Updated on 2025/09/16

写真a

 
OHKUBO Masaki
 
Organization
Academic Assembly Institute of Medicine and Dentistry Health Sciences Professor
Faculty of Medicine School of Health Sciences Professor
Graduate School of Health Sciences Health Sciences Professor
Title
Professor
Homepage
http://www.clg.niigata-u.ac.jp/~mook/
Other name(s)
Okubo Masaki
External link

Degree

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

  • 工学修士 ( 1988.3   新潟大学 )

Research History

  • Niigata University   Graduate School of Health Sciences Health Sciences   Professor

    2013.4

  • Niigata University   Faculty of Medicine School of Health Sciences   Professor

    2013.4

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

    2004.4 - 2013.3

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

    1999.10 - 2004.3

  • Niigata University   Associate Professor (as old post name)

    1997.4 - 1999.9

  • Niigata University   Research Assistant

    1988.4 - 1997.3

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Professional Memberships

  • Japanese Society of Radiological Technology

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  • Japanese Society for Magnetic Resonance in Medicine

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Papers

  • A simplified method for generating maximum slope maps in ultrafast dynamic contrast-enhanced breast magnetic resonance imaging. Reviewed

    Ayumu Funaki, Masaki Ohkubo, Kazunori Ohashi, Toshiro Shukuya, Yuka Yashima, Kazunori Kubota

    Radiological physics and technology   2025.7

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

    Clinical measurement of the maximum slope (MS) using ultrafast dynamic contrast-enhanced (UF-DCE) breast magnetic resonance imaging (MRI) is typically performed by placing a region of interest (ROI) in the most enhanced area within a lesion. However, previous studies have not clarified whether visually identified enhanced areas consistently exhibit the highest MS values. These ROI-based MS measurements require MS maps to ensure appropriate ROI placement. However, generating MS maps requires specialized software capable of pixel-by-pixel MS calculations, which are available only at a few facilities. Therefore, this study proposed a simplified method for generating MS maps. This method involves subtracting consecutive UF-DCE images, applying temporal maximum intensity projection, normalizing the resulting image by dividing it by the pre-contrast image signal intensity, and converting it to a slope by dividing it by the temporal resolution. The MS maps generated using the proposed method were compared with those obtained using a robust pixel-by-pixel curve-fitting method, in addition to the final-phase UF-DCE images. In all cases with breast lesions (n = 13), the signal intensity distributions on the proposed MS maps closely resembled those on the curve-fitting maps, with a significantly higher similarity than those on the final-phase UF-DCE images (p < 0.001). The derived mean absolute error of MS values after regression-based modification was 0.78 ± 0.72 (%/s). The proposed method improves the reliability of ROI placement in conventional ROI-based MS measurements and supports the direct quantification of MS values from map pixel data.

    DOI： 10.1007/s12194-025-00931-0

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  • [Simulation Image Generation Used to Produce Contrast-detail Diagram in X-ray CT]. Reviewed

    Kenichi Sakai, Masaki Ohkubo, Akihiro Narita, Naoya Takahashi, Yoshiyuki Noto

    Nihon Hoshasen Gijutsu Gakkai zasshi   81 ( 5 )   2025

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

    PURPOSE: To propose a method for generating simulated images that are used to produce a contrast detail (C-D) diagram in X-ray computed tomography (CT). METHODS: We numerically generated object functions assuming ideal spheres of 7 diameters and 9 contrasts between sphere density and background density. Sphere images were calculated from the object functions by the simulation technique of image blurring based on the 3-dimensional spatial resolution measured in the CT system. The calculated sphere images were added in images of the uniform water-equivalent section of a phantom acquired at different tube currents. Obtained images were arranged according to the sphere diameter and contrast and were applied to produce the C-D diagram. For each tube current, the C-D diagram was created by a board-certified diagnostic radiologist. RESULTS: The calculated sphere images showed good agreements with actually acquired sphere images of the phantom. Standard deviations (SDs) in subtraction images of them were equivalent to the SD in the background region of the actual image, suggesting the accuracy of the calculated sphere images. The obtained C-D diagram showed that smaller spheres and spheres with lower contrast tended to be detected as the tube current increased. CONCLUSION: The proposed method was suggested to be feasible for producing the C-D diagram for CT.

    DOI： 10.6009/jjrt.25-1443

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  • [Measurement for Maximum Leaf Velocity Using Piecewise Linear Approximation under Constant Acceleration of Multileaf Collimator]. Reviewed

    Masato Fujisawa, Takahide Hayakawa, Masaki Ohkubo, Ryuta Sasamoto

    Nihon Hoshasen Gijutsu Gakkai zasshi   81 ( 5 )   2025

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

    PURPOSE: The purpose of this study was to propose a method for measuring the maximum leaf velocity (Vmax) of the multileaf collimator (MLC) in a dynamic MLC irradiation. METHODS: The irradiation was carried out with a plan in which the MLC leaves were constantly and gradually accelerated. Based on this plan, it was assumed that the velocity of each leaf v(t) (t is the elapsed time) would initially increase but plateau once it reached its maximum velocity. In the proposed method, v(t) was calculated from the log file data during irradiation, and fitted by a piecewise linear function consisting of 2 linear segments (constant acceleration and constant velocity segments); Vmax was determined as the velocity in the constant velocity segments. The Vmax values in each accelerator were obtained periodically for 7 months (20 measurements in total). RESULTS: In all measurements, the constant acceleration and constant velocity segments in v(t) were clearly distinguished by the piecewise linear approximation, and the Vmax was determined. The mean Vmax value of each leaf ranged from 3.63 to 4.32 cm/s with standard deviations (SD) less than 0.04 cm/s. CONCLUSION: The proposed method made it possible to confirm the long-term stability of the Vmax easily.

    DOI： 10.6009/jjrt.25-1454

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  • [A Simple Method for Measuring the Anisotropic Two-dimensional Noise Power Spectrum in Helical CT Scan]. Reviewed

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

    Nihon Hoshasen Gijutsu Gakkai zasshi   81 ( 4 )   2025

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

    PURPOSE: Recently, a new method has been devised to measure the anisotropic 2-dimensional noise power spectrum (2D-NPS) in computed tomography. The 2D-NPS varied with the X-ray tube angle θ in the helical scan; it was defined as 2D-NPSθ. However, the method requires many scans to obtain the 2D-NPSθ for each θ with less statistical variability and is laborious. In the present study, the 2D-NPSθ was assumed to be an identical anisotropic 2D-NPS that rotated around the origin of the spatial frequency domain in conjunction with the rotation of the X-ray tube. We defined the identical 2D-NPS as 2D-NPSrot and proposed its measurement method with fewer scans. METHODS: The 2D-NPSθ (θ from 0° to 180° in an increment of 30°) were obtained from noise images acquired by a hundred scans of a water phantom. In the proposed method, the 2D-NPSθ were obtained from noise images by 2 scans, rotated backward around the origin by θ to generate the identical 2D-NPS, and averaged to generate the 2D-NPSrot. RESULTS: The 2D-NPSrot, when it was rotated by θ, agreed well with the corresponding 2D-NPSθ. Absolute values of the mean and standard deviation of percentage errors of the 2D-NPSrot with the corresponding 2D-NPSθ at each θ were less than 0.70% and 6.12%, respectively. CONCLUSION: The proposed method was suggested to be valid for simple measurement of anisotropic 2D-NPS.

    DOI： 10.6009/jjrt.25-1528

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

    Akihiro Narita, Masaki Ohkubo, Yuki Ohsugi

    Nihon Hoshasen Gijutsu Gakkai zasshi   80 ( 9 )   923 - 927   2024.9

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

    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

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

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

    Nihon Hoshasen Gijutsu Gakkai zasshi   2023.9

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

    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

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

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

    Radiological Physics and Technology   2023.7

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    Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1007/s12194-023-00733-2

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    Other Link： https://link.springer.com/article/10.1007/s12194-023-00733-2/fulltext.html

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

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

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

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

    DOI： 10.6009/jjrt.2022-1267

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

    Akihiro Narita, Kazuki Okamoto, Kengo Toyonaga, Masaki Ohkubo

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

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

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

    DOI： 10.6009/jjrt.2022-1222

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

    Yuta Yagi, Masaki Ohkubo, Hiroaki Saito, Tsutomu Kanazawa

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

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

    DOI： 10.6009/jjrt.2022-1189

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

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

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

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    DOI： 10.6009/jjrt.2022-1217

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

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

    Contrast Media & Molecular Imaging   2021   1 - 8   2021.12

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

    The glycine level in the brain is known to be altered in neuropsychiatric disorders, such as schizophrenia and Alzheimer’s disease (AD). Several studies have reported the in vivo measurement of glycine concentrations in the brain using proton magnetic resonance spectroscopy (1H-MRS), but 1H-MRS is not capable of imaging the distribution of glycine concentration with high spatial resolution. Chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI) is a new technology that can detect specific molecules, including amino acids, in tissues. To validate the measurements of glycine concentrations in living tissues using CEST from glycine to water (GlyCEST), we extracted the brain tissues from mice and performed biochemical tests. In wild-type C57BL/6 mice, GlyCEST effects were found to be higher in the thalamus than in the cerebral cortex (<inline-formula>
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    <mn>0.0001</mn>
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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>
    <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2">
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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

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

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

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

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

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    Language：Japanese   Publisher：(一社)日本脳循環代謝学会  

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

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

    Radiological physics and technology   2021.9

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

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

    DOI： 10.1007/s12194-021-00636-0

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

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

    Medical physics   48 ( 3 )   1125 - 1130   2021.3

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

    DOI： 10.1002/mp.14668

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

    Akihiro Narita, Masaki Ohkubo, Takahiro Fukaya, Yoshiyuki Noto

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

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

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

    DOI： 10.6009/jjrt.2021_JSRT_77.8.828

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

    Daisuke Mugishima, Akihiro Narita, Masaki Ohkubo

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

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

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

    DOI： 10.6009/jjrt.2021_JSRT_77.5.445

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

    Akihiro Narita, Masaki Ohkubo

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

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

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

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

    Contrast media & molecular imaging   2020   8831936 - 8831936   2020

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

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

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

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

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    DOI： 10.11323/jjmp.39.4_77

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

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

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

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    DOI： 10.11323/jjmp.39.2_42

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

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

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

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    DOI： 10.11323/jjmp.39.3_61

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

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

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

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

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

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    DOI： 10.1007/s12194-017-0417-2

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

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

    MEDICAL PHYSICS   44 ( 10 )   5303 - 5313   2017.10

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    DOI： 10.1002/mp.12503

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  • Magnetic Resonance Imaging of Neurotransmitter-Related Molecules Reviewed

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

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

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    DOI： 10.1272/jnms.84.160

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

    Kanazawa T, Ohkubo M, Kondo T

    European Congress of Radiology   C-1063   1 - 14   2017.3

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    DOI： 10.1594/ecr2017/C-1063

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

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

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

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    Other Link： 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 Reviewed

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

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

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    DOI： 10.1259/bjr.20160313

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

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

    MEDICAL PHYSICS   43 ( 7 )   4098 - 4105   2016.7

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    DOI： 10.1118/1.4953247

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

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

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

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

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

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

    European Congress of Radiology   C-0946   1 - 24   2015.3

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    DOI： 10.1594/ecr2015/C-0946

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

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

    European Congress of Radiology   C-1125   1 - 11   2015.3

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

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

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

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    DOI： 10.1159/000371575

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

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

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

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

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

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

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    DOI： 10.4236/ijmpcero.2014.32016

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

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

    Kakuigaku   51 ( 4 )   373 - 382   2014

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

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

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

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

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

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

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    DOI： 10.1007/s12194-013-0225-2

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

    Akihiro Kayugawa, Masaki Ohkubo, Shinichi Wada

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

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    DOI： 10.1120/jacmp.v14i4.3905

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

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

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

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

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

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

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    DOI： 10.1007/s12194-012-0150-9

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

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

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

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    DOI： 10.6009/jjrt.2012_JSRT_68.5.593

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  • 脳動脈瘤クリップにおける磁化率アーチファクトの角度依存性の検討

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

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

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

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

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

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    DOI： 10.1120/jacmp.v13i6.3868

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

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

    MEDICAL PHYSICS   38 ( 7 )   3915 - 3923   2011.7

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    DOI： 10.1118/1.3590363

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

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

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

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

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

    Igaku Butsuri   30 ( 2 )   39 - 48   2010.11

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    DOI： 10.11323/jjmp.30.2_39

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

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

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

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    DOI： 10.6009/jjrt.66.1197

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

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

    Igaku Butsuri   30 ( 1 )   3 - 9   2010.8

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    DOI： 10.11323/jjmp.30.1_3

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

    和田真一, 松本 徹, 西沢かな枝, 大久保真樹

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

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

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

    MEDICAL PHYSICS   36 ( 6 )   2089 - 2097   2009.6

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    DOI： 10.1118/1.3123762

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  • Accurate determination of CT PSF with high precision Reviewed

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

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

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    DOI： 10.1007/978-3-642-03879-2_225

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

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

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

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    DOI： 10.1007/s11517-007-0283-x

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

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

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

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

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

    CLINICAL RADIOLOGY   62 ( 4 )   376 - 381   2007.4

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    DOI： 10.1016/j.crad.2006.11.010

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

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

    JOURNAL OF NEUROSURGERY   106 ( 4 )   609 - 613   2007.4

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    DOI： 10.3171/jns.2007.106.4.609

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

    山野井理恵, 河村和紀, 岡本浩一郎, 大久保真樹

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

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

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

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

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    DOI： 10.1117/12.708888

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

    Masaki Ohkubo, Sinichi Wada, Toru Matsumoto, Kanae Nishizawa

    MEDICAL PHYSICS   33 ( 8 )   2757 - 2764   2006.8

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    DOI： 10.1118/1.2214168

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

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

    ACTA PSYCHIATRICA SCANDINAVICA   114 ( 2 )   101 - 108   2006.8

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    DOI： 10.1111/j.1600-0447.2006.00858.x

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

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

    Igaku Butsuri   26 ( 2 )   57 - 64   2006.6

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    DOI： 10.11323/jjmp2000.26.2_57

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

    Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, Kanae Nishizawa

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

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    DOI： 10.1117/12.654087

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

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

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

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

    Ohkubo M, Wada S, Saito M

    Igaku Butsuri   25 ( 3 )   132 - 140   2005.9

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

    DOI： 10.11323/jjmp2000.25.3_132

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

    N Takahashi, K Okamoto, M Ohkubo, M Kawana

    CLINICAL RADIOLOGY   60 ( 3 )   349 - 354   2005.3

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

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

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

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

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

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

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

    S Wada, M Ohkubo, T Matsumoto

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

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    DOI： 10.1117/12.596683

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

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

    Igaku Butsuri   24 ( 3 )   115 - 122   2004.12

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    DOI： 10.11323/jjmp2000.24.3_115

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

    DY Tsai, Y Lee, M Sekiya, M Ohkubo

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

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

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

    胸部CT検診   10 ( 2 )   200 - 209   2004.4

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  • spiral SPGR法の基礎的検討 Reviewed

    八木下裕子, 大越幸和, 内藤健一, 柴木充朗, 大久保真樹

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

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

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

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

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    DOI： 10.6009/jjrt.KJ00000921687

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

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

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

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    DOI： 10.6009/jjrt.KJ00003174218

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

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

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

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  • 3D FIESTA法の基礎的検討 Reviewed

    内藤健一, 大越幸和, 八木下裕子, 柴木充朗, 大久保真樹

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

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

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

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

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

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

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

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    DOI： 10.2463/mrms.1.121

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

    NAITO Kenichi, OHGSHI Yukio, INOUE Tomoko

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

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

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

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

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

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

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

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

    7 ( 2 )   265 - 270   2000.12

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

    大久保真樹, 中田 力, 松沢 等, 松田 豪

    INNERVISION   15 ( 8 )   66   2000.8

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  • 超高磁場MRI装置による顎関節画像撮影の初期検討 Reviewed

    山川智子, 大久保真樹, 羽柴正夫, 中田 力, 伊藤壽助

    日磁医誌   20 ( 2 )   80 - 92   2000.4

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

    M Ohkubo, Odano, I

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

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    DOI： 10.1007/BF02988590

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

    Odano, I, M Ohkubo, T Yokoi

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

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

    Odano, I, M Ohkubo

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

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    DOI： 10.1007/s002590050384

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

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

    Kaku Igaku   35 ( 3 )   147 - 151   1998.3

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

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

    Kakuigaku   35 ( 2 )   74 - 75   1998

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

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

    Kakuigaku   35 ( 8 )   702 - 703   1998

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

    藤田勝三, 大久保真樹, 日向浩, 酒井邦夫, 伊藤猛, 末山博男

    関越UFT研究会   10   7 - 10   1997.12

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

    6 ( 2 )   229 - 232   1997.12

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

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

    Kaku Igaku   34 ( 12 )   1111 - 1117   1997.12

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

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

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

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

    Odano, I, M Ohkubo, M Takahashi

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

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

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   34 ( 5 )   323 - 328   1997.5

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

    M Ohkubo, Odano, I, M Takahashi

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

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

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   34 ( 3 )   189 - 194   1997.3

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

    Shozo Fujita, Kunio Sakai, Shoichi Higuchi

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

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

    kyogo Nakamura, Masaki Ohkubo

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

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

    Makoto Takahashi, Ikuo Odano, Shozo Fujita, Masaki Ohkubo

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

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    DOI： 10.1007/BF03164770

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

    藤田勝三, 樋口正一, 末山博男, 酒井邦夫, 大久保真樹

    関越UFT研究会   9   21 - 24   1996.12

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

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

    NEUROLOGY   47 ( 4 )   1093 - 1095   1996.10

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    DOI： 10.1212/WNL.47.4.1093

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

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

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

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  • I-123 IMPによる新しい脳機能定量法 Reviewed

    大久保真樹, 小田野行男, 高橋 誠 他

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

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

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

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

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    DOI： 10.1097/00004647-199609000-00003

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

    小田野 行男, 大久保 真樹, 高橋 誠

    核医学   33 ( 6 )   579 - 586   1996.6

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

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

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

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

    Masaki Ohkubo

    Kakuigaku   33 ( 3 )   241 - 249   1996

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

    Masaki Ohkubo

    Kakuigaku   33 ( 6 )   647 - 654   1996

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

    藤田勝三, 大久保真樹, 酒井邦夫

    関越UFT研究会   8   9 - 14   1995.12

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

    藤田勝三, 大久保真樹, 酒井邦夫, 日向 浩

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

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

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

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

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

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

    NUCLEAR MEDICINE COMMUNICATIONS   16 ( 12 )   1026 - 1033   1995.12

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

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

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

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

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

    Ohkubo M, Odano I, Takahashi N, Sakai K

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

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

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

    CLINICAL NUCLEAR MEDICINE   20 ( 9 )   807 - 809   1995.9

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

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

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

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

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

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

    INNERVISION   9 ( 7 )   19 - 19   1994.7

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  • ５-FUと放射線の併用効果に関する基礎的研究 Reviewed

    藤田勝三, 大久保真樹, 酒井邦夫

    関越UFT研究会   7   43 - 46   1994.7

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

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

    NUCLEAR MEDICINE COMMUNICATIONS   15 ( 7 )   560 - 564   1994.7

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    DOI： 10.1097/00006231-199407000-00011

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

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

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

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

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

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

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

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

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

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

    NEUROLOGY   44 ( 3 )   557 - 559   1994.3

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

    渡邊浩之, 桑原武夫, 大久保真樹

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

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

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

    Clinical Neurology   34 ( 5 )   504 - 507   1994

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

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

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

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    DOI： 10.6009/jjrt.KJ00003326310

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

    Masaki Ohkubo, Ikuo Odano, Naoya Takahashi

    17   33 - 39   1993.11

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

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

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

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

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

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

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

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

    桑原武夫, 渡辺浩之, 辻 省次, 田中恵子, 大久保真樹

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

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

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

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

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

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

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

    Ohkubo M

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

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    DOI： 10.1620/tjem.169.215

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

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

    Kakuigaku   30 ( 2 )   189 - 196   1993

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

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

    Brain and Nerve   45 ( 10 )   941 - 944   1993

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

    Masaki Ohkubo

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

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    DOI： 10.1620/tjem.169.215

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

    大久保真樹, 藤田勝三, 酒井邦夫

    関越UFT研究会   5   37 - 41   1992.12

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

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

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

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  • DEVELOPMENT OF AN ANALOG INSTRUMENTATION WITH AC VOLTMETERS Reviewed

    Kyugo NAKAMURA, Masaki OHKUBO

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

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

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

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

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  • 154. Visualization of Aortic Valve Using Cine MRI

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

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    DOI： 10.6009/jjrt.KJ00003533684

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  • 154. Visualization of Aortic Valve Using cine MRI

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

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    DOI： 10.6009/jjrt.KJ00003500551

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  • 温熱・放射線併用療法の細胞回転に及ぼす影響 Reviewed

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

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

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

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

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

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  • 放射線とUFTの併用による実験腫瘍の増殖抑制効果 Reviewed

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

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

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

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

    104 ( 9 )   738 - 744   1990.9

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  • R-C濾波器の周波数応答測定の一つの試み Reviewed

    中村久吾, 大久保真樹

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

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

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

    INNERVISION   5 ( 6 )   7 - 8   1990.6

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

    Ito T, Sakai K, Ohkubo M, Fujita S

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

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  • Recognition of concatenated vowels by natural observation coefficients Reviewed

    Ohkubo M, Kiryu T, Saitoh Y, Iijima T

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

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

    Kiryu T, Ookubo M, Iijima T, Saitoh Y

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

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  • 有限次元の自然観測システムによる音声信号のモデル化

    木竜 徹, 大久保真樹, 斎藤義明, 飯島泰蔵

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

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  • 自然観測法における音声の調音結合・個人差の検討

    大久保真樹, 木竜 徹, 斎藤義明, 飯島泰蔵

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

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  • 咀嚼運動時のEMGにおける時変性反射係数の推定

    木竜 徹, 大久保真樹, 斉藤義明

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

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  • 筋活動様式とkパラメータとの関連性について

    木竜 徹, 大久保真樹, 斉藤義明

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

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Books

  • 学生のためのExcel

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

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

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Research Projects

  • 逐次近似再構成CT画像における高精度な空間分解能測定法の開発

    Grant number：20K08046

    2020.4 - 2024.3

    System name：科学研究費助成事業 基盤研究(C)

    Research category：基盤研究(C)

    Awarding organization：日本学術振興会

    大久保 真樹, 成田 啓廣

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

    X線CTにおける逐次近似再構成（iterative reconstruction：IR）法による画像（IR画像）の、体軸方向におけるスライス感度分布（slice sensitivity profile：SSP）の測定法の開発を行った。この考案法では、低コントラストの球体を撮像した画像を用いて、各スライス画像のスキャン平面における積分により得られた体軸方向のCT値プロファイルを用いてSSPを算出する。この算出過程において、得られたSSPからCT値プロファイルを計算し実際のプロファイルデータとの比較を行うことから、SSPの測定精度の評価（検証）も伴う手法といえる。まず、従来のフィルタ補正逆投影（filtered back-projection：FBP）法による再構成画像を用いた検討をした。すると、標準的な方法（コイン法）で測定したSSPと考案法によるSSPは非常に近い形状となり、それらの半値幅は一致する結果となった。次に、2機種のCT装置における異なるIRアルゴリズムであるiterative model reconstruction：IMR（Phlips社）およびadvanced modeled iterative reconstruction：ADMIRE（Siemens社）を用いて、スライス厚1 mmおよび2 mmの画像に考案法を適用した。その結果、いずれの条件においても得られたSSPから算出したCT値プロファイルが実際のプロファイルデータによく一致することが確認され、SSPの測定精度の高いことが示唆された。

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

    Grant number：18H02762

    2018.4 - 2023.3

    System name：科学研究費助成事業 基盤研究(B)

    Research category：基盤研究(B)

    Awarding organization：日本学術振興会

    五十嵐 博中, 大久保 真樹, 鈴木 清隆

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

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

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

    Grant number：17K09059

    2017.4 - 2020.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category：Grant-in-Aid for Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

    Ohkubo Masaki

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

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

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

    Grant number：26460722

    2014.4 - 2017.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category：Grant-in-Aid for Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

    OHKUBO Masaki, MATSUMOTO Toru, MURAO Kohei

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    Grant type：Competitive

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

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

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  • Performance evaluation of lung cancer CT screening CAD and developmant

    Grant number：25461803

    2013.4 - 2016.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category：Grant-in-Aid for Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

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

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

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

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

    Grant number：23602005

    2011.4 - 2014.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category：Grant-in-Aid for Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

    OHKUBO Masaki, WADA Shinichi, MATSUMOTO Toru, MURAO Kohei

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    Authorship：Principal investigator  Grant type：Competitive

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

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

    Grant number：20500389

    2008.4 - 2011.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Research category：Grant-in-Aid for Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

    OHKUBO Masaki, WADA Shinichi, MATSUMOTO Toru, MURAO Kohei

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    Grant type：Competitive

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

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

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  • 超高磁場MR装置を用いたプロトンスペクトロスコピーに関する基礎研究

    Grant number：10770440

    1998.4 - 2000.3

    System name：科学研究費助成事業 奨励研究(A)

    Research category：奨励研究(A)

    Awarding organization：日本学術振興会

    大久保 真樹

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    Grant type：Competitive

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

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

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

    Grant number：08457240

    1996.4 - 1999.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Research category：Grant-in-Aid for Scientific Research (B)

    Awarding organization：Japan Society for the Promotion of Science

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

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

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

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

    Grant number：06670907

    1994.4 - 1995.3

    System name：科学研究費助成事業 一般研究(C)

    Research category：一般研究(C)

    Awarding organization：日本学術振興会

    小田野 幾雄, 大久保 真樹, 中島 孝

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

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

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

    Grant number：06770699

    1994.4 - 1995.3

    System name：科学研究費助成事業 奨励研究(A)

    Research category：奨励研究(A)

    Awarding organization：日本学術振興会

    大久保 真樹

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    Grant type：Competitive

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

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

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

    Grant number：05454301

    1993.4 - 1996.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (B)

    Research category：Grant-in-Aid for General Scientific Research (B)

    Awarding organization：Japan Society for the Promotion of Science

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

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

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

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

    Grant number：04770734

    1992.4 - 1993.3

    System name：科学研究費助成事業 奨励研究(A)

    Research category：奨励研究(A)

    Awarding organization：日本学術振興会

    大久保 真樹

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    Grant type：Competitive

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

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  • MRスペクトロスコピーによる腫瘍組織の代謝に関する研究

    1991.4 - 1992.3

    System name：科学研究費助成事業

    Research category：奨励研究(A)

    大久保真樹

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    Authorship：Principal investigator  Grant type：Competitive

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

    Grant number：02805044

    1990.4 - 1991.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (C)

    Research category：Grant-in-Aid for General Scientific Research (C)

    Awarding organization：Japan Society for the Promotion of Science

    HORI Jun-ichi, OHKUBO Masaki, KIRYU Tohru

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

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

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

    Grant number：01440046

    1989.4 - 1991.3

    System name：Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (A)

    Research category：Grant-in-Aid for General Scientific Research (A)

    Awarding organization：Japan Society for the Promotion of Science

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

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

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

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Teaching Experience (researchmap)

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Teaching Experience

  • 医用システム工学実験

    2024
    Institution name：新潟大学

  • 診療画像機器学実験I

    2024
    Institution name：新潟大学

  • 診療画像機器学実験II

    2024
    Institution name：新潟大学

  • 放射線撮影技術学III

    2024
    Institution name：新潟大学

  • 診療画像機器学II

    2024
    Institution name：新潟大学

  • 診療画像機器学演習

    2024
    Institution name：新潟大学

  • 情報科学実習

    2023
    Institution name：新潟大学

  • 診療画像機器学I

    2023
    Institution name：新潟大学

  • 医学物理学特講演習

    2021
    Institution name：新潟大学

  • 医学物理学特講

    2021
    Institution name：新潟大学

  • 情報リテラシー

    2021
    Institution name：新潟大学

  • 保健学特定研究(放射線技術科学)

    2021
    Institution name：新潟大学

  • 保健学特別研究(放射線技術科学)

    2021
    Institution name：新潟大学

  • リサーチ・メソッズ・アドバンスト

    2020
    Institution name：新潟大学

  • 医療英語ベーシック(放射)

    2020
    Institution name：新潟大学

  • 放射線撮影技術学実習

    2020
    Institution name：新潟大学

  • 保健学総合

    2020
    -
    2021
    Institution name：新潟大学

  • 放射線機器工学Ⅰ

    2018
    -
    2023
    Institution name：新潟大学

  • 放射線撮影技術学演習

    2018
    -
    2023
    Institution name：新潟大学

  • 放射線機器工学Ⅱ

    2018
    -
    2023
    Institution name：新潟大学

  • 医用放射線機器科学演習

    2017
    Institution name：新潟大学

  • 医用放射線機器科学特論

    2016
    Institution name：新潟大学

  • 卒業研究

    2016
    Institution name：新潟大学

  • 医療英語(放射)

    2016
    Institution name：新潟大学

  • 医用機器工学及び演習

    2016
    -
    2023
    Institution name：新潟大学

  • 医学物理学概論

    2014
    Institution name：新潟大学

  • 放射線機器工学実験Ⅰ

    2014
    -
    2023
    Institution name：新潟大学

  • 保健学特別研究(放射線技術科学)

    2014
    -
    2019
    Institution name：新潟大学

  • 放射線機器工学実験Ⅱ

    2013
    -
    2023
    Institution name：新潟大学

  • 電子工学

    2012
    -
    2015
    Institution name：新潟大学

  • 保健学特定研究(放射線技術科学)

    2011
    -
    2017
    Institution name：新潟大学

  • スタディスキルズ (放射)

    2008
    -
    2023
    Institution name：新潟大学

  • 医療と画像技術

    2007
    Institution name：新潟大学

  • 磁気共鳴画像技術学演習

    2007
    Institution name：新潟大学

  • 放射線科学セミナー

    2007
    Institution name：新潟大学

  • 電子・システム工学実験

    2007
    -
    2023
    Institution name：新潟大学

  • 電子情報学実習

    2007
    -
    2023
    Institution name：新潟大学

  • 情報リテラシー

    2007
    -
    2019
    Institution name：新潟大学

  • 電気工学及び演習

    2007
    -
    2018
    Institution name：新潟大学

  • 入門医療英語

    2007
    -
    2018
    Institution name：新潟大学

  • 電気工学実験

    2007
    -
    2018
    Institution name：新潟大学

  • 生体機能情報解析学特講

    2007
    -
    2015
    Institution name：新潟大学

  • 生体構造機能解析工学特論

    2007
    -
    2014
    Institution name：新潟大学

  • 生体機能情報解析学特講演習

    2007
    -
    2014
    Institution name：新潟大学

  • 生体構造機能解析工学演習

    2007
    -
    2014
    Institution name：新潟大学

  • 医用物理学概論

    2007
    -
    2013
    Institution name：新潟大学

  • 医用放射線科学特別研究

    2007
    -
    2013
    Institution name：新潟大学

  • 脳学概論

    2007
    Institution name：新潟大学

  • 磁気共鳴画像技術学

    2007
    Institution name：新潟大学

  • 医用画像機器

    2007
    Institution name：新潟大学

▶ display all