研究者詳細 - 大久保　真樹

論文 - 大久保　真樹

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[Simple Method to Measure Slice Sensitivity Profile in Non-helical CT Using Tilted Metal Wire]. 査読

Akihiro Narita, Masaki Ohkubo, Yuki Ohsugi

Nihon Hoshasen Gijutsu Gakkai zasshi 80 ( 9 ) 923 - 927 2024年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）

PURPOSE: The measurement of slice sensitivity profile (SSP) in non-helical CT is conventionally performed by repeated scans with moving a micro-coin phantom little by little in the longitudinal direction at a small interval, which is reliable but laborious and time-consuming. The purpose of this study was to propose a simple method for measuring the SSP in non-helical CT based on a previous method that measured the slice thickness using a tilted metal wire. METHODS: In the proposed method, a CT image was obtained by scanning a wire tilted at an angle θ=30° to the scan plane. By deconvolving the image with the point spread function (PSF) measured at the scanner, we obtained an image that was not affected by the PSF blurring. The CT value profile along the wire was acquired on the obtained image. The SSP was determined by multiplying the profile by tan θ. In addition, the SSP was measured by the conventional method using a micro-coin phantom and compared with the SSP obtained by the proposed method. RESULTS: The SSP measured by the proposed method agreed well with that measured by the conventional method. The full-width at half-maximum values of these SSPs were the same. CONCLUSION: The proposed method was demonstrated to easily and accurately measure the SSP in non-helical CT.

DOI： 10.6009/jjrt.2024-1486

[Method for Measuring Noise Power Spectrum Depending on X-ray Tube Angle in Spiral Orbit of Helical CT Scan]. 査読

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

Nihon Hoshasen Gijutsu Gakkai zasshi 2023年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）

PURPOSE: The noise power spectrum (NPS) in computed tomography (CT) images potentially varies with the X-ray tube angle in a spiral orbit of the helical scan. The purpose of this study was to propose a method for measuring the NPS for each angle of the X-ray tube. METHODS: Images of the water phantom were acquired using a helical scan. As a conventional method, we measured the two-dimensional (2D) NPS from each image and averaged them; the obtained 2D-NPS was referred to as NPSconventional. In the proposed method, we made the X-ray tube angle θ (0°≤θ<360°) to correspond to the image according to each slice position of the images that located within the travel distance of the CT scan table per 360° rotation of the X-ray tube. We obtained the 2D-NPS from each image and assigned the θ (0°, 30°, 60°, 90°, 120°, 150°, 180°); the obtained 2D-NPS was referred to as NPSsθ. The NPSsθ was compared to the NPSconventional. Also, we investigated the dependency of the NPSsθ on the θ. RESULTS: The NPSconventional was found to be isotropic, and in contrast, the NPSsθ was anisotropic. The NPSsθ showed a continuously rotational change while increasing the θ. There was an excellent correlation (R2>0.999) between the rotation angle of NPSθ and the θ. CONCLUSION: The proposed method was demonstrated to be effective for evaluating anisotropic noise characteristics depending on the X-ray tube angle.

DOI： 10.6009/jjrt.2023-1363

Method for measuring noise-power spectrum independent of the effect of extracting the region of interest from a noise image 査読

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

Radiological Physics and Technology 2023年7月

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

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

Nihon Hoshasen Gijutsu Gakkai zasshi 78 ( 7 ) 719 - 725 2022年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）

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

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

Akihiro Narita, Kazuki Okamoto, Kengo Toyonaga, Masaki Ohkubo

Nihon Hoshasen Gijutsu Gakkai zasshi 78 ( 7 ) 732 - 740 2022年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）

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

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

Yuta Yagi, Masaki Ohkubo, Hiroaki Saito, Tsutomu Kanazawa

Nihon Hoshasen Gijutsu Gakkai zasshi 78 ( 4 ) 357 - 363 2022年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）

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

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

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

Nihon Hoshasen Gijutsu Gakkai Zasshi 78 ( 4 ) 342 - 347 2022年4月

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

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

Contrast Media & Molecular Imaging 2021 1 - 8 2021年12月

掲載種別：研究論文（学術雑誌）出版者・発行元：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>
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</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>
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</inline-formula>, unpaired t-test) and thalamus (<inline-formula>
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</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

その他リンク： 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査読

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年11月

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

Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

Radiological physics and technology 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

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

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

Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

Medical physics 48 ( 3 ) 1125 - 1130 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

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

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

Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

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

記述言語：日本語掲載種別：研究論文（学術雑誌）

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

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

Daisuke Mugishima, Akihiro Narita, Masaki Ohkubo

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

記述言語：日本語掲載種別：研究論文（学術雑誌）

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

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

Akihiro Narita, Masaki Ohkubo

Journal of applied clinical medical physics 21 ( 2 ) 144 - 151 2020年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

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

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

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年

記述言語：英語掲載種別：研究論文（学術雑誌）

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

[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]. 査読

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年

[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]. 査読

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年

[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]. 査読

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年

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

Manabu Natsumeda, Hironaka Igarashi, Kunio Motohashi, Yuji Suzuki, Masaki Ohkubo, Kouichirou Okamoto, Masaki Watanabe, Tsutomu Nakada, Yukihiko Fujii

Neuropsychiatry (London) 8 ( 6 ) 1831 - 1838 2018年7月

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

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

Radiological Physics and Technology 10 ( 4 ) 446 - 453 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

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

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

MEDICAL PHYSICS 44 ( 10 ) 5303 - 5313 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Magnetic Resonance Imaging of Neurotransmitter-Related Molecules 査読

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

JOURNAL OF NIPPON MEDICAL SCHOOL 84 ( 4 ) 160 - 164 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

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

Kanazawa T, Ohkubo M, Kondo T

European Congress of Radiology C-1063 1 - 14 2017年3月

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)) 査読

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年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：新潟大学医学部保健学科

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。

その他リンク： http://dspace.lib.niigata-u.ac.jp/dspace/bitstream/10191/47194/1/14%281%29_27-33.pdf

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

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年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BRITISH INST RADIOLOGY

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> 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.

DOI： 10.1259/bjr.20160313

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

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

MEDICAL PHYSICS 43 ( 7 ) 4098 - 4105 2016年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS

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.

DOI： 10.1118/1.4953247

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

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

Nihon Hoshasen Gijutsu Gakkai zasshi 72 ( 1 ) 63 - 72 2016年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

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.

DOI： 10.6009/jjrt.2016_JSRT_72.1.63

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

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

European Congress of Radiology C-0946 1 - 24 2015年3月

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

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年3月

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

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

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

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：KARGER

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

DOI： 10.1159/000371575

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

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年6月

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

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年5月

[15O]H2O OSEM法PET画像でのsubset とiterationの組み合わせによる画素値の検討： FBP法を基準として査読

山野井理恵, 岡本浩一郎, 河村和紀, 大久保真樹, 鈴木雄治, 中村亨弥

日本核医学会機関紙 51 ( 4 ) 373 - 382 2014年

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

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

MEDICAL PHYSICS INTERNATIONAL Journal 1 ( 2 ) 350 - 350 2013年9月

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

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

Radiological Physics and Technology 6 ( 2 ) 492 - 499 2013年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

DOI： 10.1007/s12194-013-0225-2

Accurate determination of ct point-spread-function with high precision 査読

Akihiro Kayugawa, Masaki Ohkubo, Shinichi Wada

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

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：John Wiley and Sons Ltd

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.

DOI： 10.1120/jacmp.v14i4.3905

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

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年12月

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

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

Radiological Physics and Technology 5 ( 2 ) 166 - 171 2012年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

DOI： 10.1007/s12194-012-0150-9

放射線治療における位置照合の容易化を目的としたEPID ポータル画像の周波数処理に関する検討査読

山田昌法, 大久保真樹, 粥川啓廣, 山田宏美, 松浦将孝, 三浦貴, 楠本敏久

日本放射線技術学会雑誌 68 ( 5 ) 593 - 601 2012年5月

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年1月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）出版者・発行元：(公社)日本放射線技術学会-東北支部

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。

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

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

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

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MULTIMED INC

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.

DOI： 10.1120/jacmp.v13i6.3868

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

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

MEDICAL PHYSICS 38 ( 7 ) 3915 - 3923 2011年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS

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]

DOI： 10.1118/1.3590363

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年11月

肺結節体積評価のための濃度閾値設定に関する3次元CT画像シミュレーション解析査読

大野健, 舟木歩, 大久保真樹, 和田真一, 粥川啓廣, 松本徹, 村尾晃平

医学物理 30 ( 2 ) 39 - 48 2010年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本医学物理学会

胸部CTによる肺内結節に対する精度の高い診断や、三次元的な評価を行う際、濃度閾値が重要な因子の一つになる場合が多い。結節を想定した球体を被写体関数に設定し、PSF(点拡がり関数)を用いた三次元画像シミュレーションに基づき、濃度閾値設定を行った。閾値設定と、それによって抽出される領域の体積との関係は、球体ファントムを用いた結果と比べ約5%の差異であったことから、シミュレーションの妥当性が確認された。結節の体積を正確に算出するための設定閾値は、結節の濃度が一定である場合でも大きさによって変動し、更に画像再構成関数、スライス厚およびスライス位置にも大きく依存することが定量的に示された。

DOI： 10.11323/jjmp.30.2_39

Gd-EOB-DTPA を用いた肝ダイナミックMRI の動脈優位相における画像アーチファクトに関するシミュレーション査読

深谷貴広, 内藤健一, 齋藤宏明, 瀧本宗徳, 粥川啓廣, 大久保真樹

日本放射線技術学会雑誌 66 ( 9 ) 1197 - 1203 2010年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

ガドキセト酸ナトリウムを用いた肝ダイナミックMRIの動脈優位相における画像アーチファクトについてシミュレーションした。撮像は、5通りの時刻範囲(撮像タイミングt1〜t5)で行われたと想定し、いずれも撮像に要する時間は、横軸の50%に相当する時間とした。Sequential法は、いずれのタイミングにおける画像も、明らかなアーチファクトはみられなかった。Centric法の場合、t4およびt5の場合、原画像に比べ、大きなボケが生じ、t2の場合、輪郭強調のような効果がみられた。Centric法では、sequentia1法に比べ、撮像タイミングによってアーチファクトが生じやすかった。撮像時間を25%にした。Sequential法での撮像の場合、明らかなアーチファクトはみられず、Centric法での撮像の場合、t4とt5の場合にボケが生じ、t2の場合に輪郭強調の効果がみられた。

DOI： 10.6009/jjrt.66.1197

SSPを用いたCT画像の体軸方向空間分解能変換査読

粥川啓廣, 大久保真樹, 和田真一, 松本徹, 村尾晃平, 山本眞司

医学物理 30 ( 1 ) 3 - 9 2010年8月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本医学物理学会

薄いスライス厚の画像が再構成・保存された後、rawデータが消去された状況を想定し、このとき、薄いスライス厚の画像から厚いスライス厚の画像を計算によって求める手法を提案した。CT装置における体軸方向の空間分解能指標であるSlice Sensitivity Profile(SSP)を利用した。SSP変換法と加重平均法との比較を行い、SSP変換法の変換精度を検討した。胸部CT検診の画像データベースにおいて、充実性の結節が確認された7例の画像データを用いた。5mm厚画像から8mm厚画像への変換について検討した。変換画像の精度は非常に高く、RMSEは7例平均で約6.0HUであった。加重平均法ではSSP変換法に比べ精度が低く、RMSEの平均値は約10.0HUであった。CT画像rawデータが保存されていない場合でも、異なるスライス厚の画像を高精度に算出できる可能性が示された。

DOI： 10.11323/jjmp.30.1_3

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査読

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年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(NPO)日本CT検診学会

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)

Determination of point spread function in computed tomography accompanied with verification 査読

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

MEDICAL PHYSICS 36 ( 6 ) 2089 - 2097 2009年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS

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.

DOI： 10.1118/1.3123762

Accurate determination of CT PSF with high precision 査読

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年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPRINGER

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.

DOI： 10.1007/978-3-642-03879-2_225

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

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

MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING 46 ( 3 ) 273 - 282 2008年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER HEIDELBERG

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.

DOI： 10.1007/s11517-007-0283-x

MR用簡易ファントムを用いた磁化率強調画像（Susceptibility-weighted Imaging：SWI）の基礎的検討査読

太田絢子, 内藤健一, 大久保真樹, 猪又聖美, 大越幸和, 岡本浩一郎, 伊藤周子

日本放射線技術学会雑誌 63 ( 9 ) 1093 - 1098 2007年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

既製のゲル状ファントムを撮像し、磁化率強調画像(SWI)によって磁化率効果の生じている低信号領域の検出を行い、従来のgradient-recalled-echo(GRE)法によるT2*強調画像と比較した。また、SWIにおけるスライス厚と低信号領域の検出能との関連を調べた。磁化率効果が生じている低信号領域の検出能は、従来のT2*強調画像に比べ、SWIの方が明らかに優れていた。T2*強調画像(スライス厚4mm)では、SWI(実効スライス厚4mm)に比べ、低信号ピクセルのコントラストは平均で約88%低下した。SWIの実効スライス厚を4mmより厚くすると、低信号ピクセルのコントラストは低下した。実効スライス厚を4mmから7mmに上げた場合、コントラストは平均で約75〜65%に低下するが、従来のT2*強調画像よりも高いコントラストを呈し、全脳を対象とした検査における撮像時間の短縮が示唆された。

DOI： 10.6009/jjrt.63.1093

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

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

CLINICAL RADIOLOGY 62 ( 4 ) 376 - 381 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：W B SAUNDERS CO LTD

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 < 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.

DOI： 10.1016/j.crad.2006.11.010

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

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

JOURNAL OF NEUROSURGERY 106 ( 4 ) 609 - 613 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC NEUROLOGICAL SURGEONS

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 < 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.

DOI： 10.3171/jns.2007.106.4.609

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査読

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年4月

The CT image standardization based on the verified PSF. 査読

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年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING

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.

DOI： 10.1117/12.708888

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

Masaki Ohkubo, Sinichi Wada, Toru Matsumoto, Kanae Nishizawa

MEDICAL PHYSICS 33 ( 8 ) 2757 - 2764 2006年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS

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.

DOI： 10.1118/1.2214168

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

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

ACTA PSYCHIATRICA SCANDINAVICA 114 ( 2 ) 101 - 108 2006年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BLACKWELL PUBLISHING

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.

DOI： 10.1111/j.1600-0447.2006.00858.x

CT画像系において測定された line spread function (PSF) および point spread function (PSF) の精度評価法に関する研究査読

國井正之, 和田真一, 大久保真樹, 原田正紘, 西澤かな枝, 松本徹

医学物理 26 ( 2 ) 57 - 64 2006年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本医学物理学会

CT画像系において測定されたline spread function(LSF)及びponit spread function(PSF)の精度を画像上で検証する方法を提案した。CT画像のスキャン平面x-yにおける被写体関数とCT値が、直交するz軸の位置によらず一定と仮定し、CT画像の空間分解能をCTスキャン系において計算した。そのLSF値の妥当性は、直径が一定の円柱構造物がz軸と平行になるように配置して撮影を行い、得られたCT画像と計算値から得られた画像とを比較して行った。LSF値を使って計算された画像は撮影された画像と良く一致し、LSF値の妥当性が確認された。不適当な方法で得られた他のLSF値では撮影画像と一致しなかった。本法を利用することによって、LSFやPSF、或いはそれらを基に導出したmodulation transfer function(MTF)の精度を評価できることが示唆された。

DOI： 10.11323/jjmp2000.26.2_57

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

Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, Kanae Nishizawa

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

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING

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's body (z-direction). Scanned images of such a phantom were characterized according to spatial resolution in the scan-plane, and didn'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.

DOI： 10.1117/12.654087

肝臓ダイナミック MRI における 3D-VIBE法の至適フリップ角の検討査読

内藤健一, 大越幸和, 大久保真樹, 八木下裕子, 岡純子, 太田絢子, 山本哲史, 駒澤絵美

日本放射線技術学会雑誌 61 ( 10 ) 1441 - 1446 2005年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

three-dimensional volumetric interpolated breath-hold examination(3D-VIBE)法を用いた肝臓ダイナミックMRIにおいて,多血性の肝細胞癌の描出を想定した至適なフリップ角(FA)を検討した.いずれのファントムにおいても,FAが30度よりも大きくなるとSNRは低下し,特に正常肝臓を想定したファントムにおける低下が著しかった.正常被験者を撮像した肝臓における信号強度は,ファントム実験における結果と同様の傾向がみられた.T1値が394msecのファントムを正常肝臓ファントムと想定した.いずれのファントムもFAが大きくなるとCNRが高くなった.すなわち,造影効果で肝細胞癌のT値が短縮すると想定した場合,FAが大きい方がCNRは高くなることが判明した

DOI： 10.6009/jjrt.KJ00004039788

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

Ohkubo M, Wada S, Saito M

Igaku Butsuri 25 ( 3 ) 132 - 140 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本医学物理学会

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.

DOI： 10.11323/jjmp2000.25.3_132

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 査読

N Takahashi, K Okamoto, M Ohkubo, M Kawana

CLINICAL RADIOLOGY 60 ( 3 ) 349 - 354 2005年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：W B SAUNDERS CO LTD

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.

DOI： 10.1016/j.crad.2004.06.018

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

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年1月

肝臓 dynamic MRI における 3D VIBE の有用性査読

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年1月

Measurements and precisions of point spread function of multi-slice CT 査読

S Wada, M Ohkubo, T Matsumoto

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

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING

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.

DOI： 10.1117/12.596683

CT画像系におけるline spread function(LSF)およびslice sensitivity profile(SSP)とpoint spread function(PSF)の関連査読

大久保真樹, 和田真一, 小林悌二, 李鎔範, 蔡篤儀

医学物理 24 ( 3 ) 115 - 122 2004年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本医学物理学会

多列Multi-slice CTの開発に伴い,これまでのline spread function(LSF)やslice sensitivity profile(SSP)を用いた1次元での検討から,2次元や3次元に拡張しての検討が重要になるが,LSFやSSPとpoint spread function(PSF)の関係について詳細に論ずる報告はみあたらない.そこで,LSFおよびSSPとPSFの関係について理論的に考察し,シミュレーションを加えて,それらの関連を明らか場合,その系のPSF'(x,y,z)はLSSFx(X)とLSFy(Y)およびSSP(z)の積で表すことができ,PSF(x,y)はLSFx(X)とLSFy(Y)の積で表すことができた

DOI： 10.11323/jjmp2000.24.3_115

Medical image classification using genetic-algorithm based fuzzy-logic approach 査読

DY Tsai, Y Lee, M Sekiya, M Ohkubo

JOURNAL OF ELECTRONIC IMAGING 13 ( 4 ) 780 - 788 2004年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：I S & T - SOC IMAGING SCIENCE TECHNOLOGY

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.

DOI： 10.1117/1.1786607

CT angiographyの血管描出能とpoint spread functionの関係査読

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年4月

spiral SPGR法の基礎的検討査読

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年1月

Elliptical Centric法を用いた造影三次元MR Angiographyにおける造影効果持続時間および撮像タイミングに関する検討査読

八木下裕子, 大越幸和, 大久保真樹, 内藤健一, 井上智子, 蔡篤儀

日本放射線技術学会雑誌 59 ( 12 ) 1555 - 1560 2003年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

elliptical centric法において描出される血管の信号強度が,造影効果持続時間や撮像タイミングにより,どのように変化するかを定量的に評価した.ファントム実験を行い,centric法との比較を交えて検討した.elliptical centric法を用いた造影三次元(3D)MR angiography(MRA)において,造影効果持続時間及び撮像タイミングと,描出される血管の信号強度との関連を定量的にとらえることができた.elliptical centric法は,スラブ分割数が少ない場合にはcentric法と大きな差異はみられないが,高分解能撮像等においてスラブ分割数が多くなると,造影効果持続時間の短縮や撮像タイミングの遅れに対してcentric法よりも有利であることが明らかとなった

DOI： 10.6009/jjrt.KJ00000921687

Fast RecoveryパルスによるFast Spin Echo画像の信号強度の増加に関する検討査読

大久保真樹, 大越幸和, 内藤健一, 八木下裕子, 蔡篤儀

日本放射線技術学会雑誌 59 ( 7 ) 879 - 882 2003年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

種々のT2値を持つファントムを用いて,fast recovery fast spin echo(PR-PSB)法で撮像した画像の信号強度をfast spin echo(PSE)法と比較し,fast recovery(PR)パルスによる信号強度の増加を定量的に評価した.PR-PSE法による画像の信号強度をPSE法と比較し,PRパルスによる信号強度の増加を定量的に評価できた.PRパルスの効果は,対象物のT2が長い,TRが短い,ETLが少ない,場合に大きくなる傾向がみられる

DOI： 10.6009/jjrt.KJ00003174218

An integrated fuzzy-GA-based CAD system for disease discriminations 査読

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年6月

3D FIESTA法の基礎的検討査読

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年1月

造影三次元MR angiography における撮像タイミングに関するシミュレーション査読

大久保真樹, 大越幸和, 井上智子, 内藤健一, 八木下裕子, 蔡篤儀

日本放射線技術学会雑誌 58 ( 5 ) 705 - 710 2002年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(公社)日本放射線技術学会

標題のシミュレーション手法を考案し,撮像のタイミングと血管描出能との関連を評価する試みを行った.その結果,撮像タイミングの変化に伴う血管の信号強度の変化を定量的に評価することができた.太い血管の描出には適切な撮像タイミングの設定が重要であり,細い血管の描出には長い造影効果持続時間(或いは撮像時間の短縮を要することが明らかになった

DOI： 10.6009/jjrt.KJ00001364431

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

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

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

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

DOI： 10.2463/mrms.1.121

GE社製MRI装置Signaの頭頚部用Neurovascular Array Coilの評価査読

内藤健一, 大越幸和, 井上智子, 大久保真樹, 八木下裕子

新大医保紀要 7 ( 3 ) 357 - 361 2001年12月

造影三次元 MR angiography における造影効果の持続時間に関するシミュレーション査読

大久保真樹, 大越幸和, 井上智子, 内藤健一, 鈴木清隆

日本磁気共鳴医学会雑誌 21 ( 5 ) 186 - 192 2001年7月

A Morphology-Based Method for Automated Detection of Clustered Microcalcifications 査読

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年7月

造影3次元MR angiographyに関する基礎的検討ー造影効果持続時間および撮像のタイミングについてー査読

井上智子, 大越幸和, 大久保真樹, 内藤健一

新大医保紀要 7 ( 2 ) 265 - 270 2000年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：新潟大学医学部保健学科

造影三次元MRアンギオグラフィーの造影効果持続時間と撮像のタイミングが画像に及ぼす影響について検討した.造影剤を封入した血管ファントムを用いて造影効果の有無を模擬実験した.その結果,造影時間が長くなるに従い,画像のコントラストは対数関数的に高くなった.造影効果の中心時刻がk-space中央となるデータ収集時刻と一致すれば,造影効果持続時間が多少短くなった場合でもコントラストは大きく低下することはなかった.又,造影効果中心時刻がk-space中央の時刻からずれた場合,コントラストが低下することが確認された.ただしある程度の長さの造影効果持続時間があれば,造影効果中心時刻がk-space中央から多少ずれた場合でもコントラストが大きく低下することはなかった

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招待査読

大久保真樹, 中田力, 松沢等, 松田豪

INNERVISION 15 ( 8 ) 66 2000年8月

超高磁場MRI装置による顎関節画像撮影の初期検討査読

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年4月

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 査読

M Ohkubo, Odano, I

ANNALS OF NUCLEAR MEDICINE 14 ( 2 ) 115 - 120 2000年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE SOCIETY NUCLEAR MEDICINE

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 < 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.

DOI： 10.1007/BF02988590

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

Odano, I, M Ohkubo, T Yokoi

JOURNAL OF NUCLEAR MEDICINE 40 ( 10 ) 1737 - 1744 1999年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC NUCLEAR MEDICINE INC

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.

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

Odano, I, M Ohkubo

EUROPEAN JOURNAL OF NUCLEAR MEDICINE 26 ( 3 ) 246 - 252 1999年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER VERLAG

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.

DOI： 10.1007/s002590050384

Diamox負荷時における123I-IMP SPECTを用いたマイクロスフェアモデルに基づく局所脳血流量定量法の精度の検討査読

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, 横井孝司

核医学 35 ( 3 ) 147 - 151 1998年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(一社)日本核医学会

検討した定量法は,N-isopropyl-p-[123I]iodoamphetamine(IMP)静注5分後のSPECT撮像と持続動脈採血を行う超早期マイクロスフェア法と,静注30分後のSPECT撮像と1点動脈採血を行う早期マイクロスフェア法である.5名の被検者において,Diamox投与10分後にIMPを静注し直後からダイナミックSPECT撮像と頻回動脈採血を行い,2コンパートメントモデル解析によって局所脳血流(rCBF)を算出した.超早期マイクロスフェア法と早期マイクロスフェア法で求めたrCBFは,いずれも2コンパートメントモデル解析による値と高い相関を示し(r=0.982,0.930),偏りは殆どみられなかった.マイクロスフェアモデルに基づく定量法は,安静時のみならずDiamox負荷時においても適用可能であることが確認された.特に,1点採血法による早期マイクロスフェア法は侵襲性が低く簡便で,より臨床に適する方法と考えられる

分割投与99mTc-ECD SPECTと静脈採血によるDiamox負荷前後の脳血流測定法査読

小田野行男, 大久保真樹, 野口栄吉, 大滝広雄, 柴木充朗, 土橋幸夫

核医学 35 ( 2 ) 74 - 75 1998年

99mTc-ECD SPECTを用いた3-コンパートメントモデルに基づく脳血流測定法査読

小田野行男, 大久保真樹, 野口栄吉, 大滝広雄, 柴木充朗, 土橋幸夫

核医学 35 ( 8 ) 702 - 703 1998年

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査読

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年12月

FM3A細胞における5-FU+CDDPの放射線増感効果の細胞動態学的検討査読

藤田勝三, 大久保真樹, 日向浩, 酒井邦夫

新大医短紀要 6 ( 2 ) 229 - 232 1997年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：新潟大学医療技術短期大学部

対数増殖期のFM3A細胞に対して5-FU 0.5μg/mlとcisplatin(CDDP)0.1μg/mlの24時間同時処理を行った.薬剤処理開始30分後に37℃恒温槽中で60Coγ線を2Gy照射した.薬剤除去直後,24,48,72時間後に細胞DNAをPI染色し,FACScanにより細胞動態解析を行った.FM3A細胞は2剤同時処理と2Gy併用により,薬剤除去72時間後に著明なG2ブロックが認められた.長時間G2ブロックされた細胞の多くは巨大細胞,多核細胞となりやがて死滅する.FM3A細胞における,(5-FU+CDDP)2剤同時処理による放射線増感効果は,コロニー法による細胞生存曲線と共に細胞動態の面からも支持される

99mTc-ECD SPECTを用いたマイクロスフェアーモデルに基づく非侵襲的な脳血流測定1点動脈または静脈採血法査読

小田野行男, 大久保真樹, 野口栄吉, 大滝広雄, 柴木充朗, 土橋幸夫

核医学 34 ( 12 ) 1111 - 1117 1997年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(一社)日本核医学会

1点採血法と99mTc-ECD SPECTを用いる本法は,頭部や大動脈等のdynamic測定が不要であり,1回のSPECT撮像と1回の動脈ないし静脈採血データから脳血流を簡便に精度よく定量測定できる有用な検査法である

I-123 IMP SPECTによる簡便なrCBF定量測定法の臨床応用，招待査読

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年11月

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

Odano, I, M Ohkubo, M Takahashi

JOURNAL OF NUCLEAR MEDICINE 38 ( 8 ) 1248 - 1253 1997年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC NUCLEAR MEDICINE INC

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.

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

小田野行男, 大久保真樹, 高橋誠

核医学 34 ( 5 ) 323 - 328 1997年5月

記述言語：日本語出版者・発行元：(一社)日本核医学会

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

その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=1997&ichushi_jid=J00251&link_issn=&doc_id=19970702210003&doc_link_id=10008538423&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10008538423&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

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

M Ohkubo, Odano, I, M Takahashi

JOURNAL OF NUCLEAR MEDICINE 38 ( 4 ) 597 - 601 1997年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC NUCLEAR MEDICINE INC

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.

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

小田野行男, 大久保真樹, 高橋誠

核医学 34 ( 3 ) 189 - 194 1997年3月

記述言語：日本語出版者・発行元：(一社)日本核医学会

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

その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=1997&ichushi_jid=J00251&link_issn=&doc_id=19970418590007&doc_link_id=10008538268&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10008538268&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

FM3A細胞に対する５-FU＋CDDPの放射線増感効果－細胞増殖と色素排除能による解析－査読

藤田勝三, 酒井邦夫, 樋口正一, 末山博男, 大久保真樹

新潟大学医療技術短期大学部紀要 6 ( 1 ) 103 - 108 1997年2月

学生用計測機器操作支援システム査読

中村久吾, 大久保真樹

新潟大学医療技術短期大学部紀要 6 ( 1 ) 123 - 128 1997年2月

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

Makoto Takahashi, Ikuo Odano, Shozo Fujita, Masaki Ohkubo

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

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Tokyo

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.

DOI： 10.1007/BF03164770

FM-3A細胞に対する５-FU＋CDDPの放射線増感効果査読

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年12月

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

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

NEUROLOGY 47 ( 4 ) 1093 - 1095 1996年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：LITTLE BROWN CO

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.

DOI： 10.1212/WNL.47.4.1093

Radiosensitization of FM3A cells by 5-fluorouracil plus cisplatin 査読

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

Acta Medica et Biologica 44 ( 3 ) 141 - 145 1996年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：新潟大学

The effects of radiation in combination with either 5-fluorouracil (5-FU), cisplatin (CDDP), or both on FM3A cell survival were evaluated in vitro. Cell survival following treatment with the drugs and/or radiation was determined by colony formation assays. Prolonged exposure of 5-FU as well as CDDP was very effective in killing cells. The combination of radiation with 24-hour continuous exposure of the drugs resulted in radiosensitization, while 1-hour pulse exposure of CDDP combined with radiation did not enhance cell killing, indicating that radiosensitization by CDDP may require a longer duration of drug exposure following irradiation. In addition, concurrent continuous exposure of 5-FU and CDDP in combination with radiation resulted in a greater radiosensitizing effect.

その他リンク： http://dspace.lib.niigata-u.ac.jp/dspace/handle/10191/33172

I-123 IMPによる新しい脳機能定量法査読

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年9月

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

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年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：LIPPINCOTT-RAVEN PUBL

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 < 0.001 for all subjects; overall regression equation, y = 15.14 + 0.54x) and those measured by the [I-123]IMP-microsphere method (p < 0.001 for all subjects; y = 2.0 + 0.80x). Significant correlation (p < 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.

DOI： 10.1097/00004647-199609000-00003

123I-IMPの分布容積を用いたSPECTによる脳機能診断査読

小田野行男, 大久保真樹, 高橋誠

核医学 33 ( 6 ) 579 - 586 1996年6月

記述言語：日本語出版者・発行元：(一社)日本核医学会

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

その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=1996&ichushi_jid=J00251&link_issn=&doc_id=19960702070001&doc_link_id=10008536256&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10008536256&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

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

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年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER VERLAG

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.

N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) SPECTによる局所脳血流及び分布容積の新しい定量測定法査読

大久保真樹, 小田野行男, 高橋誠, 他

核医学 33 ( 3 ) 241 - 249 1996年

N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) SPECTによる局所脳血流の定量測定法の比較・検討査読

大久保真樹, 小田野行男, 高橋誠, 他

核医学 33 ( 6 ) 647 - 654 1996年

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年12月

５-FUおよびCDDPのFM3A細胞の細胞回転に及ぼす影響査読

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年12月

記述言語：日本語掲載種別：研究論文（大学，研究機関等紀要）出版者・発行元：新潟大学医療技術短期大学部

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

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

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

Bull Coll Biomed Technol Niigata Univ 5 ( 3 ) 265 - 269 1995年12月

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? 査読

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

NUCLEAR MEDICINE COMMUNICATIONS 16 ( 12 ) 1026 - 1033 1995年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHAPMAN HALL LTD

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.

123I-IMP SPECTを用いたmicrosphere modelに基づく局所脳血流量測定法(簡便法)の精度の検討査読

大久保真樹, 小田野行男, 高橋直也

核医学 32 ( 12 ) 1323 - 31 1995年12月

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 査読

Ohkubo M, Odano I, Takahashi N, Sakai K

Acta Medica et Biologica 43 ( 3 ) 165 - 171 1995年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：新潟大学

The microsphere model and the continuous withdrawal of arterial blood have been commonly used in clinical studies when measuring regional cerebral blood flow (rCBF) by N-isopropyl-p- [^<123>I]iodoamphetamine (IMP) SPECT. The method is considered to underestimate rCBF because of the washout of the tracer from brain tissue with increasing time after injection; however, the extent of this underestimation is not known. To assess whether this underestimation can be quantitatively determined and until how long after injection the microsphere model can be applied to obtain accurate measurements of rCBF, we performed a simulation analysis. Simulation was based on the microsphere model and the 2-compartment model using the standard time-activity course of ^<123>I-IMP in arterial blood (standard input function), the accuracy of which could be validated. The values of rCBF calculated by the microsphere method following the injection of ^<123>I-IMP were compared with those given in the 2-compartment model [influx; K_1(rCBF) and outflux; k_2 (washout)]. As results, with the microsphere method, rCBF values became lower with the time after injection. The rate of underestimation of rCBF was determined to be 4.6% at 5 min, 10.2% at 10 min and 15.1% at 15 min. Since 4.6% is considered negligible in clinical studies, we concluded that the microsphere model could be applied to obtain accurate measurements of rCBF up to approximately 5 min, regardless of washout. The results of this simulation were confirmed clinically in 11 patients with various cerebral diseases.

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

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年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：LIPPINCOTT-RAVEN PUBL

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.

動脈一点採血によるN-isopropyl-p-[123I]iodoamphetamineとSPECTを用いた簡便な脳血流測定法－One-point sampling法－査読

小田野行男, 大久保真樹, 高橋直也

核医学 31 ( 10 ) 1219 - 26 1994年10月

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，臨床的研究査読

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年7月

５-FUと放射線の併用効果に関する基礎的研究査読

藤田勝三, 大久保真樹, 酒井邦夫

関越UFT研究会 7 43 - 46 1994年7月

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 査読

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

NUCLEAR MEDICINE COMMUNICATIONS 15 ( 7 ) 560 - 564 1994年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHAPMAN HALL LTD

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.

DOI： 10.1097/00006231-199407000-00011

Microsphere modelを用いたN-isopropyl-p-〔123I〕iodoamphetamine (IMP) による局所脳血流定量法の問題点－133Xe SPECTおよび経時的123I-IMP SPECTとの比較検討－査読

高橋直也, 大久保真樹, 小野田行男

核医学 31 ( 4 ) 319 - 26 1994年4月

N-isopropyl-p-〔123I〕iodoamphetamine (IMP) と回転型ガンマカメラを用いたmicrosphere modelに基づく脳血流測定法の精度の検討 PaCO2による補正の必要性査読

小田野行男, 高橋直也, 大久保真樹

核医学 31 ( 3 ) 223 - 9 1994年3月

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

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

NEUROLOGY 44 ( 3 ) 557 - 559 1994年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：LITTLE BROWN CO

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.

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

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年

1H-magnetic resonance spectroscopyにて脳局所での乳酸の上昇を認めた片頭痛査読

渡邊浩之, 桑原武夫, 大久保真樹

臨床神経学 34 ( 5 ) 504 - 507 1994年

511. ^<123>I-IMP を用いた Magic Square 法による k_2, Vd 画像の描出(核医学脳 SPECT-2) 査読

大滝広雄, 野口栄吉, 羽田野政義, 長沢弘, 小田野行男, 高橋直也, 大久保真樹, 佐藤友彦

日本放射線技術学会雑誌 50 ( 8 ) 1426 - 1426 1994年

123I-IMP SPECTを用いたmicrosphere modelによるrCBF測定法における洗い出し(k2)の影響査読

大久保真樹, 小田野行男, 高橋直也

新潟核医学懇話会記録集 17 33 - 39 1993年11月

N-isopropyl-p-[123I]iodoamphetamine (IMP) の分配定数(Distribution volume)とSPECTを用いた新しい診断 Magic Square法の開発査読

小田野行男, 大久保真樹, 高橋直也

核医学 30 ( 10 ) 1211 - 9 1993年10月

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年8月

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－査読

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年5月

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査読

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年5月

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

Ohkubo M

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

123I-IMP脳血流シンチにおけるCrossed Cerebellar Diaschisis（CCD）の発現と再分布現象に関する研究査読

小田野行男, 高橋直也, 西原真美子, 大久保真樹

核医学 30 ( 2 ) 189 - 196 1993年

MRIによる脳神経活動の画像化 MR functional brain imaging 査読

渡辺浩之, 桑原武夫, 大久保真樹

脳と神経 45 ( 10 ) 941 - 944 1993年

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

Masaki Ohkubo

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

記述言語：英語掲載種別：研究論文（学術雑誌）

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

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年12月

FM3A細胞に対する温熱併用2分割照射の細胞致死効果査読

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年8月

記述言語：日本語掲載種別：研究論文（大学，研究機関等紀要）出版者・発行元：新潟大学医療技術短期大学部

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

交流電圧計を用いたアナログ計測の開発査読

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 ( 3 ) 313 - 318 1992年8月

31P-MR spectroscopy of experimental tumors following irradiation 査読

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

Acta Medica et Biologica 40 ( 1 ) 29 - 34 1992年8月

154. シネ MRI による大動脈弁描出の試み(第 48 回総会学術大会一般研究発表予稿)

大越幸和, 荒井誠, 笠原敏文, 井上智子, 長沢弘, 木村元政, 大久保真樹

日本放射線技術学会雑誌 48 ( 3 ) 507 - 507 1992年

154. シネ MRI による大動脈弁描出の試み(MR-4 撮像技術 (1))

大越幸和, 荒井誠, 笠原敏文, 井上智子, 長沢弘, 木村元政, 大久保真樹

日本放射線技術学会雑誌 48 ( 8 ) 1238 - 1238 1992年

温熱・放射線併用療法の細胞回転に及ぼす影響査読

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年8月

記述言語：日本語掲載種別：研究論文（大学，研究機関等紀要）出版者・発行元：新潟大学医療技術短期大学部

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

マウス移植腫瘍の増殖に伴う31P-MRSの変化査読

大久保真樹, 酒井邦夫, 伊藤猛, 他

日本磁気共鳴医学会雑誌 10 ( 4 ) 285 - 293 1990年10月

放射線とUFTの併用による実験腫瘍の増殖抑制効果査読

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年9月

MRSの臨床応用査読

伊藤猛, 木村元政, 酒井邦夫, 大久保真樹, 藤田勝三

新潟医学会雑誌 104 ( 9 ) 738 - 744 1990年9月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）出版者・発行元：新潟医学会

Magnetic resonance spectroscopy (MRS) is a non-invasive method that can provide information of metabolism in-vivo. Recently some clinical trials of MRS using whole body scannar had been performed, but its clinical usefulness remains to be answered. In this article, we presented our clinical experiences of MRS using 1.5T superconducting magnet imager (Magnetom H15, Siemens) and discussed its problems to be resolved for future development.

R-C濾波器の周波数応答測定の一つの試み査読

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年8月

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査読

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年6月

表在性悪性腫瘍の治療に伴う31P-MRSの変化査読

伊藤猛, 酒井邦夫, 大久保真樹

日本磁気共鳴医学会雑誌 10 ( 2 ) 75 - 83 1990年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：(一社)日本磁気共鳴医学会

臨床用MRI装置を用いて表在性悪性腫瘍の31P-MRSを測定した.腫瘍からえられたスペクトルはPDE(ホスホジエステラーゼ)とPME(リン酸モノエステラーゼ)の領域にピークが認められ,周囲の筋肉組織とはあきらかに異なる波型を示した.治療によるスペクトルの変化は一様ではないが,PME/NTP(ヌクレオシド三リン酸)とPDE/NTPの比が,治療に反応する群では治療開始から早い時期に減少し,PCr/Piは増加する傾向が認められ,これらの値は腫瘍の治療効果の判定に使用できると考えられた.腫瘍の縮小に伴う筋組織の信号混入を避けるためにも,腫瘍の大きさのあまり変化しない時期での測定が有用である

自然観測係数による母音連鎖の認識査読

大久保真樹, 木竜徹, 斉藤義明, 飯島泰蔵

電子情報通信学会論文誌D−2 72 ( 12 ) 1985 - 1991 1989年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：電子情報通信学会

認識に有用な特徴パラメータの多くは，信号の周期成分に強く依存している．このため調音結合や個人差の影響が直接パラメータに現れ，従来の複雑な統計処理が必要になってきたと思われる．そこで，本論文では先に提案した有限次元の自然観測システムに基づき，新たな音声認識用パラメータを提案する．有限次元の自然観測システムによれば，観測信号はシステムを構成するディジタルフィルタの出力信号値系列と重み係数との線形結合で再構成できた．この際，重み係数はパワースペクトルの変化に直接的な影響を受けないと考えられた．更にフィルタの遮断周波数に依存して，重み係数に影響する信号の帯域を選択できるという特長があった．そこで，音素の分類および調音結合・個人差の影響の抑制に有利となるような遮断周波数を検討し，切出し母音の認識を行った．今回は重み係数を更に規格化した自然観測係数を認識用パラメータとして利用し，遮断周波数は1kHzに設定した．その結果，簡単な認識方法による母音連鎖の認識実験では，男声・女声の母音連鎖から切り出した合計480個の母音に対し平均91.5％（closed test）の認識率が得られた．

その他リンク： http://hdl.handle.net/10191/19367

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査読

木竜徹, 大久保真樹, 飯島泰蔵, 斉藤義明

電子情報通信学会論文誌A 72 ( 6 ) 902 - 908 1989年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：電子情報通信学会

筆者らは，音声認識の個人差・調音結合の問題に新たな方向付けを与えるために，従来のFourier解析とは異なる自然観測システムの構造的な波形再構成に着目した．本論文では，その特徴を音声信号のモデル化の観点から明らかにする．自然観測法の基礎理論によれば，アナログの1次低減フィルタと1次高域フィルタを基本構成とし，それらの無限次元の縦続接続で原信号を完全に再構成できる．しかし，無限次元で再構成することは現実的ではない．そこで，必要な重み係数を最小2乗推定することにより，ディジタル形式（双1次変換）で表した有限次元の自然観測システムを提案する．この場合，原信号は完全には再構成できないが，自然観測システムのもつ構造的な特徴は残されている．更に，有限次元の自然観測システムを形成フィルタと考えたときに，原信号のモデルパワースペクトルを定義できる．ここで，モデルパワースペクトルおよび再構成波形は，基本構成の観測時定数および次数の関数となる．この特徴は観測系を適当に工夫できるため，原信号の合目的なモデル化を可能とした．特に，母音の主要周波数帯域をモデル化した場合の重み係数は，調音結合等の影響を受けない安定な認識用パラメータと考えられた.

その他リンク： 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年5月

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年12月

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年9月

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年9月

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