodules of 5-, 7- and 10-mm-diameter (uniform spheres) included in a commercial CT test phantom. The nodule-like object functions were calculated from the sphere images obtained with two scanners (Scanner A and Scanner B); these functions were referred to as nodule-like object functions A and B, respectively. From these, virtual nodules were generated based on the spatial resolution of another scanner (Scanner C). By investigating the agreement of the virtual nodules generated from the nodule-like object functions A and B, the equivalence of the nodule-like object functions obtained from different scanners could be assessed. In addition, these virtual nodules were compared with the real (true) sphere images obtained with Scanner C. As a practical validation, five types of laboratory-made physical nodules with various complicated shapes and heterogeneous densities, similar to real lesions, were used. The nodule-like object functions were calculated from the images of these laboratory-made nodules obtained with Scanner A. From them, virtual nodules were generated based on the spatial resolution of Scanner C and compared with the real images of laboratory-made nodules obtained with Scanner C.
    Results: Good agreement of the virtual nodules generated from the nodule-like object functions A and B of the phantom spheres was found, suggesting the validity of the nodule-like object functions. The virtual nodules generated from the nodule-like object function A of the phantom spheres were similar to the real images obtained with Scanner C; the root mean square errors (RMSEs) between them were 10.8, 11.1, and 12.5 Hounsfield units (HU) for 5-, 7-, and 10-mm-diameter spheres, respectively. The equivalent results (RMSEs) using the nodule-like object function B were 15.9, 16.8, and 16.5 HU, respectively. These RMSEs were small considering the high contrast between the sphere density and background density (approximately 674 HU). The virtual nodules generated from the nodule-like object functions of the five laboratory-made nodules were similar to the real images obtained with Scanner C; the RMSEs between them ranged from 6.2 to 8.6 HU in five cases.
    Conclusions: The nodule-like object functions calculated from real nodule images would be effective to generate realistic virtual nodules. The proposed method would be feasible for generating virtual nodules that have the characteristics of the spatial resolution of the CT system used in each institution, allowing for site-specific nodule generation. (C) 2017 American Association of Physicists in Medicine

    DOI: 10.1002/mp.12503

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  • Magnetic Resonance Imaging of Neurotransmitter-Related Molecules Reviewed

    Hironaka Igarashi, Satoshi Ueki, Ken Ohno, Masaki Ohkubo, Yuji Suzuki

    JOURNAL OF NIPPON MEDICAL SCHOOL   84 ( 4 )   160 - 164   2017.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:MEDICAL ASSOC NIPPON MEDICAL SCH  

    Molecular imaging implies the method capable of pictorially displaying distribution of target molecules and their relative concentration in space. In clinical medicine, where non-invasiveness is mandatory, diagnostic molecular imaging has been considered virtually identical to positron emission tomography (PET). However, there is another powerful, apparently underutilized molecular imaging, namely, proton magnetic resonance spectroscopic imaging (H-1-MRSI). The technique can detect target molecules endogenous in brain in virtue of their own specific resonance frequencies (chemical shift) and can create quantitative images of each molecule. H-1-MRSI is conventionally utilized for imaging relatively easily detectable molecules such as N-acetyl-aspartate or lactate. More recently, however, the method is extended into imaging of more challenging molecules such as glutamate or gamma-aminobutyric acid (GABA). In this small review, we summarize basic concept of H-1-MRSI and introduce an advanced technique, i.e. chemical exchange saturation transfer magnetic resonance imaging (CEST MRI), which made realistic glutamate imaging in vivo possible.

    DOI: 10.1272/jnms.84.160

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  • Measurement of thin slice thickness in MRI using an improved wedge method Reviewed

    Kanazawa T, Ohkubo M, Kondo T

    European Congress of Radiology   C-1063   1 - 14   2017.3

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    DOI: 10.1594/ecr2017/C-1063

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  • パーソナルコンピュータ上で動作するDICOMデータのCT画像からの体積測定プログラムの開発と評価(PC用のDICOM体積測定プログラムの開発と評価)(The development and assessment of program for volume measurement for CT images of: DICOM data running on a personal computer: (Development and assessment of volume measurement program for DICOM on PC)) Reviewed

    Takahashi Naoya, Kobayashi Arashi, Nishihama Saori, Minamizawa Natsuki, Suzuki Noriko, Higuchi Takeshi, Ohkubo Masaki, Narita Akihiro, Sasamoto Ryuta

    新潟大学保健学雑誌   14 ( 1 )   27 - 33   2017.3

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    著者等は数値計算言語(MATLAB)を使ってPC上で動作するDICOM画像から体積を算出するプログラムを開発し、その有用性と正確度を検討した。CTの水平断像上に関心領域(ROI)を設置し、設定した閾値で必要な領域を抽出して三次元表示し、体積測定を行うこととした。本プログラムを用いて、64列CTで実施した死後CT検査5例について、肝、脾、腎を抽出した。ImageJにて目的とする臓器にROIを設定して面積を算出し、厚さを乗じて体積を測定した。臓器ごとに、ImageJにて求めた体積に最も近い値が得られるように閾値を決定した。著者等が開発したプログラムとImageJで測定した平均体積は、肝がそれぞれ1690.3±505.1cm3と107.9±60.7cm3、脾が107.9±60.7cm3と105.5±62.4cm3、腎が141.1±26.4cm3と143.9±32.1cm3であり、有意差は認められなかった。体積測定に要した平均時間は開発したプログラムの方が有意に短かった。著者等が開発したPC上で動作するDICOM画像の体積測定プログラムを用いると、簡便かつ正確に臓器の体積を測定することが可能であった。

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  • A method for evaluating the performance of computeraided detection of pulmonary nodules in lung cancer CT screening: detection limit for nodule size and density Reviewed

    Hajime Kobayashi, Masaki Ohkubo, Akihiro Narita, Janaka C. Marasinghe, Kohei Murao, Toru Matsumoto, Shusuke Sone, Shinichi Wada

    BRITISH JOURNAL OF RADIOLOGY   90 ( 1070 )   1 - 10   2017

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    Objective: We propose the application of virtual nodules to evaluate the performance of computer-aided detection (CAD) of lung nodules in cancer screening using lowdose CT.
    Methods: The virtual nodules were generated based on the spatial resolution measured for a CT system used in an institution providing cancer screening and were fused into clinical lung images obtained at that institution, allowing site specificity. First, we validated virtual nodules as an alternative to artificial nodules inserted into a phantom. In addition, we compared the results of CAD analysis between the real nodules (n=6) and the corresponding virtual nodules. Subsequently, virtual nodules of various sizes and contrasts between nodule density and background density (Delta CT) were inserted into clinical images (n=10) and submitted for CAD analysis.
    Results: In the validation study, 46 of 48 virtual nodules had the same CAD results as artificial nodules (kappa coefficient = 0.913). Real nodules and the corresponding virtual nodules showed the same CAD results. The detection limits of the tested CAD system were determined in terms of size and density of peripheral lung nodules; we demonstrated that a nodule with a 5- mm diameter was detected when the nodule had a Delta CT&gt; 220 HU.
    Conclusion: Virtual nodules are effective in evaluating CAD performance using site-specific scan/reconstruction conditions.
    Advances in knowledge: Virtual nodules can be an effectivemeans of evaluating site-specific CAD performance. The methodology for guiding the detection limit for nodule size/density might be a useful evaluation strategy.

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  • Technical Note: Image filtering to make computer-aided detection robust to image reconstruction kernel choice in lung cancer CT screening Reviewed

    Masaki Ohkubo, Akihiro Narita, Shinichi Wada, Kohei Murao, Toru Matsumoto

    MEDICAL PHYSICS   43 ( 7 )   4098 - 4105   2016.7

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    Purpose: In lung cancer computed tomography (CT) screening, the performance of a computer-aided detection (CAD) system depends on the selection of the image reconstruction kernel. To reduce this dependence on reconstruction kernels, the authors propose a novel application of an image filtering method previously proposed by their group.
    Methods: The proposed filtering process uses the ratio of modulation transfer functions (MTFs) of two reconstruction kernels as a filtering function in the spatial-frequency domain. This method is referred to as MTFratio filtering. Test image data were obtained from CT screening scans of 67 subjects who each had one nodule. Images were reconstructed using two kernels: f(STD) (for standard lung imaging) and f(SHARP) (for sharp edge-enhancement lung imaging). The MTFratio filtering was implemented using the MTFs measured for those kernels and was applied to the reconstructed f(SHARP) images to obtain images that were similar to the f(STD) images. A mean filter and a median filter were applied (separately) for comparison. All reconstructed and filtered images were processed using their prototype CAD system.
    Results: The MTFratio filtered images showed excellent agreement with the f(STD) images. The standard deviation for the difference between these images was very small, similar to 6.0 Hounsfield units (HU). However, the mean and median filtered images showed larger differences of similar to 48.1 and similar to 57.9 HU from the f(STD) images, respectively. The free-response receiver operating characteristic (FROC) curve for the f(SHARP) images indicated poorer performance compared with the FROC curve for the f(STD) images. The FROC curve for the MTFratio filtered images was equivalent to the curve for the f(STD) images. However, this similarity was not achieved by using the mean filter or median filter.
    Conclusions: The accuracy of MTFratio image filtering was verified and the method was demonstrated to be effective for reducing the kernel dependence of CAD performance. (C) 2016 American Association of Physicists in Medicine.

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  • [Measurement of the Dose Rate Using Dosimeters in Interventional Radiology and Its Difficulty]. Reviewed

    Hidenori Yoshida, Chiharu Takahashi, Nobuhiro Narita, Yasuhiko Mizusawa, Masaru Sekiya, Masaki Ohkubo

    Nihon Hoshasen Gijutsu Gakkai zasshi   72 ( 1 )   63 - 72   2016.1

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    In equipment used for interventional radiology (IVR), automatic exposure control (AEC) is incorporated to obtain the X-ray output suitable for the treatment of targeted lesions. For the AEC, users select a region as the signal sensing region (measuring field, MF) in the flat panel detector; MFs with various sizes and shapes were pre-defined and prepared in the system. The aim of this study was to examine the change of measured dose rate with the selection of MFs, the type of dosimeters (the ionization chamber dosimeter and the semiconductor dosimeter), and the dosimeter placement relative to the direction of X-ray tube (from cathode to anode). The IVR equipment was Allura Xper FD20/10 (Philips Medical Systems), and six kinds of built-in MFs were used. It was found that dose rate measured by the ionization chamber dosimeter showed a variation of -2 mGy/min with the MFs and the ionization chamber dosimeter placement. The dose rate measured by the semiconductor dosimeter showed more variation than the ionization chamber dosimeter. The change of dose rate with the dosimeter placement would be caused by the MF overlapping the dosimeter which would affect the AEC (the X-ray output). Also, the change of dose rate with the dosimeter placement was considered to be related to the heel effect of the X-ray beam. When performing dose rate measurements, we should notice that the selection of MFs, the type of dosimeters, and the dosimeter placement would affect the measured values.

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  • Characterization of the model-based iterative reconstruction algorithm: Confirmation of coexistence of dose reduction and spatial resolution improvement Reviewed

    Kayugawa A, Noto Y, Taga T, Fukaya T, Tasaki K, Fujioka T, Ohkubo M

    European Congress of Radiology   C-0946   1 - 24   2015.3

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  • Quality assurance of lung cancer CT screening CAD system by applying PSF-based reference virtual nodule set Reviewed

    Marasinghe JC, Ohkubo M, Kobayashi H, Yoshida A, Murao K, Matsumoto T, Sone S, Wada S

    European Congress of Radiology   C-1125   1 - 11   2015.3

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  • Diffuse Brain Abnormalities in Myotonic Dystrophy Type 1 Detected by 3.0 T Proton Magnetic Resonance Spectroscopy Reviewed

    Yuhei Takado, Kenshi Terajima, Masaki Ohkubo, Kouichirou Okamoto, Takayoshi Shimohata, Masatoyo Nishizawa, Hironaka Igarashi, Tsutomu Nakada

    EUROPEAN NEUROLOGY   73 ( 3-4 )   247 - 256   2015

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    Patients with myotonic dystrophy type 1 (DM1) (n = 14) were compared with healthy controls (n = 13) using 3.0 T proton magnetic resonance spectroscopy (H-1-MRS) to investigate brain pathophysiology. H-1-MRS imaging revealed reduced N-acetylaspartate to creatine ratio (NAA/Cr) in multiple brain regions (average 24%), suggesting diffuse brain abnormalities among patients with DM1. Single-voxel H-1-MRS among patients with DM1 showed (1) reduced NAA in both the frontal cortex (23%) and frontal white matter (31%) and unaltered myo-inositol, suggesting neuronal abnormalities without significant gliosis; and (2) elevated glutamine in the frontal cortex (36%) and reduced glutamate in the frontal white matter (20%) among patients with DM1, suggesting abnormalities in the glutamatergic system in the brain of patients with DM1. We consider that these results reflect brain abnormalities that cannot be detected by neuropathological assessment in patients with DM1. (C) 2015 S. Karger AG, Basel

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  • Validation of using PSF-based virtual nodules to assess the basic performances of lung cancer CT screening CAD system Reviewed

    Marasinghe JC, Ohkubo M, Wada S, Kobayashi H, Yoshida A, Murao K, Matsumoto T, Sone S

    Computer Assisted Radiology and Surgery 2014, 28th International and Exhibition   9 ( 1 (S236) )   2014.6

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  • Feasible method to assess the performance of a lung cancer CT screening CAD system in clinical practice: dependence on nodule size and density Reviewed

    Marasinghe JC, Ohkubo M, Kobayashi H, Murao K, Matsumoto T, Sone S, Wada S

    International Journal of Medical Physics, Clinical Engineering and Radiation Oncology   3 ( 2 )   107 - 116   2014.5

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    DOI: 10.4236/ijmpcero.2014.32016

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  • Pixel values of [15O]H2O PET images with OSEM algorithm depending on numbers of subset and iteration times: Comparative assessment to FBP Reviewed

    Rie Yamanoi, Kouichirou Okamoto, Kazunori Kawamura, Masaki Ohkubo, Yuji Suzuki, Yukihiro Nakamura

    Kakuigaku   51 ( 4 )   373 - 382   2014

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    To investigate a potential application of ordered subsets expectation maximization (OSEM) algorithm for clinical [15O]H2O PET studies, region of interest (ROI) measurements were performed on both images with OSEM and fitered back projection (FBP). Forty OSEM images were reconstructed with variable combinations of numbers of the subset (1-40) and iteration times (2-12). PET scans were acquired using a PET/CT scanner (Discovery ST Elite, GE), and 3T-MRI images were obtained for fusion images. The mean values were measured on the frontal cortical regions in the middle cerebral artery distribution. Differences of the values between the OSEM and FBP were evaluated as %Error. Relationship between ROI mean values and the iteration times was investigated on the OSEM images. The smallest %Error 0.4% was measured in the combination of the subset number 10 and iteration times 8 [10, 8], and in that of [28, 2]. The mean values were stable with iteration number 8 or more. OSEM image with [28, 2] was reconstructed in a shorter time (2.5 min) than that with [10, 8] (6 min). OSEM image with [28, 2] was superior to that with [10, 8] in the qualitative evaluation. The mean values on OSEM images with [28, 2] were comparable with those on FBP images with little artifacts and higher spatial resolution. OSEM with optimal parameter setting seemed applicable for both quantitative and qualitative [15O]H2O PET studies.

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  • Evaluation of lung CT CAD performance by using PSF-based virtual nodules: a validation of the methodology Reviewed

    Marasinghe JC, Ohkubo M, Kobayashi H, Murao K, Matsumoto T, Sone S, Wada S

    MEDICAL PHYSICS INTERNATIONAL Journal   1 ( 2 )   350 - 350   2013.9

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  • Observer-independent nodule-detectability index for low-dose lung cancer screening CT: A pilot study Reviewed

    Masaki Ohkubo, Shinichi Wada, Satoshi Kanai, Kazuhiro Ishikawa, Janaka C. Marasinghe, Toru Matsumoto

    Radiological Physics and Technology   6 ( 2 )   492 - 499   2013.7

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    For the wide dissemination of lung cancer screening by low-dose computed tomography (CT), it is important to determine the optimal conditions for scan and image reconstruction based on objective standards of evaluation. Our aim in this study was to propose a quantitative index of nodule detectability without an observer test. It was essential to determine the apparent size and density of nodules visible on CT images for developing the nodule-detectability index based on a statistical observer-independent method. Therefore, we introduced a computer simulation technique for CT images based on the spatial resolution of the system to evaluate the size and density accurately. By use of scan/reconstruction parameter settings as employed for low-dose CT screening, a detectability index was obtained for target nodules (ideal spheres) of various sizes and with varying contrast (ΔCT) between nodule density and background density. The index was compared with the qualitative results of observer tests of nodule detectability. As the target nodule diameter or ΔCT was increased, the index value increased, implying improved nodule visibility. According to the index, the detection limits for nodules with ΔCTs of 70, 100, or 150 Hounsfield units were approximately 6, 5, and 4 mm in diameter, respectively. Index values were well correlated with nodule detectability as assessed by four observers. The proposed index was effective for quantifying nodule detectability, and its validity was confirmed by an observer test. This index has potential use in the determination of optimal scan/reconstruction parameters for lung cancer screening by low-dose CT without observer test. © 2013 Japanese Society of Radiological Technology and Japan Society of Medical Physics.

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  • Accurate determination of ct point-spread-function with high precision Reviewed

    Akihiro Kayugawa, Masaki Ohkubo, Shinichi Wada

    Journal of Applied Clinical Medical Physics   14 ( 4 )   216 - 226   2013

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    The measurement of modulation transfer functions (MTFs) in computed tomography (CT) is often performed by scanning a point source phantom such as a thin wire or a microbead. In these methods the region of interest (ROI) is generally placed on the scanned image to crop the point source response. The aim of the present study was to examine the effect of ROI size on MTF measurement, and to optimize the ROI size. Using a 4 multidetector-row CT, MTFs were measured by the wire and bead methods for three types of reconstruction kernels designated as 'smooth', 'standard', and 'edge-enhancement' kernels. The size of a square ROI was changed from 30 to 50 pixels (approximately 2.9 to 4.9 mm). The accuracies of the MTFs were evaluated using the verification method. The MTFs measured by the wire and bead methods were dependent on ROI size, particularly in MTF measurement for the 'edge-enhancement' kernel. MTF accuracy evaluated by the verification method changed with ROI size, and we were able to determine the optimum ROI size for each method (wire/bead) and for each kernel. Using these optimal ROI sizes, the MTF obtained by the wire method was in strong agreement with the MTF obtained by the bead method in each kernel. Our data demonstrate that the difficulties in obtaining accurate MTFs for some kernels such as edge-enhancement can be overcome by incorporating the verification method into the wire and bead methods, allowing optimization of the ROI size to accurately determine the MTF.

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  • Application of PSF-based virtual nodules to assess the performance of lung cancer CT screening CAD system Reviewed

    Marasinghe JC, Ohkubo M, Kobayashi H, Murao K, Matsumoto T, Niizuma S, Sone S, Wada S

    Proceedings of Asia-Oceania Congress of Medical Physics   12 ( 1 )   249 - 252   2012.12

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  • Application of CT-PSF-based computer-simulated lung nodules for evaluating the accuracy of computer-aided volumetry Reviewed

    Ayumu Funaki, Masaki Ohkubo, Shinichi Wada, Kohei Murao, Toru Matsumoto, Shinji Niizuma

    Radiological Physics and Technology   5 ( 2 )   166 - 171   2012.7

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    With the wide dissemination of computed tomography (CT) screening for lung cancer, measuring the nodule volume accurately with computer-aided volumetry software is increasingly important. Many studies for determining the accuracy of volumetry software have been performed using a phantom with artificial nodules. These phantom studies are limited, however, in their ability to reproduce the nodules both accurately and in the variety of sizes and densities required. Therefore, we propose a new approach of using computer-simulated nodules based on the point spread function measured in a CT system. The validity of the proposed method was confirmed by the excellent agreement obtained between computer-simulated nodules and phantom nodules regarding the volume measurements. A practical clinical evaluation of the accuracy of volumetry software was achieved by adding simulated nodules onto clinical lung images, including noise and artifacts. The tested volumetry software was revealed to be accurate within an error of 20 % for nodules[5 mm and with the difference between nodule density and background (lung) (CT value) being 400-600 HU. Such a detailed analysis can provide clinically useful information on the use of volumetry software in CT screening for lung cancer. We concluded that the proposed method is effective for evaluating the performance of computer-aided volumetry software. © Japanese Society of Radiological Technology and Japan Society of Medical Physics 2012.

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  • Electronic Portal Imaging Device (EPID) Portal Image Filtering for Simplifying Registration on Radiation Therapy Reviewed

    Yamada M, Ohkubo M, Kayugawa A, Yamada H, Matsuura M, Miura T, Kusumoto T

    Nihon Hoshasen Gijutsu Gakkai Zasshi   68 ( 5 )   593 - 601   2012.5

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  • 脳動脈瘤クリップにおける磁化率アーチファクトの角度依存性の検討

    金沢 勉, 内藤健一, 斉藤宏明, 粥川啓廣, 岩崎友也, 大久保真樹, 木村元政

    日本放射線技術学会東北部会雑誌   21 ( 21 )   86 - 89   2012.1

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    磁化率アーチファクトによる画像歪みの影響が、静磁場(Bo)方向と脳動脈瘤クリップの長軸方向とのなす角度に依存するか検討した。磁化率アーチファクトの影響を低減させるには、バンド幅が非常に重要であることが再認識された。Boと脳動脈瘤クリップの長軸方向とのなす角度が大きくなると、磁化率アーチファクト領域は大きくなり、0度〜90度でSE系が2.3倍、GE系が1.5倍となり、Boと垂直で最大となった。また、SE系に比べGE系の撮像法は磁化率アーチファクト領域が2.5〜3倍ほど大きくなった。Bo方向に対する脳動脈瘤クリップの長軸方向の角度が、磁化率アーチファクト領域に対し依存性があることが示唆された。

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  • Accuracy of lung nodule density on HRCT: analysis by PSF-based image simulation Reviewed

    Ken Ohno, Masaki Ohkubo, Janaka C. Marasinghe, Kohei Murao, Toru Matsumoto, Shinichi Wada

    JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS   13 ( 6 )   277 - 292   2012

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    A computed tomography (CT) image simulation technique based on the point spread function (PSF) was applied to analyze the accuracy of CT-based clinical evaluations of lung nodule density. The PSF of the CT system was measured and used to perform the lung nodule image simulation. Then, the simulated image was resampled at intervals equal to the pixel size and the slice interval found in clinical high-resolution CT (HRCT) images. On those images, the nodule density was measured by placing a region of interest (ROI) commonly used for routine clinical practice, and comparing the measured value with the true value (a known density of object function used in the image simulation). It was quantitatively determined that the measured nodule density depended on the nodule diameter and the image reconstruction parameters (kernel and slice thickness). In addition, the measured density fluctuated, depending on the offset between the nodule center and the image voxel center. This fluctuation was reduced by decreasing the slice interval (i.e., with the use of overlapping reconstruction), leading to a stable density evaluation. Our proposed method of PSF-based image simulation accompanied with resampling enables a quantitative analysis of the accuracy of CT-based evaluations of lung nodule density. These results could potentially reveal clinical misreadings in diagnosis, and lead to more accurate and precise density evaluations. They would also be of value for determining the optimum scan and reconstruction parameters, such as image reconstruction kernels and slice thicknesses/intervals.

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  • Image filtering as an alternative to the application of a different reconstruction kernel in CT imaging: Feasibility study in lung cancer screening Reviewed

    Masaki Ohkubo, Shinichi Wada, Akihiro Kayugawa, Toru Matsumoto, Kohei Murao

    MEDICAL PHYSICS   38 ( 7 )   3915 - 3923   2011.7

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    Purpose: While the acquisition of projection data in a computed tomography (CT) scanner is generally carried out once, the projection data is often removed from the system, making further reconstruction with a different reconstruction filter impossible. The reconstruction kernel is one of the most important parameters. To have access to all the reconstructions, either prior reconstructions with multiple kernels must be performed or the projection data must be stored. Each of these requirements would increase the burden on data archiving. This study aimed to design an effective method to achieve similar image quality using an image filtering technique in the image space, instead of a reconstruction filter in the projection space for CT imaging. The authors evaluated the clinical feasibility of the proposed method in lung cancer screening.
    Methods: The proposed technique is essentially the same as common image filtering, which performs processing in the spatial-frequency domain with a filter function. However, the filter function was determined based on the quantitative analysis of the point spread functions (PSFs) measured in the system. The modulation transfer functions (MTFs) were derived from the PSFs, and the ratio of the MTFs was used as the filter function. Therefore, using an image reconstructed with a kernel, an image reconstructed with a different kernel was obtained by filtering, which used the ratio of the MTFs obtained for the two kernels. The performance of the method was evaluated by using routine clinical images obtained from CT screening for lung cancer in five subjects.
    Results: Filtered images for all combinations of three types of reconstruction kernels ("smooth," "standard," and "sharp" kernels) showed good agreement with original reconstructed images regarded as the gold standard. On the filtered images, abnormal shadows suspected as being lung cancers were identical to those on the reconstructed images. The standard deviations (SDs) for the difference between filtered images and reconstructed images ranged from 1.9 to 23.5 Hounsfield units for all kernel combinations; these SDs were much smaller than the noise SDs in the reconstructed images.
    Conclusions: The proposed method has good performance and is clinically feasible in lung cancer screening. This method can be applied to images reconstructed on any scanner by measuring the PSFs in each system. (C) 2011 American Association of Physicists in Medicine. [DOI:10.1118/1.3590363]

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  • 3T MRIを用いた筋強直性ジストロフィー1型患者の大脳皮質・白質の非侵襲的評価

    高堂 裕平, 五十嵐 博中, 寺島 健史, 大久保 真樹, 下畑 享良, 岡本 浩一郎, 西澤 正豊, 中田 力

    新潟県医師会報   728 ( 728 )   7 - 8   2010.11

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  • 3D CT image simulation-based analysis of threshold setting for pulmonary nodule volumetric evaluation Reviewed

    Ohno K, Funaki A, Ohkubo M, Wada S, Kayugawa A, Matsumoto T, Murao K

    Igaku Butsuri   30 ( 2 )   39 - 48   2010.11

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  • Simulation study for artifacts on Gd-EOB-DTPA-enhanced liver dynamic MR imaging in arterial dominant phase Reviewed

    Fukaya T, Naito K, Saitoh H, Takimoto M, Kayugawa A, Ohkubo M

    Nippon Hoshasen Gijutsu Gakkai Zasshi   66 ( 9 )   1197 - 1203   2010.9

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  • Spatial resolution conversion in z-axis using CT SSP Reviewed

    Kayugawa A, Ohkubo M, Shinichi W, Matsumoto T, Murao K, Yamamoto S

    Igaku Butsuri   30 ( 1 )   3 - 9   2010.8

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  • 低線量MDCT検診における画質と線量の最適化のための一考察 Reviewed

    和田真一, 松本 徹, 西沢かな枝, 大久保真樹

    日本CT検診学会誌   16 ( 3 )   187 - 194   2009.12

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    MDCT装置を用いたCT検診の撮影条件の最適化を考える上で必要な画質と線量の関係について解説した。画質を左右する因子としてコントラスト分解能と空間分解能が主要な因子であり、コントラスト分解能に関係するSNRと線量の関係、SNRとPSFの関係について考察した。CT肺がん検診で検出対象となる直径10mm以下の結節のコントラストに対する、MDCTの撮影条件・再構成条件による影響を、3次元PSFを用いた計算機シミュレーションにより定量的に推定し、X線量と画像再構成関数によるノイズの影響を総合した検討が必要であることを述べた。また、多様な列数のMDCTにおけるCT検診撮影条件決定に際して考慮すべき点、検討の手順について解説した。(著者抄録)

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  • Determination of point spread function in computed tomography accompanied with verification Reviewed

    Masaki Ohkubo, Shinichi Wada, Satoshi Ida, Masayuki Kunii, Akihiro Kayugawa, Toru Matsumoto, Kanae Nishizawa, Kohei Murao

    MEDICAL PHYSICS   36 ( 6 )   2089 - 2097   2009.6

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    A method for verifying the point spread function (PSF) measured by computed tomography has been previously reported [Med. Phys. 33, 2757-2764 (2006)]; however, this additional PSF verification following measurement is laborious. In the present study, the previously described verification method was expanded to PSF determination. First, an image was obtained by scanning a phantom. The image was then two-dimensionally deconvolved with the object function corresponding to the phantom structure, thus allowing the PSF to be obtained. Deconvolution is implemented simply by division of spatial frequencies (corresponding to inverse filtering), in which two parameters are used as adjustable ones. Second, an image was simulated by convolving the object function with the obtained PSF, and the simulated image was compared to the above-measured image of the phantom. The difference indicates the inaccuracy of the PSF obtained by deconvolution. As a criterion for evaluating the difference, the authors define the mean normalized standard deviation (SD) in the difference between simulated and measured images. The above two parameters for deconvolution can be adjusted by referring to the subsequent mean normalized SD (i.e., the PSF is determined so that the mean normalized SD is decreased). In this article, the parameters were varied in a fixed range with a constant increment to find the optimal parameter setting that minimizes the mean normalized SD. Using this method, PSF measurements were performed for various types of image reconstruction kernels (21 types) in four kinds of scanners. For the 16 types of kernels, the mean normalized SDs were less than 2.5%, indicating the accuracy of the determined PSFs. For the other five kernels, the mean normalized SDs ranged from 3.7% to 4.8%. This was because of a large amount of noise in the measured images, and the obtained PSFs would essentially be accurate. The method effectively determines the PSF, with an accompanying verification, after one scanning of a phantom.

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  • Accurate determination of CT PSF with high precision Reviewed

    A. Kayugawa, S. Wada, M. Ohkubo, T. Matsumoto, K. Murao

    WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 2 - DIAGNOSTIC IMAGING   25 ( II )   806 - 809   2009

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    A method for verifying the point spread function (PSF) measured by computed tomography has been previously reported [1]. However, this additional PSF verification following measurement is laborious. In the present study, the previously described verification method was expanded to PSF determination [2], that is, the PSF determination and verification were performed concurrently by one scanning of the phantom. Using this method, PSF measurements were performed for 10 types of image reconstruction kernels in two kinds of scanners. As a result, accurate PSF determinations were achieved. Also, reproducibility for determining the PSF was investigated by using four slice images. Using each image, the PSF was determined by the proposed method. The MTFs were derived from the PSFs, and that variation was evaluated. The standard deviation (SD) of the MTFs was found to be small, suggesting the stability for determining the PSF. Our method was concluded to be accurate with high precision determining the CT PSF.

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  • Imaging of small spherical structures in CT: simulation study using measured point spread function Reviewed

    Masaki Ohkubo, Shinichi Wada, Masayuki Kunii, Toru Matsumoto, Kanae Nishizawa

    MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING   46 ( 3 )   273 - 282   2008.3

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    Size and density measurements of objects undertaken using computed tomography (CT) are clinically significant for diagnosis. To evaluate the accuracy of these quantifications, we simulated three-dimensional (3D) CT image blurring; this involved the calculation of the convolution of the 3D object function with the measured 3D point spread function (PSF). We initially validated the simulation technique by performing a phantom experiment. Blurred computed images showed good 3D agreement with measured images of the phantom. We used this technique to compute the 3D blurred images from the object functions, in which functions are determined to have the shape of an ideal sphere of varying diameter and assume solitary pulmonary nodules with a uniform density. The accuracy of diameter and density measurements was determined. We conclude that the proposed simulation technique enables us to estimate the image blurring precisely of any 3D structure and to analyze clinical images quantitatively.

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  • Study of susceptibility-weighted imaging (SWI) using a simple MR phantom Reviewed

    Ohta A, Naito K, Ohkubo M, Inomata M, Ohgoshi Y, Okamoto K, Ito A

    Nippon Hoshasen Gijutsu Gakkai Zasshi   63 ( 9 )   1093 - 1098   2007.9

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    DOI: 10.6009/jjrt.63.1093

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  • Identification of the anterior ethmoid arteries on thin-section axial images and coronal reformatted orbit images by means of multidetector row CT Reviewed

    N. Takahashi, M. Ohkubo, T. Higuchi, H. Maeda

    CLINICAL RADIOLOGY   62 ( 4 )   376 - 381   2007.4

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    AIM: The aim of this study was to identify anterior ethmoid arteries on thin-section axial images and coronal reformatted images of the orbits using multidetector row computed tomography (CT).
    MATERIALS AND METHODS: One hundred and thirty-two patients underwent paranasal CT using a 16-row detector CT (n = 59) or a 6-row detector CT machine (n = 73) at 1 or 1.25 mm section width, respectively. Coronal images were reformatted at section widths of 3 and 1 mm. The anterior ethmoid arteries were identified for each patient. Differences were assessed using the chi-square test.
    RESULTS: All CT images were of approximately average diagnostic quality. Anterior ethmoid arteries were identified in 97.5 and 96.6% at section thicknesses of 1 and 1.25 mm on the axial images, respectively. There was no statistically significant difference in the detection rate (p=0.89). On the corona[ images, anterior ethmoid arteries were presented tangentially in 75.4 and 90.2% at section widths of 3 and 1 mm, respectively. The visibility of the anterior ethmoid arteries was rated significantly better on coronal images at a section width of 1 mm than on those at section widths of 3 mm (p &lt; 0.001).
    CONCLUSION: Thin-section axial images and corona[ reformatted images using multi-detector row CT mostly depict anterior ethmoid arteries, and are useful to identify anterior ethmoid arteries for preoperative evaluation of paranasal sinuses. (c) 2006 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

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  • Increase in glutamate as a sensitive indicator of extracellular matrix integrity in peritumoral edema: a 3.0-tesla proton magnetic resonance spectroscopy study Reviewed

    Teruo Kimura, Masaki Ohkubo, Hironaka Igarashi, Ingrid L. Kwee, Tsutomu Nakada

    JOURNAL OF NEUROSURGERY   106 ( 4 )   609 - 613   2007.4

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    Object. The authors of previous studies based on diffusion tensor imaging have indicated that there are two types of peritumoral edema-namely, edema with preserved structural integrity of the glial matrix and edema with compromised glial matrix. The authors of this study hypothesized that functionality of the glutamate (Glu)-glutamine shuttle, a vital neuron-glia interaction, may be differentially affected by peritumoral edema. They tested this hypothesis using proton magnetic resonance (MR) spectroscopy on a 3.0-tesla system that is capable of quantifying Glu without need of editing.
    Methods. Twenty-three patients, each with a single brain tumor mass and peritumoral edema (nine high-grade gliomas, eight metastatic brain tumors, and six meningiomas), and nine healthy individuals participated in this study. Single-voxel proton MR imaging targeting the region of peritumoral edema was performed using a 3.0-tesla system.
    Glutamate levels in the peritumoral edema of nonglial tumors was significantly elevated (p &lt; 0.01) compared with edema associated with glial tumors or normal white matter. The finding confirmed that peritumoral edema in nonglial tumors is distinct from that of glial tumors, as previously indicated in diffusion tensor imaging studies. The authors hypothesized that the former condition represents a compensatory increase in activities of the Glu-glutamine shuttle brought about by simple expansion of the extracellular space due to edema.
    Conclusions. The assessment of Glu concentrations in peritumoral edema using 3.0-tesla proton MR spectroscopy may be developed into an objective index of the structural integrity of the glial matrix.

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  • 脳血流PET 検査における15O-H2O投与量の違いに対する画像の評価 Reviewed

    山野井理恵, 河村和紀, 岡本浩一郎, 大久保真樹

    新潟核医学懇話会記録集   35   22 - 26   2007.4

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  • The CT image standardization based on the verified PSF. Reviewed

    Shinichi Wada, Masaki Ohkubo, Masayuki Kunii, Toru Matsumoto, Kohei Murao, Kazuo Awai, Mitsuru Ikeda

    MEDICAL IMAGING 2007: PHYSICS OF MEDICAL IMAGING, PTS 1-3   6510 ( 65104D )   1 - 8   2007

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    This study discusses a method of CT image quality standardization that uses a point-spread function (PSF) in MDCT. CT image I(x,y,z) is represented by the following formula: I(x,y,z) = O(x,y,z)***PSF(x,y,z). Standardization was performed by measuring the three-dimensional (3-D) PSFs of two CT images with different image qualities. The image conversion method was constructed and tested using the 3-D PSFs and CT images of the CT scanners of three different manufacturers. The CT scanners used were Lightspeed QX/i, Somatom Volume Zoom, and Brilliance-40. To obtain the PSF(x,y) of these CT scanners, the line spread functions of the respective reconstruction kernels were measured using a phantom described by J.M. Boone. The kernels for each scanner were: soft, standard, lung, bone, and bone plus (GE); B20f, B40f, B41f, B50f, and B60f (Siemens); and B, C, D, E, and L (Philips). Slice sensitivity profile (SSP) were measured using a micro-disk phantom (50 mu m* phi 1 mm) with 5 mm slice thickness and beam pitch of 1.5 (GE, Siemens) and 0.626 (Philips). 3-D PSF was verified using an MDCT QA phantom. Real chest CT images were converted to images with contrasting standard image quality. Comparison between the converted CT image and the original standard image showed good agreement. The usefulness of the image conversion method is discussed using clinical CT images acquired by CT scanners produced by different manufacturers.

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  • An effective method to verify line and point spread functions measured in computed tomography Reviewed

    Masaki Ohkubo, Sinichi Wada, Toru Matsumoto, Kanae Nishizawa

    MEDICAL PHYSICS   33 ( 8 )   2757 - 2764   2006.8

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    This study describes an effective method for verifying line spread function (LSF) and point spread function (PSF) measured in computed tomography (CT). The CT image of an assumed object function is known to be calculable using LSF or PSF based on a model for the spatial resolution in a linear imaging system. Therefore, the validities of LSF and PSF would be confirmed by comparing the computed images with the images obtained by scanning phantoms corresponding to the object function. Differences between computed and measured images will depend on the accuracy of the LSF and PSF used in the calculations. First, we measured LSF in our scanner, and derived the two-dimensional PSF in the scan plane from the LSF. Second, we scanned the phantom including uniform cylindrical objects parallel to the long axis of a patient's body (z direction). Measured images of such a phantom were characterized according to the spatial resolution in the scan plane, and did not depend on the spatial resolution in the z direction. Third, images were calculated by two-dimensionally convolving the true object as a function of space with the PSF. As a result of comparing computed images with measured ones, good agreement was found and was demonstrated by image subtraction. As a criterion for evaluating quantitatively the overall differences of images, we defined the normalized standard deviation (SD) in the differences between computed and measured images. These normalized SDs were less than 5.0% (ranging from 1.3% to 4.8%) for three types of image reconstruction kernels and for various diameters of cylindrical objects, indicating the high accuracy of PSF and LSF that resulted in successful measurements. Further, we also obtained another LSF utilizing an inappropriate manner, and calculated the images as above. This time, the computed images did not agree with the measured ones. The normalized SDs were 6.0% or more (ranging from 6.0% to 13.8%), indicating the inaccuracy of the PSF and LSF. We could verify LSFs and PSFs for three types of reconstruction kernels, and demonstrated differences between modulation transfer functions (MTFs) derived from validated LSFs and inaccurate LSFs. Our technique requires a simple phantom that is suitable for clinical scanning, and does not require a particular phantom containing some metals or specific fine structures, as required in methods previously used for measurements of spatial resolution. Therefore, the scanned image of the phantom will be reliable and of good quality, and this is used directly as a confident reference image for the verification. When one obtains LSF, PSF or MTF values, verification using our method is recommended. Further, when another method for the measurement of LSF and PSF is developed, it could be validated using our technique, as illustrated in the method proposed by Boone [Med. Phys. 28, 356-360 (2001)] and used in this paper. (C) 2006 American Association of Physicists in Medicine.

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  • Parietal white matter abnormalities in obsessive-compulsive disorder: a magnetic resonance spectroscopy study at 3-Tesla Reviewed

    H. Kitamura, T. Shioiri, T. Kimura, M. Ohkubo, T. Nakada, T. Someya

    ACTA PSYCHIATRICA SCANDINAVICA   114 ( 2 )   101 - 108   2006.8

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    Objective: To identify a neurochemical basis for the hypothesis that an aberrant cortico-subcortical circuit underlies obsessive-compulsive disorder (OCD). The white matter was also investigated because of recent research which suggests the altered connectivity of axons.
    Method: Using 3-Tesla magnetic resonance spectroscopy, the relative concentrations of N-acetylaspartate (NAA) and choline-containing compounds (Cho) to creatine/phosphocreatine (Cr) were measured in the anterior cingulate, basal ganglia, thalamus, frontal and parietal white matter of 12 OCD patients, and 32 control subjects.
    Results: The mean concentration of Cho/Cr was significantly higher in the patients than in the controls, but only in the parietal white matter, while no significant group differences in NAA/Cr were observed in any of the brain regions. Parietal Cho/Cr correlated positively with the severity of OCD symptoms.
    Conclusion: This finding provides indirect evidence for the parietal white matter involvement in OCD, thus suggesting a change in the phospholipids of myelinated axons and/or glia cells.

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  • Evaluation of the accuracy of line spread function (LSF) and point spread function (PSF) measured in the computed tomography Reviewed

    Kunii M, Wada S, Ohkubo M, Harada M, Nishizawa K, Matsumoto T

    Igaku Butsuri   26 ( 2 )   57 - 64   2006.6

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    DOI: 10.11323/jjmp2000.26.2_57

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  • A method of accuracy evaluation of line spread function (LSF) and point spread function (PSF) measured in computed tomography. Reviewed

    Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, Kanae Nishizawa

    MEDICAL IMAGING 2006: PHYSICS OF MEDICAL IMAGING, PTS 1-3   6142   61423I-1 - 61423I-8   2006

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    This study describes a method of accuracy evaluation of verifying the line spread function (LSF) and point spread function (PSF) measured in computed tomography (CT). The CT image of an assumed object-function was calculated using LSF or PSF based on a model to understand spatial resolution in the imaging system. Validities of LSF and PSF were confirmed by comparing the calculated image with the scanned image of the phantom corresponding to the object-function. Differences between the scanned and calculated images depended on accuracies of LSF and PSF used in the calculations. First, we measured LSF in a scanner, and derived the two-dimensional PSF in the scan-plane from LSF. Second, we scanned the phantom including uniform cylindrical objects parallel to the long axis of a patient&apos;s body (z-direction). Scanned images of such a phantom were characterized according to spatial resolution in the scan-plane, and didn&apos;t depend on spatial resolution in the z-direction. Third, images were calculated by two-dimensionally convolving the object-function with PSF, which object-function was determined to correspond to the phantom. Calculated images agreed with scanned images, confirming validities of PSF and LSF. On the other hand, we obtained another LSF with an inappropriate manner, and calculated images as mentioned above. On this case, the calculated images did not agree with the scanned images, indicating the inaccuracy of LSF. We could verify LSFs and PSFs for three types of reconstruction kernels. When one obtains LSF, PSF or MTF, verification using the proposed method is recommended.

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  • Optimization of flip angle for 3D-VIBE technique in liver dynamic MRI Reviewed

    Naito K, Ohgoshi Y, Ohkubo M, Yagishita Y, Oka J, Ohta A, Yamamoto T, Komazawa E

    Nippon Hoshasen Gijutsu Gakkai Zasshi   61 ( 10 )   1441 - 1446   2005.10

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  • Validation of the blurring of a small object on CT images calculated on the basis of three-dimensional spatial resolution Reviewed

    Ohkubo M, Wada S, Saito M

    Igaku Butsuri   25 ( 3 )   132 - 140   2005.9

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    We determine three-dimensional (3D) blurring of a small object on computed tomography (CT) images calculated on the basis of 3D spatial resolution. The images were characterized by point spread function (PSF), line spread function (LSF) and slice sensitivity profile (SSP). In advance, we systematically arranged expressions in the model for the imaging system to calculate 3D images under various conditions of spatial resolution. As a small object, we made a blood vessel phantom in which the direction of the vessel was not parallel to either the xy scan-plane or the z-axis perpendicular to the scan-plane. Therefore, when scanning the phantom, non-sharpness must be induced in all axes of the image. To predict the image blurring of the phantom,3D spatial resolution is essential. The LSF and SSP were measured on our scanner, and two-dimensional (2D) PSF in the scan-plane was derived from the LSF by solving an integral equation. We obtained 3D images by convolving the 3D object-function of the phantom with both 2D PSF and SSP, corresponding to the 3D convolution. Calculated images showed good agreement with scanned images. Our technique of determining 3D blurring offers an accuracy advantage in 3D shape (size) and density measurements of small objects.

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  • High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil Reviewed

    N Takahashi, K Okamoto, M Ohkubo, M Kawana

    CLINICAL RADIOLOGY   60 ( 3 )   349 - 354   2005.3

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    AIM: To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial. facial nerve, compared with surgical findings.
    MATERIALS AND METHODS: Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery.
    RESULTS: Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases.
    CONCLUSION: High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours. (C) 2005 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

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  • Endorectal Coil の特性評価 MRS での使用を目的とした検討 Reviewed

    八木下裕子, 内藤健一, 太田絢子, 岡 純子, 大越幸和, 大久保真樹

    日本放射線技術学会東北部会雑誌   14 ( 14 )   149 - 151   2005.1

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  • 肝臓 dynamic MRI における 3D VIBE の有用性 Reviewed

    内藤健一, 八木下裕子, 岡 純子, 太田絢子, 大越幸和, 大久保真樹

    日本放射線技術学会東北部会雑誌   14 ( 14 )   139 - 141   2005.1

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  • Measurements and precisions of point spread function of multi-slice CT Reviewed

    S Wada, M Ohkubo, T Matsumoto

    Medical Imaging 2005: Physics of Medical Imaging, Pts 1 and 2   5745 ( 22 )   1209 - 1216   2005

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    The determination of point spread function (PSF) is essential for the assessment of the performance of multi-slice CT corresponding to particular scanning or reconstruction condition. We studied the accuracy of the method for determination of PSF. The precision were evaluated with use of special made phantom and computer simulations. The PSF of some kinds of multi-slice CT were evaluated under the several scanning or reconstruction conditions. The performances were compared with each other and discussed. The PSF (x, y, z) was measured with separate components of PSF (x, y)) and LSF(z). In the measurement of PSF(x, y) and LSF(z), we used Boone phantom and delta phantom respectively. The PSF(x,y) was calculated from LSF(x) and LSF(y). The LSF(z) obtained from delta phantom was added for the calculation of PSF(x,y,z) with use of the following formula..
    PSF(x, y, z) = PSF(x, y) (.) LSF(Z) = LSF(x) (.) LSF(y) (.) LSF(z)
    The precision for the obtained LSF and PSF were evaluated by phantom experiment with computer simulation using following equations.
    I (x) = LSF(x) * O(x)
    I(x, y, z) = integral(infinity)(-infinity)integral(infinity)(-infinity)integral O-infinity(-infinity)(x, y, z) (.) PSF(x - x', y - y', z - z') dx dy dz
    The precision of the measured PSF(x, y) was evaluated to be a good approximation for the image of the blood-vessel phantom. The results propose the method for the evaluation of the precision of measured point spread function.. At the same time this results suggests the method of the calculation of the CT image affected by spatial resolution.

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  • Relationship between line spread function (LSF), or slice sensitivity profile (SSP), and point spread function (PSF) in CT image system Reviewed

    Ohkubo M, Wada S, Kobayashi T, Lee Y, Tsai DY

    Igaku Butsuri   24 ( 3 )   115 - 122   2004.12

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  • Medical image classification using genetic-algorithm based fuzzy-logic approach Reviewed

    DY Tsai, Y Lee, M Sekiya, M Ohkubo

    JOURNAL OF ELECTRONIC IMAGING   13 ( 4 )   780 - 788   2004.10

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    In this paper we present a genetic-algorithm-based fuzzy-logic approach for computer-aided diagnosis scheme in medical imaging. The scheme is applied to discriminate myocardial heart disease from echocardiographic images and to detect and classify clustered microcalcifications from mammograms. Unlike the conventional types of membership functions such as trapezoid, triangle, S curve, and singleton used in fuzzy reasoning, Gaussian-distributed fuzzy membership functions (GDMFs) are employed in the present study. The GDMFs are initially generated using various texture-based features obtained from reference images. Subsequently the shapes of GDMFs are optimized by a genetic-algorithm learning process. After optimization, the classifier is used for disease discrimination. The results of our experiments are very promising. We achieve an average accuracy of 96% for myocardial heart disease and accuracy of 88.5% at 100% sensitivity level for micro-calcification on mammograms. The results demonstrated that our proposed genetic-algorithm-based fuzzy-logic approach is an effective method for computer-aided diagnosis in disease classification. 2004, SPIE and IST.

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  • CT angiographyの血管描出能とpoint spread functionの関係 Reviewed

    和田真一, 大久保真樹, 田中 孝, 吉村宣彦, 笹井啓資, 松本 徹

    胸部CT検診   10 ( 2 )   200 - 209   2004.4

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  • spiral SPGR法の基礎的検討 Reviewed

    八木下裕子, 大越幸和, 内藤健一, 柴木充朗, 大久保真樹

    日本放射線技術学会東北部会雑誌   13   112 - 115   2004.1

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  • Duration of enhancement and scan timing in three-dimensional contrast-enhanced MR angiography using the elliptical centric phase-encoding technique Reviewed

    Yagishita Y, Ohgoshi Y, Ohkubo M, Naito K, Inoue T, Tsai DY

    Nippon Hoshasen Gijutsu Gakkai Zasshi   59 ( 12 )   1555 - 1560   2003.12

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  • Evaluation of the increase in signal intensity from applying the fast recovery technique to fast spin echo images Reviewed

    Ohkubo M, Ohgoshi Y, Naito K, Yagishita Y, Tsai DY

    Nippon Hoshasen Gijutsu Gakkai Zasshi   59 ( 7 )   879 - 882   2003.7

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  • An integrated fuzzy-GA-based CAD system for disease discriminations Reviewed

    Tsai D-Y, Lee Y, Sekiya M, Ohkubo M, Kojima K, Yamada I

    Proceedings of the IASTED International Conference on BIOMEDICAL ENGINEERING   166 - 171   2003.6

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  • 3D FIESTA法の基礎的検討 Reviewed

    内藤健一, 大越幸和, 八木下裕子, 柴木充朗, 大久保真樹

    日本放射線技術学会東北部会雑誌   12   124 - 127   2003.1

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  • Simulation study of scan timing in three-dimensional contrast-enhanced MR angiography Reviewed

    Ohkubo M, Ohgoshi Y, Inoue T, Naito K, Yagishita Y, Tsai DY

    Nippon Hoshasen Gijutsu Gakkai Zasshi   58 ( 5 )   705 - 710   2002.5

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  • Evaluation of efficacy of an automated single-voxel proton MRS algorithm on a 3T system Reviewed

    Masaki Ohkubo, Teruo Kimura, Hitoshi Matsuzawa, Tsuyoshi Matsuda, Ingrid L. Kwee, Tsutomu Nakada

    Magnetic Resonance in Medical Sciences   1 ( 2 )   121 - 124   2002

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    Purpose: To evaluate the efficacy of a fully automatic, single-voxel, proton MR spectroscopy algorithm on a 3.0T MR system. Methods: The PROBE/SVQ algorithm (GE Medical Systems) was evaluated on a General Electric (GE) Signa LX-3T system. Ten normal volunteers (female, 21.1±2.0 years old) participated in the study. Nine representative regions of interest were examined, namely, right and left frontal white matter
    right and left parietal white matter
    right and left basal ganglia
    right and left dentate nucleus
    and pons. Results: The mean coefficients of variation in all regions for the N-acetyl-aspartate to creatine ratio (NAA/Cr), choline to creatine ratio (Cho/Cr), and choline to N-acetyl-aspartate ratio (Cho/NAA) were 10.2±2.4%, 11.4±3.2% and 12.6±1.4%, respectively. Conclusion: A fully automated spectroscopic examination under clinical setting utilizing the PROBE/SVQ algorithm appears to be a reliable method, extending the window of routine clinical assessment of brain metabolism. © 2002 by Japanese Society for Magnetic Resonance in Medicine.

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  • A Preliminary Study for Neurovascular Array Coil on GE MRI-ScannerSigna Reviewed

    NAITO Kenichi, OHGSHI Yukio, INOUE Tomoko

    Bulletin of School of Health Sciences Faculty of Medicine Niigata University   7 ( 3 )   357 - 361   2001.12

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  • A Simulation Study of Enhancement Duration in Three-dimensional Contrast-enhanced MR Angiography Reviewed

    OHKUBO Masaki, OHGOSHI Yukio, INOUE Tomoko, NAITO Kenichi, SUZUKI Kiyotaka

    Japanese Journal of Magnetic resonance in medicine   21 ( 5 )   186 - 192   2001.7

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  • A Morphology-Based Method for Automated Detection of Clustered Microcalcifications Reviewed

    Tsai D-Y, Sekiya M, Lee Y, Yamazaki Y, Ohkubo M, Kojima K, Yamaada I

    Proceedings of the IASTED International Conference SIGNAL PROCESSING, PATTERN RECOGNITION & APPLICATIONS   159 - 162   2001.7

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  • A Preliminary Study for Three-Dimensional Dynamic Contrast-EnhancedMR Angiography : Duration of Enhancement and Timing of Image Acquisition Reviewed

    7 ( 2 )   265 - 270   2000.12

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  • 超高磁場MR装置を用いたプロトンスペクトロスコピーに関する基礎研究 Invited Reviewed

    大久保真樹, 中田 力, 松沢 等, 松田 豪

    INNERVISION   15 ( 8 )   66   2000.8

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  • 超高磁場MRI装置による顎関節画像撮影の初期検討 Reviewed

    山川智子, 大久保真樹, 羽柴正夫, 中田 力, 伊藤壽助

    日磁医誌   20 ( 2 )   80 - 92   2000.4

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  • A comparative study of simple methods to quantify cerebral blood flow with acetazolamide challenge by using iodine-123-IMP SPECT with one-point arterial sampling Reviewed

    M Ohkubo, Odano, I

    ANNALS OF NUCLEAR MEDICINE   14 ( 2 )   115 - 120   2000.4

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    The aim of this study was to compare the accuracy of simplified methods for quantifying rCBF with acetazolamide challenge by using I-123-N-isopropyl-p-iodoamphetamine (IMP) and SPECT with one-point arterial sampling. After acetazolamide administration we quantified rCBF in 12 subjects by the following three methods: (a) the modified microsphere method, (b) the IMP-autoradiographic (ARG) method based on a two-compartment one-parameter model, and (c) the simplified method based on a two-compartment two-parameter model (functional IMP method). The accuracy of these methods was validated by comparing rCBF values with those obtained by the standard method: the super-early microsphere method with continuous withdrawal of arterial blood. On analyzing rCBF in each flow range (0-0.25, 0.25-0.5, 0.5-0.75 and more than 0.75 ml/g/min), rCBF values obtained by both methods (a) and (c) showed significant correlations (p &lt; 0.01) with those obtained by the standard method in every range, but rCBF values obtained by method (b) did not significantly correlated in the high flow range (0.5-0.75 and more than 0.75 ml/g/min). Method (c) was found to be the most accurate, even though it needs two serial SPECT scans. When requiring one SPECT scan, method (a) was considered to be superior to method (b) because of its accuracy, especially in high flow regions loaded with acetazolamide.

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  • Noninvasive quantification of cerebral blood flow using Tc-99m-ECD and SPECT Reviewed

    Odano, I, M Ohkubo, T Yokoi

    JOURNAL OF NUCLEAR MEDICINE   40 ( 10 )   1737 - 1744   1999.10

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    The aim of this study was to develop a simple, noninvasive method for quantifying regional cerebral blood flow (rCBF) using Tc-99m-ethyl cysteinate dimer (ECD) by a single SPECT scan and single venous sampling. Methods: Using a three-compartment model, we introduced the regional brain fractionation index (BF!); Cb(T-s)/integral(0)(Ts) Ca(tau)d tau[Ca(t), arterial input; Cb(t), brain activity]. Regional BFI obtained at the optimum time T-s (min) was converted to rCBF using an exponential function, which was obtained by analyzing the relationship between regional BFI and rCBF (= F) obtained by the standard Xe-133 inhalation SPECT method. The integral of the concentration of Tc-99m-ECD in arterial blood corrected for physical decay [Ca(t)] in BFI was estimated from a single venous blood sample obtained at the optimum time T-v using the regression line obtained by analyzing the relationship between the integral of Ca(t) and venous sample data. The data come from three groups of patients. The first group of patients (n = 16) underwent a complete Tc-99m-ECD BFI study with measurement of Ca(t) and dynamic SPECT scanning, as well as a Xe-133 inhalation study to measure rCBF. The results were used to analyze the relationship between regional BFI and rCBF (obtained with Xe-133) and to determine the optimum time T-s for obtaining BFI. Data from the second group of patients (n = 15) were used to analyze the relationship between the integral of Ga(t) and venous sample data and to determine the optimum time T-v for one-point Venous blood sampling. Finally, the third group of patients (8 patients, 10 studies) was used to validate the current method by comparing the results with Xe-133 inhalation SPECT. Results: Regional BFI obtained at time T-s = 20 min showed good agreement (r = 0.907; a = 0.552, b = 0.962) with rCBF. The venous sample data obtained at time T-v = 6 min showed a good correlation (r = 0.988) with BFI. In comparing rCBF Values thus obtained and those obtained by the Xe-133 method, we found a good correlation (r = 0.917, slope = 1.01). Conclusion: The proposed method has three advantages: (a) accurate quantification of rCBF without underestimation in the high flow range, (b) simplicity and noninvasiveness and (c) the ability to use any type of SPECT camera for the study.

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  • Quantification of cerebral blood flow using technetium-99m ethyl cysteinate dimer and single-photon emission tomography Reviewed

    Odano, I, M Ohkubo

    EUROPEAN JOURNAL OF NUCLEAR MEDICINE   26 ( 3 )   246 - 252   1999.3

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    The aim of this study was to develop a new method for quantifying regional cerebral blood flow (rCBF) with technetium-99m ethyl cysteinate dimer (ECD) and single-photon emission tomography (SPET). Employing a three-compartment model, we introduced a parameter, regional brain fractionation index (BFI), that reflects rCBF values and is obtained by a single SPET scan at optimum time T (min) after tracer injection and the integral of arterial input. By analysing the dynamic SPET and arterial blood sampling data of 15 subjects, including the results of acetazolamide challenges, with the graphical plot method, optimum time T was determined to be approximately 20 min post injection. Regional BFI values of each subject were calculated from the single SPET data at 20 min and arterial input. The relationship between the values of regional BFI and rCBF obtained by xenon-133 inhalation SPET was analysed by approximation with an exponential function, resulting in good agreement (r = 0.907). In the present method, I CBF values were determined from regional BFI values by using the inverse exponential function as a non-linear regression curve. To validate the method, we applied it to six other subjects, in whom acetazolamide challenges were also performed. In comparing rCBF values thus obtained and those obtained by Xe-133 inhalation SPET, we found a good correlation (r = 0.901) with an inclination approximating 1 (= 1.02) and without underestimation of rCBF in the high-flow range. Since the present method does not require dynamic planar imaging or dynamic SPET scanning, it can be applied to any type of SPET scanner and is useful in clinical SPET studies.

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  • A study on accuracy of rCBF measurements loaded with acetazolamide based on the microsphere model using iodine-123-IMP SPECT Reviewed

    Ohkubo M, Odano I, Noguchi E, Ohtaki H, Shibaki M, Dobashi Y, Yokoi T

    Kaku Igaku   35 ( 3 )   147 - 151   1998.3

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  • Quantification of regional cerebral blood flow at the control state and loaded with Diamox using split-dose 99mTc-ECD SPECT and venous blood samples Reviewed

    Ikuo Odano, Masaki Ohkubo, Eikichi Noguchi, Hiro Ohtaki, Mitsurou Shibaki, Sachio Dobashi

    Kakuigaku   35 ( 2 )   74 - 75   1998

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    The purpose of the study is to develop a simple and less invasive method for quantifying regional cerebral blood flow (rCBF) at pre- and post Diamox test using split-dose 99mTc-ECD and SPECT. By employing a microsphere model, integral of input function was calculated by the one-point venous sampling method previously reported. The study was performed on 5 subjects with cerebrovascular diseases. A split dose of 99mTc-ECD was injected pre- and post Diamox injection, and rCBF was measured by two SPECT scans and single venous samples, respectively. Mean CBF obtained by the present method was 0.47 ± 0.07 m//g/min at the control state, and 0.63 ± 0.12 m//g/min loaded with Diamox (mean % increase
    35%), showing good agreement with those obtained by the 133Xeinhalation method. Since the present method does not require arterial blood sampling, dynamic data acquisition and dose corrections, it is simple, less invasive and useful in clinical SPECT studies.

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  • Quantification of cerebral blood flow with 99mTc-ECD SPECT based on a 3-compartment model Reviewed

    Ikuo Odano, Masaki Ohkubo, Eikichi Noguchi, Hiro Ohtaki, Mitsurou Shibaki, Sachio Dobashi

    Kakuigaku   35 ( 8 )   702 - 703   1998

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    In the present study we developed a method for quantifying regional cerebral blood flow (rCBF) using 99mTc-ECD SPECT based on a 3-compartment model. The dynamic SPECT scanning and sequential sampling of arterial blood were performed on 12 subjects with cerebrovascular diseases and etc. We defined brain fractionation index (BFI) as a parameter of rCBF, which was obtained from a single SPECT data and arterial input. The relationship between the values of BFI and rCBF obtained by the 133Xe inhalation method was analyzed by approximation with exponential function. In this method, rCBF was calculated from the values of BFI using the inverse function of the exponential function as a regression curve. The method was applied seven other patients with cerebrovascular diseases and the values of rCBF were compared with those obtained by the 133Xe inhalation method. We observed a good correlation (r=0.854), and the inclination was approximately 1. This method can be applied to not only large field SPECT cameras but also conventional SPECT cameras.

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  • 細胞動態からみた薬剤併用放射線照射における細胞致死効果 Reviewed

    藤田勝三, 大久保真樹, 日向浩, 酒井邦夫, 伊藤猛, 末山博男

    関越UFT研究会   10   7 - 10   1997.12

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  • CELL KINETIC ANALYSIS ON THE RADIOSENSITIZING EFFECT OFFM3A-CELLS BY 5-FLUOROURACIL PLUS CISPLATIN Reviewed

    6 ( 2 )   229 - 232   1997.12

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  • Quantification of cerebral blood flow with 99mTc-ECD SPECT by a single arterial or venous blood sample Reviewed

    Odano I, Ohkubo M, Takahashi M, Noguchi E, Ohtaki H, Shibaki M, Dobashi S

    Kaku Igaku   34 ( 12 )   1111 - 1117   1997.12

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  • I-123 IMP SPECTによる簡便なrCBF定量測定法の臨床応用, Invited Reviewed

    大久保真樹, 小田野行男, 野口栄吉, 大滝広雄, 柴木充朗, 土橋幸夫

    映像情報メディカル   29 ( 22 )   1330 - 1333   1997.11

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  • Quantification of cerebral blood flow and partition coefficient using iodine-123-iodoamphetamine Reviewed

    Odano, I, M Ohkubo, M Takahashi

    JOURNAL OF NUCLEAR MEDICINE   38 ( 8 )   1248 - 1253   1997.8

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    The aim of this study was to develop a simple, noninvasive method for quantifying both regional cerebral blood flow (rCBF) and the partition coefficient (lambda) using N-isopropyl-p-[I-123]iodoamphetamine and SPECT. Methods: By employing a two-compartment model (influx, K-1; outflux, k(2)), a new method was introduced that requires two serial SPECT scans at 30 min and 60 min, and a single arterial sample 5 min after tracer injection. The integral of the arterial input function is inferred from the sample by using the correlation obtained from 25 subjects. Two original mathematical functions, Phi for K-1 and Gamma for h (= K-1/k(2)), were obtained from the input functions of 12 subjects. The values of K-1 and lambda are determined from the two scans and the single arterial sample by using these functions. The values obtained for K-1 (= rCBF) and lambda weve compared with those obtained by nonlinear least-squares fitting analysis and the Xe-133 inhalation SPECT method, Results: K-1 and lambda were in good agreement with the values obtained by nonlinear least-squares fitting analysis (r = 0.873 in K-1 and r = 0.825 in lambda), and rCBF values were closely correlated with those obtained by the Xe-133 method (r = 0.843). Conclusion: The proposed method has three advantages: (a) accurate, simultaneous quantification of both rCBF and the partition coefficient; (b) simplicity and noninvasiveness; and (c) a relatively short period (approximately 70 min) for the study.

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  • 99mTc-ECD SPECTにおける2分割投与法(split-dose法)の問題点と改良法 Reviewed

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   34 ( 5 )   323 - 328   1997.5

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    2分割投与99mTc-ECD脳血流SPECTにおいて,投与比によりSPECTカウントを補正する方法の妥当性を検討した.何らかの負荷を加えた場合に有意な脳血流の変化を検出するためには,安静時SPECTカウントの約20%以上の変化が必要であると考えられた.したがって脳血流の増減が少ない負荷検査において,脳血流の変化を投与比補正法で評価することは困難であると思われた.また,投与比による補正法を用いない方法を考案した.この方法では2回のSPECTカウントを脳内のある参照領域で規格化し,その変化率で脳血流の増減を評価する.本法は,投与比補正法が有する問題点の影響を受けないので,起立負荷や手指運動負荷などの負荷検査には有用と考えられた

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  • A comparative study of simple methods to measure regional cerebral blood flow using iodine-123-IMP SPECT Reviewed

    M Ohkubo, Odano, I, M Takahashi

    JOURNAL OF NUCLEAR MEDICINE   38 ( 4 )   597 - 601   1997.4

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    The aim of this study was to compare the accuracy and reliability of simple methods of quantifying regional cerebral blood Row (rCBF) with I-123-labeled N-isopropyl-p-iodoamphetamine (IMP) and SPECT and to determine which method was best. Methods: Four methods were examined: (a) the microsphere method with continuous withdrawal of arterial blood, which was based on a microsphere model using the SPECT image obtained 5 min after tracer injection, (b) the microsphere method with one-point sampling, which was the same as the first method except that one-point sampling was used instead of continuous withdrawal, (c) the modified microsphere method with one-point sampling, which was the same as the second method except that a later SPECT image (30-min postinjection) with correction was used and (d) a table look-up method based on a two-compartment model with one-point arterial blood sampling and two SPECT scans obtained 40- and 180-min postinjection. The accuracy of these methods was validated by comparing the rCBF values with those obtained by nonlinear least squares fitting analysis based on the two-compartment model in 15 subjects. Results: Regional cerebral blood flow values obtained by the first method correlated most closely with those obtained by nonlinear least squares fitting analysis (error, 6.8%). The second method estimated rCBF with a mean error of 10.4%. The third method estimated rCBF with a mean error of 13.1%, even though it tended to slightly overestimate rCBF. The fourth method was inclined to underestimate rCBF with a mean error of 17.1%, and it greatly overestimated regional distribution volume. Conclusion: The first method was the most accurate and reliable. For less invasiveness, the first method should be combined with one-point sampling instead of continuous withdrawal, which was used in the second method. When using a delayed SPECT image with a conventional SPECT scanner, the third method was considered to be superior to the fourth method.

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  • 123I-IMP,99mTc-HMPAO及び99mTc-ECDによる脳血流SPECT画像の比較検討 Reviewed

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   34 ( 3 )   189 - 194   1997.3

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    変性疾患や脳梗塞など7例を対象に,同一の時期に3種のトレーサによるSPECT検査を施行した.領域/大脳比(Uptake ratio)の変動係数は,HMPAO補正(+)>IMP>ECD>HMPAO補正(-)の順で低くなり,画像のコントラストはHMPAO補正(+)が最もよく,HMPAO補正(-)が最も不良であった.HMPAOは画像コントラストを改善するためにLassen補正を行うべきと考えた.Uptake ratioは,脳幹,視床,後頭葉及び白質で有意差が見られた.ECDのUptake ratioはIMPに比較して脳幹,視床で有意な低値となり,HMPAO(補正(+))のそれは脳幹で有意に低値であった.IMPに比較して,ECD及びHMPAO(補正(-))のUptake ratioは後頭葉で有意な高値を示した.脊髄小脳変性症など脳幹病変の有無が問題となる場合には,ECD及びHMPAOには問題があり,IMPを使用するのがよいと思われた

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  • COMBINED EFFECTS OF 5-FLUOROURACIL, CISPLATIN AND LOW DOSE RADIATIONON FM3A CELLS : FROM THE VIEWPOINT OF CELL GROWTH AND DYE EXCLUSION Reviewed

    Shozo Fujita, Kunio Sakai, Shoichi Higuchi

    Bulletin of the College of Biomedical Technology Niigata University   6 ( 1 )   103 - 108   1997.2

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  • AN INSTRUMENTATION SUPPORTING SYSTEM FOR STUDENTS OF THE RADIOLOGICALTECHNOLOGIST COURSE Reviewed

    kyogo Nakamura, Masaki Ohkubo

    Bulletin of the College of Biomedical Technology Niigata University   6 ( 1 )   123 - 128   1997.2

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  • 125I-iomazenil binding shows stress- and/or diazepam-induced reductions in mouse brain: Supporting data for 123I-iomazenil SPECT study of anxiety disorders Reviewed

    Makoto Takahashi, Ikuo Odano, Shozo Fujita, Masaki Ohkubo

    Annals of Nuclear Medicine   11 ( 3 )   243 - 250   1997

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    Effects of repeated swim stress on the binding of 125I-iomazenil were examined in the brains of diazepam-treated and non-treated mice. The mice were orally administered diazepam or vehicle (0.5% ethylene glycol) and subjected to daily swim stress (at 20°C for 10 min) for seven consecutive days. The distribution and the amount of 125I-iomazenil binding were analyzed autoradiographically after in vivo and in vitro binding experiments. Repeated swim stress decreased the in vivo binding in the hippocampus (p &lt
    0.05) and cerebral cortex (p &lt
    0.05) of vehicle-treated mice but caused no significant changes in diazepam-treated mice. Subchronic treatment with diazepam decreased the in vivo binding approximately 50% in all brain regions examined (p &lt
    0.01). The in vitro experiment, however, revealed no significant changes except in the hippocampus, where a small but significant decrease in the binding was observed after subchronic treatment with diazepam (p &lt
    0.01). The stress- or diazepam-induced reductions seem to represent alterations in the in vivo environment related to 125I-iomazenil binding. These results suggest that we can investigate the pathophysiology of stress and anxiety with 123I-iomazenil SPECT. Care must be taken concerning the effects of benzodiazepines.

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  • FM-3A細胞に対する5-FU+CDDPの放射線増感効果 Reviewed

    藤田勝三, 樋口正一, 末山博男, 酒井邦夫, 大久保真樹

    関越UFT研究会   9   21 - 24   1996.12

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  • Elevation of cerebral lactate detected by localized H-1-magnetic resonance spectroscopy in migraine during the interictal period Reviewed

    H Wantanabe, T Kuwabara, M Ohkubo, S Tsuji, T Yuasa

    NEUROLOGY   47 ( 4 )   1093 - 1095   1996.10

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    We used localized H-1-magnetic resonance spectroscopy (MRS) to study the metabolic changes in the brains of patients with migraine during the interictal period. Measurement of metabolite levels in the occipital visual cortex in six normal subjects and six patients disclosed high lactate levels in the five patients who had experienced a migraine attack within the previous 2 months. One patient who had not experienced a migraine attack in the previous 4 years did not show a lactate peak. We speculate that anaerobic glycolysis occurs in the brains of patients with migraine during the interictal period, and a long attack-free period may normalize the subclinical metabolic disturbance.

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  • Radiosensitization of FM3A cells by 5-fluorouracil plus cisplatin Reviewed

    Higuchi S, Fujita S, Sueyama H, Ohkubo M, Sakai K

    Acta Medica et Biologica   44 ( 3 )   141 - 145   1996.9

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  • I-123 IMPによる新しい脳機能定量法 Reviewed

    大久保真樹, 小田野行男, 高橋 誠 他

    映像情報メディカル   28 ( 18 )   1079 - 1083   1996.9

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  • A multicenter validation of regional cerebral blood flow quantitation using [I-123]iodoamphetamine and single photon emission computed tomography Reviewed

    H Iida, T Akutsu, K Endo, H Fukuda, T Inoue, H Ito, S Koga, A Komatani, Y Kuwabara, T Momose, S Nishizawa, Odano, I, M Ohkubo, Y Sasaki, H Suzuki, B Tanada, H Toyama, Y Yonekura, T Yoshida, K Uemura

    JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM   16 ( 5 )   781 - 793   1996.9

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    Recently, two methods have been proposed for regional cerebral blood flow (rCBF) quantitation using [I-123]iodoamphetamine (IMP) and single-photon emission computed tomography (SPECT). The table look-up (TLU) method has been shown to provide both rCBF and volume of distribution, V-d, images from two SPECT scans, while a single-scan autoradiographic (ARG) technique provided rCBF using a fixed and assumed V-d. In both methods, a single blood sample was referred to calibrate the previously determined standard input function The present multicenter project was designed to evaluate the accuracy of both methods for use as clinical investigative tools. Ten independent institutions performed [I-123]IMP-SPECT studies according to both methods in 76 subjects (10 normal volunteers, 32 patients with cerebrovascular disease, and 34 patients with other diseases). Calculated rCBF values were compared with those obtained by the following reference methods available in the participating institutions; [O-15] H2O positron emission tomography (PET) (five institutions), [Xe-133]SPECT (four institutions), and the [I-123]IMP microsphere method (three institutions). Both ARG and TLU methods provided rCBF values that were significantly correlated with those measured by the [O-15] H2O PET technique (p &lt; 0.001 for all subjects; overall regression equation, y = 15.14 + 0.54x) and those measured by the [I-123]IMP-microsphere method (p &lt; 0.001 for all subjects; y = 2.0 + 0.80x). Significant correlation (p &lt; 0.05) was observed in 18 of 24 subjects studied with the [Xe-133] SPECT reference technique (overall regression equation, y = 15.0 + 0.55x). Mean cortical gray matter rCBF in a group of normal subject was 43.9 +/- 3.3 and 33.4 +/- 2.0 ml/min/100 g for the ARG and TLU methods, respectively. Regional V-d of [I-123]IMP estimated by the TLU method was 45 ml/ml +/- 20% in the normal cortical region, Close agreement between ARG and TLU rCBF values was observed (y = -3.21 + 1.07x, r = 0.97), confirming the validity of assuming a fixed V-d in the ARG method. Results of this study demonstrate that both the ARG and TLU methods accurately and reliably estimate rCBF in a variety of clinical settings.

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  • 123I-IMPの分布容積を用いたSPECTによる脳機能診断 Reviewed

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   33 ( 6 )   579 - 586   1996.6

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    1)123I-IMPの再分布現象を分布容積という定量可能な変数に変換するMagic square法をプログラム化してSPECT装置に導入し,機能画像として日常診療に応用する方法を開発した. 2)本システムは,一点動脈採血法(マイクロスフェアー法)による脳血流測定と2回のSPECTスキャンにより稼働する. 3)最終的な分布容積像の他に脳血流像,k2像及びdelayed/early ratio像を作成し,計4種の機能画像として作成・表示可能である.又,それらの数値データと標準偏差を得ることができる. 4)分布容積は123I-IMPの脳内保持機能の程度を反映すると考えられるので,この変数を用いた新たな脳機能診断が日常診療として可能になると思われた

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  • Decrease in benzodiazepine receptor binding in a patient with Angelman syndrome detected by iodine-123 iomazenil and single-photon emission tomography Reviewed

    Odano, I, T Anezaki, M Ohkubo, Y Yonekura, Y Onishi, T Inuzuka, M Takahashi, S Tsuji

    EUROPEAN JOURNAL OF NUCLEAR MEDICINE   23 ( 5 )   598 - 604   1996.5

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    A receptor mapping technique using iodine 123 iomazenil and single-photon emission tomography (SPET) was employed to examine benzodiazepine receptor binding in a patient with Angelman syndrome (AS). AS is characterized by developmental delay, seizures, inappropriate laughter and ataxic movement. In this entity there is a cytogenic deletion of the proximal long arm of chromosome 15q11-q13, where the gene encoding the GABA(A) receptor beta 3 subunit (GABRB3) is located. Since the benzodiazepine receptor is constructed as a receptor-ionophore complex that contains the GABA(A) receptor, it is a suitable marker for GABA-ergic synapsis. To determine whether benzodiazepine receptor density, which indirectly indicates changes in GABA(A) receptor density, is altered in the brain in patients with AS, we investigated a 27-year-old woman with AS using I-123-iomazenil and SPET. Receptor density was quantitatively assessed by measuring the binding potential using a simplified method. Regional cerebral blood flow was also measured with N-isopropyl-p-[I-123]iodoampheramine. We demonstrated that benzodiazepine receptor density is severely decreased in the cerebellum, and mildly decreased in the frontal and temporal cortices and basal ganglia, a result which is considered to indicate decreased GABA(A) receptor density in these regions. Although the deletion of GABRB3 was not observed in the present study, we indirectly demonstrated the disturbance of inhibitory neurotransmission mediated by the GABA(A) receptor in the investigated patient. I-123-iomazenil with SPET was useful to map benzodiazepine receptors, which indicate GABA(A) receptor distribution and their density.

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  • A new method for measurement of both regional cerebral blood flow and distribution volume using N-Isopropyl-p-[123I]iodoamphetamine (123I-IMP) and SPECT Reviewed

    Masaki Ohkubo

    Kakuigaku   33 ( 3 )   241 - 249   1996

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    We developed a new method (functional IMP SPECT) to quantitate both regional cerebral blood flow (rCBF) and distribution volume (Vd) using 123I-IMP and SPECT based on a 2-compartment model (influx
    K1=rCBF and outflux
    k2). This method requires one arterial blood sampling at 5 min after injection of the tracer and two SPECT scans at 30 min and 60 min. It takes approximately 60 min for total measurements. The integration of arterial input function is estimated by one blood sample taken at 5 min after injection of the tracer without octanol treatment, by using the correlation between one blood sample and the integration, which was obtained from studies on 25 subjects. With the value of integration, K1 and Vd are calculated from the data of two SPECT scans by using the mathematical functions based on the 2-compartment model, which were obtained from studies on 12 subjects. In the practical range of K1 (0.3-0.7 ml/g/min) and Vd (15-35 ml/g) given in the 2-compartment model, statistical errors of K1 and Vd obtained by the functional IMP SPECT were evaluated at approximately 14.0% and 17.2%, respectively. In clinical studies for eight subjects including two healthy volunteers, three patients with cerebral infarction and three patients with degenerative disease, K1 and Vd values estimated by the functional IMP SPECT were significantly correlated with those estimated by non-linear least squares fitting analysis based on the 2-compartment model, and the mean errors of K1 and Vd estimated by the functional IMP SPECT were approximately 8.0% and 11.2% respectively, suggesting the validity of the new method. We conclude that the functional IMP SPECT is clinically useful because of the accuracy, less-invasiveness and convenience.

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  • Validation study in quantitative measurement of regional cerebral blood flow using N-isopropyl-p-[ 123I]iodoamphetamine ( 123I-IMP) and SPECT Reviewed

    Masaki Ohkubo

    Kakuigaku   33 ( 6 )   647 - 654   1996

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    We validated following five methods to quantitate regional cerebral blood flow (rCBF) using 123I-IMP and SPECT
    1) microsphere method, which is based on a microsphere model using the SPECT image at five minutes after 123I-IMP injection with continuous withdrawal of arterial blood, 2) microsphere+one-point sampling method, which is the same as the microsphere method except for using one-point sampling instead of continuous withdrawal, 3) conventional microsphere+one-point sampling method, which is the same as the microsphere+one-point sampling method except for using a later SPECT image corrected with the ratio of alteration of measured entire brain activity. 4) Table look-up method, which is based on a two-compartment model (influx
    K 1 and outflux
    k 2) using one arterial blood sample taken at 10 min and two SPECT images at 30 min and 180 min post-injection, and 5) functional IMP SPECT, which is bused on the two-compartment model using one arterial blood sample taken at 5 min and two SPECT images at 30 min and 60 min post-injection. Those methods were applied to six patients with cerebral infarction and degenerative diseases, and rCBF results were compared with those estimated by nonlinear least squares fitting (NLLSF) analysis based on the two-compartment model. The rCBF values obtained by the microsphere method was best correlated with those by NLLSF analysis (r=0.940), followed by the microsphere+one-point sampling method (r= 0.885) and the functional IMP SPECT (r=0.882). The table look-up method underestimated rCBF especially at the high flow level, however showed good correlation (r=0.859). The conventional microsphere+one-point sampling method overestimated rCBF, however showed good correlation (r=0.849). Distribution volume (V(d)=K 1/k 2) was also estimated by both the table look-up method and the functional IMP SPECT. While values of V(d) by the functional IMP SPECT were significantly correlated with those by NLLSF analysis (r=0.785), the table look-up method overestimated V(d) (43.4±6.6 ml/g) and showed not good correlation (r=0.287).

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  • FM3A細胞に対する5-FU,CDDPおよび放射線の併用効果に関する研究

    藤田勝三, 大久保真樹, 酒井邦夫

    関越UFT研究会   8   9 - 14   1995.12

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  • [A study on accuracy of rCBF measurements using the conventional microsphere method with N-isopropyl-p-[123I]iodoamphetamine and SPECT]. Reviewed

    M Ohkubo, I Odano, N Takahashi, M Takahashi, H Ohtaki, E Noguchi, T Kasahara, M Hatano, T Yokoi

    Kaku igaku. The Japanese journal of nuclear medicine   32 ( 12 )   1323 - 31   1995.12

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    To evaluate the accuracy of conventional microsphere method for the measurement of regional cerebral blood flow (rCBF) based on the microsphere model with N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) and SPECT, we performed simulation analysis and clinical studies. Although the microsphere method requires early SPECT scan at a few minutes after injection of the tracer for the accurate measurement of rCBF, the conventional microsphere method, which is generally used, requires more delayed SPECT scan with long scan-duration. In the conventional microsphere method, the delayed SPECT image is corrected to the image at a few minutes after injection of the tracer by using the monitored entire brain activity. By the simulation analysis based on the 2-compartment model (influx; K1 and outflux; k2) using the input function and the entire brain activity obtained from eight subjects respectively, it was found that the conventional microsphere method overestimated the rCBF in the practical range of rCBF and Vd (= K1/k2) given in the 2-compartment model. When the values of rCBF and Vd in the 2-compartment model were given at 0.5 (ml/g/min) and 30 (ml/g) respectively, the rate of overestimation of rCBF by the conventional microsphere method was determined to be 17.3 +/- 0.7% (mean +/- S.D.). Also in clinical studies for eight subjects, the conventional microsphere method overestimated the rCBF compared with those evaluated by non-linear least squares fitting (NLLSF) analysis based on the 2-compartment model. Those results agreed well with the simulation analysis, suggesting the validity of the simulation. The rCBF values clinically estimated by the conventional method were, however, significantly correlated with those calculated by NLLSF analysis, and there were not so much difference between the two quantitative rCBF images obtained by the conventional microsphere method and the microsphere method. Therefore, we conclude that the conventional microsphere method is clinically useful in spite of the overestimation of rCBF.

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  • 5-FUおよびCDDPのFM3A細胞の細胞回転に及ぼす影響 Reviewed

    藤田勝三, 大久保真樹, 酒井邦夫, 日向 浩

    新潟大学医療技術短期大学部紀要   5 ( 3 )   259 - 263   1995.12

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    FM3A細胞に対する5-FUとCDDPの細胞回転に及ぼす影響をフローサイトメトリーにより解析した. 1)5-FU単独処理により,濃度0.1μg/mlでは僅かに早期S期細胞が増加し,0.5μg/ml以上ではG1期からS期への細胞周期の移行が阻害された.CDDP単独処理では,0.1μg/ml以上でG2ブロックが認められた. 2)5-FU(0.1μg/ml),CDDP(0.1μg/ml)それぞれ単独処理では,薬剤除去24時間後のDNAヒストグラムは元のパターンに戻り,部分同調は認められなかった. 3)5-FU処理(0.1μg/ml,24時間)終了直後にCDDP処理を併用した場合,CDDP濃度0.01μg/mlでは細胞回転に大きな変化はなかった.CDDP濃度0.1μg/mlでは18時間後に顕著なS期細胞の増加,24時間後にはS期細胞の減少とG2M期細胞の著しい増加がみられ,明らかな部分同調が認められた

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  • Combined effect of radiation and 5-fluorouracil on survival of FM3A mouse mammary adenocarcinoma cells Reviewed

    Fujita S, Sakai K, Hicughi S, Sueyama H, Ohkubo M

    Bull Coll Biomed Technol Niigata Univ   5 ( 3 )   265 - 269   1995.12

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  • Can the microsphere model be applied to cerebral blood flow measurement using N-isopropyl-p-[I-123]iodoamphetamine with SPET regardless of washout from brain tissue? Reviewed

    M Ohkubo, Odano, I, N Takahashi, K Sakai

    NUCLEAR MEDICINE COMMUNICATIONS   16 ( 12 )   1026 - 1033   1995.12

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    The microsphere model and the continuous withdrawal of arterial blood have commonly been used in clinical studies when measuring regional cerebral blood flow (rCBF) by N-isopropyl-p-[I-123]iodoamphetamine (IMP) single photon emission tomography. The method is considered to underestimate rCBF because of the washout of tracer from brain tissue; however, the extent of this underestimation is not known. To assess whether this underestimation can be determined quantitatively, we performed simulation analysis based on the microsphere model and the two-compartment model [influx, K-1(rCBF); and outflux, k(2)(washout)] using the time-activity curves of I-123-IMP in arterial blood [C-a(t)] of 10 subjects. With the microsphere method, rCBF values fell as time post-injection increased. The extent of underestimation of rCBF was 4.7 +/- 0.28% (mean +/- S.D.) at 5 min, 10.2 +/- 0.42% at 10 min and 15.2 +/- 0.55% at 15 min. There was little variation in the extent of underestimation and it was not dependent on the C-a(t) of the subjects. We therefore considered the results to be generally applicable to various studies of the microsphere model. As 4.7% is considered to be negligible in clinical studies, we conclude that the microsphere model can be applied to obtain accurate measurement of rCBF up to 5 min regardless of washout.

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  • Quantitative assessment of cerebral blood flow measurement using the microsphere model with N-isopropyl-p-[123I]-iodoamphetamine SPECT: simulation analysis for the influence of washout from brain tissue Reviewed

    Ohkubo M, Odano I, Takahashi N, Sakai K

    Acta Medica et Biologica   43 ( 3 )   165 - 171   1995.9

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  • EVALUATION OF CEREBRAL BLOOD-FLOW IN PATIENTS WITH IDIOPATHIC ORTHOSTATIC HYPOTENSION USING TC-99M HMPAO BRAIN SPECT DURING POSTURAL TESTING Reviewed

    ODANO, I, N TAKAHASHI, T HIGUCHI, M OHKUBO, S HAMA, A TSUDA, H OTAKI, E NOGUCHI, M HATANO

    CLINICAL NUCLEAR MEDICINE   20 ( 9 )   807 - 809   1995.9

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    To determine whether regional cerebral blood flow (rCBF) would change on standing in patients with idiopathic orthostatic hypotension (IOH), Tc-99m HMPAO SPECT studies were performed during postural testing in five patients with IOH. After 10 minutes of quiet rest on a bed, the patients arose quickly and, at the same time, the radiotracer was injected intravenously. SPECT data were obtained with a ring-type SPECT scanner. Another dose of Tc-99m HMPAO was injected with the subjects in the supine position, and SPECT was performed again, Image subtraction was used to evaluate the change in rCBF caused by postural testing. In all patients, the authors observed a decrease of rCBF in the frontal cortex and basal ganglia. This preliminary study suggests that changes in rCBF occur In patients with IOH on standing, and Tc-99m HMPAO SPECT performed during postural testing may have an important role in evaluating these changes.

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  • [Quantifying regional cerebral blood flow with N-isopropyl-p-[123I]iodoamphetamine and SPECT by one-point sampling method]. Reviewed

    I Odano, M Ohkubo, N Takahashi, E Noguchi, H Ohtaki, M Hatano, Y Yamazaki, T Higuchi

    Kaku igaku. The Japanese journal of nuclear medicine   31 ( 10 )   1219 - 26   1994.10

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    We developed a new non-invasive technique; one-point sampling method, for quantitative measurement of regional cerebral blood flow (rCBF) with N-isopropyl-p-[123I]iodoamphetamine and SPECT. Although the continuous withdrawal of arterial blood and octanol treatment of the blood are required in the conventional microsphere method, the new technique does not require these two procedures. The total activity of 123I-IMP obtained by the continuous withdrawal of arterial blood is inferred by the activity of 123I-IMP obtained by the one point arterial sample using a regression line. To determine when one point sampling time was optimum for inferring integral input function of the continuous withdrawal and whether the treatment of sampled blood for octanol fraction was required, we examined a correlation between the total activity of arterial blood withdrawn from 0 to 5 min after the injection and the activity of one point sample obtained at time t, and calculated a regression line. As the results, the minimum % error for the inference using the regression line was obtained at 6 min after the 123I-IMP injection, moreover, the octanol treatment was not required. Then examining an effect on the values of rCBF when the sampling time was deviated from 6 min, we could correct the values in approximately 3% error when the sample was obtained at 6 +/- 1 min after the injection. The one-point sampling method provides accurate and relatively non-invasive measurement of rCBF without octanol extraction of arterial blood.

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  • 5-FU少量持続静注と放射線の同時併用療法に関する基礎的,臨床的研究 Reviewed

    酒井邦夫, 末山博男, 小田純一, 樋口正一, 土田恵美子, 杉田 公, 松本康男, 藤田勝三, 大久保真樹, 稲越英樹

    INNERVISION   9 ( 7 )   19 - 19   1994.7

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  • 5-FUと放射線の併用効果に関する基礎的研究 Reviewed

    藤田勝三, 大久保真樹, 酒井邦夫

    関越UFT研究会   7   43 - 46   1994.7

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  • A NEW METHOD OF REGIONAL CEREBRAL BLOOD-FLOW MEASUREMENT USING ONE-POINT ARTERIAL SAMPLING BASED ON THE MICROSPHERE MODEL WITH N-ISOPROPYL-P-[I-123]-IODOAMPHETAMINE SPECT Reviewed

    ODANO, I, M OHKUBO, N TAKAHASHI, T HIGUCHI

    NUCLEAR MEDICINE COMMUNICATIONS   15 ( 7 )   560 - 564   1994.7

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    We developed a new method for quantitative measurement of regional cerebral blood flow (rCBF) using one-point arterial sampling with N-isopropyl-p-[I-123]-iodoamphetamine (I-123-IMP) and single photon emission computed tomography (SPECT) based on the microsphere model. Although the conventional microsphere method requires both the continuous withdrawal of arterial blood (integral of Ca(t)) and treatment of the blood with octanol to obtain the fraction of true tracer activity in the integral of Ca(t) (N), the new method does not require these two procedures. We examined 14 patients to analyse the correlation between the integral of Ca(t)N and a small arterial sample obtained at one time point [one-point Ca(t)] after the injection of I-123-IMp Without octanol treatment. The integral of Ca(t)N was calculated from one point Ca(t) using the regression line of the correlation. An error of 8.1% in the calculated value compared to the actual value of the integral of Ca(t)N, could be inferred from one-point Ca(t) obtained at 6 min after the injection. Then regional cerebral blood flow was measured by the method and a significant correlation was obtained with rCBF measured using the Xe-133 inhalation method (r = 0.773). The one-point Ca(t) method provides fast, easy, accurate and non-invasive measurement of rCBF without inserting catheters and without treatment of arterial blood with octanol.

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  • [A problem of quantitative measurement of regional cerebral blood flow using microsphere model and N-isopropyl-p-[123I]iodoamphetamine (IMP): comparison with 133Xe SPECT and sequential dynamic 123I-IMP SPECT]. Reviewed

    N Takahashi, M Ohkubo, I Odano, H Ohtaki, E Noguchi, Y Yamazaki, M Hatano, K Sakai

    Kaku igaku. The Japanese journal of nuclear medicine   31 ( 4 )   319 - 26   1994.4

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    Regional cerebral blood flow (rCBF) was measured in 13 patients with various cerebral disease by N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT with the microsphere model (rCBF (CbST)), which was compared with 133Xe inhalation SPECT (rCBFXe). Continuous withdrawal of arterial blood was performed for 5 minutes and SPECT image was obtained from 25 min to 55 min after the tracer injection. The reconstructed counts at 5 min was corrected using entire cerebral counts collected at 5 min, 20 min, and 60 min after the tracer injection. As compared with rCBFXe, rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. Regional CBF was also measured using one minute short time SPECT images at 5 min (rCBF (Cb5)), 20 min (rCBF (Cb20)), and 60 min (rCBF (Cb60)) after the injection. Regional CBF tended to be underestimated with time from the tracer injection due to the wash-out from brain tissue to blood. In comparison with rCBF (Cb5), rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. This error was considered to be due to the correction of reconstruct counts using entire cerebral counts, because of the kinetic behavior of 123I-IMP was different in each region of the brain.

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  • [A study on evaluation of CBF measurement based on microsphere model with N-isopropyl-p-[123I]iodoamphetamine (IMP) and SPECT--its correction with the value of PaCO2]. Reviewed

    I Odano, N Takahashi, M Ohkubo, H Ohtaki, E Noguchi, Y Hatano, Y Yamazaki, M Nishihara

    Kaku igaku. The Japanese journal of nuclear medicine   31 ( 3 )   223 - 9   1994.3

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    To evaluate the regional cerebral blood flow measurement with N-isopropyl-p-[123I]iodoamphetamine (IMP), we performed 123I-IMP SPECT and 133Xe inhalation method on 9 patients with mild cerebrovascular diseases and so on. A tracer dose of 123I-IMP (111 MBq) was injected i.v. and the data were obtained 15 min later. Regional CBF was measured by the microsphere model and arterial blood sampling method. However, mean cerebral blood flow values was not in agreement with both methods. We supposed the reason of the disagreement was due to the difference of PaCO2 when the studies were performed. Hence, CBF measurement with 123I-IMP was performed on the other patient's population with loading of hyperventilation before the IMP injection. Comparing with the control state with normal breathing, we calculated the rate of change of mean CBF between the state with normal breathing and the state with hyperventilation that was 1.02 ml/100 g/min/mmHg PaCO2. After the correction with the rate, we observed a much significant relation between the mean CBF measured with 123I-IMP SPECT and 133Xe inhalation method. When compared CBF values with loading studies or certain therapies, the correction of CBF with the rate of change of PaCO2 is one of the very important factors to be considered. Moreover, 133Xe inhalation method without the correction of PaCO2 can not be a golden standard method for rCBF measurement.

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  • MITOCHONDRIAL ENCEPHALOMYOPATHY - ELEVATED VISUAL-CORTEX LACTATE UNRESPONSIVE TO PHOTIC-STIMULATION - A LOCALIZED H-1-MRS STUDY Reviewed

    T KUWABARA, H WATANABE, K TANAKA, S TSUJI, M OHKUBO, T ITO, K SAKAI, T YUASA

    NEUROLOGY   44 ( 3 )   557 - 559   1994.3

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    We used localized H-1-magnetic resonance spectroscopy (MRS) to study the metabolic changes in the visual cortex of patients with mitochondrial encephalomyopathy. Measurement of metabolite levels in the occipital visual cortex obtained in the dark with seven normal subjects and with four patients (all four of whom had Kearns-Sayre syndrome [KSS]) showed high lactate levels in the patients. Photic stimulation (PS) in four normal volunteers showed that lactate increased immediately after the start of PS and that it decreased to the baseline level with continued PS. Lactate in the resting state was higher in the KSS patients than in the controls, and, unlike the controls, the KSS patients showed no significant elevation of lactate with PS.

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  • H-magnetic resonance spectroscopyにて脳局所での乳酸の上昇を認めた片頭痛 Reviewed

    渡邊浩之, 桑原武夫, 大久保真樹

    新潟大学脳研究所業績集   27   127 - 127   1994

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  • Elevation of cerebral lactate detected by localized 1H magnetic resonance spectroscopy in a patient with migraine Reviewed

    H. Watanabe, T. Kuwabara, M. Ohkubo, K. Sakai, S. Tsuji

    Clinical Neurology   34 ( 5 )   504 - 507   1994

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    Localized 1H magnetic resonance spectroscopy was performed in a 45-year-old woman with migraine. She developed throbbing headache attacks without aura since thirteen years ago and the attack was accompanied with right hemiplegia since seven years ago. Brain MRI showed no abnormalities and 123I-IMP SPECT revealed mild frontal dominant decrease of cerebral blood flow. It seemed that her condition was positioned between migraine with prolonged aura and migrainous infarction of complicated migraine in the classification of International Headache Society. Spectra obtained from bilateral frontal lobe interictally showed elevation of lactate at left side. Choline, creatine, and N-acetylaspartate were almost equal on both side. The above results suggest that slight ischemia which is not detected by MRI is present or there is a disturbance of oxidative glycolysis, which is induced by mitochondrial dysfunction.

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  • 511. k_2 and Vd Image by the Magic Square Method with ^<123>I-IMP SPECT Reviewed

    OHTAKI HIROO, NOGUCHI EIKICHI, HATANO MASAYOSHI, NAGASAWA HIROMU, ODANO IKUO, TAKAHASHI NAOYA, OHKOBO MASAKI, SATOH TOMOHIKO

    Japanese Journal of Radiological Technology   50 ( 8 )   1426 - 1426   1994

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    DOI: 10.6009/jjrt.KJ00003326310

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  • Simulation Analysis for Underestimation of rCBF Caused byWashout (K_2) based on the Microsphere Model withN-isopropyl-p-[^123I] iodoamphetamine SPECT Reviewed

    Masaki Ohkubo, Ikuo Odano, Naoya Takahashi

    17   33 - 39   1993.11

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  • [A new graphic method for evaluation of distribution volume on N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT]. Reviewed

    I Odano, M Ohkubo, N Takahashi, H Ohtaki, E Noguchi, M Hatano, Y Yamasaki, T Yokoi, M Nishihara

    Kaku igaku. The Japanese journal of nuclear medicine   30 ( 10 )   1211 - 9   1993.10

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    We developed a new graphic method using N-isopropyl-p-[123I]iodoamphetamine (IMP) and SPECT of the brain, the graph on which all three parameters, cerebral blood flow, distribution volume (Vd) and delayed count to early count ratio (Delayed/Early ratio), were able to be evaluated simultaneously. The kinetics of 123I-IMP in the brain was analyzed by a 2-compartment model, and a standard input function was prepared by averaging the time activity curves of 123I-IMP in arterial blood on 6 patients with small cerebral infarction etc. including 2 normal controls. Being applied this method to the differential diagnosis between Parkinson's disease and progressive supranuclear palsy, we were able to differentiate both with a glance, because the distribution volume of the frontal lobe significantly decreased in Parkinson's disease (Mean +/- SD; 26 +/- 6 ml/g). This method was clinically useful. We think that the distribution volume of 123I-IMP may reflect its retention mechanism in the brain, and the values are related to amine, especially to dopamine receptors and its metabolism.

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  • N-isopropyl-p-[123I] iodoamphetamine (IMP) SPECTにおける分配定数(Distribution volume)を算定するMagic Square法の理論

    小田野行男, 高橋直也, 大滝広雄, 野口栄吉, 羽田野政義, 山崎芳裕, 西原真美子, 大久保真樹

    新潟核医学懇話会記録集   16   35 - 39   1993.8

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  • 光刺激で誘発される大脳後頭葉視覚野における乳酸の変化-1H-MRSによるミトコンドリア脳筋症2例の観察- Reviewed

    桑原武夫, 渡辺浩之, 辻 省次, 田中恵子, 大久保真樹

    医学のあゆみ   165 ( 8 )   491 - 492   1993.5

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    Other Link: http://mol.medicalonline.jp/library/journal/abstract?GoodsID=aa7ayuma/1993/016508/017&name=0491-0492j

  • 食道癌高線量率腔内照射用の新しい二重バルーンアプリケータと新しい照射計画プログラム Reviewed

    稲越英機, 井上富夫, 関谷昌四, 日向 浩, 酒井邦夫, 大久保真樹

    臨床放射線   38 ( 5 )   565 - 569   1993.5

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    Other Link: http://search.jamas.or.jp/link/ui/1994069648

  • Changes of 31P-MR Spectroscopy in Experimental Tumors Following Radiotherapy Combined with 5-Fluorouracil Compound (UFT) Reviewed

    Ohkubo M

    The Tohoku Journal of Experimental Medicine   169 ( 3 )   215 - 223   1993.3

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    DOI: 10.1620/tjem.169.215

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  • A study of crossed cerebellar diaschisis on 123I-IMP SPECT images and its redistribution phenomenon Reviewed

    I. Odano, N. Takahashi, M. Nishihara, M. Okubo, H. Otaki, E. Noguchi, Y. Yamazaki, M. Kimura, K. Sakai

    Kakuigaku   30 ( 2 )   189 - 196   1993

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    Crossed cerebellar diaschisis (CCD) is interpreted as a functional deactivation, presumably caused by a loss of excitatory or inhibitory afferent inputs on the corticopontocerebellar pathway and others. A redistribution phenomenon (RD) is usually observed in the contralateral cerebellum with CCD on delayed images of 123I-IMP SPECT. This phenomenon was analyzed in a view point of rCBF measurement in 24 patients with brain tumor, infarction and so forth. Regional CBF was measured by the microsphere method with 123I-IMP and a delayed-to-early counts ratio (D/E ratio) was used. As a result, there was no relation between rCBF and the D/E ratio in the cerebellum, which means that RD is occurred by other factors except for rCBF in the cerebellum. Regional CBF and the D/E ratio in the contralateral and ipsilateral cerebellum was 46.3 ml/100 g/min, 1.01 and 57.0 ml/100 g/min, 0.86, respectively. These results mean that the high activity of IMP gradually decreased in the ipsilateral cerebellum, while, the low activity in the contralateral cerebellum was almost stable, and the difference of both activity reduced after 5 hours and RD was observed on the delayed image. The data indicate that retention mechanism of IMP and vascular permeability are not affected in the cerebellum with CCD.

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  • Visualization of brain function using MRI - MR functional brain imaging Reviewed

    H. Watanabe, T. Kuwabara, M. Ohkubo, K. Sakai, S. Tsuji, T. Yuasa

    Brain and Nerve   45 ( 10 )   941 - 944   1993

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  • Changes of 31P-MR Spectroscopy in Experimental Tumors Following Radiotherapy Combined with 5-Fluorouracil Compound (UFT) Reviewed

    Masaki Ohkubo

    Tohoku Journal of Experimental Medicine   169 ( 3 )   215 - 223   1993

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    The energy metabolism of FM3A tumors in C3H mice following radiotherapy (20 Gy or 40 Gy), 5-fluorouracil compound (UFT) chemotherapy or radiotherapy (20 Gy) combined with UFT was investigated by in vivo 31P-MR spectroscopy on day 2 after treatment. The effects were compared with the growth curves of the tumors and with the cytokinetic and histological changes in the tumors on day 5 after treatment. The combined group (20 Gy+UFT) showed growth curves similar to the 40 Gy group. Cytokinetic and histological changes of the combined group were also similar to those of the 40 Gy group, suggesting supra-additive effect of UFT. 31P-MR spectra of the combined group were similar to those of the 40 Gy group which were characterized by increase of intracellular pH(pHi), decrease of Pi/β-NTP and of PME/total phosphorus-signal ratios. Spectra of the UFT group and the 20 Gy group, on the contrary, showed decrease of pHi, increase of Pi/β-NTP and of PME/total phosphorus-signal ratios. Changes detected by 31P-MR spectroscopy on day 2 were considered to reflect early metabolic events which were correlated to the growth curve, cytokinetic and histological alterations observed on day 5 after treatment. © 1993, Tohoku University Medical Press. All rights reserved.

    DOI: 10.1620/tjem.169.215

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  • 31P-MRスペクトロスコピーからみた放射線単独ならびにUFT併用照射の効果

    大久保真樹, 藤田勝三, 酒井邦夫

    関越UFT研究会   5   37 - 41   1992.12

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  • FM3A細胞に対する温熱併用2分割照射の細胞致死効果 Reviewed

    藤田勝三, 大久保真樹, 樋口健史, 樋口正一, 日向 浩, 酒井邦夫

    新潟大学医療技術短期大学部紀要   4 ( 3 )   285 - 288   1992.8

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    対数増殖期のFM3A細胞に対して温熱併用2分割照射を行い,照射間隔と細胞生存率の関係を調べた.細胞の温熱処理は,恒温槽中で42.5°C, 60分間行った.温熱直後に60Co γ線2 Gyを室温にて照射した.さらに,種々の照射間隔で2回目の2 Gy照射を行い,コロニー法により細胞生存率を求めた.これをフローサイトメトリーによる細胞動態解析の結果と対比し,細胞致死効果を検討した.細胞生存率の変化はElkind型の回復曲線を示し,照射間隔が6〜12時間の時点で生存率の一時的減少を認めた.放射線感受性の高いG2+M期細胞の割合は,非処理のコントロール群では18.6%であったが,温熱併用2 Gy群では照射6時間後から増加し,8〜12時間後には80%以上になった.細胞生存率の一時的減少は,このようなG2+M期細胞の蓄積を反映していたものと考えられた

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  • DEVELOPMENT OF AN ANALOG INSTRUMENTATION WITH AC VOLTMETERS Reviewed

    Kyugo NAKAMURA, Masaki OHKUBO

    Bulletin of the College of Biomedical Technology Niigata University   4 ( 3 )   313 - 318   1992.8

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  • 31P-MR spectroscopy of experimental tumors following irradiation Reviewed

    Ohkubo M, Sakai K, Fujita S, Ito T, Higuchi T, Kimura M, Yuasa T

    Acta Medica et Biologica   40 ( 1 )   29 - 34   1992.8

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    Other Link: http://dspace.lib.niigata-u.ac.jp/dspace/handle/10191/33374

  • 154. Visualization of Aortic Valve Using Cine MRI

    Japanese Journal of Radiological Technology   48 ( 3 )   507 - 507   1992

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    DOI: 10.6009/jjrt.KJ00003533684

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  • 154. Visualization of Aortic Valve Using cine MRI

    Japanese Journal of Radiological Technology   48 ( 8 )   1238 - 1238   1992

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    DOI: 10.6009/jjrt.KJ00003500551

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  • 温熱・放射線併用療法の細胞回転に及ぼす影響 Reviewed

    藤田勝三, 大久保真樹, 樋口健史, 樋口正一, 日向 浩, 酒井邦夫

    新潟大学医療技術短期大学部紀要   4 ( 2 )   201 - 205   1991.8

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    フローサイトメトリーにより,対数増殖期における培養細胞(FM3A)の細胞回転に対する温熱・放射線併用療法の影響を調べた.温熱処理は恒温槽により42.5 °C, 60分間行った.放射線は60Co γ線2 Gyを室温で照射した.併用療法は温熱処理直後と8時間後に放射線照射を行った.細胞浮遊液を経時的に遠心,固定,PI染色し,Cytofluorograf (Ortho, ICP22A)により細胞のDNA量を測定した.DNAヒストグラムから細胞周期各期の割合を求めた.非処理群では,G1期27.6%,S期53.8%,G2+M期18.6%であった.温熱処理直後に2 Gy照射した場合,G2+M期は8〜12時間後に80%を超え,8時間後照射では直後から10時間にわたり50〜60%であった.併用療法により,G2+M期への高い集積を認めた

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  • Growth-associated changes in the phosphate metabolism of experimental tumors detected by 31P-MR spectroscopy Reviewed

    Ohkubo M, Sakai K, Ito T, Higuchi T, Kimura M, Fujita S

    Japanese Journal of Magnetic Resonance in Medicine   10 ( 4 )   285 - 293   1990.10

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  • 放射線とUFTの併用による実験腫瘍の増殖抑制効果 Reviewed

    藤田勝三, 大久保真樹, 酒井邦夫, 日向 浩, 伊藤 猛, 樋口健史

    日本医学放射線学会生物部会誌   3 ( 1 )   65 - 67   1990.9

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  • Clinical Application of Magnetic Resonance Spectroscopy (MRS)(Clinical Usefulness of MRI (Magnetic Resonance Imaging)) Reviewed

    Ito Takeshi, Kimura Motomasa, Sakai Kunio, Ookubo Masaki, Fujita Shozo

    104 ( 9 )   738 - 744   1990.9

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  • R-C濾波器の周波数応答測定の一つの試み Reviewed

    中村久吾, 大久保真樹

    新潟大学医療技術短期大学部紀要   4 ( 1 )   111 - 118   1990.8

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  • MRスペクトロスコピーによる放射線治療効果の予測に関する研究 Reviewed

    酒井邦夫, 木村元政, 伊藤 猛, 樋口健史, 大久保真樹, 藤田勝三

    INNERVISION   5 ( 6 )   7 - 8   1990.6

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  • 31P-MR spectrum changes in human superficial malignant tumors during treatments Reviewed

    Ito T, Sakai K, Ohkubo M, Fujita S

    Japanese Journal of Magnetic Resonance in Medicine   10 ( 2 )   75 - 83   1990.6

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  • Recognition of concatenated vowels by natural observation coefficients Reviewed

    Ohkubo M, Kiryu T, Saitoh Y, Iijima T

    The Transactions of the Institute of Electronics, Information and Communication Engineers D-2   72 ( 12 )   1985 - 1991   1989.12

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  • A modeling of speech signals by natural observation system with finite order Reviewed

    Kiryu T, Ookubo M, Iijima T, Saitoh Y

    The Transactions of the Institute of Electronics, Information and Communication Engineers A   72 ( 6 )   902 - 908   1989.6

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    Other Link: http://hdl.handle.net/10191/20304

  • 有限次元の自然観測システムによる音声信号のモデル化

    木竜 徹, 大久保真樹, 斎藤義明, 飯島泰蔵

    電子情報通信学会技術報告   88 ( 4 )   19 - 26   1988.5

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  • 自然観測法における音声の調音結合・個人差の検討

    大久保真樹, 木竜 徹, 斎藤義明, 飯島泰蔵

    電子情報通信学会技術報告   87 ( 70 )   29 - 38   1987.12

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  • 咀嚼運動時のEMGにおける時変性反射係数の推定

    木竜 徹, 大久保真樹, 斉藤義明

    電子通信学会技術報告   86 ( 36 )   13 - 20   1986.9

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  • 筋活動様式とkパラメータとの関連性について

    木竜 徹, 大久保真樹, 斉藤義明

    電子通信学会技術報告   86 ( 36 )   13 - 20   1986.9

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Books

  • 学生のためのExcel

    大久保真樹, 湊 孝子( Role: Joint author ,  区分不可能)

    株式会社 考古堂書店  2004.4  ( ISBN:4874996086

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Research Projects

  • 逐次近似再構成CT画像における高精度な空間分解能測定法の開発

    Grant number:20K08046  2020.4 - 2024.3

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    大久保 真樹, 成田 啓廣

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    Grant amount:\4290000 ( Direct Cost: \3300000 、 Indirect Cost:\990000 )

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  • 化学交換飽和移動MRIを用いたアルツハイマー病における認知予備能評価法の開発

    Grant number:18H02762  2018.4 - 2023.3

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    五十嵐 博中, 大久保 真樹, 鈴木 清隆

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    Grant amount:\9100000 ( Direct Cost: \7000000 、 Indirect Cost:\2100000 )

    本年度も研究は順調に進み、アルツハイマーモデル動物を用いたPOC研究を完了した。アルツハイマー病では、中枢病理学的変化の一つであるシナプスの喪失は、脳の障害領域に対応する局所的な神経学的症状を引き起こす。グルタミン酸化学交換飽和移動(gluCEST)MRIは、シナプスの機能障害や喪失を評価するための候補の一つである。本年度は、5xFADアルツハイマー病モデルマウスを用いてgluCESTの経時的変化を評価し、gluCEST効果と局所脳血流(CBF)を比較した。5xFADマウスと対照群のGluCEST効果とCBFを生後1ヶ月から15ヶ月までの期間で測定した。また、7ヶ月齢のマウスを対象に、樹状細胞/軸索密度を反映したNODDI MRIを測定し、神経密度を反映していると考えられているFicvfを計算し、gluCESTとの比較を行った。その結果、局所CBF は7ヶ月目から減少し始めたが、側頭葉と海馬ではgluCESTの減少がCBFの低下に先行した。5xFADマウス縦断測定では、局所的なgluCEST効果はCBFと相関していたが、一般化線形混合モデルでは大脳皮質では基底部とは統計的に異なる相関を示した。また、頭頂皮質ではNODDI由来のFicvfはgluCEST効果と相関していたが、海馬では相関しておらず、病態生理学的なメカニズムの地域差が明らかになった。これらの結果から、gluCESTは微妙な病態変化を評価することが可能であり、アルツハイマー病の診断やバイオマーカーの候補となるイメージング手法の一つとなり得ると考えられた。

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  • Realistic three-dimensional virtual nodule based on spatial resolution in lung computed tomography

    Grant number:17K09059  2017.4 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Ohkubo Masaki

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    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

    To evaluate the performance of computer-aided detection (CAD) of lung cancer CT screening, we proposed a new method for generating computer-simulated nodule images ‘virtual nodules’. The performance of a CAD system is affected by CT scanning and image reconstruction conditions. Therefore, CAD performance should be evaluated by image data obtained under the same CT conditions as those used at each site providing CT screening. The virtual nodules were generated based on the spatial resolution of a CT system used in an institution providing cancer screening and were fused into lung images obtained at that institution, allowing site-specific virtual nodules with a realistic appearance. In phantom experiments using laboratory-made physical nodules, the virtual nodules were confirmed to agree well with CT images obtained by scanning the phantom nodules. Virtual nodules can be an effective means of evaluating site-specific CAD performance.

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  • Virtual nodule based on 3D spatial resolution in lung CT and its application to performance evaluation of computer-aided detection (CAD) system

    Grant number:26460722  2014.4 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    OHKUBO Masaki, MATSUMOTO Toru, MURAO Kohei

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    Grant type:Competitive

    Grant amount:\1950000 ( Direct Cost: \1500000 、 Indirect Cost:\450000 )

    We proposed an application of virtual nodules to evaluate the performance of computer-aided detection (CAD) of lung cancer CT screening. When a CAD system is introduced in an institution providing CT screening, its performance should be evaluated by image data obtained under the same scan and image reconstruction conditions as those used at that site, because CAD performance is affected by CT scanning and image reconstruction conditions. The virtual nodules were generated based on the spatial resolution of a CT system used in an institution providing cancer screening and were fused into lung images obtained at that institution, allowing site specificity. The detection limits of a CAD system were determined in terms of the size and density of lung nodules. This methodology for guiding the detection limit might be a useful evaluation strategy. Virtual nodules can be an effective means of evaluating site-specific CAD performance.

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  • Performance evaluation of lung cancer CT screening CAD and developmant

    Grant number:25461803  2013.4 - 2016.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    WADA SHINICHI, OHKUBO Masaki, MATSUMOTO Toru, MURAO Kohei, MARASINGHE Janaka C, KOBAYASHI Hajime, YOSHIDA Akifumi, GOUDO Makoto, NARITA Akihiro, SUGAWARA Hideyoshi

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    Grant amount:\4940000 ( Direct Cost: \3800000 、 Indirect Cost:\1140000 )

    AAPM-CADSC have published the CAD- Quality Assurance (QA) guideline in Medical Physics recently. We also believe the study of CAD-QA is essential to establish the high quality lung cancer CT screening. The purpose of this study is to develop a method of QA of lung cancer CT screening CAD systems. The research strategy is aimed to cover the image quality characteristic problem caused by a variety of CT image quality due to the difference of the CT manufactures, image acquisition and reconstruction parameters. PSF and SSP were measured to know the 3D-PSF. Using 3D-PSF the virtual nodules were generated. The following 4 issues were discussed in applying the virtual nodule for CAD-QA, (1) Verification of PSF-based virtual nodule method using a CT screening database, (2) virtual nodule application to CAD study as a performance evaluation method, (3) study for the sophistication of the Virtual Nodule,(4) robustness evaluation of CAD performance of algorithm differences.

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  • Conversion of CT image quality to suitable quality for images input into a computer-aided detection (CAD) system for lung cancer

    Grant number:23602005  2011.4 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    OHKUBO Masaki, WADA Shinichi, MATSUMOTO Toru, MURAO Kohei

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    Authorship:Principal investigator  Grant type:Competitive

    When computer-aided detection (CAD) is applied to lung cancer screening, it is important to choose a reconstruction kernel suitable for images input into a CAD system. However, if the kernel suitable for CAD is different from the kernel that has been clinically used by a radiologist until the introduction of CAD, the change in kernel could cause difficulty. To overcome this problem, we proposed a new technique of image filtering as an alternative to the application of a different reconstruction kernel, based on the quantitative analysis of the modulation transfer function (MTF) measured in the system. It was demonstrated that the proposed method had good performance and improved the worsening in performance of CAD caused by the use of kernels unsuitable for images input into a CAD system.

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  • Quantitative evaluation of small spherical structures in PSF-based CT image simulation

    Grant number:20500389  2008.4 - 2011.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    OHKUBO Masaki, WADA Shinichi, MATSUMOTO Toru, MURAO Kohei

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    Grant type:Competitive

    Grant amount:\1300000 ( Direct Cost: \1000000 、 Indirect Cost:\300000 )

    A technique of three-dimensional (3D) CT image simulation based on the point spread function (PSF) was developed. We simulated CT images from the object functions of ideal spheres, assuming solitary pulmonary nodules, and calculated the sphere volumes with a simple threshold technique in which the relationship between the threshold and the volume was analyzed. We determined the threshold (defined as T') so that the sphere volume obtained in simulated image was equal to its object function (true volume). It was quantitatively shown that the T' changed with the object sphere diameter, the image reconstruction kernel, slice thickness and slice location while maintaining a constant density in the object. Our simulation technique and present results will be effective for basic research on 3D nodule analysis.

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  • 超高磁場MR装置を用いたプロトンスペクトロスコピーに関する基礎研究

    Grant number:10770440  1998.4 - 2000.3

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    大久保 真樹

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    Grant type:Competitive

    Grant amount:\1100000 ( Direct Cost: \1100000 )

    昨年度,超高磁場(3テスラ)MR装置用のプロトンスペクトロスコピー測定シーケンスに改良を加えた.このシーケンスを用いてヒト脳におけるスペクトルの測定を試みたところ,従来のMR装置(〜1.5テスラ)では測定が難しい小さな領域におけるスペクトルを比較的短時間で測定することができた.観測されたスペクトルのピークはCholine,Phosphocreatine/Creatine,N-acetylasparate等の信号であり,Glutamine/Glutamateと思われるの信号も観察される場合があった.部位によりスペクトルパターンが異なっており,生化学的な状態や代謝及び組織構成などに差があるものと考えられた.またスペクトルの測定手順を一連の命令(マクロ)にまとめ簡易化することにより,測定法の確立を図った.
    測定したスペクトルデータの処理・解析を行うためにデータをフォーマット変換・転送し,広く普及しているパーソナルコンピュータ(PC)を用いて別途に処理を行う簡易なシステムをこれまでに作成した.このシステムを用いたところ,ヒト脳におけるスペクトルを容易に処理・解析することができ,スペクトルピーク位置や面積等を求め半定量的な評価が可能となった.一連の操作は非常に簡単であり,プログラムの変更なども容易である.PCを利用していることから汎用性が高く,データベースの構築や他のMR装置で測定したスペクトルデータとの比較などにも有用である.

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  • BASICAND CLINICAL RESEARCH ON CONCURRENT CHEMORADIOTHERAPY WITH PROTRACTED LOW DOSE CONTINUOUS INFUSION OF 5-FU + CDDP FOR ESOPHAGEAL CANCER

    Grant number:08457240  1996.4 - 1999.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    SAKAI Kunio, OHKUBO Masaki, MATSUMOTO Yasuo, TSUCHIDA Emiko, SUGITA Tadashi, FUJITA Shozo

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    Grant amount:\5900000 ( Direct Cost: \5900000 )

    In the basic study using flow cytometry, a pronounced G_2M phase accumulation of FM3A cells was observed at 72 hours after the combined treatment of 5-FU and CDDP, Most of the cells blocked in G_2 phase for a long time became giant cells or multinuclear cells, which seemed todie later. Combining 5-FU plus CDDP with radiation showed synergistic cytotoxic effect on the experiments using cell growth analysis, dye exclusion test, and morphological analysis.
    In the clinical study, 31 patients with stage II - III esophageal cancer treated between 1992 and 1994 with the concurrent chemoradiotherapy using low-dose continuous infusion of 5-PU (RT+5FU group) were compared with 27 patients treated previously with radiotherapy alone (RT group). Response rate and local-progression free rate of the RT+5FU group were sigificantly higher than the RT group (p<0.05). Since 1995.32 patients with stage II - III esophageal cancer were treated with the concurrent chemoradiotherapy using low-dose continuous infusion of 5-FU (250 rng/m^2/day) plus CDDP (3 mg/m^2/day) (RTFC group). The RT+FC group showed response rate, local-progression free rate, and cummulative survival rate to be significantly higher than the RT group (p<0.05). We conclude that low-dose continuous infusion of 5-FU*CCDDP given during entire course of conventional radiotherapy is significantly superior to conventional radiotherapy alone in the local control of stage II - III esophageal cancer.

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  • SPECT用の新しい放射性リガンドの合成と動態解析モデルの実験的研究

    Grant number:06670907  1994.4 - 1995.3

    日本学術振興会  科学研究費助成事業 一般研究(C)  一般研究(C)

    小田野 幾雄, 大久保 真樹, 中島 孝

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    Grant amount:\1300000 ( Direct Cost: \1300000 )

    【目的】single photon emission computed tomography(SPECT)によってドーパミンD2受容体をイメージングするために、新しい放射性リガンドI-125 NCQ298を合成し、小動物(ラット)を用いて動態解析などの基礎的検討を行った。
    【対象】雄成熟ラット(Sprangue-Dawley rat:体重約200g,N=20)を用いた。【方法】まず、クロラミンT法を用いて、NCQ298の前駆物質にI-125を標識した。収率98%であった。次に、ラットをハロセン麻酔下に開腹し、大腿静脈ヘカテーテルを挿入して血管を確保した。麻酔が完全に覚醒してから、I-125I NCQ298 100μCi(=0.3ml)を静注した。静注5分、10分、15分、30分、60分の時点で断頭(各4匹)し、速やかに全脳を摘出して、全頭皮質、綿条体、海馬、小脳の4つに分離した。その際できるだけ血管成分を除去し、試料に混入しないようにした。断頭直後に頚部断端から採血した。各試料の重量を計測後、well counterで放射能を計測し、count/mgを測定した。また血中の放射能count/mlを測定した。以上のデータを用いて3-コンパートメントモデル解析を行った。
    【結果】前頭皮質、海馬、小脳の放射能は、約10分でプラトーに達して漸減した(図)。一方、綿条体の放射能は速やかに上昇して、約15分でプラトーに達し、その後60分まで平衡状態にあった。綿条体の放射能は、前頭皮質や小脳に比較して、約3倍であった。血中の放射能は10分でプラトーになり、その後漸減した。
    【考察】I-125INCQは綿条体に著しく集積し、約15分で平衡状態に達する。一方、小脳や前頭皮質への集積は約1/3と少なく、コントラストが明瞭になった。I-125INCQは、ドーパミンD2をイメージングする放射性リガンドとしてきわめて有用であると考えられた。今後は、ヒト脳を対象にしてこの放射性リガンドの有用性を検討する予定である。

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  • 123I-IMP SPECTを用いたマイクロスフェア法による脳血流量測定法の評価

    Grant number:06770699  1994.4 - 1995.3

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    大久保 真樹

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    Grant type:Competitive

    Grant amount:\900000 ( Direct Cost: \900000 )

    Single photon emission computed tomography(SPECT)及びN-isopropyl-p-〔^<123>I〕iodoamphetamine(^<123>I-IMP)を用いたmicrosphere modelに基づく局所脳血流量定量測定法(microsphere法)における2つの問題点,1)脳組織から^<123>I-IMPが洗い出されることを無視している点,2)通常は^<123>I-IMP静注後早期での短時間の撮像が困難なため静注数十分後に撮像した画像を補正したものを使用していること,による局所脳血流量の算出誤差を定量的に評価した.その結果を以下に述べる.
    問題点1)に対する検討結果:被検者10名から測定した動脈血中の^<123>I-IMP時間放射能曲線(microsphere modelの入力関数)を用いてシミュレーション解析を行ったところ,^<123>I-IMP静注後5分以内であれば約5%以下の誤差率で局所脳血流量を測定可能であると算定された.臨床では,5%程度の誤差は無視できうる大きさであると考えられ,静注5分後までならばmicrosphere法にて精度よく局所脳血流血の測定が可能である.
    問題点2)に対する検討結果:被検者8名について,入力関数と静注数十分後に撮像した画像を補正する係数(頭部全体の放射能カウントの変化率)を実測し,それらを用いてシミュレーション解析を行ったところ,局所脳血流量が過大に算出されることがわかった.過大に算出される割合を定量的にとらえその補正を試みたところ,^<133>Xe吸入法によって測定した局所脳血流量の値との誤差率は平均約7%改善した.
    microsphere法による局所脳血流量測定における誤差を定量的にとらえることができた.さらに問題点2)についての補正法を提案し,その有用性を認めた.

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  • BASIC AND CLINICAL RESEARCH ON THE CONCURRENT CHEMORADIOTHERAPY WITH PROTRACTED LOW DOSE CONTINUOUS INFUSION OF 5-FLUOROURACIL

    Grant number:05454301  1993.4 - 1996.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (B)  Grant-in-Aid for General Scientific Research (B)

    SAKAI Kunio, OHKUBO Masaki, SUGITA Tadashi, ITO Takeshi, SUEYAMA Hiroo, FUJITA Shozo

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    Grant amount:\4700000 ( Direct Cost: \4700000 )

    In the basic study, the effects of radiation simultaneously combined with 5-fluorouracil (5-FU), cisplatin (CDDP), or both drugs on FM3A cell survival were investigated in vitro. Cell survival following treatment with the drugs and/or radiation was evaluated bycolony formation assays. Prolonged exposure of 5-FU as well as CDDP were far more effective in killing cells than pulse exposure. The combination of radiation with 24-hr continuous exposure of these drugs resulted in radiosensitization, while 1-hr pulse exposure of CDDP combined with radiation did not show an enhanced cell killing. In addition, concurrent continuous exposure of 5-FU and CDDP combined with radiation resulted in a supra-additive radiosensitizing effect. Although the mechanism of this supra-additive radiosensitization is unknown, the biochemical modulation of CDDP on the intracellular 5-FU metabolism may be related .
    In the clinical study, 28 patients with inoperable esophageal squamous cell carcinoma were treated with the concurrent chemoradiotherapy consisting of conventional external radiotherapy and protoracted low dose continuous infusion of 5-FU (300mg/m^2/day) .The acute toxicity of this combined treatment consisted of swallowing pain (39%), anorexia (39%), nausea (32%) and diarrhea (14%), which were usually controlled by medication . The planned treatment was accomplished in 25/28 (89%) . Patients with localized esophageal carcinoma who were treated with this regimen (n=24) or the conventional radiotherapy alone (n=24) were analyzed by the multivariate method, which revealed the treatment to be significant in the local relapse-free rate . The multivariate analysis on survival also demonstrated the treatment to be significant . In conclusion, the combined treatment was clinically feasible and was considered to be effective in increasing the local control rate and survival of esophageal cancer .

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  • 13C-MRスペクトロスコピーによる実験腫瘍の増殖・放射線照射に伴う組織代謝変化

    Grant number:04770734  1992.4 - 1993.3

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    大久保 真樹

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    Grant type:Competitive

    Grant amount:\900000 ( Direct Cost: \900000 )

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  • MRスペクトロスコピーによる腫瘍組織の代謝に関する研究

    1991.4 - 1992.3

    科学研究費助成事業  奨励研究(A)

    大久保真樹

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    Authorship:Principal investigator  Grant type:Competitive

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  • Classification of Japanese Consonants in terms of Structured Modeling and Geometrical Interpretation of Dynamic Characteristics in Transient Parts

    Grant number:02805044  1990.4 - 1991.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (C)  Grant-in-Aid for General Scientific Research (C)

    HORI Jun-ichi, OHKUBO Masaki, KIRYU Tohru

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    Grant amount:\1900000 ( Direct Cost: \1900000 )

    Transient part of speech signals has been of great interest these years in speech recognition. Furui proposed delta cepstrum coefficients to extract a dynamic characteristic of speech signals and achieved higher recognition rate than ever [1986]. It should be noted, however, that conventional approaches including the dynamic characteristics depend on a linear prediction that features formats of speech signals. We employed a structural model named the natural observation system for speech modeling and a geometrical interpretation to classify the types of transient parts.
    A natural observation filter (NOF) consists of a series of first order filters with the same cutoff frequency : a low pass filter of a first stage followed by high pass filters. The NOF can reconstruct an input signal with a linear combination of outputs at each stage of first order filters, employing appropriate coefficients. We called them natural observation coefficients (NOCs). We can analyze signals by the time courses of NOCs with multi-cutoff frequencies (NOC pattern), because each NOC is a function of the cutoff frequency. We applied the NOC pattern for Japanese consonants, fricatives and stops, to study the transient parts of speech signals. Consequently, we obtained distinguishable NOC patterns that probably reflect an instantaneous structure of Japanese consonants, fricatives and stops, and following vowels.
    On the other hand, we used a geometrical interpretation of the transient parts. A two-dimensional plane in the p-dimensional Hilbert space was determined so that the trajectory of coefficients vector becomes as straight as possible. We use three types of parameters, including linear prediction coefficients, LPC cepstrum coefficients, and NOCs which are structured parameters. As a result, NOCs show a rather straight line than the other two. Limiting to LPC cepstrum coefficients, the smoothly progressive trajectory to a following vowel contributed to the high recognition rate.

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  • A Study on Prediction of effects of Radiotherapy by Magnetic Resonance Spectroscory

    Grant number:01440046  1989.4 - 1991.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (A)  Grant-in-Aid for General Scientific Research (A)

    SAKAI Kunio, ITO Takeshi, OHKUBO Masaki, HINATA Hiroshi, KIMURA Motomasa, FUJITA Shozo

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    Grant amount:\12600000 ( Direct Cost: \12600000 )

    (1) IN VIVO ^<31>P-MR SPECTROSCOPY OF EXPERIMENTAL TUMORS
    In vivo ^<31>P-MR spectroscopy of various sizes of experimental tumors revealed progressive increase of Pi/beta -NTP, PME/beta -NTP and Pi/PME ratios in proportion with the tumors increasing in size. On the other hand, PCr/Pi, PDE/PME, PDE/Pi ratios and pHi decreased with the tumor size. Spectral changes after irradiation of tumors of the same size were as follows. (1) Transient marked decrease of NTP levels found immediately after irradiation had no direct relation to the later tumor growth. (2) Sequential changes of Pi/PME roughly correlated with the radiation dose. (3) Relative sequential changes of pHi, Pi/beta -NTP and PME/ beta -NTP observed from the 1st to the 2nd day were related to the later tumor growth. (4) These spectral changes correlated with the grade of G2+M accumulation in DNA histograms and the grade of necrosis or degeneration in histological examinations which were performed on the 5th day after irradiation.
    (2) ^<31>P-MR SPECTROSCOPY IN HUMAN SUPERFICIAL MALIGNANT TUMORS
    ^<31>P-MR spectra obtained from human superficial malignant tumors were characterized by the presence of PME and PDE peaks and by alkaline shift of PHi.
    Although there are many variations in the spectral changes after treatments, decrease of PME and PDE peaks seems to be an early indicator of tumor response.

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Teaching Experience (researchmap)

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Teaching Experience

  • 医学物理学特講演習

    2021
    Institution name:新潟大学

  • 医学物理学特講

    2021
    Institution name:新潟大学

  • 情報リテラシー

    2021
    Institution name:新潟大学

  • 保健学特定研究(放射線技術科学)

    2021
    Institution name:新潟大学

  • 保健学特別研究(放射線技術科学)

    2021
    Institution name:新潟大学

  • リサーチ・メソッズ・アドバンスト

    2020
    Institution name:新潟大学

  • 医療英語ベーシック(放射)

    2020
    Institution name:新潟大学

  • 放射線撮影技術学実習

    2020
    Institution name:新潟大学

  • 保健学総合

    2020
    -
    2021
    Institution name:新潟大学

  • 放射線機器工学Ⅰ

    2018
    Institution name:新潟大学

  • 放射線撮影技術学演習

    2018
    Institution name:新潟大学

  • 放射線機器工学Ⅱ

    2018
    Institution name:新潟大学

  • 医用放射線機器科学演習

    2017
    Institution name:新潟大学

  • 医用放射線機器科学特論

    2016
    Institution name:新潟大学

  • 卒業研究

    2016
    Institution name:新潟大学

  • 医用機器工学及び演習

    2016
    Institution name:新潟大学

  • 医療英語(放射)

    2016
    Institution name:新潟大学

  • 医学物理学概論

    2014
    Institution name:新潟大学

  • 放射線機器工学実験Ⅰ

    2014
    Institution name:新潟大学

  • 保健学特別研究(放射線技術科学)

    2014
    -
    2019
    Institution name:新潟大学

  • 放射線機器工学実験Ⅱ

    2013
    Institution name:新潟大学

  • 電子工学

    2012
    -
    2015
    Institution name:新潟大学

  • 保健学特定研究(放射線技術科学)

    2011
    -
    2017
    Institution name:新潟大学

  • スタディスキルズ (放射)

    2008
    Institution name:新潟大学

  • 電子・システム工学実験

    2007
    Institution name:新潟大学

  • 医療と画像技術

    2007
    Institution name:新潟大学

  • 磁気共鳴画像技術学演習

    2007
    Institution name:新潟大学

  • 放射線科学セミナー

    2007
    Institution name:新潟大学

  • 電子情報学実習

    2007
    Institution name:新潟大学

  • 情報リテラシー

    2007
    -
    2019
    Institution name:新潟大学

  • 電気工学及び演習

    2007
    -
    2018
    Institution name:新潟大学

  • 入門医療英語

    2007
    -
    2018
    Institution name:新潟大学

  • 電気工学実験

    2007
    -
    2018
    Institution name:新潟大学

  • 生体機能情報解析学特講

    2007
    -
    2015
    Institution name:新潟大学

  • 生体構造機能解析工学特論

    2007
    -
    2014
    Institution name:新潟大学

  • 生体機能情報解析学特講演習

    2007
    -
    2014
    Institution name:新潟大学

  • 生体構造機能解析工学演習

    2007
    -
    2014
    Institution name:新潟大学

  • 医用放射線科学特別研究

    2007
    -
    2013
    Institution name:新潟大学

  • 医用物理学概論

    2007
    -
    2013
    Institution name:新潟大学

  • 磁気共鳴画像技術学

    2007
    Institution name:新潟大学

  • 医用画像機器

    2007
    Institution name:新潟大学

  • 脳学概論

    2007
    Institution name:新潟大学

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