研究者詳細 - 大久保　真樹

論文 - 大久保　真樹

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

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

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

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

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

DOI： 10.1120/jacmp.v13i6.3868

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

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

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

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

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

DOI： 10.1118/1.3590363

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

高堂裕平, 五十嵐博中, 寺島健史, 大久保真樹, 下畑享良, 岡本浩一郎, 西澤正豊, 中田力

新潟県医師会報 728 ( 728 ) 7 - 8 2010年11月

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

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

医学物理 30 ( 2 ) 39 - 48 2010年11月

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

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

DOI： 10.11323/jjmp.30.2_39

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

深谷貴広, 内藤健一, 齋藤宏明, 瀧本宗徳, 粥川啓廣, 大久保真樹

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

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

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

DOI： 10.6009/jjrt.66.1197

SSPを用いたCT画像の体軸方向空間分解能変換査読

粥川啓廣, 大久保真樹, 和田真一, 松本徹, 村尾晃平, 山本眞司

医学物理 30 ( 1 ) 3 - 9 2010年8月

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

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

DOI： 10.11323/jjmp.30.1_3

低線量MDCT検診における画質と線量の最適化のための一考察査読

和田真一, 松本徹, 西沢かな枝, 大久保真樹

日本CT検診学会誌 16 ( 3 ) 187 - 194 2009年12月

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

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

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

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

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

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

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

DOI： 10.1118/1.3123762

Accurate determination of CT PSF with high precision 査読

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

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

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

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

DOI： 10.1007/978-3-642-03879-2_225

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

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

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

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

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

DOI： 10.1007/s11517-007-0283-x

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

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

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

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

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

DOI： 10.6009/jjrt.63.1093

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

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

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

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

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

DOI： 10.1016/j.crad.2006.11.010

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

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

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

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

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

DOI： 10.3171/jns.2007.106.4.609

脳血流PET 検査における15O-H2O投与量の違いに対する画像の評価査読

山野井理恵, 河村和紀, 岡本浩一郎, 大久保真樹

新潟核医学懇話会記録集 35 22 - 26 2007年4月

The CT image standardization based on the verified PSF. 査読

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

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

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

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

DOI： 10.1117/12.708888

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

Masaki Ohkubo, Sinichi Wada, Toru Matsumoto, Kanae Nishizawa

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

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

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

DOI： 10.1118/1.2214168

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

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

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

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

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

DOI： 10.1111/j.1600-0447.2006.00858.x

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

國井正之, 和田真一, 大久保真樹, 原田正紘, 西澤かな枝, 松本徹

医学物理 26 ( 2 ) 57 - 64 2006年6月

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

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

DOI： 10.11323/jjmp2000.26.2_57

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

Shinichi Wada, Masaki Ohkubo, Toru Matsumoto, Kanae Nishizawa

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

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

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

DOI： 10.1117/12.654087

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

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

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

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

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

DOI： 10.6009/jjrt.KJ00004039788

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