Faculty Profiles - KOYAMA Shuji

Papers - KOYAMA Shuji

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A Comparison and Evaluation of Two Commercially Available Metal Artifact Reduction Applications Reviewed

JOURNAL OF NEUROENDOVASCULAR THERAPY Vol. 18 ( 8 ) page： 213 - 218 2024.6

Estimating organ dose with optimized peak dose index in cone-beam CT scans Reviewed

PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS Vol. 118 page： 103215 2024.2

EXAMINATION OF LENS EXPOSURE DOSES OF CARDIOLOGISTS, NEUROSURGEONS AND RADIOLOGISTS IN INTERVENTIONAL RADIOLOGY Reviewed

Osawa Mitsuharu, Tawada Yuka, Kaneda Naoki, Fujita Naotoshi, Koyama Shuji

RADIATION PROTECTION DOSIMETRY Vol. 198 ( 20 ) page： 1585 - 1597 2022.12

Reproducibility of functional connectivity metrics estimated from resting-state functional MRI with differences in days, coils, and global signal regression Reviewed

Kato Sanae, Bagarinao Epifanio, Isoda Haruo, Koyama Shuji, Watanabe Hirohisa, Maesawa Satoshi, Hara Kazuhiro, Katsuno Masahisa, Naganawa Shinji, Ozaki Norio, Sobue Gen

RADIOLOGICAL PHYSICS AND TECHNOLOGY Vol. 15 ( 4 ) page： 298 - 310 2022.12

Functional connector hubs in the cerebellum Reviewed

Kawabata Kazuya, Bagarinaob Epifanio, Watanabe Hirohisa, Maesawab Satoshi, Mori Daisuke, Hara Kazuhiro, Ohdake Reiko, Masuda Michihito, Ogura Aya, Kato Toshiyasu, Koyama Shuji, Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

NEUROIMAGE Vol. 257 page： 119263 2022.8

Reserve and Maintenance in the Aging Brain: A Longitudinal Study of Healthy Older Adults Reviewed

Bagarinao Epifanio, Watanabe Hirohisa, Maesawa Satoshi, Kawabata Kazuya, Hara Kazuhiro, Ohdake Reiko, Ogura Aya, Mori Daisuke, Yoneyama Noritaka, Imai Kazunori, Yokoi Takamasa, Kato Toshiyasu, Koyama Shuji, Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

ENEURO Vol. 9 ( 1 ) 2022

Effects of Head Motion on the Evaluation of Age-related Brain Network Changes Using Resting State Functional MRI. Reviewed

Kato S, Bagarinao E, Isoda H, Koyama S, Watanabe H, Maesawa S, Mori D, Hara K, Katsuno M, Hoshiyama M, Naganawa S, Ozaki N, Sobue G

Magnetic resonance in medical sciences : MRMS : an official journal of Japan Society of Magnetic Resonance in Medicine Vol. 20 ( 4 ) page： 338 - 346 2021.12

Bridging large-scale cortical networks: Integrative and function-specific hubs in the thalamus Reviewed

Kawabata Kazuya, Bagarinao Epifanio, Watanabe Hirohisa, Maesawa Satoshi, Mori Daisuke, Hara Kazuhiro, Ohdake Reiko, Masuda Michihito, Ogura Aya, Kato Toshiyasu, Koyama Shuji, Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

ISCIENCE Vol. 24 ( 10 ) page： 103106 2021.10

Distribution of scatter radiation by C-arm cone-beam computed tomography in angiographic suite: measurement of doses and effectiveness of protection devices Reviewed

Yamaji Mayako, Ishiguchi Tsuneo, Koyama Shuji, Ikeda Shuji, Kitagawa Akira, Hagihara Makiyo, Itoh Yuji, Nakamura Masaru, Ota Toyohiro, Suzuki Kojiro

NAGOYA JOURNAL OF MEDICAL SCIENCE Vol. 83 ( 2 ) page： 277 - 286 2021.5

A new cone-beam computed tomography dosimetry method providing optimal measurement positions: A Monte Carlo study Reviewed

Haba Tomonobu, Yasui Keisuke, Saito Yasunori, Kobayashi Masanao, Koyama Shuji

PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS Vol. 81 page： 130 - 140 2021.1

Identifying the brain's connector hubs at the voxel level using functional connectivity overlap ratio Reviewed

Bagarinao Epifanio, Watanabe Hirohisa, Maesawa Satoshi, Mori Daisuke, Hara Kazuhiro, Kawabata Kazuya, Ohdake Reiko, Masuda Michihito, Ogura Aya, Kato Toshiyasu, Koyama Shuji, Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

NEUROIMAGE Vol. 222 page： 117241 2020.11

Aging Impacts the Overall Connectivity Strength of Regions Critical for Information Transfer Among Brain Networks Reviewed

Bagarinao Epifanio, Watanabe Hirohisa, Maesawa Satoshi, Mori Daisuke, Hara Kazuhiro, Kawabata Kazuya, Yoneyama Noritaka, Ohdake Reiko, Imai Kazunori, Masuda Michihito, Yokoi Takamasa, Ogura Aya, Taoka Toshiaki, Koyama Shuji, Tanabe Hiroki C., Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

FRONTIERS IN AGING NEUROSCIENCE Vol. 12 page： 592469 2020.10

Automatic measurement of mandibular cortical bone width on cone-beam computed tomography images Reviewed

Mizukuchi Takashi, Naitoh Munetaka, Hishikawa Toshimitsu, Nishida Satoshi, Mitani Akio, Ariji Eiichiro, Koyama Shuji

ORAL RADIOLOGY Vol. 37 ( 3 ) page： 412 - 420 2020.8

Changes in white matter fiber density and morphology across the adult lifespan: A cross-sectional fixel-based analysis Reviewed

Choy Shao Wei, Bagarinao Epifanio, Watanabe Hirohisa, Ho Eric Tatt Wei, Maesawa Satoshi, Mori Daisuke, Hara Kazuhiro, Kawabata Kazuya, Yoneyama Noritaka, Ohdake Reiko, Imai Kazunori, Masuda Michihito, Yokoi Takamasa, Ogura Aya, Taoka Toshiaki, Koyama Shuji, Tanabe Hiroki C., Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Ozaki Norio, Sobue Gen

HUMAN BRAIN MAPPING Vol. 41 ( 12 ) page： 3198 - 3211 2020.8

ORGAN ABSORBED DOSE ESTIMATION REFLECTING SPECIFIC ORGAN MASSES WITH SIMPLE SCALING OF REFERENCE DOSES USING THE ORGAN MASSES Reviewed

Manabe Kentaro, Koyama Shuji

RADIATION PROTECTION DOSIMETRY Vol. 189 ( 4 ) page： 489 - 496 2020.5

Automatic Remasking of Digital Subtraction Angiography Images in Pulmonary Angiography Reviewed

Mizukuchi Takashi, Uemura Takeshi, Kondo Satoru, Abe Shinji, Adachi Shiro, Okumura Naoki, Kondo Takahisa, Koyama Shuji

JOURNAL OF DIGITAL IMAGING Vol. 33 ( 2 ) page： 531 - 537 2020.4

Size-specific dose estimates for various weighting factors of CTDI equation Reviewed

Haba Tomonobu, Kobayashi Masanao, Koyama Shuji

PHYSICAL AND ENGINEERING SCIENCES IN MEDICINE Vol. 43 ( 1 ) page： 155 - 162 2020.3

Reorganization of brain networks and its association with general cognitive performance over the adult lifespan Reviewed

Bagarinao Epifanio, Watanabe Hirohisa, Maesawa Satoshi, Mori Daisuke, Hara Kazuhiro, Kawabata Kazuya, Yoneyama Noritaka, Ohdake Reiko, Imai Kazunori, Masuda Michihito, Yokoi Takamasa, Ogura Aya, Taoka Toshiaki, Koyama Shuji, Tanabe Hiroki C., Katsuno Masahisa, Wakabayashi Toshihiko, Kuzuya Masafumi, Ozaki Norio, Hoshiyama Minoru, Isoda Haruo, Naganawa Shinji, Sobue Gen

SCIENTIFIC REPORTS Vol. 9 ( 1 ) page： 11352 2019.8

Study on regional activities in the human brain caused by low-level clenching and tooth separation: Investigation with functional magnetic resonance imaging

Ariji Yoshiko, Kondo Hisataka, Miyazawa Ken, Sakuma Shigemitsu, Tabuchi Masako, Kise Yoshitaka, Nakayama Miwa, Koyama Shuji, Togari Akifumi, Goto Shigemi, Ariji Eiichiro

ORAL SCIENCE INTERNATIONAL Vol. 16 ( 2 ) page： 87-94 2019.8

A novel mammographic fusion imaging technique: the first results of tumor tissues detection from resected breast tissues using energy resolved photon counting detector Reviewed

Sasaki Mariko, Koyama Shuji, Kodera Yoshie, Suzuki Reina, Kimura Hiroto, Nishide Hiroko, Mizutani Mitsuhiro, Watanabe Megumi, Yoshida Naoko, Hayashi Hiroaki, Kimoto Natsumi, Yamamoto Shuichiro, Hashimoto Daisuke, Okada Masahiro

MEDICAL IMAGING 2019: PHYSICS OF MEDICAL IMAGING Vol. 10948 2019

Importance of Considering the Response Function of Photon Counting Detectors with the Goal of Precise Material Identification Reviewed

Asakawa Takumi, Hayashi Hiroaki, Kimoto Natsumi, Asahara Takashi, Maeda Tatsuya, Koyama Shuji, Yamamoto Shuichiro, Okada Masahiro

2019 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC) 2019

未来へ繫ぐCTの線量評価技術 Invited

小山修司

インナービジョン Vol. 33 ( 10 ) page： 10-14 2018.10

Accuracy validation of incident photon fluence on detective quantum efficiency in mammography. Reviewed

Haba T, Koyama S, Otani N

Australasian physical & engineering sciences in medicine page： https://doi.org/10.1007/s13246-018-0679-y 2018.8

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

X-ray image evaluation is commonly performed by determining the detective quantum efficiency (DQE). DQE is calculated with a presampled modulation transfer function (MTF), incident photon fluence, and digital noise power spectrum (NPS). Accurate evaluation of MTF, incident photon fluence, and NPS is important for precise DQE determination. In this study, we focused on the accuracy of the incident photon fluence in mammography. The incident photon fluence is calculated using the squared signal-to-noise ratio (SNRin2) value as specified in the International Electrotechnical Commission (IEC) 62220-1-2 report. However, the reported SNRin2 values were determined using a computer program, and the reported values may differ from those calculated from an X-ray spectrum that is measured with actual mammography equipment. Therefore, we evaluated the error range of reported SNRin2 values in mammography to assess the accuracy of the incident photon fluence. First, X-ray spectra from various mammography systems were measured with a CdTe spectrometer. Six mammographic X-ray units were used in this study. Second, the SNRin2 values were calculated from the measured X-ray spectra. The calculated values were compared to the reported values. The results show that the percentage differences between the calculated and reported SNRin2 values were within -4.1% of each other. The results obtained in this study indicate that the SNRin2 values provided in the IEC report are a robust and convenient tool for calculating the incident photon fluence for DQE evaluation in mammography.

DOI： 10.1007/s13246-018-0679-y

PubMed

Using Scattered X-Rays to Improve the Estimation Accuracy of Attenuation Coefficients: A Fundamental Analysis Reviewed

Toda Naohiro, Nakagami Tetsuya, Yamazaki Yoichi, Yoshioka Hiroki, Koyama Shuji

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E101A ( 7 ) page： 1101 - 1114 2018.7

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

In X-ray computed tomography, scattered X-rays are generally removed by using a post-patient collimator located in front of the detector. In this paper, we show that the scattered X-rays have the potential to improve the estimation accuracy of the attenuation coefficient in computed tomography. In order to clarify the problem, we simplified the geometry of the computed tomography into a thin cylinder composed of a homogeneous material so that only one attenuation coefficient needs to be estimated. We then conducted a Monte Carlo numerical experiment on improving the estimation accuracy of attenuation coefficient by measuring the scattered X-rays with several dedicated toroidal detectors around the cylinder in addition to the primary X-rays. We further present a theoretical analysis to explain the experimental results. We employed a model that uses a T-junction (i.e., T-junction model) to divide the photon transport into primary and scattered components. This division is processed with respect to the attenuation coefficient. Using several T-junction models connected in series, we modeled the case of several scatter detectors. The estimation accuracy was evaluated according to the variance of the efficient estimator, i.e., the Cramer-Rao lower bound. We confirmed that the variance decreases as the number of scatter detectors increases, which implies that using scattered X-rays can reduce the irradiation dose for patients. Copyright © 2018 The Institute of Electronics, Information and Communication Engineers.

DOI： 10.1587/transfun.E101.A.1101

Web of Science

Effects of Gradient Coil Noise and Gradient Coil Replacement on the Reproducibility of Resting State Networks Reviewed

Bagarinao Epifanio, Tsuzuki Erina, Yoshida Yukina, Ozawa Yohei, Kuzuya Maki, Otani Takashi, Koyama Shuji, Isoda Haruo, Watanabe Hirohisa, Maesawa Satoshi, Naganawa Shinji, Sobue Gen

FRONTIERS IN HUMAN NEUROSCIENCE Vol. 12 page： 148 2018.4

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

The stability of the MRI scanner throughout a given study is critical in minimizing hardware-induced variability in the acquired imaging data set. However, MRI scanners do malfunction at times, which could generate image artifacts and would require the replacement of a major component such as its gradient coil. In this article, we examined the effect of low intensity, randomly occurring hardware-related noise due to a faulty gradient coil on brain morphometric measures derived from T1-weighted images and resting state networks (RSNs) constructed from resting state functional MRI. We also introduced a method to detect and minimize the effect of the noise associated with a faulty gradient coil. Finally, we assessed the reproducibility of these morphometric measures and RSNs before and after gradient coil replacement. Our results showed that gradient coil noise, even at relatively low intensities, could introduce a large number of voxels exhibiting spurious significant connectivity changes in several RSNs. However, censoring the affected volumes during the analysis could minimize, if not completely eliminate, these spurious connectivity changes and could lead to reproducible RSNs even after gradient coil replacement.

DOI： 10.3389/fnhum.2018.00148

Web of Science

PubMed

Orthodontic tooth separation activates the hypothalamic area in the human brain Reviewed

Ariji Yoshiko, Kondo Hisataka, Miyazawa Ken, Tabuchi Masako, Koyama Syuji, Kise Yoshitaka, Togari Akifumi, Gotoh Shigemi, Ariji Eiichiro

INTERNATIONAL JOURNAL OF ORAL SCIENCE Vol. 10 page： https://doi.org/10.1038/s41368-017-0001-y 2018.3

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

OBJECTIVES: An animal experiment clarified that insertion of an orthodontic apparatus activated the trigeminal neurons of the medulla oblongata. Orthodontic tooth movement is known to be associated with the sympathetic nervous system and controlled by the nucleus of the hypothalamus. However, the transmission of both has not been demonstrated in humans. The purpose of this study were to examine the activated cerebral areas using brain functional magnetic resonance imaging (MRI), when orthodontic tooth separators were inserted, and to confirm the possibility of the transmission route from the medulla oblongata to the hypothalamus.
METHODS: Two types of alternative orthodontic tooth separators (brass contact gauge and floss) were inserted into the right upper premolars of 10 healthy volunteers. Brain functional T2*-weighted images and anatomical T1-weighted images were taken. RESULTS: The blood oxygenation level dependent (BOLD) signals following insertion of a brass contact gauge and floss significantly increased in the somatosensory association cortex and hypothalamic area.
CONCLUSION: Our findings suggest the possibility of a transmission route from the medulla oblongata to the hypothalamus.

DOI： 10.1038/s41368-017-0001-y

Web of Science

Stability and linearity of luminescence imaging of water during irradiation of proton-beams and X-ray photons lower energy than the Cerenkov light threshold Reviewed

Yamamoto Seiichi, Koyama Shuji, Yabe Takuya, Komori Masataka, Tada Junki, Ito Shiori, Toshito Toshiyuki, Hirata Yuho, Watanabe Kenichi

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Vol. 883 page： 48-56 2018.3

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

Luminescence of water during irradiations of proton-beams or X-ray photons lower energy than the Cerenkov-light threshold is promising for range estimation or the distribution measurements of beams. However it is not yet obvious whether the intensities and distributions are stable with the water conditions such as temperature or addition of solvable materials. It remains also unclear whether the luminescence of water linearly increases with the irradiated proton or X-ray energies. Consequently we measured the luminescence of water during irradiations of proton-beam or X-ray photons lower energy than the Cerenkov-light threshold with different water conditions and energies to evaluate the stability and linearity of luminescence of water. We placed a water phantom set with a proton therapy or X-ray system, luminescence images of water with different conditions and energies were measured with a high-sensitivity cooled charge coupled device (CCD) camera during proton or X-ray irradiations to the water phantom. In the stability measurements, imaging was made for different temperatures of water and addition of inorganic and organic materials to water. In the linearity measurements for the proton, we irradiated with four different energies below Cerenkov light threshold. In the linearity measurements for the X-ray, we irradiated X-ray with different supplied voltages. We evaluated the depth profiles for the luminescence images and evaluated the light intensities and distributions. The results showed that the luminescence of water was quite stable with the water conditions. There were no significant changes of intensities and distributions with the different temperatures. Results from the linearity experiments showed that the luminescence of water linearly increased with their energies. We confirmed that luminescence of water is stable with conditions of water. We also confirmed that the luminescence of water linearly increased with their energies.

DOI： 10.1016/j.nima.2017.11.073

Web of Science

A proposed new image display method with high contrast-to-noise ratio using energy resolved photon-counting mammography with a CdTe series detector

Suzuki R., Nakajima A., Sasaki M., Kodera Y., Iida Y., Ito F., Koshiba Y., Yamakawa T., Yamamoto S., Okada M., Hashimoto D., Koyama S.

MEDICAL IMAGING 2018: PHYSICS OF MEDICAL IMAGING Vol. 10573 2018

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

In this study, we propose a new image display method to obtain high contrast-to-noise ratio (CNR) using energy resolved photon-counting mammography (ERPCM) with a cadmium telluride (CdTe) series detector manufactured by JOB CORPOLATION. The CdTe series detector can detect high-energy photons with high sensitivity, enabling users to image with high-energy X-rays. Using this detector, it is possible to reduce the dose given to a patient while increasing the CNR. First, the spectrum was divided into three bins and their corresponding linear attenuation coefficients were calculated from input and output photon numbers. Further, absorption vector length (AVL) and average absorption length (AAL) were calculated from the linear attenuation coefficients and from thicknesses of objects after beam-hardening correction. We further compared the CNR between ERPCM and general mammography images under the constant average glandular dose (AGD). We imaged an acrylic plate (1 mm thick) on RMI-156 phantom, determined regions of interest (ROIs) on an acrylic plate and background, and calculated the CNR. Our ERPCM generated two types of images: an AVL image and an AAL image. AMULET Innovality manufactured by FUJIFILM generated an integrated image. MicroDose SI manufactured by Philips generated a count image and removed electrical noise by the photon-counting technique. The four images, in order of decreasing CNR, were the AAL image, AVL image, MicroDose image, and AMULET image. The proposed method using ERPCM generated an image with higher CNR than images using general mammography under the constant AGD.

DOI： 10.1117/12.2292871

Web of Science

Development of energy-resolved photon-counting mammography with a cadmium telluride series detector to reduce radiation exposure and increase contrast-to-noise ratio using the high-energy X-rays

Suzuki Reina, Koyama Shuji, Kodera Yoshie, Nakajima Ai, Sasaki Mariko, Kimura Hiroto, Hayashi Hiroaki, Yamakawa Tsutomu, Yamamoto Shuichiro, Hashimoto Daisuke, Okada Masahiro

14TH INTERNATIONAL WORKSHOP ON BREAST IMAGING (IWBI 2018) Vol. 10718 2018

Identification of breast tissue using the X-ray image measured with an energy-resolved cadmium telluride series detector based on photon-counting technique

Sasaki Mariko, Koyama Shuji, Kodera Yoshie, Suzuki Reina, Nakajima Ai, Nishide Hiroko, Mizutani Mitsuhiro, Watanabe Megumi, Yoshida Naoko, Hayashi Hiroaki, Yamakawa Tsutomu, Yamamoto Shuichiro, Hashimoto Daisuke, Okada Masahiro

14TH INTERNATIONAL WORKSHOP ON BREAST IMAGING (IWBI 2018) Vol. 10718 2018

New weighting factor of weighted CTDI equation for PMMA phantom diameter from 8 to 40 cm: A Monte Carlo study Reviewed

Haba Tomonobu, Koyama Shuji, Kinomura Yutaka, Ida Yoshihiro, Kobayashi Masanao

MEDICAL PHYSICS Vol. 44 ( 12 ) page： 6603 - 6609 2017.12

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

PURPOSE:The weighted computed tomography dose index (CTDIw ) uses measured CTDI values at the center and periphery of a cylindrical phantom. The CTDIw value is calculated using conventional, Bakalyar's, and Choi's weighting factors. However, these weighting factors were produced from only 16- and 32-cm-diameter cylindrical phantoms. This study aims to devise new weighting factors to provide more accurate average dose in the central cross-sectional plane of cylindrical phantoms over a wide range of object diameters, by using Monte Carlo simulations.
METHODS:Simulations were performed by modeling a Toshiba Aquilion ONE CT scanner, in order to compute the cross-sectional dose profiles of polymethyl methacrylate (PMMA) cylindrical phantoms of each diameter (8-40 cm at 4-cm steps), for various tube voltages and longitudinal beam widths. Two phantom models were simulated, corresponding to the CTDI100 method and the method recommended by American Association of Physicists in Medicine (AAPM) task group 111. The dose-computation PMMA cylinders of 1 mm diameter were located between the phantom surfaces and the centers at intervals of 1 mm, from which cross-sectional dose profiles were calculated. By using linear least-squares fits to the obtained cross-sectional dose profiles data, we determined new weighting factors to estimate more accurate average doses in the PMMA cylindrical phantoms by using the CTDIw equation: CTDIw = Wcenter x CTDIcenter + Wperiphery * CTDIperiphery. In order to demonstrate the validity of the devised new weighting factors, the percentage difference between average dose and CTDIw value was evaluated for the weighting factors (conventional, Bakalyar's, Choi's, and devised new weighting factors) in each calculated cross-sectional dose profile.
RESULTS:With the use of linear least-squares techniques, new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8 where Wcenter and Wperiphery are weighting factors for CTDIcenter and CTDIperiphery ) were determined. The maximum percentage differences between average dose and CTDIw value were 16, -12, -8, and -6% for the conventional, Bakalyar's, Choi's, and devised new weighting factors, respectively.
CONCLUSIONS:We devised new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8) to provide more accurate average dose estimation in PMMA cylindrical phantoms over a wide range of diameter. The CTDIw equation with devised new weighting factors could estimate average dose in PMMA cylindrical phantoms with a maximum difference of -6%. The results of this study can estimate the average dose in PMMA cylindrical phantoms more accurately than the conventional weighting factors (Wcenter = 1/3 and Wperiphery = 2/3).

DOI： 10.1002/mp.12601

Web of Science

PubMed

Luminescence imaging of biological subjects during X-ray irradiations lower energy than Cerenkov-light threshold Reviewed

Yamamoto Seiichi, Koyama Shuji, Yamauchi-Kawaura Chiyo, Komori Masataka

OPTICAL REVIEW Vol. 24 ( 3 ) page： 428-435 2017.6

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

It is commonly thought that UV or visible-light luminescence imaging of biological subjects during X-ray irradiation at the energy below 120 keV is impossible because the secondary electrons produced in this energy range do not emit Cerenkov light. Contrary to this consensus, we found UV or visible-light luminescence imaging of the subjects were possible with X-ray irradiations of this energy range. We placed one of the biological subjects in a black box; visible-light luminescence images were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray irradiation at energy below 120 keV. We also conducted the imaging of air without subjects during irradiation of the same X-ray. The biological subjects emitted visible-light luminescence, and the imaging was possible with the irradiation of the X-ray below 120 keV. The luminescence images were observed in only the X-ray irradiated areas. Also air luminescence images could be obtained and the intensity of the luminescence measured from the images was proportionally increased with the exposure dose. UV or visible-light luminescence imaging of biological subjects was possible during X-ray irradiations lower energy than the Cerenkov-light threshold. The phenomenon was different from general X-ray fluorescence because wavelength of the luminescence is UV or visible-light. The luminescence imaging method is promising for estimating the irradiated area with X-ray, which could be used for interventional radiology (IVR). Also air luminescence imaging would be applied to the exposure dose distribution measurements for X-ray of diagnostic X-ray systems.

DOI： 10.1007/s10043-017-0325-z

Web of Science

Detection of microcalcifications and tumor tissue in mammography using a CdTe-series photon-counting detector

Nakajima Ai, Ihori Akiko, Nishide Hiroko, Koyama Shuji, Yamakawa Tsutomu, Yamamoto Shuichiro, Okada Masahiro, Kodera Yoshie

MEDICAL IMAGING 2017: PHYSICS OF MEDICAL IMAGING Vol. 10132 2017

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

In this study, we proposed a method for detecting microcalcifications and tumor tissue using a cadmium telluride (CdTe) series linear detector. The CdTe series detector was used as an energy resolved photon-counting (hereafter referred to as the photon-counting) mammography detector. The CdTe series linear detector and two types of phantom were designed using a MATLAB simulation. Each phantom consisted of mammary gland and adipose tissue. One phantom contained microcalcifications and the other contained tumor tissue. We varied the size of these structures and the mammary gland composition. We divided the spectrum of an x-ray, which is transmitted to each phantom, into three energy bins and calculated the corresponding linear attenuation coefficients from the numbers of input and output photons. Subsequently, the absorption vector length that expresses the amount of absorption was calculated. When the material composition was different between objects, for example mammary gland and microcalcifications, the absorption vector length was also different. We compared each absorption vector length and tried to detect the microcalcifications and tumor tissue. However, as the size of microcalcifications and tumor tissue decreased and/or the mammary gland content rate increased, there was difficulty in distinguishing them. The microcalcifications and tumor tissue despite the reduction in size or increase in mammary gland content rate can be distinguished by increasing the x-ray dosage. Therefore, it is necessary to find a condition under which a low exposure dose is optimally balanced with high detection sensitivity. It is a new method to indicate the image using photon counting technology.

DOI： 10.1117/12.2253576

Web of Science

Ｘ線ＣＴの診断参考レベル（DRL）:CTDIvolとDLP Invited

小山修司

Rad Fan Vol. 14 ( 15 ) page： 35-38 2016.11

ＣＴにおける医療被ばくの指標 Invited

小山修司

日獨医報 Vol. 61 ( 1 ) page： 13-25 2016.9

Authorship：Lead author Language：Japanese

X線CTにおける医療被ばく線量の最適化を図るための診断参考レベルとして使用されている，CTDI_vol（volume CT Dose Index）とDLP（Dose Length Product）について解説した．また，米国医学物理学会（AAPM）の提案する新しい指標である，SSDE（Size Specific Dose Estimation）についても解説した．

DOI： 13-25

Influence of 320-detector-row volume scanning and AAPM report 111 CT dosimetry metrics on size-specific dose estimate: a Monte Carlo study Reviewed

HABA Tomonobu, KOYAMA Shuji, KINOMURA Yutaka, IDA Yoshihiro, KOBAYASHI Masanao

Australasian Physical & Engineering Sciences in Medicine Vol. 39 ( 3 ) page： 697-703 2016.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The American Association of Physicists in Medicine (AAPM) task group 204 has recommended the use of size-dependent conversion factors to calculate size-specific dose estimate (SSDE) values from volume computed tomography dose index (CTDI_vol) values. However, these conversion factors do not consider the effects of 320-detector-row volume computed tomography (CT) examinations or the new CT dosimetry metrics proposed by AAPM task group 111. This study aims to investigate the influence of these examinations and metrics on the conversion factors reported by AAPM task group 204, using Monte Carlo simulations. Simulations were performed modelling a Toshiba Aquilion ONE CT scanner, in order to compute dose values in water for cylindrical phantoms with 8-40-cm diameters at 2-cm intervals for each scanning parameter (tube voltage, bow-tie filter, longitudinal beam width). Then, the conversion factors were obtained by applying exponential regression analysis between the dose values for a given phantom diameter and the phantom diameter combined with various scanning parameters. The conversion factors for each scanning method (helical, axial, or volume scanning) and CT dosimetry method (i.e., the CTDI₁₀₀ method or the AAPM task group 111 method) were in agreement with those reported by AAPM task group 204, within a percentage error of 14.2 % for phantom diameters 11.2 cm and over. The results obtained in this study indicate that the conversion factors previously presented by AAPM task group 204 can be used to provide appropriate SSDE values for 320-detector-row volume CT examinations and the CT dosimetry metrics proposed by the AAPM task group 111.

DOI： 10.1007/s13246-016-0465-7

Luminescence imaging of water during alpha particle irradiation Reviewed

Seiichi Yamamoto, Masataka Komori, Shuji Koyama, Toshiyuki Toshito

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 819 page： 6 - 13 2016.5

Luminescence imaging of water during carbon-ion irradiation for range estimation Reviewed

Seiichi Yamamoto, Masataka Komori, Takashi Akagi, Tomohiro Yamashita, Shuji Koyama, Yuki Morishita, Eri Sekihara, Toshiyuki Toshito

Medical Physics Vol. 43 ( 5 ) page： 2455 - 2463 2016.4

人体ファントムを用いた前置癒着胎盤に対する総腸骨動脈バルーン閉塞術時の胎児被曝線量の推定 Reviewed

西條貴哉，瀬口繁信，石川芳信，小山修司，祖父江亮嗣，加藤紀子

IVR会誌 Vol. 30 ( 2 ) page： 148-153 2015.6

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

胎盤は受梢卵が子宮内膜に着床することにより形成され始め,子宮底部近くに付着することが一般的であるが,その胎盤が通常よりも低位に形成され,内子宮口の全部または一部を覆っている状態を前置胎盤といい,その頻度は全分娩の0.26~0.57%といわれている')。また,その中でも胎盤と子宮との癒着が強く胎盤が剥がれない前置癒着胎盤は,前置胎盤での癒着胎盤発生率が0.04%であり,常位の癒着胎盤の発生率である 0.0045%に比べ10倍高く2),剥離する際の大量出血により出血性ショックや播種性血管内凝固症候群(DIC) を併発し母体死亡につながるリスクの高い重大な産科合併症である。そのため,前置癒着胎盤が強く疑われる患者の帝王切開術の直前には,総腸骨動脈バルーン閉塞術(commoniliacarteryballoonocclusion，以下, CIABO)が併用される。これは,局所麻酔下でバルーンカテーテルを両側の鼠径部から対側の総腸骨動脈に留置し,帝王切開の術中.胎児を取り出した後にバルーンを拡張させ.胎盤の剥離手技に伴う出血量の軽減を目的とした処置である.しかし,この手技はX線透視を使用したinterventionalradiology(以下,IVR)であり,X線照射範囲内に胎児が位置するため,母体はもとより子宮内の胎児に対してX線が照射される。胎児では成人に比べて放射線感受性が高いため,放射線被曝による影響が懸念される。しかしながら,CIABO における胎児の被曝線鼠について記述された論文はない．そこで,本研究は小型のフォトダイオード線量計を人体ファントムの各臓器位置に埋め込んだ臓器吸収線避計測システムを使用して,当院での臨床データをもとに人体ファントム内の胎児の位置における吸収纏量(以下,胎児線量)を実測し,評価するとともに.胎児線量低減方法の検討を目的とする．

DOI： 148-153

脳動脈瘤の患者がX線診断・治療・経過観察によって受ける放射線被ばく線量

瀬口繁信，西條貴哉，石川芳信，小島隆生，小山修司

脳神経外科 Vol. 43 ( 5 ) page： 411-418 2015.5

モンテカルロシミュレーションの応用-CT領域- Invited

小山修司

日本放射線技術学会雑誌 Vol. 71 ( 4 ) page： 371-379 2015.4

Authorship：Lead author Language：Japanese

放射線医療において吸収線量を評価する場合の基本は,測定器を用いた実測であることはいうまでもない.いろいろなモダリティや X 線照射の状況の中で, 多くの場合,実測値があればそれで十分評価が可能である.ところが,場合によっては,実測が困難であるとか,不可能な状況が存在する.この場合に有効なのが,モンテカルロシミュレーションである.例えば, マンモグラフィ撮影において,乳腺組織と脂肪組織が混在する場合の乳腺組織だけの吸収線量を求める場合などがそれに相当する.この場合,実際に乳房に入射する X 線の空気カーマから平均乳腺線量を求める係数は,モンテカルロシミュレーションによって求められたものである1).X 線 CT についても,少し手の込んだ線量評価を行う場合,モンテカルロシミュレーションは非常に有効なツールとなる.
モンテカルロシミュレーションには,研究者自身が一から作成するものと,物理現象を組み込んだ計算のエンジン部分が用意されていてそこにユーザが任意のシミュレーション体系や線源情報を作成して合体する汎用モンテカルロコードがある.汎用モンテカルロシミュレーションコードには,有名な Geant や MCNP, 純国産の Phits などがあるが,われわれは低エネルギー放射線の計算精度が高い汎用モンテカルロシミュレーションコード Electron Gamma Shower 5(EGS5)2) を使用しており,ここでは,この EGS5 についてと, その X 線 CT での応用について述べる.

DOI： 10.6009/jjrt.2015_JSRT_71.4.371

A Monte Carlo simulation based on measured tube current modulation data in X-ray computed tomogramphy

Masaki Inoue, Shuji Koyama, Tomonobu Haba, Tomoki Shibahara

Proceedings of the Twenty-Second EGS User's Meeting in Japan page： 14-17 2015

Regional brain activity during jaw clenching with natural teeth and with occlusal splints: a preliminary functional MRI study Reviewed

ARIJI Yoshiko, KOYAMA Shuji, SAKUMA Shigemitsu, NAKAYAMA Miwa, ARIJI Eiichirou

The Journal of Craniomandibular & Sleep Practice 2015

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

Objective: The purpose of this study was to investigate regional brain activity during jaw clenching with natural teeth and with two types of occlusal splints using functional magnetic resonance imaging (fMRI). Methods: Sixteen healthy volunteers were enrolled in this study. Blood oxygenation level-dependent (BOLD) fMRI signals were compared under three conditions: during clenching with natural teeth, with a soft splint, and with a hard splint. For each condition, 30-second jaw clenching followed a 60-second rest, and was repeated three times, with intervening 30-second rests. SPM 8 was used for the fMRI analysis.
Results: Blood oxygenation level-dependent signals during clenching with natural teeth increased in BA44, 45, and the cerebellum. Blood oxygenation level-dependent signals increased in those areas and in BA17, 18 during clenching with a soft splint. Use of the hard splint increased the BOLD signals in BA6 and BA20, 37 in addition to the areas previously mentioned. Blood oxygenation level-dependent signals in the left BA6, the left BA20, 37, and the right BA44, 45 were significantly higher during clenching with a hard splint than with natural teeth. These regions are associated with motor coordination, memory, and cognition, respectively.

DOI： 10.1179/2151090315Y.0000000017

Relationship between the tube voltage dependence of cross-sectional absorbed profile and exposed dose of superficial radiosensitive organs

Tomoki Shibahara, Shuji Koyama, Masaki Inoue, Tomonobu Haba

Proceedings of the Twenty-Second EGS User's Meeting in Japan page： 19-24 2015

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

There has been a growing concern regarding exposure to superficial radiosensitive organs with the rapid increase of computed tomography examinations. Manufacturers have been developing various dose reduction methods in order to prevent harm to these organs. Our previous study revealed a unique phenomenon in X-ray computed tomography scanning, in which the maximum absorbed dose position shifts to a deeper region from the surface in a water cylindrical phantom. We considered that this result could be applied as a dose reduction method. Therefore, in this study, we investigate the tube voltage dependence of this unique phenomenon. The results show that the peak dose position shifts to a deeper region with increasing tube voltage. The superficial radiosensitive organs can thus be protected from peak dose exposure by adjusting the tube voltage.

DOI： 19-24

DRシステムにおけるDQE測定時の各因子の測定精度に関する検討 Reviewed

國友博史，小山修司，東出了，市川勝弘，服部真澄，岡田陽子，林則夫，澤田道人

日本放射線技術学会雑誌 Vol. 70 ( 7 ) page： 653-661 2014.7

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

診断用X線装置におけるDQE測定にかかわる誤差因子とその影響について検討を行った．4種類のX線装置を用いてX線エネルギースペクトル測定に基づいた検討による光子数の推定結果から，IEC法の規定光子数は妥当であることが示された．また間接変換型FPDにおいてRQA5の線質を中心に約±5kVの範囲で，NNPSの誤差は1%以下に収まり，ある程度の管電圧誤差が許容されることが示された.また．NNPS測定における IEC法の規定する面積外の測定は，X線量子数分布の不均一による影響からDQEを過小評価する可能性が示唆された．また，エッジ法のMTF測定においては，天板上配置による拡大率の影響は無視できず，エッジデバイスと検出器との密着性の必要性が明らかとなった．

DOI： 10.6009/jjrt.2014_JSRT_70.7.653

フラットパネルディテクタによる3Dローテーションアンギオグラフィ，コーンビーム CTの被ばく線量評価 Reviewed

瀬口繁信，西條貴哉，石川芳信，小山修司

日本放射線技術学会雑誌 Vol. 70 ( 7 ) page： 646-652 2014.7

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

フラットパネルアンギオクラフィ装置による3D回転アンギオグラフィとコーンビームCTにおける組織・臓器線量測定を，人体ファントムに埋め込まれた半導体線量計により行った．これを16列MDCTと比較したところ，脳の位置の臓器線量では，コーンビームCTでMDCTの約半分の25mGy程度，３D回転アンギオグラフィではMDCTの約15分の1の3.5mGyとなった．また，放射線感受性の高い水晶体を避けるような軌道を設定することが，放射線防護に非常に有用であることが示された．

DOI： 10.6009/jjrt.2014_JSRT_70.7.646

Influence of difference in cross-sectional dose profile in a CTDI phantom on X-ray CT dose estimation : a Monte Carlo study Reviewed

HABA Tomonobu, KOYAMA Shuji, IDA Yoshihiro

Radiation Physics and Technology Vol. 7 ( 1 ) page： 133-140 2014.1

Accuracy validation of incident photon fluence on DQE for various measurement conditions and X-ray units Reviewed

HABA Tomonobu, KONDO Shimpei, HAYASHI Daiki, KOYAMA Shuji

Radiation Physics and Technology Vol. 6 ( 2 ) page： 423-430 2013.6

Investigation of Backscatter Factor in Mammography using EGS5

NUMAMOTO Hitomi, ISHII Takanori, HIRAI Yuta, KOYAMA Shuji

Proceedings of the Twentieth EGS Users' Meeting in Japan page： in press 2013

Verification of In-phantom X-ray Energy Spectra in Dual-Energy Computed Tomography

ISHII Takanori, NUMAMOTO Hitomi, HIRAI Yuta, KOYAMA Shuji

Proceedings of the Twentieth EGS Users' Meeting in Japan page： in press 2013

Estimation of glandular dose distribution in mammography using EGS5

NUMAMOTO Hitomi, HABA Tomonobu, KONDO Shinpei. HAYASHI Daiki. ISHII Takanori, KOYAMA Shuji

Proceedings of the Nineteenth EGS Users' Meeting in Japan page： 53-57 2012.10

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

The aim of this research is to analyze the absorbed dose distribution by changes of thickness of subcutaneous adipose and target-filter combination in mammography using EGS5. Assume the mammography examination, x-ray tube voltage, compression plate, breast model phantom, and image receptor were included in EGS5 code. That breast model phantom had various thicknesses of subcutaneous adipose. Our results showed that absorbed dose was a tendency to increase with thinning of the subcutaneous adipose thickness. It indicated that average glandular dose (AGD) that is recently used could have been underestimated. Also relative absorbed dose of glandular tissues tended to be low when the energy of incident x-ray became large. It indicated that target/filter combinations have strong effect to incident x-ray supectrum, so that we must choose most proper target/filter combinations that reduce the radiation dose while maintaining image contrast.

Reduction of Radiation Dose to Children in X-Ray Head CT : Investigation Using EGS5

ISHII Takanori, KONDO Shinpei, HABA Tomonobu, HAYASHI Daiki, NUMAMOTO Hitomi, KOYAMA Shuji

Proceedings of the Nineteenth EGS Users' Meeting in Japan page： 48-52 2012.10

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

In this study, the absorbed dose for organs in infant, child, and adult patients undergoing head computed tomography (CT) scans was determined. The CT examinations were simulated using the Electron Gamma Shower ver. 5 (EGS5) Monte Carlo code. The eye lens dose among child and infant patients was higher than that among adult patients by 15.0% and 69.7%, respectively. The effectiveness of a bismuth shield in reducing the eye lens dose for children undergoing head X-ray head CT scans was also evaluated. Application of a bismuth shield over the eyes of children undergoing head X-ray CT reduced the eye lens dose by 47.6% from the dose value in the case wherein shielding was not used. The use of metallic shields was found effective in reducing the radiation dose to children.

Verification of the effect of dose reduction system in computed tomography - Evaluation of organ and tissue dose distribution using EGS5 simulation -

HAYASHI Daiki, KOYAMA Shuji

Proceedings of the Nineteenth EGS Users' Meeting in Japan page： 41-47 2012.10

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

Computed tomography auto exposure control (CT-AEC) is designed to reduce exposed radiation dose and to equalize overall image quality in X-ray CT. This study aims to validate the dose reduction effect of CT-AEC with dose distribution maps created in an anthropomorphic phantom using the Electron Gamma Shower ver. 5 (EGS5) Monte Carlo simulation code. Further we actually measured the absorbed doses of each organ and tissue in the phantom with and without CT-AEC. The organ doses in the simulation result were in good agreement with the measurement results. The dose reduction effect was assessed by a comparison of dose distribution maps with and without CT-AEC. In conclusion, the results of this study revealed that the combination of dosimetry in anthropomorphic phantoms and calculation by simulation enables a detail assessment of the dose reduction effect of CT-AEC.

Verification of Pin-photo Diode Detector Characteristics Using EGS5

KONDO Shimpei, HABA Tomonobu, HAYASHI Daiki, NUMAMOTO Hitomi, ISHII Takanori, KOYAMA Shuji

Proceedings of the Nineteenth EGS Users' Meeting in Japan page： 16-20 2012.10

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

We developed a novel X-ray beam analyzing system with eight sensors using commercially available pin silicon photodiodes to estimate the effective energy and intensity of incident X-ray in each angle undergoing computerized tomography (CT). The aim of this study was to verify characteristics of photodiodes of X-ray beam analyzing system in a diagnostic energy region using Electron Gamma Shower ver.5 (EGS5). X-ray energy and angular dependence were assessed for the X-ray beam analyzing system by irradiating one of eight sensors, and which were also calculated by EGS5 under the same conditions as those considered during the measurement. Measurement results is that the output value of photodiode was correlated with any effective energy of incident X-rays, which suggested that when a sensor in the X-ray beam analyzing system is irradiated, the system can estimate the effective energy of the incident X-rays. X-ray energy and angular dependence calculated by EGS5 are in good agreement with measurement, which can be helpful in further experiments. In this study, the characteristics of photodiodes of X-ray beam analyzing system were obtained through measurement experiment, and were verified by EGS5. X-ray beam analyzing system can accurately estimate the effective energy of any incident X-rays which has any maximum energy and the shape of X-ray energy spectra.

Effectiveness of the message passing interface method in reducing computation time

HABA Tomonobu, KONDO Shimpei, HAYASHI Daiki, TAKEUCHI Akihiko, ISHII Takanori, NUMAMOTO Hitomi, KOYAMA Shuji

Proceedings of the Nineteenth EGS Users' Meeting in Japan page： 1-3 2012.10

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

In this study, we validated the effectiveness of using a message passing interface (MPI) method in reducing computation time and enhancing calculation accuracy. A chest and abdominal X-ray computed tomography scan was simulated. Our results indicated that the MPI method was accurately incorporated into the Electron Gamma Shower ver. 5 (EGS5) MC code. The MPI method could reduce computation time from 34 hours to 6 hours. We believe that MC simulation is going to be used widely. Therefore, incorporating the MPI method into EGS5 is very useful for EGS5 users.

診断X線検査による乳幼児，小児，成人の被ばく線量 — X線単純撮影の場合 Reviewed

青山隆彦，小山修司，川浦稚代，杉本成人，藤井啓輔，川崎稔生

保健物理 Vol. 47 ( 2 ) page： 130-140 2012.6

2種類の歯科用コーンビームCTの吸収線量と実効線量に関する検討 Reviewed

岡野恒一，松尾綾江，後藤賢一，横井みどり，蛭川亜紀子，奥村信次，小山修司

日本放射線技術学会雑誌 Vol. 68 ( 3 ) page： 216-225 2012.3

Comparison of Radiation Doses between Newborns and 6-y-old Children undergoing Head, Chest and Abdominal CT Examinations - a Phantom Study Reviewed

SUGIMOTO Naruto, AOYAMA Takahiko, KOYAMA Shuji, YAMAUCHI-KAWAURA Chiyo, FUJII Keisuke

Radiation Protection Dosimetry 2012

Organ Dose and Effective Dose Estimation in Paediatric Chest Radiographic Examinations by Using PIN Silicon Photodiode Dosemeters Reviewed

KAWASAKI Toshio, AOYAMA Takahiko, YAMAUCHI-KAWAURA Chiyo, FUJII Keisuke, KOYAMA Shuji

Radiation Protection Dosimetry 2012

Evaluation of Maximum Dose Position Shifting in Phantom in X-ray CT Reviewed

HABA Tomonobu, KOYAMA Shuji

Progress in NUCLEAR and TECHNOLOGY ( 3 ) page： 72-75 2012

Estimation of Effective Energy in Phantom in X-ray CT using Monte Carlo Simulation Reviewed

KONDO Shinpei, KOYAMA Shuji

Progress in NUCLEAR and TECHNOLOGY ( 3 ) page： 82-85 2012

回転パノラマ撮影装置を用いた顎関節撮影における吸収線量と実効線量 Reviewed

松尾綾江，岡野恒一，後藤賢一，横井みどり，蛭川亜紀子，奥村信次，小山修司

日本放射線技術学会雑誌 Vol. 67 ( 10 ) page： 1275-1283 2011.10

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

回転パノラマ撮影装置を用いた顎関節撮影における組織の吸収線量を測定し，さらに，異なる撮影法の相対的線量比較を行うため，予測的な線量評価として実効線量を算出した．オルビトラームス法やシュラー氏法の吸収線量と実効線量を比較し，患者の受ける線量からみたパノラマ顎関節撮影の有用性について検討した．パノラマ顎関節正面撮影はオルビトラームス法と比較して水晶体の吸収線量は1/40 であり，実効線量はオルビトラームス法小照射野と同程度で約10μSvであった．パノラマ顎関節側面撮影はシュラー氏法と比較して脳の吸収線量は低く，唾液腺は高い値を示した．実効線量はシュラー氏法中照射野と同程度で，シュラー氏法の小照射野が最も低い実効線量（5μSv）だった．

In-phantom beam quality change in x-ray CT : Detailed analysis using EGS5

KONDO Shinpei, KOYAMA Shuji

Proceedings of the Eighteenth EGS User's Meeting in Japan page： 62-67 2011.10

Detail analysis of dose distribution in phantom in X-ray CT using EGS5

HABA Tomonobu, KOYAMA Shuji

Proceedings of the Eighteenth EGS User's Meeting in Japan page： 58-61 2011.10

Simulation of X-ray CT using Monte Carlo method

MORISHITA Yuki, KOYAMA Shuji

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2010 page： USB-Memory E6 10304.pdf 2010.11

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

The purpose of this study is to calculate accurate radiation exposure doses in patient using voxel phantom and incorporating specific effects of x-ray radiation in x-ray CT examination. In x-ray CT, a special filter called beam-shaping filter is positioned in front of x-ray tube. As the other factor, CT table reduces radiation dose. These factors were measured and incorporated in simulation code of Electron Gamma Shower version 5 (EGS5). Difference of measurement and calculation based on CT Dose Index (CTDI) in an acrylic cylindrical phantom was within 2.8 %. Detailed dose distribution in the voxel anthropomorphic phantom was obtained using the simulation. Measurement and calculation of organ doses denoted the same tendency of the location in the phantom, but near the end of scan area the calculation value was smaller than the measurement value. In the measurement, organ dose was under estimated by partial irradiation of the organ at the border of scan area.

医療被ばく測定テキストにおける小さな疑問，大きなわだかまりを解決しよう-X線CT-

小山修司

日本放射線技術学会計測分科会誌 Vol. 18 ( 2 ) page： 36-40 2010.11

Estimation pf patient exposure doses using anthropomorphic phantom undergoing X-ray CT examination

MORISHITA Yuki, KOYAMA Shuji

Proceedings of the Seventeenth EGS Users' Meeting in Japan page： 82-88 2010.11

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

The purpose of this study is to calculate accurate radiation exposure doses in anthropomorphic phantom using voxel thchnique and incorporating specific effects of x-ray radiation in x-ray CT examination. In x-ray CT, a special filter called beam-shaping filter is positioned in front of x-ray tube. As the other factor, CT table reduces radiation dose. These factors were measured and incorporated in simulation code of Electron Gamma Shower version 5 (EGS5). Difference of measurement and calculation based on CT Dose Index (CTDI) in an acrylic cylindrical phantom was within 2.8 %. Detailed dose distribution in the voxel anthropomorphic phantom was obtained using the simulation. Measurement and calculation of organ doses denoted the same tendency of the location in the phantom, but near the end of scan area the calculation value was smaller than the measurement value. In the measurement, organ dose was under estimated by partial irradiation of the organ at the border of scan area.

Patient radiation dose in prospectively gated axial CT coronary angiography and retrospectively gated helical technique with a 320-detector row CT scanner Reviewed

SEGUCHI Shigenobu, AOYAMA Takahiko, KOYAMA Shuji, FUJII Keisuke, YAMAUCHI-KAWAURA Chiyo

Med Phys Vol. 37 ( 11 ) page： 5579-5585 2010.11

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

PMID: 21158269

PURPOSE: The aim of this study was to evaluate radiation dose to patients undergoing computed tomography coronary angiography (CTCA) for prospectively gated axial (PGA) technique and retrospectively gated helical (RGH) technique.

METHODS: Radiation doses were measured for a 320-detector row CT scanner (Toshiba Aquilion ONE) using small sized silicon-photodiode dosimeters, which were implanted at various tissue and organ positions within an anthropomorphic phantom for a standard Japanese adult male. Output signals from photodiode dosimeters were read out on a personal computer, from which organ and effective doses were computed according to guidelines published in the International Commission on Radiological Protection Publication 103.

RESULTS: Organs that received high doses were breast, followed by lung, esophagus, and liver. Breast doses obtained with PGA technique and a phase window width of 16% at a simulated heart rate of 60 beats per minute were 13 mGy compared to 53 mGy with RGH technique using electrocardiographically dependent dose modulation at the same phase window width as that in PGA technique. Effective doses obtained in this case were 4.7 and 20 mSv for the PGA and RGH techniques, respectively. Conversion factors of dose length product to the effective dose in PGA and RGH were 0.022 and 0.025 mSv mGy(-1) cm(-1) with a scan length of 140 mm.

CONCLUSIONS: CTCA performed with PGA technique provided a substantial effective dose reduction, i.e., 70%-76%, compared to RGH technique using the dose modulation at the same phase windows as those in PGA technique. Though radiation doses in CTCA with RGH technique were the same level as, or some higher than, those in conventional coronary angiography (CCA), the use of PGA technique reduced organ and effective doses to levels less than CCA except for breast dose.

Radiation dose evaluation in tomosynthesis and C-arm cone-beam CT examinations with an anthropomorphic phantom Reviewed

KOYAMA Shuji, AOYAMA Takahiko, ODA Nobuhiro, YAMAUCHI-KAWAURA Chiyo

Med Phys Vol. 37 ( 8 ) page： 4298-4306 2010.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Access below to see full text;
http://ir.nul.nagoya-u.ac.jp/jspui/handle/2237/14184

PMID: 20879590

PURPOSE: The objective of this study was to evaluate organ dose and the effective dose to patients undergoing tomosynthesis (TS) and C-arm cone-beam computed tomography (CBCT) examinations and to compare the doses to those in multidetector CT (MDCT) scans.

METHODS: Patient doses were measured with small sized silicon-photodiode dosimeters, 48 in number, which were implanted at various tissue and organ positions within an anthropomorphic phantom. Output signals from photodiode dosimeters were read out on a personal computer, from which organ and effective doses were computed. The doses in head, chest, abdomen, and hip-joint TS, and in head and abdomen C-arm CBCT were evaluated for routine protocols on Shimadzu TS and C-arm CBCT systems, and the doses in MDCT with the same scan regions as in TS and CBCT were on Toshiba 64-detector-row CT scanners.

RESULTS: In TS examination of the head, chest, abdomen, and hip-joint, organ doses for organs within scan ranges were 1-4 mGy, and effective doses were 0.07 mSv for the head scan and around 1 mSv for other scans. In C-arm CBCT examinations of the head and abdomen, organ doses within scan range were 2-37 mGy, and effective doses were 1.2 mSv for the head scan and 4-5 mSv for abdominal scans. Effective doses in TS examinations were approximately a factor of 10 lower, while the doses in CBCT examinations were nearly the same level, compared to the doses in the corresponding MDCT examinations.

CONCLUSIONS: TS examinations with low doses and excellent resolutions in coronal images compared to recent MDCT would widely be used in tomographic examinations of the chest, abdomen, pelvis, skeletal-joints, and knee instead of MDCT examinations with significantly high doses. Since patient dose in C-arm CBCT was nearly the same level as that in recent MDCT, the same consideration for high radiation dose would be required for the use of CBCT.

口腔および顎顔面エックス線撮影における唾液腺に着目した実効線量評価 Reviewed

岡野恒一，松尾綾江，後藤賢一，横井みどり，蛭川亜希子，奥村信次，小山修司

日本放射線技術学会雑誌 Vol. 65 ( 5 ) page： 594-602 2009.5

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

口腔外科領域の被曝線量評価のため，人体ファントム内に線量計を配置し，各部の臓器線量を求めた。これに，放射線荷重係数と組織荷重係数を乗じ積算すると実効線量となる。ICRP1990年Pub.60による組織荷重係数に対し，2007年Pub.103のそれでは，新しく唾液腺などが加わり，この前後の違いを検討した結果，前者に対して後者の実効線量は，口内撮影で1.6～4.5倍，パノラマ法で約2.2倍高くなった。

植込み型心臓ペースメーカおよび植込み型除細動器に対する診断Ｘ線の影響とその対策 Reviewed

小田敍弘，中島　博，安倍治彦，小山修司，掛田伸吾，興梠征典

日本放射線技術学会雑誌 Vol. 64 ( 7 ) page： 805-813 2008.7

Evaluation of exposure dose to patiensts undergoing catheter ablation procedures - a phantom study Reviewed

Sigenobu Seguchi, Takahiko Aoyama, Shuji Koyama, Chiyo Kawaura, Keisuke Fujii

Europian Radiology Vol. 18 page： 2559-2567 2008.5

X線CTの被曝

小山修司

総合臨床 Vol. 57 ( 4 ) page： 766-768 2008.4

Analysis of x-ray energy change at various points in two types of cylindrical phantome undergoing x-ray CT scan using monte carlo simulation

Yuya Sasada, Shuji Koyama

Proceedings of the Fourteenth EGS Users' Meeting in Japan page： 92-101 2007.11

Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal CT examinations Reviewed

Keisuke Fujii,Takahiko Aoyama, Shuji Koyama, Chiyo Kawaura

British Journal of Radiology Vol. 80 ( 8 ) page： 657-667 2007.8

動的輪郭モデルを用いた側脳室下角領域抽出法の改良 Reviewed

服部真澄，小山修司，小寺吉衞

日本放射線技術学会雑誌 Vol. 63 ( 8 ) page： 862-870 2007.8

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

アルツハイマー型痴呆を，X線CTの頭部画像より自動計測により診断支援するシステムを開発している．このシステムでは，しきい値処理に基づき，側脳室下角を自動検出しているが少なからず誤検出が見受けられた．本研究では，輪郭抽出法に着目し，動的輪郭モデルSnakesを一部改良し取り入れた．これにより，側脳室下角をより良好に抽出することができた．（小寺吉衞教授との共同研究）

Automated measurement of medial temporal lobe atrophy by computed tomography Reviewed

Masumi Hattori,Shuji Koyama,Yoshie Kodera,Yosuke Kogure,Yasushi Ido,Hirofumi Asano

International Journal of Computer Assisted Radiology and Surgery, DOI10.1007/s11548-007-0071-y page： 321-330 2007.2

人体ファントム線量計測に基づいた冠動脈造影と冠動脈インターベンション術における患者の被曝線量評価 Reviewed

瀬口繁信，青山隆彦，小山修司，川浦稚代

保健物理 Vol. 41 ( 4 ) page： 234-248 2006.12

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

狭心症や虚血性心疾患の検査や治療に用いられる冠動脈造影，冠動脈IVRでは，専用の血管造影装置を用い比較的長時間の手技を行う．近年，この手技による，放射線皮膚障害が何件か報告されており，患者被曝が問題となっている．本研究では，人体ファントムと半導体線量計による計測システムを用い，これらの手技における皮膚線量や臓器・組織線量を測定した．皮膚線量では1.4Gy程度，実効線量では最大44mGyであった．（青山隆彦教授，川浦稚代助教との共同研究）

CT被曝の評価と問題点 Invited

小山修司，青山隆彦，川浦稚代，藤井啓輔

臨床放射線 Vol. 51 ( 13 ) page： 1811-1819 2006.12

Authorship：Lead author Language：Japanese

X線CTの被曝線量評価について，従来の方法としてのCTDIやDLPによる方法と人体の被ばくを表す臓器線量の測定方法について述べた．後者の方法により測定された様々なモダリティでの臓器線量を示し，本法における様々な問題点について示した．特に，このような測定法に換えて，モンテカルロシミュレーションによる推定などがあるが，数学ファントムの体型の違いなどにより測定値と一致しないことが起こった．

Patient Exposure Dose Delivered by Modern Multi-Detector Helical Computed Tomography

Shuji Koyama,Keisuke Fujii,Takahiko Aoyama,Chiyo Kawaura

The Second Asian Oceanic Congress for Radiation Protection Proceeding(CD-ROM) page： 1376-1379 2006.10

CTDI再入門

小山修司

日本放射線技術学会計測分科会誌 Vol. 14 ( 2 ) page： 68-74 2006.10

Patient Exposure Dose Delivered by Modern Multi-Detector Helical Computed Tomography

Shuji Koyama,Keisuke Fujii,Takahiko Aoyama,Chiyo Kawaura

The Second Asian Oceanic Congress for Radiation Protection Proceeding(CD-ROM) page： 1376-1379 2006.10

Organ and Effective Dose Evaluation in Diagnostic Radiology Based on In-phantom Dose Measurements with Novel Photodiode-dosimeters Reviewed

Chiyo Kawaura,Takahiko Aoyama,Shuji Koyama,Masataka Achiwa,Masaki Mori

Radiation Protection Dosimetry Vol. 118 ( 4 ) page： 421-430 2006.1

人体ファントム内線量計測に基づいた上部消化管X線検査における被験者の被ばく線量評価 Reviewed

広藤喜章，青山隆彦，小山修司，川浦稚代

保健物理 Vol. 40 ( 4 ) page： 341-353 2005.12

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

腹部CT検査と上部消化管X線検査について，人体ファントムに線量計を埋め込んだシステムを用いて，臓器線量並びに実効線量評価を行った．腹部CT検査による実効線量は十数mSvとなるのに対して，上部消化管検査では10mSvとなり，大きな差はなかった．ただし，上部消化管検査では，膵臓など直接線のあたる部分での臓器線量が最大57mGyまで上昇することもあり．臓器ごとの分析が必要であることもわかった．

Spherical Photodiode Dosimeter for X-rays and Its Application to the Measurement of Exposure Dose in Pediatric CT Examinations

Keisuke FUjii,Takahiko Aoyama,Shuji Koyama,Chiyo Kawaura

Proceedingsof the 19th Workshop on Radiation Detectors and Their Users page： 126-135 2005.12

Organ and Effective Dose Evaluation for Pediatric and Adult Patients Undergoing CT Examinations Based on the Dosimetry within Anthropomorphic Phantoms

Takahiko Aoyama,Shuji Koyama,Chiyo Kawaura,Keisuke Fujii

Biomedizinische Technik Vol. 50 page： 1290-1291 2005.9

人体ファントム線量測定に基づいた各種頭部X線検査における患者の臓器線量および実効線量評価 Reviewed

川浦稚代，青山隆彦，小山修司

RADIOISOTOPES Vol. 54 ( 3 ) page： 55-66 2005.3

人体ファントム内の臓器線量の測定

小山修司，青山隆彦，川浦稚代

日本放射線技術学会計測分科会誌 Vol. 13 ( 1 ) page： 70-75 2005.3

Authorship：Lead author Language：Japanese

人体ファントム内の各種臓器位置に，自作の半導体線量計を配置して，X線検査による患者被曝線量を測定するシステムを開発した．ここでは，システムの概要および，代表的に使用されているX線CTによる患者体内臓器の吸収線量と，それらから計算される実効線量について解説を行った．

頭部CT画像を用いた側頭葉内側部の自動計測法の開発 Reviewed

服部真澄，小山修司

日本放射線技術学会雑誌 Vol. 60 ( 7 ) page： 993-999 2004.7

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

アルツハイマー型痴呆は，早期診断と治療薬により，その進行を遅延させる効果が期待されている．ここでは，我が国においてMRIよりも普及率が高いX線CTによる頭部横断像から，側脳室下角を自動的に抽出し，側脳室下角横径，側頭葉内側径，鈎間距離，下角面積を計測し，文献の値と比較を行った．

Evaluation of Neutron Dose to Radiotherapy Patients Treated with 10MV X-ray Beams Based on Photoneutron Spectrometry Reviewed

Takahiko Aoyama,Tetsuo Iguchi,Manabu Miyata,Yoshimune Ogata,Shuji Koyama,Hiroshi Miyahara

Vol. 39 ( 2 ) page： 130-137 2004.6

X線医学診断検査における生殖腺防護措置の有効性評価 Reviewed

川浦稚代，青山隆彦，小山修司

医学物理 Vol. 24 ( 1 ) page： 21-28 2004.3

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

腰椎や股関節部のX線撮影では，観察部分を隠さない程度に鉛板や鉛シートで生殖腺部分を覆う場合と覆わない場合がある．また，X線CTで，胸部の撮影を行う場合も，散乱線による生殖腺被曝を低減するために鉛のシートで下腹部を覆う場合と覆わない場合がある．これらの，状況について，我々の開発した臓器線量計測システムを用いて，各部臓器の線量を測定し被曝線量の多寡を比較検討した．（川浦稚代助教，青山隆彦教授との共同研究）

Visual Comparisons between Cherenkov Radiation from Water and Fluorescence from a Scintillator Reviewed

Katsuyoshi Tabushi,Tadashi Tamiya,Akira Maruhashi,Shuji Koyama,Mitsuhiko Homma,Yasunori Obata,Kouhei Shimomura,Hiroyuki Ikagawa

Vol. 23 ( 4 ) page： 215-220 2003.12

Usefulness of a Method for Changing Tube Current during Helical Scanning in Multislice CT Reviewed

Miho Kojima,Shigeki Itoh,Mitsuru Ikeda,Hiroko Satake,Shuji Koyama,Takahiko Aoyama,Naofumi Watanabe, Takeo Ishigaki

Radiation Medicine Vol. 21 ( 5 ) page： 193-204 2003.10

A Photodiode X-ray Dosimetry System for Measuring Organ Doses Delivered by Diagnostic Radiology

Shuji Koyama,Chiyo Kawaura,Takahiko Aoyama

Proceedingsof the 17th Workshop on Radiation Detectors and Their Users page： 57-65 2003.8

Influence of monitor luminance Change Reviewed

Mitsuru Ikeda, Takeo Ishigaki, Kazuhiro Shimamoto, Yoshie Kodera, Shuji Koyama, Hisashi Usami, Katsuhiko Kato

Investigative Radiology Vol. 38 ( 1 ) page： 57-63 2003.1

An in-phantom dosimetry system using pin silicon photodiode radiation sensors for measuring organ doses in x-ray CT and other diagnostic radiology Reviewed

Takahiko Aoyama, Shuji Koyama, Chiyo Kawaura

Medical Physics Vol. 29 ( 7 ) page： 1504-1510 2002.7

A method for Measuring the dose distribution of the radiotherapy domain using the computed radiography system Reviewed

Mitsuhiko Honma, Katsuyoshi Tabushi, Yasunori Obata,Tadashi Tamiya, Shuji Koyama, Takeo Ishigaki

Vol. 22 ( 2 ) page： 487-494 2002.6

アプリケータのない電子線照射野の軸外平均入射エネルギーの測定：シンチレーションファイバ電子線エネルギーモニタの利用 Reviewed

青山裕一，小山修司

日本放射線技術学会雑誌 Vol. 58 ( 6 ) page： 826-832 2002.6

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

放射線治療の手技の一つに．高エネルギー電子線を用いた全身照射法がある．全身を照射する際，装置の制約から上・下半身２回に分けて照射しなくてはならないが，その場合の照射野内の電子線エネルギー分布を，自作のエネルギーモニタで測定し検討した．その結果，電子線エネルギーは，照射野内で最大５％程度の低下しか示さず．実際の照射においては特に問題にならないことがわかった．

全身照射のためのファントムによる線量測定 Reviewed

手塚貴子，坂倉規之，小幡康範，田伏勝義，小山修司，青山裕一，下平晃代，近藤　悟

日本放射線技術学会雑誌 Vol. 58 ( 4 ) page： 511-516 2002.4

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

放射線治療で，難治性白血病の治療に用いる骨髄移植を伴う全身照射の線量評価について検討を行った．患者投与線量を正確に定めるために，通常，一辺３０ｃｍのファントムで事前に測定を行うが，ここでは人体と同程度の大きさのファントムで測定を行い，前者に比較し２％程度線量が大きくなることを示した．

ＭＲＩにおける実用ＭＴＦ測定法－エッジ法を使用して－ Reviewed

服部真澄，小山修司，前田尚利

日本放射線技術学会雑誌 Vol. 58 ( 4 ) page： 487-494 2002.4

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

磁気共鳴画像診断装置（ＭＲＩ）の性能評価の一つとして，空間分解能の測定があげられる．過去の報告において，アクリルと硫酸銅溶液の境界面を使用してエッジ法による方法が報告されているが，この方法では画像再構成時の絶対値演算において，画像にひずみを生じ正確なＭＴＦが得られない．そこで，われわれは水とサラダ油を用いた境界面で，正確なＭＴＦ測定を可能とした．

平均乳腺線量と皮膚近傍の吸収線量との比較検討

小山修司

日本放射線技術学会計測分科会誌 Vol. 10 ( 1 ) page： 61-66 2002.3

Authorship：Lead author Language：Japanese

乳房撮影において患者被曝線量を評価する方法としては，乳房全体が吸収する線量を平均的に見る平均乳腺線量という概念が使用される．一般に吸収線量は，入射表面が最も高いことが知られておりこれもあわせて評価することを提案した．また，乳房各深さでの吸収線量も深部量百分率を用いて評価した．

治療用Co-60照射装置を利用したチェレンコフ光の観察 Reviewed

日比野幸子，田宮　正，小山修司，本間光彦，田伏勝義，小幡康範

医学物理 Vol. 21 ( 2 ) page： 111-117 2001.6

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

Co-60照射装置から放出されるγ線を，水ファントムに当て，二次電子により放出される微弱なチェレンコフ光を観察する方法を開発した．チェレンコフ光は極めて微弱であるので，水槽の周りに鏡を配置して，光を集めることにより観察が可能になった．

Further reduction of radiation dose in helical CT for lung cancer screening using small tube current and a newly designed filter Reviewed

Shigeki Itoh, Shuji Koyama, Mitsuru Ikeda, Masahiro Ozaki, Akiko Sawaki, Shingo Iwano, Takeo Ishigaki

Thoracic Imaging Vol. 16 ( 2 ) page： 81-88 2001.4

Segmental cardiac function computed from ECG-gated SPECT images through solution of equations of continuity for fluids Reviewed

Hisatoshi Maeda, Shuji Koyama, Seiya Tsuchiya

Physics in Medicine and Biology Vol. 46 page： 347-367 2001.3

Evaluation of linearity for the radiophotolumi-nescence glass dosimeter based on monochromatic X-rays Reviewed

Tomohiro Shimozato, Tadashi Tamiya, Katsuyoshi Tabushi, Shuji Koyama, Setsu Yoshioka, Yasunori Obata, Masatoshi Tsuzaka, Norihiko Narita, Tomoya Uruga, Shuuichi Ban, Yoshito Namito, Toru Ikegami

Vol. 20 ( 4 ) page： 151-158 2001.2

肝細胞癌の動脈塞栓法における患者と術者の被曝測定 Reviewed

石口恒男，中村仁信，岡崎正敏，澤田　敏，高安幸生，橋本　統，林　信成，古井　滋，小山修司，前越　久

日本医学放射線学会雑誌 Vol. 60 ( 14 ) 2000.12

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

肝臓血管塞栓術によるＩＶＲにおいて患者および術者の被曝線量について，８施設での調査を行った．線量測定器には，ＴＬＤ（ＬｉＦ）を用い，これを患者皮膚入射面および術者頭部および腹部に貼付し一検査ごとに積算線量を評価した．これを８施設，各施設５症例について行いまとめた結果を検討した．

PINフォトダイオード線量計を使用したマルチスライスＸ線ＣＴ検査における胸部被曝線量の測定 Reviewed

青山隆彦，小山修司，成田憲彦，伊藤茂樹，阿知波正剛，野口由美子

日本放射線技術学会雑誌 Vol. 56 ( 12 ) page： 1437-1446 2000.12

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

Ｘ線ＣＴの患者被曝線量測定において，照射法が複雑になってきたことに伴い，ＴＬＤ等のポイント型線量計の適応性が見直されると考えられる．ただし，TLDは取り扱いが面倒であること，また，線量指示値のばらつきが大きいこと，エネルギー依存性が比較的大きいことなどから，より簡便に再現性良く使用できるポイント線量計が望まれる．我々は，市販のPINフォトダイオードを２個背中合わせに張り合わせることにより方向依存性の小さい検出器を開発した．これと人体等価胸部ファントムを用い人体各部の線量評価を行った．またこれらのデータより実効線量を試算した．

肺癌検診に用いる高速螺旋ＣＴにおける管電流可変方式の有用性 Reviewed

伊藤茂樹，小山修司，青山隆彦，尾嵜真浩，佐竹弘子，新畑昌滋

胸部ＣＴ検診 Vol. 7 ( 2 ) page： 120-123 2000.8

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

高速螺旋CTによる肺癌検診において，より適切な肺の低線量撮影を実現するために管電流可変方式による撮影法の開発を試みた．使用機種は東芝Asteionで，ヘリカルスキャン前に管電流を１回転ごとに設定することにより管電流を変化しながら撮影する機能を備えている．これを用い，肺尖部のようにＸ線吸収の大きいところでは電流を大きく，肺野部のように吸収の少ないところでは電流を小さく変化させ，ノイズ特性を良好に保ちながら被曝線量を低減することを可能にした．

長尺シンチレーションファイバ線量計によるＸ線ＣＴ検査時における積分線量飽和値の測定 Reviewed

小山修司，青山隆彦，前越　久，伊藤茂樹

日本放射線技術学会雑誌 Vol. 56 ( 6 ) page： 819-825 2000.6

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

新たに開発した長尺シンチレーションファイバ線量計と人体等価胸部ファントムを用いて螺旋軌道CTにおける患者被曝線量を測定した．検出部をＣＴ用電離箱と同じ10cmとなるように長尺シンチレーションファイバ線量計を鉛スリーブで覆うと，鉛スリーブ無しのときに比べ約30％値が小さくなった．これは，前報告の結果とも一致し，10cmのＣＴ用電離箱で測定された結果には係数1.3を乗じるとほぼ過小評価の無い結果が得られると言うことになることがわかった．

シンチレーション・ポイント線量計によるＸ線ＣＴ被曝線量の精密測定 Reviewed

青山隆彦，小山修司，前越　久

日本放射線技術学会雑誌 Vol. 56 ( 1 ) page： 87-94 2000.1

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

新たに開発したシンチレーション・ポイント線量計と独自に開発した人体等価胸部ファントムを用い，患者皮膚表面および肺野，縦隔等の被曝線量とその特徴などについて詳しく調べた．その結果，CT検査で受ける被曝線量の飽和値（ＭＳＡＤ）は最大30スキャンでも飽和値に達していないこと，ファントム表面でも前面と後面で線量値が異なること，表面よりファントム中心で線量値が大きくなることなどが判明した．

高速螺旋CTによる肺癌検診のための検討－新型被曝軽減用フィルタを応用した低線量撮影の試み－ Reviewed

伊藤茂樹，澤木明子，小山修司，前越　久，浅井英彰，尾嵜真浩，石垣武男

胸部ＣＴ検診 Vol. 6 ( 2 ) page： 163-166 1999.10

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

新たに開発したビームハードニング補正フィルタを用い低線量CT撮影被曝線量低減を図った．新型フィルタを用いた低線量撮影は肺癌検診に十分な診断能を有しており，肺癌検診に用いる高速螺旋CTの被曝線量は現行の管電流50mAよりも低く抑えることが可能であることがわかった．

シンチレーションファイバ検出器を使用したＸ線ＣＴ被曝線量計の開発 Reviewed

小山修司，青山隆彦，前越　久

日本放射線技術学会雑誌 Vol. 55 ( 10 ) page： 1027-1035 1999.10

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Ｘ線CTで，一般に行われる吸収線量（ＣＴＤＩ）測定では，アクリル円筒形ファントムに電離長10cm程度のＣＴ用電離箱が用いられる．ファントム内での吸収線量の広がりが，10cmの検出幅よりも大きく広がっているおそれがあったため，シンチレーションファイバを使用し検出長約1mの検出器を開発し，ＣＴＤＩ測定を行った結果，検出長10cmの電離箱では，全体の線量の約30％過小評価していることが明らかとなった．

ＣＴ透視法における施術者の被曝線量率の測定：ディスポーザブル鉗子を用いた被曝軽減の試み Reviewed

磯村高之，遠藤登喜子，広藤喜章，加藤力雄，小山修司，津坂昌利，前越　久，伊藤茂樹，伊藤清信，藤原寿照，石垣武男

IVR Vol. 14 ( 4 ) page： 443-448 1999.10

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

Ｘ線CTの透視モードを用いて，病変部のバイオプシが行われる．このとき，施術者は，プロテクタ等装着し放射線防護を行うが，穿刺針を操作する手指部は，その操作のため防護が困難であることに加え，高線量を受ける位置でもある．ここでは，施術者の被曝線量を低減するために，穿刺針を遠隔操作できるようディスポーザブル鉗子を用い操作を行ったところ，被曝線量を６０分の１に低減可能となった．

Breast ultrasonography:Diagnostic efficacy of a computer-aided diagnostic system using fuzzy inference Reviewed

Akiko Sawaki, Kazuhiro Shimamoto, Hiroko Satake, Takeo Ishigaki, Shuji Koyama, Yasunori Obata, Mitsuru Ikeda

Radiation Medicine Vol. 17 ( 1 ) page： 41-45 1999.2

高速螺旋ＣＴの被曝線量軽減のための新型フィルタの開発 Reviewed

伊藤茂樹，石井健裕，広瀬修宏，吉田龍彦，山田　明，臼井　喬，小山修司，前越　久，尾嵜真浩，石垣武男

胸部ＣＴ検診 Vol. 5 ( 2 ) page： 123-126 1998.9

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

高速螺旋CTの低線量撮影における被曝低減用フィルタを開発し，その使用の適否を検討した．フィルタはアルミニウム製で，中心が5.8mmの逆カマボコ型である．管電流20mAで被曝低減用フィルタ無しと管電流30mAで被曝低減用フィルタありを比較すると，後者は照射線量を低減でき，ほぼ同等の吸収線量で，ノイズが小さく，同等以上の密度分解能を有する画質を得ることができた．本フィルタは高速螺旋ＣＴの低線量撮影における被曝低減に有用である．

virtual CT endoscopy におけるstair-step artifact の現れ方について－Ｙ字型の中空アクリルファントムを使って－ Reviewed

服部真澄，棚田信春，酒井　功，小山修司

日本放射線技術学会雑誌 Vol. 54 ( 8 ) page： 953-960 1998.8

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

螺旋軌道CTを応用し，管腔臓器の内腔面を表示する方法が，virtual CT endoscopyである．この表示法を行う場合，スライス厚・テーブル移動速度の組み合わせを適切に行わないと，正常であるにもかかわらず，欠損像の形でアーチファクトが現れることがある．本研究では，どのような条件で，このアーチファクトが現れるのか，また，アーチファクトをなくすにはどうしたらよいかについて検討を行った．

実測Ｘ線スペクトルのアンフォールディング法による補正とその限界 Reviewed

加藤秀起，津坂昌利，小山修司，前越　久

日本放射線技術学会雑誌 Vol. 54 ( 5 ) page： 615-623 1998.5

Breast ultrasonography : Computer-aided diagnosis using fuzzy inference Reviewed

Shuji Koyama, Yasunori Obata, Kazuhiro Shimamoto, Takeo Ishigaki, Naohiro Ishii, Ikuo Isomoto, Katsumi Yoshine

Journal of Ultrasound in Medicine Vol. 16 page： 665-672 1997.10

A depth-dose measuring device using a multichannel scintillating fiber array for electron beam therapy Reviewed

Takahiko Aoyama, Shuji Koyama, Masatoshi Tsuzaka, Hisashi Maekoshi

Medical Physics Vol. 24 ( 8 ) page： 1235-1239 1997.8

Ｘ線光子束に対するテルル化カドミウム半導体検出器のレスポンス特性 Reviewed

加藤英起，津坂昌利，小山修司，前越　久，鈴木昇一，藤井茂久

日本放射線技術学会雑誌 Vol. 52 ( 12 ) page： 1619-1626 1996.12

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

Ｘ線光子束のエネルギースペクトルを求めるためにHP-Ge検出器が用いられる．検出器出力はGe検出器そのものの吸収スペクトルを表し，これに各エネルギーでのレスポンス補正を行うことにより入射光子束スペクトルが得られる．Geについては，このレスポンス補正のための基礎データが多数報告されているが，近年使われるようになったCdTe検出器については，このデータがほとんど無いので，モンテカルロ計算を応用し，CdTeに対するレスポンス補正を試みた．

高速螺旋CTによる肺癌検診のための基礎的検討－第三報　　低管電流とフィルタ使用による超低線量ＣＴのための基礎的検討－ Reviewed

伊藤茂樹，小山修司，津坂昌利，前越　久，佐竹弘子，石垣武男

日本医学放射線学会雑誌 Vol. 56 ( 13 ) page： 961-966 1996.11

高速螺旋CTによる肺癌検診のための基礎的検討－第一報　　ファントムによる被曝線量と画質の評価－ Reviewed

伊藤茂樹，小山修司，津坂昌利，前越　久，池田　充，太田豊裕，石口恒男，石垣武男

日本医学放射線学会雑誌 Vol. 56 ( 11 ) page： 731-735 1996.9

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

螺旋軌道ＣＴを用いて肺癌検診を行うためには，被曝線量を十分低く抑えた上で，肺癌が検出できる画質を確保する撮影条件が必要である．そのために，管電流を小さくする方法と，患者テーブル移動速度を早くする方法を試みたが，前者では比較的画像の劣化が小さかったのに対し，後者では画像劣化が大きかった．

電子線エネルギー簡易測定法の開発 Reviewed

青山隆彦，前越　久，津坂昌利，小山修司，近藤　悟，青山祐一，阿部真治

日本放射線技術学会雑誌 Vol. 52 ( 2 ) page： 422-425 1996.3

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

放射線治療に用いられる高エネルギー電子線治療装置で設定エネルギーの誤動作による事故例が報告されている．このような事故を未然に防ぐため，シンチレーションファイバーを用いて，簡便に電子線エネルギーが測定できる検出器を開発した．

A scintillating fiber beam-energy monitor for electron beam therapy Reviewed

Takahiko Aoyama, Hisashi Maekoshi, Masatoshi Tsuzaka, Shuji Koyama

Medical Physics Vol. 22 ( 12 ) page： 2101-2102 1995.12

原体照射法線量補正用多分割フィルタの基礎的特性 Reviewed

櫻井康雄，近藤　悟，阿部真治，青山裕一，成田憲彦，山口　宏，小幡康範，津坂昌利，小山修司

日本放射線技術学会雑誌 Vol. 51 ( 9 ) page： 1209-1214 1995.9

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

直線加速器で多分割絞りを用いた原体照射法においては、絞りの開度により深部線量に差が生じ、開度の大きな部分に比較して開度の小さな部分で与えられる線量が減少することが避けられない。これを補正するため可変式の多分割楔形フィルタを照射口に装着した。ここでは、可変フィルタの位置設定値と厚さの関係、可変フィルタの位置と可能な最大照射野を求め、フィルタによるビームのエネルギー変化、フィルタによる深部線量の変化などの基礎的特性につき測定を行った。

高純度ゲルマニウム半導体検出器を用いて測定したＸ線スペクトルの補正計算コードの開発 Reviewed

加藤秀起，津坂昌利，小山修司，前越　久

日本放射線技術学会雑誌 Vol. 51 ( 4 ) page： 462-468 1995.4

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

診断領域Ｘ線のエネルギースペクトル測定は，高純度ゲルマニウム半導体検出器を用いて行われる。ただし，この検出器で得られるスペクトルはゲルマニウム結晶内におけるエネルギー吸収スペクトルであるため，検出器に入射する光子のスペクトルデータを求めるには適切な補正が必要である。そこで，われわれは測定したスペクトルの補正計算コードSPCEX(Spectrum Correction code for X-rays)を開発した。本論文は，SPCEXについてその概要を説明するものである。

モンテカル法を用いた診断Ｘ線照射による人体ボクセルファントム内線量分布 Reviewed

加藤秀起，津坂昌利，小山修司，鈴木昇一，折戸武郎，前越　久，古賀佑彦

保健物理 Vol. 29 ( 4 ) page： 411-416 1994.12

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

診断Ｘ線照射による不均等な患者被曝を総括的に評価するために，被照射体内全体の吸収線量分布を正確に把握する必要がある。しかし，実際にこの線量分布を測定することは非常に困難であるため，我々は新しくモンテカルロ計算コードDDDH(Dose Distribution by Diagnostic x-ray with Human model)を用い，実際のＸ線照射に即した患者体内線量分布の評価を行った。本計算コードDDDHは，臓器線量の算出や，照射条件の違いによる患者被曝の変化の把握が容易であり，今後の医療被曝の解析に有用であると考える。

医療被曝の解析に関する研究第１報モンテカルロ計算による直方体水ファントム内の利用線錘外線量分布 Reviewed

加藤秀起，津坂昌利，小山修司，鈴木昇一，折戸武郎，前越　久，古賀佑彦

保健物理 Vol. 28 ( 3 ) page： 311-316 1993.9

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

国際放射線防護委員会の新勧告に基づく「線量拘束値」の設定に際して，患者への診断Ｘ線照射時の不均等被曝による実効線量当量を評価する必要がある。このとき，利用線束に含まれる組織の線量だけでなく，被写体内全体の吸収線量分布を把握するため，モンテカルロ法により計算を行なった。計算は，直方体水ファントムに上方から照射を行なうモデルで，照射野とＸ線エネルギーを変化させた。

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