277 results on '"Fumihiko, Nishikido"'
Search Results
2. Development of a Two-Layer Staggered GAGG Scatter Detector for Whole Gamma Imaging
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Sodai Takyu, Hideaki Tashima, Taiga Yamaya, Fujino Obata, Kei Kamada, Eiji Yoshida, Akira Yoshikawa, and Fumihiko Nishikido
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Physics ,Gamma imaging ,Optics ,business.industry ,Detector ,Two layer ,Radiology, Nuclear Medicine and imaging ,Development (differential geometry) ,business ,Instrumentation ,Atomic and Molecular Physics, and Optics - Published
- 2022
3. Study on the radiofrequency transparency of electrically floating and ground PET inserts in a 3 T clinical MRI system
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Hossain, Akram, Takayuki, Obata, Fumihiko, Nishikido, and Taiga, Yamaya
- Abstract
Purpose The positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system that implements the radiofrequency (RF) built-in body coil of the MRI system as a transmitter is designed to be RF-transparent, as the coil resides outside the RF-shielded PET ring. This approach reduces the design complexities (e.g., large PET ring diameter) related to implementing a transmit coil inside the PET ring. However, achieving the required field transmission into the imaging region of interest (ROI) becomes challenging because of the RF shield of the PET insert. In this study, a modularly RF-shielded PET insert is used to investigate the RF transparency considering two electrical configurations of the RF shield, namely the electrical floating and ground configurations. The purpose is to find the differences, advantages and disadvantages of these two configurations. Methods Eight copper-shielded PET detector modules (intermodular gap: 3 mm) were oriented cylindrically with an inner diameter of 234 mm. Each PET module included four-layer Lutetium-yttrium oxyorthosilicate scintillation crystal blocks and front-end readout electronics. RF-shielded twisted-pair cables were used to connect the front-end electronics with the power sources and PET data acquisition systems located outside the MRI room. In the ground configuration, both the detector and cable shields were connected to the RF ground of the MRI system. In the floating configuration, only the RF shields of the PET modules were isolated from the RF ground. Experiments were conducted using two cylindrical homogeneous phantoms in a 3 T clinical MRI system, in which the built-in body RF coil (a cylindrical volume coil of diameter 700 mm and length 540 mm) was implemented as a transceiver. Results For both PET configurations, the RF and MR imaging performances were lower than those for the MRI-only case, and the MRI system provided specific absorption ratio (SAR) values that were almost double. The RF homogeneity and field strength, and the signal-to-noise ratio (SNR) of the MR images were mostly higher for the floating PET configuration than they were for the ground PET configuration. However, for a shorter axial field-of-view (FOV) of 125 mm, both configurations offered almost the same performance with high RF homogeneities (e.g., 76 ± 10%). Moreover, for both PET configurations, 56 ± 6% larger RF pulse amplitudes were required for MR imaging purposes. The increased power is mostly absorbed in the conductive shields in the form of shielding RF eddy currents; as a result, the SAR values only in the phantoms were estimated to be close to the MRI-only values. Conclusions The floating PET configuration showed higher RF transparency under all experimental setups. For a relatively short axial FOV of 125 mm, the ground configuration also performed well which indicated that an RF-penetrable PET insert with the conventional design (e.g., the ground configuration) might also become possible. However, some design modifications (e.g., a wider intermodular gap and using the RF receiver coil inside the PET insert) should improve the RF performance to the level of the MRI-only case.
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- 2022
4. Study on the radiofrequency transparency of electrically floating and ground PET inserts in a 3 T clinical MRI system
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Md Shahadat Hossain, Akram, Takayuki, Obata, Fumihiko, Nishikido, and Taiga, Yamaya
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Phantoms, Imaging ,Radio Waves ,Positron-Emission Tomography ,Equipment Design ,General Medicine ,Signal-To-Noise Ratio ,Magnetic Resonance Imaging - Abstract
The positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system that implements the radiofrequency (RF) built-in body coil of the MRI system as a transmitter is designed to be RF-transparent, as the coil resides outside the RF-shielded PET ring. This approach reduces the design complexities (e.g., large PET ring diameter) related to implementing a transmit coil inside the PET ring. However, achieving the required field transmission into the imaging region of interest (ROI) becomes challenging because of the RF shield of the PET insert. In this study, a modularly RF-shielded PET insert is used to investigate the RF transparency considering two electrical configurations of the RF shield, namely the electrical floating and ground configurations. The purpose is to find the differences, advantages and disadvantages of these two configurations.Eight copper-shielded PET detector modules (intermodular gap: 3 mm) were oriented cylindrically with an inner diameter of 234 mm. Each PET module included four-layer Lutetium-yttrium oxyorthosilicate scintillation crystal blocks and front-end readout electronics. RF-shielded twisted-pair cables were used to connect the front-end electronics with the power sources and PET data acquisition systems located outside the MRI room. In the ground configuration, both the detector and cable shields were connected to the RF ground of the MRI system. In the floating configuration, only the RF shields of the PET modules were isolated from the RF ground. Experiments were conducted using two cylindrical homogeneous phantoms in a 3 T clinical MRI system, in which the built-in body RF coil (a cylindrical volume coil of diameter 700 mm and length 540 mm) was implemented as a transceiver.For both PET configurations, the RF and MR imaging performances were lower than those for the MRI-only case, and the MRI system provided specific absorption ratio (SAR) values that were almost double. The RF homogeneity and field strength, and the signal-to-noise ratio (SNR) of the MR images were mostly higher for the floating PET configuration than they were for the ground PET configuration. However, for a shorter axial field-of-view (FOV) of 125 mm, both configurations offered almost the same performance with high RF homogeneities (e.g., 76 ± 10%). Moreover, for both PET configurations, 56 ± 6% larger RF pulse amplitudes were required for MR imaging purposes. The increased power is mostly absorbed in the conductive shields in the form of shielding RF eddy currents; as a result, the SAR values only in the phantoms were estimated to be close to the MRI-only values.The floating PET configuration showed higher RF transparency under all experimental setups. For a relatively short axial FOV of 125 mm, the ground configuration also performed well which indicated that an RF-penetrable PET insert with the conventional design (e.g., the ground configuration) might also become possible. However, some design modifications (e.g., a wider intermodular gap and using the RF receiver coil inside the PET insert) should improve the RF performance to the level of the MRI-only case.
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- 2022
5. Development of a Multiuse Human-Scale Single-Ring OpenPET System
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Eiji Yoshida, Yuji Nagai, Munetaka Nitta, Taku Inaniwa, Fumihiko Nishikido, Akram Mohammadi, Taiga Yamaya, Atsushi B. Tsuji, Takafumi Minamimoto, Hidekatsu Wakizaka, Hideaki Tashima, Yasuhisa Fujibayashi, Atsushi Kitagawa, Yuma Iwao, and Chie Seki
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Physics ,Scanner ,business.industry ,Dynamic imaging ,Detector ,Field of view ,Iterative reconstruction ,Atomic and Molecular Physics, and Optics ,Optics ,Medical imaging ,Radiology, Nuclear Medicine and imaging ,business ,Instrumentation ,Image resolution ,Beam (structure) - Abstract
We developed a human-scale single-ring OpenPET (SROP) system, which had an open space allowing us access to the subject during measurement. The SROP system consisted of 160 4-layer depth-of-interaction detectors. The open space with the axial width of 430 mm was achieved with the ring axial width of 214 mm and the ring inner diameter of 660 mm. The detectors were axially shifted to each other so that the detector ring was aligned along a plane horizontally tilted by 45° against the axial direction. The system was developed as a mobile scanner to be used not only in clinical positron emission tomography (PET) rooms but also in charged-particle therapy treatment rooms as well as animal experiment rooms. Almost uniform spatial resolution better than 3 mm throughout the entire field of view (FOV) was realized with an iterative image reconstruction method. Peak absolute sensitivity was 3.1%, and there was a region with sensitivity better than 0.8% for a length of more than 700 mm. An in-beam imaging experiment conducted at the heavy ion medical accelerator in Chiba showed that the system was operable even at the highest beam intensity available for heavy-ion therapy. In addition, we conducted entire-body monkey dynamic imaging utilizing the long region inside the gantry by positioning a monkey along the direction having the longest FOV tilted by 45° against the axial direction. We concluded the developed system has a capability to realize versatile PET applications by utilizing its wide-open space and mobility in addition to high spatial resolution with sufficiently good sensitivity. -9mm]Please consider rephrasing the sentence “We concluded the developed system” for clarity.
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- 2021
6. Evaluation of a Hamamatsu TOF-PET detector module with 3.2-mm pitch LFS scintillators and a 256-channel SiPM array
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Akamatsu, Go, Takyu, Sodai, Yoshida, Eiji, Iwao, Yuma, Tashima, Hideaki, Nishikido, Fumihiko, Yamaya, Taiga, Go, Akamatsu, Sodai, Takyu, Eiji, Yoshida, Yuma, Iwao, Hideaki, Tashima, Fumihiko, Nishikido, and Taiga, Yamaya
- Abstract
Using time-of-flight (TOF) information in image reconstruction improves image signal-to-noise ratio and quantitative accuracy in positron emission tomography (PET). A new TOF-PET detector module with a 3.2 mm pitch lutetium fine silicate (LFS) scintillator array one-to-one coupled to a 16×16 (256-ch) silicon photomultiplier (SiPM) array was made commercially available (C13500 series, Hamamatsu Photonics K.K.). In this study, as a candidate detector module for the next generation brain-dedicated PET, we changed the scintillator length of 20 mm to 10 mm according to our helmet-type PET geometry and investigated the basic performance of the PET detector module, including its energy resolution, sensitivity, coincidence response function (CRF) and coincidence timing resolution (CTR). All performance values were compared with those of the 4.2 mm pitch 144-ch detector module which was selected for our current helmet-type PET prototype. The energy resolution was 12% at 511 keV. The sensitivity was about 10% lower compared with those of the 4.2 mm pitch module. The average full width at half maximum (FWHM) of the CRFs was 1.9 mm. The CTRs had values of 235–241 ps with various energy windows after applying timing calibration. The CTR was not significantly changed (
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- 2021
7. C型コンプトンPETのシミュレーション ―検出器欠損影響の低減効果の検証―
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Takumi, Nishina, Hideaki, Tashima, Sodai, Takyu, Fumihiko, Nishikido, and Taiga, Yamaya
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例えばMRI に後付けできるアドオンPET など,リングの一部を開放化したC 型PET によりPET の応用が広がる可能性がある.その一方で,測定データの欠損に起因した強いアーチファクトが再構成画像に発生してしまう.そこでわれわれは,開放部と対向する位置に散乱検出器を追加して,欠損情報をコンプトンカメラの原理により補うC 型コンプトンPET を提案し,開発を進めている.本研究では,C型コンプトンPET のアーチファクト低減効果をモンテカルロシミュレーションによって検討した.具体的には,半径20 cm,開放部の角度が115 度のC 型PET の内側に,散乱検出器を半径15 cm で円弧状に配置したジオメトリーを模擬した.視野中心に配置した円柱ファントムを再構成し,定量的に評価した結果,視野領域全体における円柱内部の画素値の割合が89%から95%に増加したことから,アーチファクト低減に有効であることが示された.
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- 2021
8. Submillimeter-Resolution PET for High-Sensitivity Mouse Brain Imaging.
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Han Gyu Kang, Hideaki Tashima, Hidekatsu Wakizaka, Fumihiko Nishikido, Makoto Higuchi, Miwako Takahashi, and Taiga Yamaya
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- 2023
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9. Optimization of phosphor concentration of surface‐modified Bi2O3 nanoparticle‐loaded plastic scintillators for high‐energy photon detection
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Tadafumi Adschiri, Keisuke Asai, Gimyeong Seong, Takaaki Tomai, Akito Watanabe, Fumihiko Nishikido, Shunji Kishiomto, Masanori Koshimizu, Rie Haruki, Akira Yoko, Yutaka Fujimoto, and Arisa Magi
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010302 applied physics ,Materials science ,Photon ,Detector ,Analytical chemistry ,Nanoparticle ,Phosphor ,Photoelectric effect ,Scintillator ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Spectral line ,Electronic, Optical and Magnetic Materials ,Yield (chemistry) ,0103 physical sciences ,Electrical and Electronic Engineering - Abstract
In this study, the 3-phenylpropionic acid (3-PPA)-modified Bi2O3 nanoparticle-loaded plastic scintillators were synthesized to obtain fast scintillators having high detection efficiency of high-energy X-rays. To reach a high light yield, the content of 2-(4-tert-butylphenyl)-5-(4-phenylphenyl))-1,3,4-oxadiazole (b-PBD) in the plastic scintillators was optimized. The detection efficiency for high-energy photons was enhanced by the incorporation of surface-modified Bi2O3 nanoparticles of less than 10 nm into scintillators at 5 or 10 wt%. In the pulse-height spectra, the photoelectric peak positions were located at the highest channels for the samples containing 0.50 or 1.0 mol% b-PBD regardless of the Bi concentration. The photoelectric peak positions shifted to lower channels with a further increase in the b-PBD concentration, which indicates that the light yield decreased due to concentration quenching. In addition, the time resolution of the detector equipped with the studied samples was of the sub-nanosecond scale, suggesting that they had a very fast response.
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- 2021
10. Optimization of phosphor concentration of surface-modified Bi2O3 nanoparticle-loaded plastic scintillators for high-energy photon detection
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Magi, Arisa, Masanori, Koshimizu, Watanabe, Akito, Akira Yoko, Seong, Gimyeong, Tomai, Takaaki, Adschiri, Tadafumi, Haruki, Rie, Fumihiko, Nishikido, Shunji Kishiomto, Fujimoto, Yutaka, and Asai, Keisuke
- Abstract
In this study, the 3-phenylpropionic acid (3-PPA)-modified Bi2O3 nanoparticle-loaded plastic scintillators were synthesized to obtain fast scintillators having high detection efficiency of high-energy X-rays. To reach a high light yield, the content of 2-(4-tert-butylphenyl)-5-(4-phenylphenyl))-1,3,4-oxadiazole (b-PBD) in the plastic scintillators was optimized. The detection efficiency for high-energy photons was enhanced by the incorporation of surface-modified Bi2O3 nanoparticles of less than 10 nm into scintillators at 5 or 10 wt%. In the pulse-height spectra, the photoelectric peak positions were located at the highest channels for the samples containing 0.50 or 1.0 mol% b-PBD regardless of the Bi concentration. The photoelectric peak positions shifted to lower channels with a further increase in the b-PBD concentration, which indicates that the light yield decreased due to concentration quenching. In addition, the time resolution of the detector equipped with the studied samples was of the sub-nanosecond scale, suggesting that they had a very fast response.
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- 2021
11. Feasibility of triple gamma ray imaging of
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Akram, Mohammadi, Hideaki, Tashima, Sodai, Takyu, Yuma, Iwao, Go, Akamatsu, Han Gyu, Kang, Fujino, Obata, Fumihiko, Nishikido, Katia, Parodi, and Taiga, Yamaya
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Gamma Rays ,Phantoms, Imaging ,Feasibility Studies ,Humans ,Polymethyl Methacrylate ,Tomography, X-Ray Computed ,Monte Carlo Method - Published
- 2022
12. Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
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Chacon, Andrew, James, Benjamin, Linh Tran, Thuy, Guatelli, Susanna, Chartier, Lachlan, Prokopvich, Dale, R. Franklin, Daniel, Mohammadi, Akram, Nishikido, Fumihiko, Iwao, Yuma, Akamatsu, Go, Takyu, Sodai, Tashima, Hideaki, Yamaya, Taiga, Parodi, Katia, Rosenfeld, Anatoly, Mitra, Safavi‐Naeini, Lachlan, Chartier, Fumihiko, Nishikido, Yuma, Iwao, Go, Akamatsu, Sodai, Takyu, Hideaki, Tashima, and Taiga, Yamaya
- Abstract
Purpose This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance. Methods The energy deposited by monoenergetic beams of urn:x-wiley:00942405:media:mp14177:mp14177-math-0001C at 350 MeV/u, urn:x-wiley:00942405:media:mp14177:mp14177-math-0002O at 250 MeV/u, urn:x-wiley:00942405:media:mp14177:mp14177-math-0003C at 350 MeV/u, and urn:x-wiley:00942405:media:mp14177:mp14177-math-0004O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. Results In the entrance region, the urn:x-wiley:00942405:media:mp14177:mp14177-math-0005 was 1.2 ± 0.1 for both urn:x-wiley:00942405:media:mp14177:mp14177-math-0006C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0007C beams, while for urn:x-wiley:00942405:media:mp14177:mp14177-math-0008O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0009O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the urn:x-wiley:00942405:media:mp14177:mp14177-math-0010 was 2.7 ± 0.4 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0011C and 2.9 ± 0.4 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0012C, while for urn:x-wiley:00942405:media:mp14177:mp14177-math-0013O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0014O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, urn:x-wiley:00942405:media:mp14177:mp14177-math-0015 could only be evaluated for carbon; the urn:x-wiley:00942405:media:mp14177:mp14177-math-0016 was 1.6 ± 0.2 and 1.5 ± 0.1 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0017C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0018C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the urn:x-wiley:00942405:media:mp14177:mp14177-math-0019O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0020C images compared with the values obtained for urn:x-wiley:00942405:media:mp14177:mp14177-math-0021O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0022C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0023C, compared to −5.6 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0024C and 0.9 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0025O vs −6.6 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0026O. Conclusions The urn:x-wiley:00942405:media:mp14177:mp14177-math-0027 values for urn:x-wiley:00942405:media:mp14177:mp14177-math-0028C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0029O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, urn:x-wiley:00942405:media:mp14177:mp14177-math-0030C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0031O beams produce much better quality images for range verification compared with urn:x-wiley:00942405:media:mp14177:mp14177-math-0032C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0033O, in particular with regard to estimating the location of the Bragg peak.
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- 2020
13. The Correlation Between Scatter Detector Performance and Spatial Resolution in a Ring-shaped Compton Imaging System
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Sodai Takyu, Hideaki Tashima, Fumihiko Nishikido, Kei Kamada, Akira Yoshikawa, and Taiga Yamaya
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Radiology, Nuclear Medicine and imaging ,Instrumentation ,Atomic and Molecular Physics, and Optics - Published
- 2023
14. High-energy X-ray detection capabilities of Hf-loaded plastic scintillators synthesized by sol–gel method
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Kei Kagami, S. Kishimoto, Yutaka Fujimoto, Rie Haruki, Fumihiko Nishikido, Keisuke Asai, and Masanori Koshimizu
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010302 applied physics ,Photoluminescence ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,Phosphor ,Radioluminescence ,Scintillator ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Hafnium ,Full width at half maximum ,chemistry ,0103 physical sciences ,Emission spectrum ,Electrical and Electronic Engineering ,Sol-gel - Abstract
The high-energy X-ray detection capabilities of hafnium oxide-doped organosilica plastic scintillators were analysed. Plastic scintillators with different concentrations of Hf were synthesized via the sol–gel method. In the photoluminescence emission spectra and X-ray-excited radioluminescence spectra, all of the plastic samples showed broad emission bands peaking between 350 and 500 nm derived from the fluorescence of the organic phosphor b-PBD. The maximum detection efficiency for a thickness of 1 mm towards 67.41 keV high-energy X-ray was estimated to be 6.3% (Hf 10 wt%) which is 3.7 times larger than that of the undoped sample and 1.9 times larger than that of the commercialized Pb 5 wt%-doped plastic scintillator EJ-256. The full width at half maximum time resolutions were estimated to be approximately 0.4 to 0.6 ns, which is almost independent of the Hf concentration of Hf. Therefore, the detection efficiency towards high-energy X-rays was successfully improved while maintaining the original high time resolution of plastic scintillators by adding Hf to the plastic scintillator at high concentrations.
- Published
- 2019
15. Development of a Two-layer Staggered GAGG Scatter Detector for Whole Gamma Imaging
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Sodai, Takyu, Eiji, Yoshida, Fumihiko, Nishikido, Fujino, Obata, Hideaki, Tashima, Kamada, Kei, Yoshikawa, Akira, and Taiga, Yamaya
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Physics::Instrumentation and Detectors - Abstract
Silicon photomultiplier (SiPM) based scintillation detectors are widely used for positron emission tomography (PET), but their application to Compton cameras should be further explored. Whole gamma imaging (WGI) is a combination of PET and a Compton camera realized by inserting a scatter detector ring into a PET ring. In a previous study, we developed a WGI prototype in which the scatter detector consists of Gd3Al2Ga3O12:Ce (GAGG) scintillators coupled with SiPM for a proof-of-concept. However, its Compton imaging performance was not as good as its PET imaging performance. In this paper, we developed a two-layer staggered GAGG scatter detector which was optimized for WGI. GAGG crystals 1.45×1.45×4.5 mm3 in size were arranged into a 13×13 array for the 1st layer and a 14×14 array for the 2nd layer with a staggered arrangement. The two-layer crystal block was optically coupled to an 8×8 SiPM array (3 mm pixel). Using radioactive sources with different energies, we investigated the energy resolution performance experimentally. Almost all crystals were clearly separated in the flood histogram at multiple energies. The developed detector showed energy resolutions of 7.7% to 8.5% at 511 keV, which was better than that of the detector of the current WGI prototype. The next generation WGI system was modeled in simulations using the obtained energy resolution data. The simulation results showed that the WGI with the developed detector had 1.2 times better sensitivity and better angular resolution in the peripheral region than the current WGI prototype.
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- 2021
16. 3次元コンプトン画像再構成が可能な検出器ジオメトリ条件の実験的検証
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Hideaki, Tashima, Eiji, Yoshida, Sodai, Takyu, Fumihiko, Nishikido, Takumi, Nishina, Mikio, Suga, Hidekatsu, Wakizaka, Miwako, Takahashi, Kotaro, Nagatsu, Atsushi, Tsuji, and Taiga, Yamaya
- Abstract
我々が開発を進めているWGI(Whole Gamma Imaging)は、散乱検出器リングを吸収検出器リングへ挿入することでPETとコンプトンイメージングを融合した構造となっており、様々なガンマ線の利用を目指している。また、これまでに開発したWGI試作機は、コンプトンイメージング装置としては世界初のフルリング型ジオメトリを実現したものであった。ここで、コンプトン画像再構成の条件に着目すると、理論的にはフルリング型である必要性はなく、検出器を削減できれば設計の柔軟性向上や、コスト削減が期待できる。しかしながら、実際には散乱角度の検出限界やブロック型検出器の配置方法などの影響で、再構成条件は保証されていない。そこで、本研究では、WGI試作機の89Zr円柱ファントム測定データに対し、後処理によって検出器を制限し、909keVのコンプトン画像のアーチファクトを評価することで3次元画像再構成に必要なジオメトリ条件の検討を行った。その結果、散乱検出器、吸収検出器共に、測定対象上のすべての領域を180°以上囲うことが必要であると示唆された。, 第61回日本核医学会学術総会
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- 2021
17. Submillimeter resolution positron emission tomography for high-sensitivity mouse brain imaging
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Han Gyu, Kang, Hideaki, Tashima, Hidekatsu, Wakizaka, Fumihiko, Nishikido, Makoto, Higuchi, Miwako, Takahashi, and Taiga, Yamaya
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Radiology, Nuclear Medicine and imaging - Abstract
Positron emission tomography (PET) is a powerful molecular imaging technique that can provide functional information of living objects. However, the spatial resolution of PET imaging has been limited to around 1 mm which makes it difficult to visualize mouse brain functions in detail. Here we report an ultrahigh resolution small animal PET scanner we developed that can provide a resolution approaching 0.6 mm to visualize the mouse brain functions with unprecedented detail.
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- 2022
18. Timing resolution of TlBr and TlBr-TlCl PET detectors based on Cerenkov radiation measurement
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Fumihiko, Nishikido, Hitomi, Keitaro, Nogami, Satoshi, Kang, Hangyu, and Taiga, Yamaya
- Abstract
TlBr is a high density (7.56 g/cm) semiconductor material composed of high effective atomic number elements. Therefore, TlBr has sufficient detection efficiency for 511 keV annihilation radiation in PET. In addition, TlBr detectors have high energy resolution due to the direct conversion to electrons. On the other hand, timing performance of typical semiconductor detectors is poor compared with scintillation detectors However, detection of Cerenkov light from TlBr offers an alternative method to get better timing resolution. This paper reports our feasibility study on the timing performance of TlBr detectors using Cerenkov light. In the experiment, a conventional TlBr crystal and TlBr mixed with TlCl (TlBr-TlCl crystal) were used. The TlBr crystals were fabricated at Tohoku University. Each TlBr crystal was 3 × 3 × 3 mm3. The TlBr crystals were covered with ESR films and Teflon tape. Cerenkov light was detected with a multi-pixel photon counter (Hamamatsu S13360-3075CS). Coincidence detection measurement was carried out using a LYSO scintillator coupled with another MPPC (Hamamatsu S13360-3050CS) as a reference detector. Signals from the detectors were amplified with high frequency amplifiers and then waveforms were recorded with a digitizer (CAEN, DT5742). We obtained the timing spectra by Cerenkov light from the TlBr and scintillation light from the LYSO. From them, the timing resolution better than 600 ps was obtained for all the event data. After selecting the events by optimizing a trigger level, the timing resolutions better than 450 ps was obtained for both the TlBr detector and the TlBr-TlCl detector., 2021 Virtual IEEE Nuclear science symposium and medical imaging conference
- Published
- 2021
19. Experimental Assessment on Data Sufficiency Condition for WGI Compton Imaging
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Hideaki, Tashima, Eiji, Yoshida, Sodai, Takyu, Fumihiko, Nishikido, Takumi, Nishina, Mikio, Suga, Hidekatsu, Wakizaka, Miwako, Takahashi, Kotaro, Nagatsu, Atsushi, Tsuji, Kamada, Kei, Yoshikawa, Akira, Parodi, Katia, and Taiga, Yamaya
- Subjects
Physics::Instrumentation and Detectors - Abstract
We developed a whole gamma imaging (WGI) prototype composed of a scatterer ring insert and an absorber ring. It was the world’s first realization of a full-ring Compton camera geometry. In this study, we focused on the data sufficiency condition (DSC) for Compton image reconstruction. Contrary to PET which requires a full-ring geometry to satisfy the DSC, Compton imaging does not require a full ring theoretically. Reducing the detector-ring coverages can improve flexibility of the geometry design and reduce manufacturing costs although sensitivity is decreased. However, the DSC for reconstruction is not guaranteed in a practical situation due to actual absorber ring arrangement and detection limits in scattering angle. In this study, we experimentally assessed the DSC for the angular coverages. We evaluated image artifacts on reconstructed Compton images because, in general, images distort and exhibit artifacts when the DSC is not satisfied, degrading quantitative accuracy. We measured a cylindrical phantom filled with 89Zr solution of 10.2 MBq by the WGI prototype for 60 min and extracted 909-keV Compton events. We selected events related to the detector blocks marked as available to change detector angular coverages defined for the phantom bottom point. First, we changed the number of detectors in the scatterer ring, keeping the full-ring absorber. Next, we changed the absorber ring angular coverage by changing the number of detectors, keeping the scatterer ring at the number where the angular coverage just exceeded 180°. As a result, when the angular coverage of the scatterer detector was less than 180°, reconstructed images exhibited artifacts. The absorber ring detector with less than 180° coverage showed artifacts when used with the scatterer detector with more than 180° coverage. We concluded that angular coverages of more than 180° for both the scatterer and absorber detectors against any region on a subject are the DSC for Compton image reconstruction., IEEE NSS MIC 2021
- Published
- 2021
20. Optimization of GFAG crystal surface treatment for SiPM based TOF PET detector
- Author
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Han Gyu Kang, Kyoung Jin Kim, Kei Kamada, Akira Yoshikawa, Eiji Yoshida, Fumihiko Nishikido, and Taiga Yamaya
- Subjects
Photons ,Positron-Emission Tomography ,Lutetium ,Signal-To-Noise Ratio ,General Nursing ,Aluminum - Abstract
Coincidence timing resolution (CTR) is an important parameter in clinical positron emission tomography (PET) scanners to increase the signal-to-noise ratio of PET images by using time-of-flight (TOF) information. Lutetium (Lu) based scintillators are often used for TOF-PET systems. However, the self-radiation of Lu-based scintillators may influence the image quality for ultra-low activity PET imaging. Recently, a gadolinium fine aluminum gallate (Ce:GFAG) scintillation crystal that features a fast decay time (∼55 ns) and no self-radiation was developed. The present study aimed at optimizing the GFAG crystal surface treatment to enhance both CTR and energy resolution (ER). The TOF-PET detector consisted of a GFAG crystal (3.0 × 3.0 × 20 mm3) and a SiPM with an effective area of 3.0 × 3.0 mm2. The timing and energy signals were extracted using a high-frequency SiPM readout circuit and then were digitized using a CAMAC DAQ system. The CTR and ER were evaluated with nine different crystal surface treatments such as partial saw-cut and chemical polishing and the 1-side saw-cut was the best choice among the treatments. The respective CTR and ER of 202 ± 2 ps and 9.5 ± 0.1% were obtained with the 1-side saw-cut; the other 5-side mechanically polished GFAG crystals had respective values which were 18 ps (9.0%) and 1.3% better than those of the all-side mechanically polished GFAG crystal. The chemically polished GFAG crystals also offered enhanced CTR and ER of about 17 ps (8.2%) and 2.1%, respectively, over the mechanically polished GFAG crystals.
- Published
- 2021
21. 有機半導体4HCBの炭素線照射に対する応答特性評価
- Author
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Han Gyu, Kang, Fumihiko, Nishikido, Eiji, Takada, Sodai, Takyu, Kang, Hangyu, and Taiga, Yamaya
- Abstract
有機半導体は生体構成物質で出来ている・任意の形状が作成可能・大型化が容易・安価であることなど、医用放射線検出器として有利な特徴を有している。そこで我々のグループでは炭素線治療下での線量測定を目的として、有機半導体を用いた炭素線計測を目指して研究を進めている。現在は有機半導体の一つである4-ヒドロキシアノベンゼン(4HCB)の炭素線照射に対する特性評価を行っている。 実験ではサイズが4 mm × 4 mm、厚さが2 mmの4HCBを作成した。4HCB結晶の両側に電極をカーボンペーストで取り付け、電圧の付加・出力信号の取り出しを行った。バイアス電圧は0 Vから900 Vまで変化をさせながら掛け、それぞれの場合での収集電荷量を測定した。評価は放医研の重粒子加速器施設HIMACの物理コースで行い、290 MeV/nの炭素線を校正用電離箱(IC)を通した後4HCBに入射させ測定を行った。ビーム強度は1.8×109 particle per secondに設定した。 図1に炭素線照射時に得られたICと4HCBで得られた0.1秒毎の収集電荷量を示す。データは4HCBに50 Vを印加した時のものである。どちらの検出器でもHIMACでの3.3秒周期のスピル構造が観測できる。図2にバイアス電圧とルブレン単結晶からの出力との関係を示す。縦軸は1スピル毎に得られた電荷量を実際に照射された炭素線の粒子数で校正されており、最も出力が大きかったデータを1としている。電圧を上げることで収集電荷量が増加していることがわかる。これらの結果から4HCBは炭素線用検出器として機能していることがわかる。講演では更に詳細な評価結果について報告を行う。, 2021年 第82回応用物理学会秋季学術講演会
- Published
- 2021
22. Initial results of a mouse brain PET insert with a staggered 3-layer DOI detector
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Han Gyu Kang, Go Akamatsu, Fumihiko Nishikido, Hidekazu Wakizaka, Hideaki Tashima, Makoto Higuchi, and Taiga Yamaya
- Subjects
Materials science ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,Phantoms, Imaging ,Resolution (electron density) ,Detector ,Brain ,Equipment Design ,Lyso ,Imaging phantom ,Mice ,Optics ,Silicon photomultiplier ,Positron emission tomography ,Positron-Emission Tomography ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Radiopharmaceuticals ,business ,Image resolution ,Sensitivity (electronics) ,Algorithms - Abstract
Objective.Small animal positron emission tomography (PET) requires a submillimeter resolution for better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution while maintaining the sensitivity. Recently, we developed a staggered 3-layer DOI detector with 1 mm crystal pitch and 15 mm total crystal thickness, but we did not demonstrate the imaging performance of the DOI detector with full ring geometry. In this study we present initial imaging results obtained for a mouse brain PET prototype developed with the staggered 3-layer DOI detector.Approach.The prototype had 53 mm inner diameter and 11 mm axial field-of-view. The PET scanner consisted of 16 DOI detectors each of which had a staggered 3-layer LYSO crystal array (4/4/7 mm) coupled to a 4 × 4 silicon photomultiplier array. The physical performance was evaluated in terms of the NEMA NU 4 2008 protocol.Main Results.The measured spatial resolutions at the center and 15 mm radial offset were 0.67 mm and 1.56 mm for filtered-back-projection, respectively. The peak absolute sensitivity of 0.74% was obtained with an energy window of 400-600 keV. The resolution phantom imaging results show the clear identification of a submillimetric rod pattern with the ordered-subset expectation maximization algorithm. The inter-crystal scatter rejection using a narrow energy window could enhance the resolvability of a 0.75 mm rod significantly.Significance.In an animal imaging experiment, the detailed mouse brain structures such as cortex and thalamus were clearly identified with high contrast. In conclusion, we successfully developed the mouse brain PET insert prototype with a staggered 3-layer DOI detector.
- Published
- 2021
23. Axial scalable add-on PET/MRI prototype based on four-layer DOI detectors integrated with a RF coil
- Author
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Fumihiko Nishikido, Takayuki Obata, Mikio Suga, Yuma Iwao, Hideaki Tashima, Eiji Yoshida, Md Shahadat Hossain Akram, and Taiga Yamaya
- Subjects
Nuclear and High Energy Physics ,Instrumentation - Published
- 2022
24. Two-dimensional positronium lifetime imaging using certified reference materials
- Author
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Sodai Takyu, Kengo Shibuya, Fumihiko Nishikido, Hideaki Tashima, Miwako Takahashi, and Taiga Yamaya
- Subjects
General Engineering ,General Physics and Astronomy - Abstract
Positronium (Ps) is generated before electron–positron annihilation in positron emission tomography (PET). As the Ps lifetime reflects the surrounding electron density, we aimed at its use for an innovative PET imaging. Here, as our first step, we demonstrated two-dimensional Ps lifetime imaging of certified reference materials using a pair of time-of-flight PET detectors. The imaged and calculated Ps lifetimes were very close to those of the reference materials, but the error values were larger than those of the reference materials. The results suggested that the accuracy of PET imaging with the ortho-positronium lifetime could be verified by those materials.
- Published
- 2022
25. Development of a dual-end detector with TOF and DOI capabilities using crystal bars segmented by subsurface laser engraving
- Author
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Toshiaki Sakai, Sodai Takyu, Fumihiko Nishikido, Eiji Yoshida, Taiga Yamaya, K. Shimizu, and Akram Mohammadi
- Subjects
Physics ,Nuclear and High Energy Physics ,010308 nuclear & particles physics ,Laser engraving ,Bar (music) ,business.industry ,Detector ,01 natural sciences ,Coincidence ,030218 nuclear medicine & medical imaging ,Crystal ,03 medical and health sciences ,Time of flight ,0302 clinical medicine ,Optics ,Silicon photomultiplier ,Pet scanner ,0103 physical sciences ,business ,Instrumentation - Abstract
The quality and uniformity of positron emission tomography (PET) images can be improved significantly using a PET scanner, which has both time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. We have already developed a DOI dual-end detector using segmented crystal bars by applying a subsurface laser engraving (SSLE) technique, and the DOI was determined by the ratio of the detected light between two readouts using the Anger calculation. In this study, we investigated the influence of the number of DOI segments on the performance of DOI identification and the coincidence timing performance of the detector. The detector consisted of a single lutetium fine silicate (LFS) crystal bar (3 × 3 × 20 mm3) with various numbers of DOI segments that were made by applying the SSLE technique and Hamamatsu silicon photomultiplier (SiPM) modules. The maximum number of DOI segments was six, and the SiPM module included one hundred forty-four 4 mm × 4 mm SiPM readouts. The coincidence resolving time (CRT) of each DOI segment was obtained from the side irradiation of the dual-end detector. All DOI segments of the detector with 2, 3, 4, 5 or 6 DOI segments were clearly identified, and average energy resolutions of 9.8 ± 0.5% and 12.5 ± 1.4% were obtained at the 511 keV photo peak for the detectors with 2 DOI and 6 DOI segments, respectively. The minimum and maximum estimated CRT of 180 ± 6 ps and 236 ± 6 ps were obtained for the detectors with 2 DOI and 6 DOI segments, respectively. Insignificant differences were observed between the CRT values of different segments of one detector. Greater CRT values were obtained for detectors with larger DOIs. The results of this study prove that there is a high potential for segmented crystal bars using the SSLE technique as a good candidate for PET scanners with TOF and DOI capabilities, which can significantly improve the quality of PET images.
- Published
- 2019
26. Four-layered DOI-PET detector with quadrisected top layer crystals
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Sodai Takyu, Fumihiko Nishikido, Hideaki Tashima, Genki Hirumi, Eiji Yoshida, and Taiga Yamaya
- Subjects
Physics ,Nuclear and High Energy Physics ,010308 nuclear & particles physics ,business.industry ,Detector ,Light guide ,01 natural sciences ,Lyso ,Pet detector ,030218 nuclear medicine & medical imaging ,Crystal ,03 medical and health sciences ,0302 clinical medicine ,0103 physical sciences ,High spatial resolution ,Optoelectronics ,business ,Instrumentation ,Layer (electronics) ,Image resolution - Abstract
Previously, we had developed a four-layered depth-of-interaction (DOI) PET detector based on the light sharing method. Reflectors , which were inserted in every two lines of crystal segments and shifted differently for each layer, projected 3D crystal positions onto a 2D position histogram without any overlapping after applying the Anger-type calculation. The best crystal separation we ever obtained was for the four-layered 32 × 32 array of LYSO crystals sized at 1.45 × 1.45 × 5 mm3. However, assembling small crystals tended to cost a lot, and fine tuning of the front-end circuit was required to get fine crystal identification. In this paper, therefore, we proposed a more practical four-layered DOI detector. Its key concept was that the crystals in the top layer, which have the highest detection efficiency, are the biggest contributors to the PET spatial resolution. We applied two new ideas: (1) using quarter size crystals only for the first (top) layer and (2) inserting a thin light guide between the first and the second layers of the crystal array. In the developed prototype detector, we used 24 × 24 LYSO crystals of quarter size (1.4 × 1.4 × 5.0 mm3) in the first layer and the other layers were 12 × 12 arrays of crystals of 2.8 × 2.8 × 5.0 mm3. For better crystal identification of small crystals in the first layer, we optimized the optical condition between crystals by using an optical adhesive and air. Also, the thin light guide of 0.5 mm thickness was inserted between the first and the second layers for improvement of crystal identification of the first layer. With the appropriate insertion of the light guide, all crystals of the first layer were identified as well as the crystals in the other layers. Our developed four-layered DOI detector showed good potential for high spatial resolution without a large increase in the number of crystals.
- Published
- 2019
27. Monte Carlo investigation of the characteristics of radioactive beams for heavy ion therapy
- Author
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Daniel Franklin, Eiji Yoshida, Hideaki Tashima, Yuma Iwao, Atsushi Kitagawa, Marie-Claude Gregoire, Mitra Safavi-Naeini, Susanna Guatelli, Go Akamatsu, Anatoly B. Rosenfeld, Fumihiko Nishikido, David Bolst, Taiga Yamaya, Andrew Chacon, and Akram Mohammadi
- Subjects
0301 basic medicine ,Materials science ,Monte Carlo method ,Physics::Medical Physics ,Biophysics ,lcsh:Medicine ,Bragg peak ,Electrons ,Heavy Ion Radiotherapy ,Imaging phantom ,Article ,Ion ,03 medical and health sciences ,0302 clinical medicine ,Positron ,Relative biological effectiveness ,Humans ,Computer Simulation ,lcsh:Science ,Radionuclide ,Multidisciplinary ,Stable isotope ratio ,Phantoms, Imaging ,lcsh:R ,Dose-Response Relationship, Radiation ,Radiotherapy Dosage ,Computational physics ,030104 developmental biology ,Radioactivity ,Physics::Accelerator Physics ,lcsh:Q ,Monte Carlo Method ,Biological physics ,030217 neurology & neurosurgery ,Relative Biological Effectiveness - Abstract
This work presents a simulation study evaluating relative biological effectiveness at 10% survival fraction (RBE10) of several different positron-emitting radionuclides in heavy ion treatment systems, and comparing these to the RBE10s of their non-radioactive counterparts. RBE10 is evaluated as a function of depth for three positron-emitting radioactive ion beams (10C, 11C and 15O) and two stable ion beams (12C and 16O) using the modified microdosimetric kinetic model (MKM) in a heterogeneous skull phantom subject to a rectangular 50 mm × 50 mm × 60 mm spread out Bragg peak. We demonstrate that the RBE10 of the positron-emitting radioactive beams is almost identical to the corresponding stable isotopes. The potential improvement in PET quality assurance image quality which is obtained when using radioactive beams is evaluated by comparing the signal to background ratios of positron annihilations at different intra- and post-irradiation time points. Finally, the incidental dose to the patient resulting from the use of radioactive beams is also quantified and shown to be negligible.
- Published
- 2019
28. Improvement of a PET Detector Performance by Setting Reflectors in Parallel With PMT Face
- Author
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Junichi Ohi, Hideo Murayama, Fumihiko Nishikido, Taiga Yamaya, and Naoko Inadama
- Subjects
Physics ,Nuclear and High Energy Physics ,Scintillation ,Photomultiplier ,010308 nuclear & particles physics ,business.industry ,Detector ,Gamma ray ,01 natural sciences ,Photocathode ,Cathode ,law.invention ,Crystal ,Optics ,Nuclear Energy and Engineering ,law ,0103 physical sciences ,Electrical and Electronic Engineering ,business ,Energy (signal processing) - Abstract
A whole-body positron emission tomography scanner must be equipped with many detectors so that they are often composed of low-cost photomultiplier tubes (PMTs), that is, large anode-type PMTs. The general detector structure has a scintillation crystal element array coupled on an array of the large anode PMTs, and for crystal element identification, the method is needed to get sufficient spread of scintillation light for distribution among distant PMT anodes. Besides the common method of using a light guide, some methods have been proposed for better element identification performance. In this paper, we introduce a new method, in which the scintillation light spread is promoted not only by removing reflectors between crystal elements but also by restricting light exit to the PMTs by placing additional reflectors at the bottom of the crystal element array. Because the additional reflectors are parallel to the PMT surface, we call them parallel reflectors. We verified our method with a detector consisting of the 2.45 mm $\times \,\, 5$ mm $\times \,\,15$ mm Lu2 x Gd2(1– x )SiO5:Ce crystal elements and two dual-photocathode PMTs. Each photocathode was 8 mm $\times \,\,18$ mm in size. We set a $9 \times 10$ crystal element array on the two PMTs and tried to identify the elements by the $2\times 2$ PMT signals. Detector performance was evaluated with 137Cs point sources (662-keV gamma rays). The results showed that despite a significant decrease in light output at the boundary of the two PMTs, the method made crystal element identification possible. We measured energy resolutions of 13.1% and 17.8% for the elements on the PMT photocathode area and the PMT boundary, respectively. Our method is applicable to the depth-of-interaction detector consisting of multilayer crystal element arrays. By inserting parallel reflectors between the layers, we would be able to control the path of scintillation light originating in the upper layer. The effect was first examined in a basic study with two layers of a $2 \times 5$ crystal element array. Then, the array of each layer was increased to $9\times 9$ for performance evaluation. It was difficult to identify all 162 crystal elements with four PMT signals; however, results suggest the possibility of scintillation light path control in each layer separately by the parallel reflectors and the potential for better performance by more precise adjustment of parallel reflectors.
- Published
- 2019
29. Development of the X’tal Cube PET Detector With Segments of (0.77 mm)3
- Author
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Taiga Yamaya, Hideaki Tashima, Hideyuki Kawai, Naoko Inadama, Munetaka Nitta, Fumihiko Nishikido, and Eiji Yoshida
- Subjects
Scintillation ,Materials science ,business.industry ,Laser engraving ,Detector ,Atomic and Molecular Physics, and Optics ,Lyso ,Crystal ,Optics ,Histogram ,Radiology, Nuclear Medicine and imaging ,Cube ,business ,Instrumentation ,Image resolution - Abstract
The depth-of-interaction detector which can identify gamma-ray detection position along the depth direction is essential for a PET scanner to reduce parallax error. The X’tal cube we have developed is composed of a scintillation crystal block segmented into cubes. Six arrays of multipixel photon counters (MPPCs) cover six surfaces of the crystal block. We developed the new X’tal cube consisting of 0.77 mm cubic segments. A (13.1 mm)3 LYSO crystal block had 3-D segmentation in a ${17 \times 17 \times 17}$ array fabricated by the laser engraving technique. $ {4 \times 4}$ MPPC arrays with a size of (13 mm)2 were used. Active area of each MPPC was (3.0 mm)2. To evaluate segment identification performance, we irradiated with gamma-rays from a 22Na source and obtained a 3-D position histogram made by the 3-D Anger-type calculation with all MPPC signals. The histogram showed 17 segments in a row can be identified clearly. Further, to measure its intrinsic spatial resolution with incident angles of 0° and 45°, gamma-rays in a fan-beam were irradiated and scanned onto the X’tal cube. Spatial resolutions of 0.74 ± 0.10 mm and 0.89 ± 0.10 mm were obtained by both scan experiments, respectively.
- Published
- 2018
30. C型コンプトンPET装置のシミュレーション検討
- Author
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Hideaki, Tashima, Takumi, Nishina, Fumihiko, Nishikido, Sodai, Takyu, Mikio, Suga, and Taiga, Yamaya
- Abstract
C型部分PETリングの内側に散乱検出器を配置し、欠損情報をコンプトンイメージングの原理により補完することで、様々な応用が可能な開放部を持ちつつ、部分リングアーチファクトの低減が可能な装置を提案し、モンテカルロシミュレーションによって有効性を検討した。その結果、提案装置によりアーチファクト低減が可能であり、また、散乱検出器によって視野を広く囲う方がより効果が高いことが示された。, 応用物理学会春季学術講演会
- Published
- 2021
31. PET・コンプトンハイブリッド画像再構成の応用
- Author
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Hideaki, Tashima, Eiji, Yoshida, Takumi, Nishina, Sodai, Takyu, Fumihiko, Nishikido, Mikio, Suga, Hidekatsu, Wakizaka, Miwako, Takahashi, Kotaro, Nagatsu, Atsushi, Tsuji, Parodi, Katia, and Taiga, Yamaya
- Abstract
我々は,PETとコンプトンイメージングの同時測定を可能とするWGIの開発を進めている.そして,2種類の異なる測定イベントを組み合わせることが可能なハイブリッド画像再構成手法を開発した.本手法を応用し,PETでは測定できないシングルガンマ線を組み合わせることによる高画質化,及び,開放部を設けた部分リング型装置を構成した際にPETのみでは避けられないアーチファクトの低減が可能であることを示した., 医用画像研究会(MI) JAMITフロンティア2021
- Published
- 2021
32. A staggered 3-layer DOI PET detector using BaSO
- Author
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Han Gyu, Kang, Fumihiko, Nishikido, and Taiga, Yamaya
- Subjects
Positron-Emission Tomography - Abstract
The spatial resolution of small animal positron emission tomography (PET) scanners can be improved by the use of crystals with fine pitch and rejection of inter-crystal scattering (ICS) events, which leads to a better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution at the PET field-of-view (FOV) periphery while keeping the sensitivity. In this study we proposed a novel staggered 3-layer DOI detector using BaSO
- Published
- 2021
33. Optimization of the surface area of laser-induced layers for PET detectors with depth-of-interaction
- Author
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Mohammadi, Akram, Naoko, Inadama, Fumihiko, Nishikido, Sakai, Toshiaki, Taiga, Yamaya, Mohammadi, Akram, Naoko, Inadama, Fumihiko, Nishikido, Sakai, Toshiaki, and Taiga, Yamaya
- Abstract
Detectors with depth-of-interaction (DOI) information are utilized in positron emission tomography (PET) scanners to improve the sensitivity of radiation detection and the uniformity of spatial resolution. We recently developed a series of dual-ended detectors using crystal bars segmented by applying the subsurface laser engraving (SSLE) technique to 7, 13 and 20 DOI segments. It is crucial to achieve the submillimeter level spatial resolution for our detector as the narrow crystal bars are highly fragile after applying the SSLE technique. In this work, we focused on optimizing the surface area of the SSLE-induced layer to the narrow crystal bars in order to resolve the issue of fragility while maintaining sufficient crystal segment separation. The SSLE layers were induced to the middle of the cross section of the five crystal bars with dimensions of 1.5×1.5×20 mm3 with a distance of 0.1, 0.2, 0.3, 0.4 or 0.5 mm from the two opposite lateral edges of each crystal bar. All crystals were segmented into four DOI segments and the performances of the five sets of dual-ended DOI detectors consisting of one crystal bar were evaluated from the viewpoints of optimum crystal segment identification and energy resolution while mitigating the fragility issue. The 3D position maps of the detectors were obtained by the Anger-type calculation, and the crystal identification performance was evaluated. Clear separation of the segments with a distance-to-width ratio (DWR) larger than 7 was obtained for the detectors in which the distances of the SSLE-induced layer from the two opposite lateral edges of the crystal were 0.1, 0.2 and 0.3 mm. The DWR for the other two detectors was less than 4.4. Average energy resolutions of 11.8 ± 0.2%, 10.6 ± 0.2% and 8.8 ± 0.2% were obtained for the detectors in which the SSLE layers were induced with 0.1, 0.3 and 0.5 mm distances from the two opposite lateral edges of the crystal, respectively. There was a compromise between energy resolution and cr
- Published
- 2021
34. A staggered 3-layer DOI PET detector using BaSO4 reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability
- Author
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Kang, Hangyu, Fumihiko, Nishikido, Taiga, Yamaya, Kang, Hangyu, Fumihiko, Nishikido, and Taiga, Yamaya
- Abstract
The spatial resolution of small animal positron emission tomography (PET)scanners can be improved by the use of crystals with fine pitch and rejection of inter-crystal scattering (ICS) events, which leads to a better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution at the PET field-of-view(FOV) periphery while keeping the sensitivity. In this study we proposed a novel staggered 3-layer DOI detector using BaSO4 reflector material for an enhanced crystal identification performance as well as ICS event rejection capability over those of ESR reflector based DOI detectors. The proposed staggered 3-layer DOI detector had 3-layer staggered LYSO crystal arrays(crystal pitch = 1 mm), an acrylic light guide, and a 4 × 4 SiPM array. The 16 SiPM anode signals were read out by using a resistive network to encode the crystal position and energy information while the timing signal was extracted from the common cathode. The crystal map quality was substantially enhanced by using the BaSO4 reflector material as compared to that of the ESR reflector due to the low optical crosstalk between the LYSO crystals. The ICS events can be rejected with BaSO4 by using simple pulse height discrimination thanks to the light collection efficiency difference that depends on the crystal layers. As a result, the total number of events was decreased around 26% with BaSO4 as compared to that of ESR. The overall energy resolution and coincidence timing resolution with BaSO4were 19.7 ± 5.6% and 591 ± 160 ps, respectively which were significantly worse than 10.9 ± 2.2% and 308 ± 23 ps values of ESR because of the relatively low light collection efficiency with BaSO4 (1057 ± 308 ADC) compared to that of ESR (1808 ± 118 ADC). In conclusion, we found the proposed staggered 3-layer DOI detector using the BaSO4 reflector material with ICS event rejection capability can be a costeffective solution for realizing hig
- Published
- 2021
35. Characterization of a 4-hydroxycyanobenzene radiation detector for dose monitoring in carbon therapy
- Author
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Fumihiko, Nishikido, Eiji, Takada, Yamagishi, Masakazu, Daiki, Satake, Sodai, Takyu, Kang, Hangyu, Taiga, Yamaya, Fumihiko, Nishikido, Eiji, Takada, Yamagishi, Masakazu, Daiki, Satake, Sodai, Takyu, Kang, Hangyu, and Taiga, Yamaya
- Abstract
Organic semiconductors are suitable for dose monitoring in carbon therapy since they are tissue equivalent materials. Here, we have evaluated a 4-hydroxycyanobenzene (4HCB) single crystal as an organic semiconductor radiation detector for carbon therapy. The thickness of the 4HCB crystal can be increased to more than 1 mm easily in order to apply a voltage over 100 V. The 4HCB crystal (4 mm × 4 mm × 2 mm) was mounted on a 10 mm × 10 mm × 1 mm black ABS plate. Readout wires were connected to two sides of the 4HCB crystal with silver paste. The applied voltages to the 4HCB detector were from +10 V to +800 V in the experiment. The experiment was performed in the PH2 course of the Heavy Ion Medical Accelerator in Chiba (HIMAC) at NIRS. The energy and beam intensity of the 12C beam were 290 MeV/u and 1.8 × 109 particles per second (pps). The diameter of the carbon beam was ~1 cm at the detector. The 4HCB detector was irradiated by the carbon beam that was passed through an ionization chamber which was used to normalize the number of irradiated particles. We clearly observed collected charges in the 4HCB single crystal obtained during each 0.1 s period of the carbon beam irradiation. The beam spill structure of the 3.3 s cycle was also clearly observed. In addition, we obtained normalized induced charges for the carbon beam irradiation as a function of applied voltages to the 4HCB detector (i.e. saturation curve). The optimum voltage was determined at 500 V for the evaluated 4HCB detector., 2021 Virtual IEEE Nuclear science symposium and medical imaging conference
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- 2021
36. Initial results of a mouse brain PET insert with a staggered 3-layer DOI detector
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Kang, Hangyu, Hideaki, Tashima, Fumihiko, Nishikido, Go, Akamatsu, Hidekatsu, Wakizaka, Makoto, Higuchi, Taiga, Yamaya, Kang, Hangyu, Hideaki, Tashima, Fumihiko, Nishikido, Go, Akamatsu, Hidekatsu, Wakizaka, Makoto, Higuchi, and Taiga, Yamaya
- Abstract
Small animal positron emission tomography (PET) requires a submillimeter resolution for better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution while maintaining the sensitivity. Recently, we developed a staggered 3-layer DOI detector with 1 mm crystal pitch and 15 mm total crystal thickness, but we did not demonstrate the imaging performance of the DOI detector with full ring geometry. In this study we present initial imaging results obtained for a mouse brain PET prototype developed with the staggered 3-layer DOI detector. The prototype had 53 mm inner diameter and 11 mm axial field-of-view. The PET scanner consisted of 16 DOI detectors each of which had a staggered 3-layer LYSO crystal array (4/4/7 mm) coupled to a 4×4 SiPM array. The physical performance was evaluated in terms of the NEMA NU 4 2008 protocol. The measured spatial resolutions at the center and 15 mm radial offset were 0.67 mm and 1.56 mm for filtered-back-projection, respectively. The peak absolute sensitivity of 0.74% was obtained with an energy window of 400-600 keV. The resolution phantom imaging results show the clear identification of a submillimetric rod pattern with the ordered-subset expectation maximization algorithm. The inter-crystal scatter rejection using a narrow energy window could enhance the resolvability of a 0.75 mm rod significantly. In an animal imaging experiment, the detailed mouse brain structures such as cortex and thalamus were clearly identified with high contrast. In conclusion, we successfully developed the mouse brain PET insert prototype with a staggered 3-layer DOI detector.
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- 2021
37. Development of dual-ended depth-of-interaction detectors using laser-induced crystals for small animal PET systems
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Mohammadi, Akram, Naoko, Inadama, Fumihiko, Nishikido, Taiga, Yamaya, Mohammadi, Akram, Naoko, Inadama, Fumihiko, Nishikido, and Taiga, Yamaya
- Abstract
Sensitivity and spatial resolution of positron emission tomography (PET) scanners can be improved by using thicker scintillation crystals with depth-of-interaction (DOI) encoding. Subsurface laser engraving (SSLE) can be used to segment crystals of a scintillation detector in order to fabricate a DOI detector. We previously applied SSLE to crystal bars of 3×3×20 mm3 and 1.5×1.5×20 mm3 and developed two dual-ended detectors with DOI segments of 3 mm and 1.5 mm, respectively. To further improve the DOI resolution, our SSLE detector design can be used with smaller pitch crystal bars, making them excellent detector candidates for small animal PET scanners with submillimetre resolution. In the present study, three small crystal bars of 1×1×20 mm3, 2×1×20 mm3, and 2×1×40 mm3 were laser engraved to 12, 20 and 40 segments, respectively, by applying SSLE in their height directions. The segmented crystal bars were characterised in three prototype detector arrangements. First, the 1×1×20 mm3 crystal bars were characterised in an 8×8 crystal array designed for DOI encoding along crystal height in a conventional small animal PET design. Second, a 4×8 crystal array of 2×1×20 mm3 crystal bars was characterised for using the DOI information for crystal interaction positioning along the axial axis of a small animal PET scanner. Finally, the third part of the study was performed on a single 2×1×40 mm3 crystal bar with 40 segments to investigate the feasibility of DOI estimation in longer crystals for application in a system with extended axial length. We evaluated the capability of segment identification and energy resolution of theses detectors. The 3D position maps of the detectors were obtained using the Anger-type calculation and the crystal identification performance was evaluated for each detector. Clear segment separation was obtained for the crystal arrays with 12 (segment pitch of 1.67 mm) and 20 (segment pitch of 1 mm) segments. Mean energy resolutions of 8.8% ± 0.4% and 9.
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- 2021
38. Comparison of two small animal PET prototypes for off-line range verification in carbon beam irradiation
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Hideaki, Tashima, Mohammadi, Akram, Fumihiko, Nishikido, Kang, Hangyu, Go, Akamatsu, Sodai, Takyu, Yuma, Iwao, Shinji, Sato, Hitoshi, Ishikawa, Taiga, Yamaya, Hideaki, Tashima, Mohammadi, Akram, Fumihiko, Nishikido, Kang, Hangyu, Go, Akamatsu, Sodai, Takyu, Yuma, Iwao, Shinji, Sato, Hitoshi, Ishikawa, and Taiga, Yamaya
- Abstract
Small animal studies in the carbon ion therapy field are still necessary to understand cancer cell behavior deeply and to explore new medical applications. For precise irradiation with dose monitoring for small animals, PET measurement of positron emitters produced via fragmentation reactions is desired. This study compared our two recently developed small animal PET prototypes with different performance characteristics. The first is a total body small-animal (TBS) PET prototype with a high sensitivity of 16.7% at the center, while the spatial resolution is limited to about 2 mm. The second is a crosshair light sharing (CLS) PET prototype having sub-millimeter spatial resolution while the sensitivity at the center is limited to 1.0%. Both are compact mobile scanners, which can be moved to an irradiation room at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) for offline PET measurement. Also, they have sufficient axial length for measuring a rat's total body at one time. In this study, cylindrical phantoms of 4 cm diameter and 10 cm length made of polymethyl methacrylate (PMMA) were irradiated with a 290 MeV/u 12C beam (1.2×109 pps) for 16 s. A brass collimator and a PMMA range shifter of 90 mm thickness were placed upstream to adjust the beam shape and the Bragg peak position to the phantom center. Off-line PET measurement start times after the end of irradiation and the measurement times were 5 min and 20 min for TBS PET and 6 min and 30 min for CLS PET, respectively. As a result, peaks in images obtained by TBS and CLS PET prototypes were observed respectively at 4 mm and 3 mm upstream from the Bragg peak position. The obtained image of the CLS PET was significantly noisier than that of TBS PET, although the measurement time of CLS PET was longer. The high sensitivity of the TBS PET prototype is preferred in cases where the number of produced positron emitters is limited., IEEE NSS MIC 2021
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- 2021
39. Dose quantification in carbon ion therapy using in-beam positron emission tomography
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Hideaki Tashima, Fumihiko Nishikido, Daniel Franklin, Andrew Chacon, Harley Rutherford, T Hofmann, M. Safavi-Naeini, Eiji Yoshida, Sodai Takyu, Marco Pinto, Susanna Guatelli, Taiga Yamaya, Katia Parodi, Akram Mohammadi, and Anatoly B. Rosenfeld
- Subjects
Materials science ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Sobp ,Dose profile ,Bragg peak ,Heavy Ion Radiotherapy ,Radiotherapy Dosage ,Radiation Dosage ,Imaging phantom ,030218 nuclear medicine & medical imaging ,Ion ,Computational physics ,03 medical and health sciences ,0302 clinical medicine ,Positron ,030220 oncology & carcinogenesis ,Positron-Emission Tomography ,Humans ,Radiology, Nuclear Medicine and imaging ,Irradiation ,Beam (structure) ,Radiotherapy, Image-Guided - Abstract
This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species - 11C, 10C and 15O. A library of basis functions is constructed by simulating a range of monoenergetic 12C ion irradiations of a homogeneous polymethyl methacrylate phantom and measuring the resulting one-dimensional positron-emitting fragment profiles and dose distributions. To estimate the dose delivered during an arbitrary polyenergetic irradiation, a linear combination of factors from the fragment profile library is iteratively fitted to the decomposed positron annihilation profile acquired during the irradiation, and the resulting weights combined with the corresponding monoenergetic dose profiles to estimate the total dose distribution. A total variation regularisation term is incorporated into the fitting process to suppress high-frequency noise. The method was evaluated with 14 different polyenergetic 12C dose profiles in a polymethyl methacrylate target: one which produces a flat biological dose, 10 with randomised energy weighting factors, and three with distinct dose maxima or minima within the spread-out Bragg peak region. The proposed method is able to calculate the dose profile with mean relative errors of 0.8%, 1.0% and 1.6% from the 11C, 10C, 15O fragment profiles, respectively, and estimate the position of the distal edge of the SOBP to within an average of 0.7 mm, 1.9 mm and 1.2 mm of its true location.
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- 2020
40. Oxygen sensing ability of positronium atom for tumor hypoxia imaging
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Kengo Shibuya, Haruo Saito, Fumihiko Nishikido, Miwako Takahashi, and Taiga Yamaya
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Materials science ,medicine.diagnostic_test ,Tumor hypoxia ,General Physics and Astronomy ,chemistry.chemical_element ,lcsh:Astrophysics ,Electron ,01 natural sciences ,Oxygen ,lcsh:QC1-999 ,030218 nuclear medicine & medical imaging ,Positronium ,03 medical and health sciences ,0302 clinical medicine ,Positron ,Nuclear magnetic resonance ,Unpaired electron ,chemistry ,Positron emission tomography ,lcsh:QB460-466 ,0103 physical sciences ,Atom ,medicine ,010306 general physics ,lcsh:Physics - Abstract
Positronium (Ps), a hydrogen-like atom consisting of a positron and an electron, is efficiently formed in the human body during positron emission tomography (PET) examination, and its decay rate into gamma-ray photons is significantly influenced by the chemical environment, especially the dissolved oxygen concentration (pO2) due to the unpaired electrons. However, the functionality of PET has been underestimated by neglecting the specific information provided by Ps. By comparing the decay rates in O2-, N2-, and air-saturated waters, here we show that Ps probes the absolute value of pO2 with a good linearity and a resolution better than 10 mmHg. This is a sufficient sensitivity for discriminating a hypoxic region in a tumor at approximately 6 mmHg from healthy tissues at approximately 40 mmHg. This method depends only on the fundamental properties of Ps and is independent of specific radiopharmaceuticals. The applications of Ps spin states and reactions will greatly enhance PET functionalities in the next decade. There is strong interest in finding way to detect oxygen starved cells with noninvasive methods able to detect small variation on oxygen in living systems for targeted therapy. The authors present a method based on the decay of the positronium generated in the human body during positron emission tomography (PET) with promising application of the PET for positronium imaging
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- 2020
41. Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
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Susanna Guatelli, Yuma Iwao, Daniel Franklin, Dale Prokopvich, Fumihiko Nishikido, Lachlan Chartier, Go Akamatsu, Akram Mohammadi, Katia Parodi, Anatoly B. Rosenfeld, Mitra Safavi-Naeini, Sodai Takyu, Linh T. Tran, Benjamin James, Hideaki Tashima, Taiga Yamaya, and Andrew Chacon
- Subjects
Particle therapy ,Materials science ,Stable isotope ratio ,Phantoms, Imaging ,medicine.medical_treatment ,Analytical chemistry ,Bragg peak ,Heavy Ion Radiotherapy ,General Medicine ,030218 nuclear medicine & medical imaging ,Ion ,03 medical and health sciences ,Nuclear Medicine & Medical Imaging ,0302 clinical medicine ,Positron ,Japan ,030220 oncology & carcinogenesis ,Ionization chamber ,medicine ,Relative biological effectiveness ,Irradiation ,Radiometry ,Tomography, X-Ray Computed ,Relative Biological Effectiveness - Abstract
Purpose This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in-beam whole-body positron emission tomography scanner for range verification quality assurance. Methods The energy deposited by monoenergetic beams of 11 C at 350 MeV/u, 15 O at 250 MeV/u, 12 C at 350 MeV/u, and 16 O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose-mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon-on-insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron-emitting nuclei were measured for each beam in a gelatin phantom using the in-beam whole-body positron emission tomography scanner at HIMAC. The depth of maximum positron-annihilation density was compared with the depth of maximum dose deposition and the signal-to-background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. Results In the entrance region, the h b o x RBE 10 was 1.2 ± 0.1 for both 11 C and 12 C beams, while for 15 O and 16 O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the RBE 10 was 2.7 ± 0.4 for 11 C and 2.9 ± 0.4 for 12 C, while for 15 O and 16 O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, RBE 10 could only be evaluated for carbon; the RBE 10 was 1.6 ± 0.2 and 1.5 ± 0.1 for 11 C and 12 C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal-to-background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5-fold and 11-fold increases in the ratios calculated for the 15 O and 11 C images compared with the values obtained for 16 O and 12 C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for 11 C, compared to -5.6 ± 0.8 mm for 12 C and 0.9 ± 0.8 mm for 15 O vs -6.6 ± 0.8 mm for 16 O. Conclusions The RBE 10 values for 11 C and 15 O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, 11 C and 15 O beams produce much better quality images for range verification compared with 12 C and 16 O, in particular with regard to estimating the location of the Bragg peak.
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- 2020
42. Biological washout modelling for in-beam PET: rabbit brain irradiation by
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Chie, Toramatsu, Akram, Mohammadi, Hidekazu, Wakizaka, Chie, Seki, Fumihiko, Nishikido, Shinji, Sato, Iwao, Kanno, Miwako, Takahashi, Kumiko, Karasawa, Yoshiyuki, Hirano, and Taiga, Yamaya
- Subjects
Oxygen Radioisotopes ,Positron-Emission Tomography ,Animals ,Brain ,Tissue Distribution ,Carbon Radioisotopes ,Rabbits ,Models, Biological - Abstract
Positron emission tomography (PET) has been used for dose verification in charged particle therapy. The causes of washout of positron emitters by physiological functions should be clarified for accurate dose verification. In this study, we visualized the distribution of irradiated radioactive beams
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- 2020
43. Influence of momentum acceptance on range monitoring of
- Author
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Akram, Mohammadi, Hideaki, Tashima, Yuma, Iwao, Sodai, Takyu, Go, Akamatsu, Han Gyu, Kang, Fumihiko, Nishikido, Eiji, Yoshida, Andrew, Chacon, Mitra, Safavi-Naeini, Katia, Parodi, and Taiga, Yamaya
- Subjects
Motion ,Oxygen Radioisotopes ,Phantoms, Imaging ,Positron-Emission Tomography ,Humans ,Heavy Ion Radiotherapy ,Carbon Radioisotopes ,Monte Carlo Method ,Relative Biological Effectiveness - Abstract
In heavy-ion therapy, the stopping position of primary ions in tumours needs to be monitored for effective treatment and to prevent overdose exposure to normal tissues. Positron-emitting ion beams, such as
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- 2020
44. Development of a multi-use human-scale single-ring OpenPET system
- Author
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Tashima, Hideaki, Yoshida, Eiji, Iwao, Yuma, Wakizaka, Hidekatsu, Mohammadi, Akram, Nitta, Munetaka, Kitagawa, Atsushi, Inaniwa, Taku, Nishikido, Fumihiko, Tsuji, Atsushi, Nagai, Yuji, Seki, Chie, Minamimoto, Takafumi, Fujibayashi, Yasuhisa, Yamaya, Taiga, Hideaki, Tashima, Eiji, Yoshida, Yuma, Iwao, Hidekatsu, Wakizaka, Munetaka, Nitta, Atsushi, Kitagawa, Taku, Inaniwa, Fumihiko, Nishikido, Atsushi, Tsuji, Yuji, Nagai, Chie, Seki, Takafumi, Minamimoto, Yasuhisa, Fujibayashi, Taiga, Yamaya, Tashima, Hideaki, Yoshida, Eiji, Iwao, Yuma, Wakizaka, Hidekatsu, Mohammadi, Akram, Nitta, Munetaka, Kitagawa, Atsushi, Inaniwa, Taku, Nishikido, Fumihiko, Tsuji, Atsushi, Nagai, Yuji, Seki, Chie, Minamimoto, Takafumi, Fujibayashi, Yasuhisa, Yamaya, Taiga, Hideaki, Tashima, Eiji, Yoshida, Yuma, Iwao, Hidekatsu, Wakizaka, Munetaka, Nitta, Atsushi, Kitagawa, Taku, Inaniwa, Fumihiko, Nishikido, Atsushi, Tsuji, Yuji, Nagai, Chie, Seki, Takafumi, Minamimoto, Yasuhisa, Fujibayashi, and Taiga, Yamaya
- Abstract
We developed a human-scale single-ring OpenPET (SROP) system, which had an open space allowing us access to the subject during measurement. The SROP system consisted of 160 4-layer depth-of-interaction detectors. The open space with the axial width of 430 mm was achieved with the ring axial width of 214 mm and the ring inner diameter of 660 mm. The detectors were axially shifted to each other so that the detector ring was aligned along a plane horizontally tilted by 45∘ against the axial direction. The system was developed as a mobile scanner to be used not only in clinical PET rooms but also in charged-particle therapy treatment rooms as well as animal experiment rooms. Almost uniform spatial resolution better than 3 mm throughout the entire FOV was realized with an iterative image reconstruction method. Peak absolute sensitivity was 3.1%, and there was a region with sensitivity better than 0.8% for a length of more than 700 mm. An in-beam imaging experiment conducted at the HIMAC showed that the system was operable even at the highest beam intensity available for heavy-ion therapy. In addition, we conducted entire-body monkey dynamic imaging utilizing the long region inside the gantry by positioning a monkey along the direction having the longest FOV tilted by 45∘ against the axial direction. We concluded the developed system realizes versatile PET applications because of its wide-open space and mobility as well as high spatial resolution with sufficiently good sensitivity.
- Published
- 2020
45. Erratum: Influence of momentum acceptance on range monitoring of 11C and 15O ion beams using in-beam PET
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Mohammadi, Akram, Tashima, Hideaki, Iwao, Yuma, Takyu, Sodai, Akamatsu, Go, Kang, Hangyu, Nishikido, Fumihiko, Yoshida, Eiji, Chacon, Andrew, Safavi naeini, Mitra, Parodi, Katia, Yamaya, Taiga, Hideaki, Tashima, Yuma, Iwao, Sodai, Takyu, Go, Akamatsu, Fumihiko, Nishikido, Eiji, Yoshida, Taiga, Yamaya, Mohammadi, Akram, Tashima, Hideaki, Iwao, Yuma, Takyu, Sodai, Akamatsu, Go, Kang, Hangyu, Nishikido, Fumihiko, Yoshida, Eiji, Chacon, Andrew, Safavi naeini, Mitra, Parodi, Katia, Yamaya, Taiga, Hideaki, Tashima, Yuma, Iwao, Sodai, Takyu, Go, Akamatsu, Fumihiko, Nishikido, Eiji, Yoshida, and Taiga, Yamaya
- Abstract
An error was introduced during the production of this article. In the published paper, figures 9 and 10 display extra axes which should not be there. The following are the corrected figures.
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- 2020
46. Energy spread estimation of radioactive oxygen ion beams using optical imaging
- Author
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Kang, Hangyu, Yamamoto, Seiichi, Takyu, Sodai, Nishikido, Fumihiko, Mohammadi, Akram, Akamatsu, Go, Sato, Shinji, Yamaya, Taiga, Seiichi, Yamamoto, Sodai, Takyu, Fumihiko, Nishikido, Go, Akamatsu, Shinji, Sato, Taiga, Yamaya, Kang, Hangyu, Yamamoto, Seiichi, Takyu, Sodai, Nishikido, Fumihiko, Mohammadi, Akram, Akamatsu, Go, Sato, Shinji, Yamaya, Taiga, Seiichi, Yamamoto, Sodai, Takyu, Fumihiko, Nishikido, Go, Akamatsu, Shinji, Sato, and Taiga, Yamaya
- Abstract
Radioactive ion (RI) beams combined with in-beam positron emission tomography enable accurate in situ beam range verification in heavy ion therapy. However, the energy spread of the radioactive beams generated as secondary beams is wider than that of conventional stable heavy ion beams which causes Bragg peak region and distal falloff region broadening. Therefore, the energy spread of the RI beams should be measured carefully for their quality control. Here, we proposed an optical imaging technique for the energy spread estimation of radioactive oxygen ion beams. A polymethyl methacrylate phantom (10.0 × 10.0 × 9.9 cm3) was irradiated with an 15O beam (mean energy = 247.7 MeV u−1, standard deviation = 6.8 MeV u−1) in the Heavy Ion Medical Accelerator in Chiba. Three different momentum acceptances of 1%, 2% and 4% were used to get energy spreads of 1.9 MeV u−1, 3.4 MeV u−1 and 5.5 MeV u−1, respectively. The in-beam luminescence light and offline beam Cerenkov light images were acquired with an optical system consisting of a lens and a cooled charge-coupled device camera. To estimate the energy spread of the 15O ion beams, we proposed three optical parameters: (1) distal-50% falloff length of the prompt luminescence signals; (2) full-width at half maximum of the Cerenkov light signals in the beam direction; and (3) positional difference between the peaks of the Cerenkov light and the luminescence signals. These parameters estimated the energy spread with the respective mean squared errors of 2.52 × 10−3 MeV u−1, 5.91 × 10−3 MeV u−1, and 0.182 MeV u−1. The distal-50% falloff length of the luminescence signals provided the lowest mean squared error among the optical parameters. From the findings, we concluded optical imaging using luminescence and Cerenkov light signals offers an accurate energy spread estimation of 15O ion beams. In the future, the proposed optical parameters will be used for energy spread estimation of other RI beams as well as stable ion beams.
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- 2020
47. Dose quantification in carbon ion therapy using in-beam positron emission tomography
- Author
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Rutherford, Harley, Chacon, Andrew, Mohammadi, Akram, Takyu, Sodai, Tashima, Hideaki, Yoshida, Eiji, Nishikido, Fumihiko, Hofmann, Teresa, Pinto, Marco, R Franklin, Daniel, Yamaya, Taiga, Parodi, Katia, B Rosenfeld, Anatoly, Guatelli, Susanna, Safavi naeini, Mitra, Sodai, Takyu, Hideaki, Tashima, Eiji, Yoshida, Fumihiko, Nishikido, Taiga, Yamaya, Rutherford, Harley, Chacon, Andrew, Mohammadi, Akram, Takyu, Sodai, Tashima, Hideaki, Yoshida, Eiji, Nishikido, Fumihiko, Hofmann, Teresa, Pinto, Marco, R Franklin, Daniel, Yamaya, Taiga, Parodi, Katia, B Rosenfeld, Anatoly, Guatelli, Susanna, Safavi naeini, Mitra, Sodai, Takyu, Hideaki, Tashima, Eiji, Yoshida, Fumihiko, Nishikido, and Taiga, Yamaya
- Abstract
This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species - 11C, 10C and 15O. A library of basis functions is constructed by simulating a range of monoenergetic 12C ion irradiations of a homogeneous polymethyl methacrylate phantom and measuring the resulting one-dimensional positron-emitting fragment profiles and dose distributions. To estimate the dose delivered during an arbitrary polyenergetic irradiation, a linear combination of factors from the fragment profile library is iteratively fitted to the decomposed positron annihilation profile acquired during the irradiation, and the resulting weights combined with the corresponding monoenergetic dose profiles to estimate the total dose distribution. A total variation regularisation term is incorporated into the fitting process to suppress high-frequency noise. The method was evaluated with 14 different polyenergetic 12C dose profiles in a polymethyl methacrylate target: one which produces a flat biological dose, 10 with randomised energy weighting factors, and three with distinct dose maxima or minima within the spread-out Bragg peak region. The proposed method is able to calculate the dose profile with mean relative errors of 0.8%, 1.0% and 1.6% from the 11C, 10C, 15O fragment profiles, respectively, and estimate the position of the distal edge of the SOBP to within an average of 0.7 mm, 1.9 mm and 1.2 mm of its true location.
- Published
- 2020
48. A validated Geant4 model of a whole-body PET scanner with four-layer DOI detectors
- Author
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M Ahmed, Abdella, Chacon, Andrew, Rutherford, Harley, Akamatsu, Go, Mohammadi, Akram, Nishikido, Fumihiko, Tashima, Hideaki, Yoshida, Eiji, Yamaya, Taiga, R Franklin, Daniel, Rosenfeld, Anatoly, Guatelli, Susanna, Safavi naeini, Mitra, Go, Akamatsu, Fumihiko, Nishikido, Hideaki, Tashima, Eiji, Yoshida, Taiga, Yamaya, M Ahmed, Abdella, Chacon, Andrew, Rutherford, Harley, Akamatsu, Go, Mohammadi, Akram, Nishikido, Fumihiko, Tashima, Hideaki, Yoshida, Eiji, Yamaya, Taiga, R Franklin, Daniel, Rosenfeld, Anatoly, Guatelli, Susanna, Safavi naeini, Mitra, Go, Akamatsu, Fumihiko, Nishikido, Hideaki, Tashima, Eiji, Yoshida, and Taiga, Yamaya
- Abstract
The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq−1 and 6.0 cps kBq−1 for experiment and simulation, respectively. The average spatial resolutions measured for point sources placed at several radial offsets were 5.2± 0.7 mm and 5.0± 0.8 mm FWHM for experiment and simulation, respectively. The peak NECR was 22.9 kcps at 7.4 kBq ml−1 for the experiment, while the NECR obtained via simulation was 23.3 kcps at the same activity. The scatter fractions were 44% and 41.3% for the experiment and simulation, respectively. Contrast recovery estimates performed in different regions of a simulated image quality phantom matched the experimental results with an average error of -8.7% and +3.4% for hot and cold lesions, respectively. The results demonstrate that the developed Geant4 model reliably reproduces the key NEMA NU 2-2012 performance metrics evaluated on the prototype PET scanner. A simplified version of the model is included as an advanced example in Geant4 version 10.5.
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- 2020
49. Fast Scintillation X-Ray Detector Using Proportional-Mode Si-APD and a HfO2-Nanoparticle-Doped Plastic Scintillator
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K. Inoue, Fumiyuki Hiyama, Masanori Koshimizu, Rie Haruki, S. Kishimoto, Fumihiko Nishikido, and Kohei Asai
- Subjects
010302 applied physics ,Nuclear and High Energy Physics ,Scintillation ,Materials science ,business.industry ,Detector ,X-ray detector ,Photodetector ,chemistry.chemical_element ,Scintillator ,Avalanche photodiode ,01 natural sciences ,Hafnium ,Nuclear Energy and Engineering ,chemistry ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,Photonics ,010306 general physics ,business - Abstract
We developed a new fast scintillation detector using proportional-mode silicon avalanche photodiode (Si-APD) for nuclear forward scattering experiments using high-energy synchrotron X-rays >30 keV. After a test of a prototype detector with a lead-loaded plastic scintillator (EJ-256, Eljen Technology) and proportional-mode Si-APD (S8664-3796(X), Hamamatsu Photonics) as a photodetector, we fabricated a four-channel detector using four $3\times 3\times 3$ mm3 EJ-256 scintillators and Si-APD arrays of $3\times 3$ mm2 pixels to increase the detection efficiency. The detector had a 12-mm beam path in the EJ-256. Moreover, a 10wt% HfO2-nanoparticle-doped plastic scintillator (Hf-PLS), 3 mm in diameter and 1 mm in thickness, was examined using the prototype detector. Hafnium is a heavy atom of atomic number 72 and the energy of the K-absorption edge is 65.351 keV. Its oxide nanoparticles, ~4 nm in diameter, were incorporated into a polymer matrix. The pulse-height distribution and time spectra for the detector with the Hf-PLS were measured at −34 °C with an APD gain of ~200 for 57.6-keV X-rays. The light yield of the Hf-PLS was 1.2 times that of the EJ-256 of the same size, and a good time resolution of 0.34 ns (full width of half maximum) was obtained better than that of 0.54 ns for the EJ-256. This was due to the difference in the scintillation solution, as only 2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3, 4-oxadiazole was added in the Hf-PLS, however, for in the EJ-256, the binary solutions, such as 2,5-diphenyloxazole and 1,4-bis (5-phenyl- 2-oxazolyl)benzene, were included.
- Published
- 2018
50. Measurement of nuclear resonant scattering on 61 Ni with fast scintillation detector using proportional-mode silicon avalanche photodiode
- Author
-
Yoshitaka Yoda, Masanori Koshimizu, Fumihiko Nishikido, Rie Haruki, Shunji Kishimoto, Keisuke Inoue, and Yasuhiro Kobayashi
- Subjects
010302 applied physics ,Physics ,Nuclear and High Energy Physics ,Scintillation ,Silicon ,Physics::Instrumentation and Detectors ,business.industry ,Forward scatter ,Detector ,chemistry.chemical_element ,Synchrotron radiation ,Scintillator ,Avalanche photodiode ,01 natural sciences ,Synchrotron ,law.invention ,Optics ,chemistry ,law ,0103 physical sciences ,Optoelectronics ,010306 general physics ,business ,Instrumentation - Abstract
We developed a new scintillation timing detector using a proportional-mode silicon avalanche photodiode (Si-APD) for synchrotron radiation nuclear resonant scattering. We report on the nuclear forward scattering measurement on 61Ni with a prototype detector using a lead-loaded plastic scintillator (EJ-256, 3 mm in diameter and 2 mm in thickness), mounted on a proportional-mode Si-APD. Using synchrotron X-rays of 67.41 keV, we successfully measured the time spectra of nuclear forward scattering on 61Ni enriched metal foil and 61Ni86V14 alloy. The prototype detector confirmed the expected dynamical beat structure with a time resolution of 0.53 ns (FWHM).
- Published
- 2018
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