Updated on 2024/02/26

写真a

 
NAKANISHI Kouhei
 
Organization
Graduate School of Medicine Assistant Professor
Graduate School
Graduate School of Medicine
Undergraduate School
School of Health Sciences
Title
Assistant Professor
Contact information
メールアドレス
External link

Degree 1

  1. 博士(医療技術学) ( 2022.3   名古屋大学 ) 

Research Areas 1

  1. Life Science / Radiological sciences  / 医学物理学

Research History 1

  1. Nagoya University   Assistant Professor

    2022.6

Professional Memberships 4

  1. 日本核医学技術学会

  2. 日本放射線技術学会

  3. 日本分子イメージング学会

  4. 日本医学物理学会

 

Papers 31

  1. A simple method to shorten the apparent dead time in the dosimetry of Lu-177 for targeted radionuclide therapy using a gamma camera Reviewed International journal

    Kohei Nakanishi, Naotoshi Fujita, Shinji Abe, Ryuichi Nishii, Katsuhiko Kato

    Physica Medica   Vol. 119   page: 103298 - 103298   2024.3

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.ejmp.2024.103298

  2. A triple-imaging-modality system for simultaneous measurements of prompt gamma photons, prompt x-rays, and induced positrons during proton beam irradiation Reviewed International journal

    Seiichi Yamamoto, Hiroshi Watabe, Kohei Nakanishi, Takuya Yabe, Mitsutaka Yamaguchi, Naoki Kawachi, Kei Kamada, Akira Yoshikawa, Masayasu Miyake, Kazuo S Tanaka, Jun Kataoka

    Physics in Medicine & Biology   Vol. 69 ( 5 ) page: 055012 - 055012   2024.2

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

    Abstract

    Objective. Prompt gamma photon, prompt x-ray, and induced positron imaging are possible methods for observing a proton beam’s shape from outside the subject. However, since these three types of images have not been measured simultaneously nor compared using the same subject, their advantages and disadvantages remain unknown for imaging beam shapes in therapy. To clarify these points, we developed a triple-imaging-modality system to simultaneously measure prompt gamma photons, prompt x-rays, and induced positrons during proton beam irradiation to a phantom. Approach. The developed triple-imaging-modality system consists of a gamma camera, an x-ray camera, and a dual-head positron emission tomography (PET) system. During 80 MeV proton beam irradiation to a polymethyl methacrylate (PMMA) phantom, imaging of prompt gamma photons was conducted by the developed gamma camera from one side of the phantom. Imaging of prompt x-rays was conducted by the developed x-ray camera from the other side. Induced positrons were measured by the developed dual-head PET system set on the upper and lower sides of the phantom. Main results. With the proposed triple-imaging-modality system, we could simultaneously image the prompt gamma photons and prompt x-rays during proton beam irradiation. Induced positron distributions could be measured after the irradiation by the PET system and the gamma camera. Among these imaging modalities, image quality was the best for the induced positrons measured by PET. The estimated ranges were actually similar to those imaged with prompt gamma photons, prompt x-rays and induced positrons measured by PET. Significance. The developed triple-imaging-modality system made possible to simultaneously measure the three different beam images. The system will contribute to increasing the data available for imaging in therapy and will contribute to better estimating the shapes or ranges of proton beam.

    DOI: 10.1088/1361-6560/ad25c6

  3. Range and light output measurements of trajectory images in a GAGG plate with different alpha particle energies Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kohei Nakanishi, Kei Kamada, Akira Yoshikawa, Jun Kataoka

    Journal of Instrumentation   Vol. 19 ( 01 ) page: P01010 - P01010   2024.1

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

    Abstract

    An imaging method that utilizes a scintillator plate combined with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera shows promise for obtaining high-resolution trajectory images. However, it is not yet clear whether the ranges of the trajectory images change with the energy of the alpha particles. Additionally, it remains unclear whether the intensity of the trajectory images is affected by the energy of the alpha particles. To address these questions in our trajectory imaging research, we conducted experiments to capture trajectory images of alpha particles with varying energy levels. To generate alpha particles with different energies, we modulated the energy using an americium-241 (Am-241) source covered with varying numbers of Mylar films. With this alpha source and imaging system, we successfully captured trajectory images with different alpha particle energies and were able to assess the ranges and intensities of these trajectories at various energy levels. The estimated ranges from the measured images with different alpha particle energies closely matched the results obtained through simulations. However, it's worth noting that the light output, as evaluated for the measured trajectory images, was slightly lower than the simulated results at lower energy levels probably due to the non-proportionality of the GAGG plate with respect to alpha particle energies.

    DOI: 10.1088/1748-0221/19/01/p01010

  4. A comparative study of EM-CCD and CMOS cameras for particle ion trajectory imaging Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kohei Nakanishi, Katsunori Yogo, Kei Kamada, Akira Yoshikawa, Jun Kataoka

    Applied Radiation and Isotopes     page: 111143 - 111143   2023.12

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

    DOI: 10.1016/j.apradiso.2023.111143

  5. Estimating blurless and noise-free Ir-192 source images from gamma camera images for high-dose-rate brachytherapy using a deep-learning approach Reviewed International journal

    Kohei Nakanishi, Seiichi Yamamoto, Takuya Yabe, Katsunori Yogo, Yumiko Noguchi, Kuniyasu Okudaira, Naoki Kawachi, Jun Kataoka

    Biomedical Physics & Engineering Express     2023.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    Abstract

    Objective: Precise monitoring of the position and dwell time of iridium-192 (Ir-192) during high-dose-rate (HDR) brachytherapy is crucial to avoid serious damage to normal tissues. Source imaging using a compact gamma camera is a potential approach for monitoring. However, images from the gamma camera are affected by blurring and statistical noise, which impact the accuracy of source position monitoring. This study aimed to develop a deep-learning approach for estimating ideal source images that reduce the effect of blurring and statistical noise from experimental images captured using a compact gamma camera.
Approach: A double pix2pix model was trained using the simulated gamma camera images of an Ir-192 source. The first model was responsible for denoising the Ir-192 images, whereas the second model performed super resolution. Trained models were then applied to the experimental images to estimate the ideal images. 
Main results: At a distance of 100 mm between the compact gamma camera and the Ir-192 source, the difference in full width at half maximum (FWHM) between the estimated and actual source sizes was approximately 0.5 mm for a measurement time of 1.5 s. This difference has been improved from approximately 2.7 mm without the use of DL. Even with a measurement time of 0.1 s, the ideal images could be estimated as accurately as in the 1.5 s measurements. This method consistently achieved accurate estimations of the source images at any position within the field of view; however, the difference increased with the distance between the Ir-192 source and the compact gamma camera.
Significance: The proposed method successfully provided estimated images from the experimental images within errors smaller than 0.5 mm at 100 mm. This method is promising for reducing blurring and statistical noise from the experimental images, enabling precise real-time monitoring of Ir-192 sources during HDR brachytherapy.

    DOI: 10.1088/2057-1976/ad0bb2

  6. Ultrahigh resolution real-time trajectory imaging of neutron induced particles in a scintillator from lithium-6 plate Reviewed International journal

    Yamamoto Seiichi, Yoshino Masao, Nakanishi Kohei, Kamada Kei, Yoshikawa Akira, Kataoka Jun

    Journal of Instrumentation   Vol. 18 ( 10 ) page: T10002 - T10002   2023.10

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

    Abstract

    It is known that a lithium-6 (<sup>6</sup>Li) absorbs a neutron and is divided into a triton and an alpha particle. However, the trajectories of the produced tritons have not yet been imaged in real time and high resolution. We developed an ultrahigh-resolution imaging system that can clearly observe the trajectories of neutron induced particles in real time. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera combined with a <sup>6</sup>Li plate and a Ce-doped Gd<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub>(GAGG) scintillator plate. Neutrons from a californium-252 (<sup>252</sup>Cf) source were irradiated to the <sup>6</sup>Li plate, which produced tritons and alpha particles. The produced tritons or alpha particles entered the GAGG plate and produced scintillation light along the trajectories. The scintillation trajectories were magnified by the unit, light intensified, and imaged by the EM-CCD camera. Using our system, we could measure the elongated trajectory images of the particles in real time. Most of these trajectories had Bragg peak like shapes in the images. The average range was 15 μm and the width was 4.6 μm FWHM. From the ranges we estimated, we found that these trajectories could be attributed to the induced tritons. Consequently, the developed real time imaging system is promising for research on the ultrahigh resolution imaging of neutron produced particles.

    DOI: 10.1088/1748-0221/18/10/t10002

  7. Sub-micrometer real-time imaging of trajectory of alpha particles using GAGG plate and CMOS camera Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kohei Nakanishi, Katsunori Yogo, Kei Kamada, Akira Yoshikawa, Nanase Koshikawa, Jun Kataoka

    Journal of Instrumentation   Vol. 18 ( 10 ) page: T10003 - T10003   2023.10

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

    Abstract

    High-resolution and real-time imaging of the trajectories of alpha particles is desired in nuclear medicine and nuclear engineering. Although an imaging method using a scintillator plate combined with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera is a possible method of obtaining high-resolution trajectory images, the spatial resolution of the system is limited to ∼2 μm. To overcome the spatial resolution limitations of this method on trajectory imaging, we used a cooled complementally metal oxide (CMOS) camera in which the sensor had a much larger number of pixels, which were also smaller. Using the CMOS camera based imaging system, we could measure the trajectories of alpha particles in real time with the spatial resolution of 0.34 μm FWHM. With smoothing of the images to reduce image noise, spatial resolution was still kept to less than 0.75 μm. We conclude that this CMOS camera-based alpha-particle trajectory-imaging system is promising for alpha-particle or other particles imaging where ultrahigh spatial resolution is required.

    DOI: 10.1088/1748-0221/18/10/t10003

  8. Development of an event-by-event based Li–ZnS(Ag) neutron imaging detector with selective neutron detection capability Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kohei Nakanishi, Kei Kamada, Akira Yoshikawa, Hiroki Tanaka, Jun Kataoka

    Applied Radiation and Isotopes     page: 111084 - 111084   2023.10

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

    DOI: 10.1016/j.apradiso.2023.111084

  9. A high-resolution real-time imaging system for observing the trajectories of neutron induced particles in a scintillator Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kohei Nakanishi, Kei Kamada, Akira Yoshikawa, Jun Kataoka

    Journal of Instrumentation   Vol. 18 ( 06 ) page: T06009 - T06009   2023.6

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

    Abstract

    High-resolution imaging of neutron induced particles is required in such methods as neutron radiography. However, the scintillation spots in a neutron-sensitive scintillator have not yet been imaged nor measured for size. We developed a high-resolution, real-time neutron induced particle imaging system for observing these particles' trajectories in a scintillator. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera combined with a lithium-containing silver-doped zinc sulfide (Li-ZnS(Ag)) scintillator plate. Neutrons from a californium-252 (<sup>252</sup>Cf) source were irradiated to the Li-ZnS(Ag) scintillator and imaged with the system. Using our system, we measured the scintillation spots of the neutron induced particles having different shapes in real time. In some of these measured scintillation spots, those with elliptical shapes were observed due to the trajectories of the particles in the scintillator. The spatial resolution calculated from the widths of the scintillation spots was ∼56 μm. Consequently, the developed imaging system is promising for research on neutron imaging that requires high spatial resolution.

    DOI: 10.1088/1748-0221/18/06/t06009

  10. Hybrid imaging of prompt x-rays and induced positrons using a pinhole gamma camera during and after irradiation of protons. Reviewed International journal

    Seiichi Yamamoto, Hiroshi Watabe, Kohei Nakanishi, Takuya Yabe, Mitsutaka Yamaguchi, Naoki Kawachi, Kei Kamada, Akira Yoshikawa, Md Rafiqul Islam, Masayasu Miyake, Kazuo S Tanaka, Jun Kataoka

    Physics in medicine and biology   Vol. 68 ( 11 )   2023.5

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

    Objective. Prompt x-ray imaging using a low-energy x-ray camera is a promising method for observing a proton beam's shape from outside the subject. Furthermore, imaging of positrons produced by nuclear reactions with protons is a possible method for observing the beam shape. However, it has not been possible to measure these two types of images with a single imaging system due to the limited imaging capability of existing systems. Imaging of both prompt x-rays and the distribution of positrons may compensate for the shortcomings of each method.Approach. We conducted imaging of the prompt x-ray using a pinhole x-ray camera during irradiation with protons in list mode. Then, after irradiation with protons, imaging of annihilation radiations from the produced positrons was conducted using the same pinhole x-ray camera in list mode. After this imaging, list-mode data were sorted to obtain prompt x-ray images and positron images.Main results. With the proposed procedure, we could measure both prompt x-ray images and induced positron images with a single irradiation by a proton beam. From the prompt x-ray images, ranges and widths of the proton beams could be estimated. The distributions of positrons were slightly wider than those of the prompt x-rays. From the time sequential positron images, we could derive the time activity curves of the produced positrons.Significance. Hybrid imaging of prompt x-rays and induced positrons using a pinhole x-ray camera was achieved. The proposed procedure would be useful for measuring prompt x-ray images during irradiation to estimate the beam structures as well as for measuring the induced positron images after irradiation to estimate the distributions and time activity curves of the induced positrons.

    DOI: 10.1088/1361-6560/acd2a2

    PubMed

  11. Comparison of organ dose from chest radiography with varying beam quality and constant exposure index Reviewed International journal

    Kohei Nakanishi

    Physical and Engineering Sciences in Medicine     2023.5

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1007/s13246-023-01281-0

    Other Link: https://rdcu.be/ddcLy

  12. Development of an ultrahigh resolution real time alpha particle imaging system for observing the trajectories of alpha particles in a scintillator Reviewed International journal

    Seiichi Yamamoto, Masao Yoshino, Kei Kamada, Ryuga Yajima, Akira Yoshikawa, Kohei Nakanishi, Jun Kataoka

    Scientific Reports   Vol. 13 ( 1 )   2023.4

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

    Abstract

    High-resolution imaging of alpha particles is required in the detection of alpha radionuclides in cells or small organs for the development of radio-compounds for targeted alpha-particle therapy or other purposes. We developed an ultrahigh resolution, real time alpha-particle imaging system for observing the trajectories of alpha particles in a scintillator. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera, combined with a 100-µm-thick Ce-doped Gd<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub> (GAGG) scintillator plate. Alpha particles from an Am-241 source were irradiated to the GAGG scintillator and imaged with the system. Using our system, we measured the trajectories of the alpha particles having different shapes in real time. In some of these measured trajectories, the line shapes of the alpha particles that flew in the GAGG scintillator were clearly observed. The lateral profiles of the alpha-particle trajectories were imaged with widths of ~ 2 µm. We conclude that the developed imaging system is promising for research on targeted alpha-particle therapy or other alpha particle detections that require high spatial resolution.

    DOI: 10.1038/s41598-023-31748-9

    Other Link: https://www.nature.com/articles/s41598-023-31748-9

  13. Optimization of the energy window setting in Ir-192 source imaging for high-dose-rate brachytherapy using a YAP(Ce) gamma camera Reviewed International journal

    Jura Nagata*, Kohei Nakanishi*, Seiichi Yamamoto, Takuya Yabe, Katsunori Yogo, Yumiko Noguchi, Kuniyasu Okudaira, Kei Kamada, Akira Yoshikawa, Jun Kataoka, (*equally contribution)

    Physica Medica   Vol. 103   page: 66 - 73   2022.11

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

    Purpose: Although real-time imaging of the high-activity iridium-192 (Ir-192) source position during high-dose -rate (HDR) brachytherapy using a high-energy gamma camera system is a promising approach, the energy window was not optimized for spatial resolution or scatter fraction.Methods: By using a list-mode data-acquisition system that can acquire energy information of a cerium-doped yttrium aluminum perovskite (YA1O3: YAP(Ce)) gamma camera, we tried to optimize the energy window's setting to improve the spatial resolution and reduce scatter fraction.Results: The spatial resolution was highest for the central energy of the window at-300 keV. The scatter fraction was also smallest for the central energy of the window at-300 keV, and the scatter fraction was more than 48 % smaller than that for the full energy window.Conclusions: We clarified that the spatial resolution can be improved and the scatter fraction can be reduced through optimizing the energy window of the YAP(Ce) gamma camera by setting the central energy of the window to-300 keV for HDR brachytherapy.

    DOI: 10.1016/j.ejmp.2022.09.017

    Web of Science

  14. Monte Carlo approach to comparison of parallel-hole collimators of clinical scintillation camera system for imaging astatine-211 (At-211) Reviewed International journal

    Kohei Nakanishi, Seiichi Yamamoto, Jun Kataoka

    JOURNAL OF INSTRUMENTATION   Vol. 17 ( 10 ) page: T10007 - T10007   2022.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    Abstract

    Astatine-211 (At-211) is a promising alpha particle emitter for targeted radionuclide therapy. Since its daughter isotope (polonium-211(Po-211)) emits characteristic X-rays of about 80 keV, the distribution of At-211 in the body can be imaged by detecting the X-rays with a scintillation camera. However, the isotopes also emit high-energy gamma photons that are collimated with difficulty for a parallel-hole collimator of a clinical scintillation camera system, and thus the selection of a collimator is important. In this study, we compared the performances of low-energy high-resolution (LEHR), low-energy all-purpose (LEAP), medium-energy (ME), and high-energy (HE) parallel-hole collimators for At-211 using Monte Carlo simulation. We simulated a clinical scintillation camera system with the collimators using the Geant4 toolkit. The energy spectra, sensitivities, and spatial resolutions for the point source of At-211 were evaluated. Moreover, we simulated imaging of six sphere sources of At-211 in a 1-cm-thick cylindrical phantom filled with At-211 solution to evaluate image contrast. All of the results in this study are simulation data. The spatial resolution with LEHR was 7.6 mm full width at half maximum (FWHM) and the highest between collimators, while the sensitivity with LEAP was 85 cps/MBq and the highest. The image contrast acquired with the ME collimator was superior to those with the other collimators. We concluded that the LEHR, LEAP, and ME collimators had their advantages, so an optimum collimator should be selected depending on the purpose of imaging of At-211, although there was no advantage in using the HE collimator for the imaging of At-211.

    DOI: 10.1088/1748-0221/17/10/T10007

    Web of Science

    Other Link: https://iopscience.iop.org/article/10.1088/1748-0221/17/10/T10007/pdf

  15. Short‐time sequential high‐energy gamma photon imaging using list‐mode data acquisition system for high‐dose‐rate brachytherapy Reviewed International journal

    Jura Nagata, Seiichi Yamamoto, Takuya Yabe, Katsunori Yogo, Kohei Nakanishi, Yumiko Noguchi, Kuniyasu Okudaira, Kei Kamada, Akira Yoshikawa, Jun Kataoka

    Medical Physics   Vol. 49 ( 12 ) page: 7703 - 7714   2022.9

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

    Purpose Measurement of the dwell time and moving speed of a high-activity iridium-192 (Ir-192) source used for high-dose-rate (HDR) brachytherapy is important for estimating the precise dose delivery to a tumor. For this purpose, we used a cerium-doped yttrium aluminum perovskite (YA1O(3):YAP(Ce)) gamma camera system, combined with a list-mode data acquisition system that can acquire short-time sequential images, and measured the dwell times and moving speeds of the Ir-192 source. Methods Gamma photon imaging was conducted using the gamma camera in list mode for the Ir-192 source of HDR brachytherapy with fixed dwell times and positions. The acquired list-mode images were sorted to millisecond-order interval time sequential images to evaluate the dwell time at each position. Time count rate curves were derived to calculate the dwell time at each source position and moving speed of the source. Results We could measure the millisecond-order time sequential images for the Ir-192 source. The measured times for the preset dwell times of 2 s and 10 s were 1.98 to 2.00 s full width at half maximum (FWHM) and 10.0 s FWHM, respectively. The dwell times at the first dwell position were larger than those at other positions. We also measured the moving speeds of the source after the dwells while moving back to the afterloader and found the speed increased with the distance from the edge of the field of view to the last dwell position. Conclusion We conclude that millisecond-order time sequential imaging of the Ir-192 source is possible by using a gamma camera and is useful for evaluating the dwell times and moving speeds of the Ir-192 source.

    DOI: 10.1002/mp.15957

    Web of Science

  16. Trials of transmission imaging using clinically used Ir-192 source for high-dose-rate brachytherapy Reviewed International journal

    J. Nagata, S. Yamamoto, K. Nakanishi, Y. Noguchi, K. Okudaira, J. Kataoka

    Journal of Instrumentation   Vol. 17 ( 06 ) page: T06009 - T06009   2022.6

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

    Abstract

    In high-dose-rate (HDR) brachytherapy, verification of an Ir-192 source's position during treatment is required. One of the methods for this used a high-energy pinhole gamma camera to image the position of the source, but the absolute position of the source cannot be measured. To confirm the absolute position, it will be useful to acquire the transmission image of a subject in addition to the gamma photon image at the same time without using an additional X-ray system. To measure the transmission images, we tried to use the high-energy gamma photons emitted from the Ir-192 source used for the therapy. We developed a high-energy gamma photon imaging system composed of 1-mm-thick Pr doped Gd<sub>2</sub>O<sub>2</sub>S (GOS), a surface mirror, and a cooled charge-coupled device (CCD) camera. The developed imaging system achieved transmission imaging of high-energy gamma photons by transporting the Ir-192 source in front of the imaging system. The spatial resolution of the imaging system was better than 2.4 mm FWHM with and without a 10-cm-thick acrylic block set between the imaging system and the source. Moderate spatial resolution and contrast images of phantoms were obtained with the system. For the dynamic imaging mode, continuous images of the phantoms were measured with 1-sec intervals. There was no observable difference in the transmission images by the movement of the Ir-192 source. Transmission imaging of subjects using an Ir-192 source for HDR brachytherapy could be achieved using our developed imaging system. The system offers a new method to measure the real-time transmission images of the subject during HDR brachytherapy.

    DOI: 10.1088/1748-0221/17/06/t06009

    Other Link: https://iopscience.iop.org/article/10.1088/1748-0221/17/06/T06009/pdf

  17. In-vivo imaging of a mouse by detecting bremsstrahlung X-rays from 14C using a La-GPS imaging system Reviewed International journal

    Seiichi Yamamoto, Hideki Tomita, Ryohei Terabayashi, Kenji Yoshida, Kouhei Nakanishi, Takako Furukawa, Kei Kamada, Akira Yoshikawa

    Journal of Nuclear Science and Technology   Vol. 59 ( 11 ) page: 1 - 12   2022.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Informa {UK} Limited  

    Imaging of 14C outside of the subject is considered to be difficult because it is a radionuclide that emits only low-energy beta particles. However, we found that bremsstrahlung X-rays form 14C could be imaged from outside of subjects and is thus applicable to in vivo small animal imaging. We developed a high-resolution low-energy X-ray imaging system using a (Gd, La)2Si2O7:Ce(La-GPS) plate combined with a flat panel photomultiplier tube (FP-PMT) for in vivo imaging of a mouse to detect the X-rays from a 14C solution administered. Without using a parallel hole collimator, accumulated 14C in the mouse’s abdomen was imaged in 1 min and dynamic in vivo imaging was possible although the spatial resolution was moderate. With a parallel hole collimator, 14C in the abdomen was obtained with a higher spatial resolution with a 60-min acquisition time. We conclude that in vivo imaging of 14C is possible by using the developed high-resolution La-GPS imaging system and may be promising for molecular imaging research.

    DOI: 10.1080/00223131.2022.2050319

    Web of Science

    Scopus

  18. Prediction of CT Images from PET Images Using Deep Learning Approach for Small Animal Systems International journal

    Kouhei Nakanishi, Seiichi Yamamoto, Tadashi Watabe

    2021 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)     2021.10

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    Authorship:Lead author   Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    DOI: 10.1109/nss/mic44867.2021.9875591

  19. Comparison of the distributions of bremsstrahlung X-rays, Cerenkov light, and annihilation radiations for positron emitters Reviewed International journal

    Kouhei Nakanishi, Seiichi Yamamoto

    Applied Radiation and Isotopes   Vol. 176   page: 109861 - 109861   2021.10

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    DOI: 10.1016/j.apradiso.2021.109861

    Web of Science

    Scopus

    PubMed

  20. Monte Carlo study of a small field of view YAlO3:Ce pinhole camera for imaging with Rb-82 by detection of bremsstrahlung X-rays Reviewed International journal

    K. Nakanishi, S. Yamamoto

    Journal of Instrumentation   Vol. 16 ( 08 )   2021.8

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.1088/1748-0221/16/08/t08005

    Web of Science

    Scopus

  21. Performance evaluation of YAlO3 scintillator plates with different Ce concentrations Reviewed International journal

    Kohei Nakanishi, Seiichi Yamamoto, Kei Kamada, Akira Yoshikawa

    Applied Radiation and Isotopes   Vol. 168   page: 109483 - 109483   2021.2

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    Since Ce-doped YAlO3 (YAP(Ce)) scintillators have small non-proportionality, it is useful to develop a radiation imaging detector for low-energy gamma photons or X-rays. However, the YAP(Ce) performance with different Ce concentrations remains unclear. Consequently, we measured the basic performance of YAP(Ce) plates with different Ce concentrations. We used three types of YAP(Ce) scintillator plates with different Ce concentrations: 0.05% Ce, 1% Ce, and 2% Ce. The YAP(Ce) plates were 10 mm × 10 mm x 0.5 mm. We measured and compared the energy spectra, the decay times, the α-γ ratio, and the non-proportionality. We also evaluated the relation between these performances and the Ce concentrations. The light output of a YAP(Ce) showed positive correlation with the Ce concentrations, and the decay time of the YAP(Ce) showed a negative correlation with them. The energy resolution slightly improved for a YAP(Ce) with higher Ce concentrations. We found the α-γ ratio were slightly larger for higher Ce concentrations. The YAP(Ce) plate with a 2% Ce had the highest light output and the best energy resolution as well as the shortest decay time. Based on these results, the YAP(Ce) plate with a concentration of 2% Ce is a better selection for the development of radiation detectors or radiation imaging detectors for low-energy gamma photons or X-rays as well as alpha particles.

    DOI: 10.1016/j.apradiso.2020.109483

    Scopus

    PubMed

  22. Development of high‐resolution YAP(Ce) x‐ray camera for the imaging of astatine‐211(At‐211) in small animals Reviewed International journal

    Kouhei Nakanishi, Seiichi Yamamoto, Tadashi Watabe, Kazuko Kaneda-Nakashima, Yoshifumi Shirakami, Kazuhiro Ooe, Atsushi Toyoshima, Atsushi Shinohara, Takahiro Teramoto, Jun Hatazawa, Kei Kamada, Akira Yoshikawa

    Medical Physics   Vol. 47 ( 11 ) page: 5739 - 5748   2020.11

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

    Purpose: Astatine-211 (At-211) is a promising alpha emitter for radionuclide therapy. High-resolution in vivo imaging of At-211 in small animals is needed for the development of At-211 radiopharmaceuticals. For this purpose, we developed a low-energy x-ray camera using a thin YAlO3:Ce (YAP(Ce)) plate to image the low-energy x rays (73–87 keV) from the daughter radionuclide of At-211 (Po-211). Method: We optically coupled a 38 × 38 × 1-mm YAP (Ce) plate to a position-sensitive photomultiplier (PSPMT) to develop an imaging detector. A pinhole or a parallel hole collimator was attached to the imaging detector, and the performance was measured for 60-keV gamma photons. With the developed x-ray camera, we carried out imaging of a mouse that had been administered At-211-NaAt. Results: The intrinsic spatial resolution of the YAP (Ce) x-ray camera was approximately 1.2 mm FWHM, and the energy resolution was 22% FWHM. With a 5-mm-thick parallel hole collimator, the spatial resolution was 3.8 mm FWHM with a sensitivity of 8 × 10−4 at 10 mm, which is a typical distance from the surface of the collimator to a subject in mouse imaging. Using a 1-mm diameter pinhole collimator, the spatial resolution was 1.8 mm FWHM with a sensitivity of 3.5 × 10−4 at 10 mm from the collimator. In the mouse images measured by the developed x-ray camera, we could clearly observe that the At-211 accumulated in the thyroid gland and the stomach of the mouse. Conclusion: We concluded that the YAP (Ce) x-ray camera is useful for in vivo imaging of At-211.

    DOI: 10.1002/mp.14455

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    PubMed

  23. Monte Carlo simulation of the bremsstrahlung X-rays emitted from H-3 and C-14 for the in-vivo imaging of small animals Reviewed International journal

    Kouhei Nakanishi, Seiichi Yamamoto

    Applied Radiation and Isotopes   Vol. 160   page: 109136 - 109136   2020.6

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    DOI: 10.1016/j.apradiso.2020.109136

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    PubMed

  24. Imaging of bremsstrahlung X-rays from tritium water in a plastic bag using a LaGPS radiation imaging system Reviewed International journal

    S. Yamamoto, K. Nakanishi, T. Furukawa, H. Tomita, K. Kamada, A. Yoshikawa

    Journal of Instrumentation   Vol. 15 ( 04 ) page: P04006 - P04006   2020.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    Tritium (H-3) is a pure beta-emitting radionuclide and beta particles have extremely low energy (maximum energy: 18.6 keV). Thus the in-vivo imaging of H-3 is thought to be impossible. However, beta particles emit bremsstrahlung X-rays in subjects that may be imaged from outside of the subjects. We tried to image the bremsstrahlung X-rays from H-3 water using a newly developed radiation imaging system. The developed imaging system used a pixelated Ce-doped (Gd, La)2Si2O7 (LaGPS) scintillator plate optically coupled to a flat-panel position-sensitive photomultiplier tube (FP-PMT). Using the imaging system, we conducted bremsstrahlung X-ray imaging from H-3 water in a plastic bag with 37-MBq radioactivity. We obtained tungsten slit mask images with a spatial resolution of ∼3 mm full width at half maximum (FWHM). The energy spectrum of the bremsstrahlung X-rays from the H-3 water showed a broad distribution with an average energy of ∼10 keV. The measured sensitivities of the LaGPS imaging system for bremsstrahlung X-rays from H-3 water in a plastic bag were 1.8 × 10-7. We conclude that the imaging of bremsstrahlung X-rays from H-3 water was really possible and it has a potential to be a new method for the in-vivo H-3 imaging of small animals, plants, or materials.

    DOI: 10.1088/1748-0221/15/04/p04006

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  25. Feasibility evaluation of a direct detection method of alpha particles in water using YGAG plate with pulse shape analysis Reviewed International journal

    S. Yamamoto, K. Nakanishi, S. Terazawa

    Journal of Instrumentation   Vol. 14 ( 10 ) page: P10013 - P10013   2019.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.1088/1748-0221/14/10/p10013

  26. Comparison of Noise Equivalent Count Rates (NECRs) for the PET Systems With Different Ring Diameter and Electronics Reviewed International journal

    Kouhei Nakanishi, Yoshiyuki Hirano, Seiichi Yamamoto

    IEEE Transactions on Radiation and Plasma Medical Sciences   Vol. 3 ( 3 ) page: 371 - 376   2019.5

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Institute of Electrical and Electronics Engineers ({IEEE})  

    DOI: 10.1109/trpms.2018.2876410

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  27. Possibility analysis of bremsstrahlung x-ray imaging of C-14 radionuclide using a LaGPS radiation imaging system Reviewed International journal

    Seiichi Yamamoto, Kouhei Nakanishi, Takako Furukawa, Hideki Tomita

    Biomedical Physics & Engineering Express   Vol. 5 ( 3 ) page: 035024 - 035024   2019.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.1088/2057-1976/ab12bd

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  28. Development of a circular shape Si-PM-based detector ring for breast-dedicated PET system Reviewed International journal

    Nakanishi, K., Yamamoto, S., Watabe, H., Abe, S., Fujita, N., Kato, K.

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   Vol. 880   page: 118 - 124   2018

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

    DOI: 10.1016/j.nima.2017.10.052

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  29. Estimation of optimum scintillator thickness of Si-PM detectors for time-of-flight (TOF)-PET Reviewed International coauthorship International journal

    Kouhei Nakanishi, Kanako Kodani, Jung Yeol Yeom, Seiichi Yamamoto

    Biomedical Physics &amp; Engineering Express   Vol. 3 ( 2 ) page: 027002 - 027002   2017.3

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:{IOP} Publishing  

    DOI: 10.1088/2057-1976/aa635e

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  30. Performance comparison of finely pixelated LYSO- and GAGG-based Si-PM gamma cameras for high resolution SPECT Reviewed International journal

    Nakanishi, K., Yamamoto, S., Kataoka, J.

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   Vol. 872   page: 107 - 111   2017

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

    Although Lu-based scintillators, including Ce-doped Lu1.8Y0.2SiO5 (LYSO) scintillators, are often used for positron emission tomography (PET) detectors, they are not commonly used in gamma cameras for single-photon emission computed tomography (SPECT) because background counts due to contamination of the natural radioisotope in Lu are detected. However, several studies report that deterioration in image contrast due to background counts of the natural radioisotope is not critical and thus LYSO is promising for use in SPECT detectors. Meanwhile, a new scintillator, the Ce-doped Gd3Al2Ga3O12 (GAGG) with a high light yield and no natural radioisotope, has been developed and is also thought to be a promising scintillator. Thus, we compared the performance of LYSO with that of GAGG to determine which is more appropriate for a silicon photomultiplier (Si-PM)-based high-resolution small field-of-view (FOV) gamma camera for SPECT. We used finely pixelated LYSO and GAGG plates that were optically coupled to Si-PM arrays to form gamma cameras and measured the basic performance for 122-keV gamma photons. The energy resolutions of the LYSO- and GAGG-based Si-PM gamma cameras were 30% and 23% full width at half maximum (FWHM), respectively. The intrinsic spatial resolution of the GAGG (∼0.5mm FWHM) based gamma camera was better than that of the LYSO (∼0.6mm FWHM). The background counts of the LYSO-based gamma camera were 28 times larger than that of the GAGG. Based on these results, we conclude that GAGG is more appropriate than LYSO for the development of a Si-PM based gamma camera for high resolution SPECT.

    DOI: 10.1016/j.nima.2017.08.013

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  31. Development of an angled Si-PM-based detector unit for positron emission mammography (PEM) system Reviewed International journal

    Nakanishi, K., Yamamoto, S.

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   Vol. 837   page: 171 - 177   2016

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

    DOI: 10.1016/j.nima.2016.09.014

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MISC 1

  1. 鉛玉を用いたMRI用不均一磁場補正padの有用性評価—Evaluation of usefulness of pad filled with lead sphere to correct inhomogeneous magnetic field for MRI Reviewed

      Vol. 69 ( 2 ) page: 142 - 149   2022.2

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Rapid communication, short report, research note, etc. (scientific journal)  

    CiNii Books

Research Project for Joint Research, Competitive Funding, etc. 1

  1. 放射線治療用放射性同位元素イリジウム-192 (Ir-192)の位置を三次元的にモニタリングするための深層学習プログラムの開発

    2023.4 - 2024.3

    中島記念国際交流財団  日本人若手研究者研究助成金 

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    Authorship:Principal investigator  Grant type:Competitive

KAKENHI (Grants-in-Aid for Scientific Research) 2

  1. Lu-177標識薬剤のガンマカメラ撮像定量性向上のための新規撮像法開発

    Grant number:23K14863  2023.4 - 2025.3

    日本学術振興会  科学研究費助成事業 若手研究  若手研究

    中西 恒平

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    Authorship:Principal investigator 

    Grant amount:\4680000 ( Direct Cost: \3600000 、 Indirect Cost:\1080000 )

  2. Medical application of luminescence of water lower energy than Cherenkov-light threshold

    Grant number:22H03019  2022.4 - 2027.3

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

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    Authorship:Coinvestigator(s)