Papers by Tomonori Fukuchi
Journal of Instrumentation
We developed a positron emission tomography (PET) system for multiple-isotope imaging. Our PET sy... more We developed a positron emission tomography (PET) system for multiple-isotope imaging. Our PET system, named multiple-isotope PET (MI-PET), can distinguish between different tracer nuclides using coincidence measurement of prompt γ-rays, which are emitted after positron emission. In MI-PET imaging with a pure positron emitter and prompt-γ emitter, because of the imperfectness of prompt γ-ray detection, an image for a pure positron emitter taken by MI-PET is superposed by a positron-γ emitter. Therefore, in order to make isolated images of the pure positron emitter, we developed image reconstruction methods based on data subtraction specific to MI-PET. We tested two methods, subtraction between reconstructed images and subtraction between sinogram data. In both methods, normalization for position dependence of the prompt γ-ray sensitivity is required in addition to detector sensitivity normalization. For these normalizations, we performed normalization scans using cylindrical phantoms of the positron-γ emitters 44m Sc (prompt γ-ray energy: 1157 keV) and 22 Na (prompt γray energy: 1274 keV). A long period measurement using the activity decay of 44m Sc (T1/2 = 58.6 hours) elucidated that the acquisition ratio between the prompt γ-rays coincided with PET event and pure PET event changes on the basis of object activities. Therefore, we developed a correction method that involves subtraction parameters dependent on the activities, i.e., the counting rate. We determined that correction for sensitivity normalization in variation of activity can be performed using only the triple-coincidence rate as an index, even if using a different nuclide from that used for normalization. From analysis of dual-tracer phantom images using 18 F and 44m Sc or 18 F and 22 Na, data subtraction in the sinogram data with sensitivity correction gives a higher quality of isolated images for the pure positron emitter than those from image subtractions. Furthermore, from dual-isotope (18 F-FDG and 44m Sc) mouse imaging, we concluded that our developed method can be used for practical imaging of a living organism.
To study the chemical origin of life, we investigated the amino acid production probability from ... more To study the chemical origin of life, we investigated the amino acid production probability from radiocarbon (C)-containing carboxylic acid via β-decay using a newly developed Monte Carlo simulator for molecular dynamics calculation. Using the simulation, we calculated the dynamical trajectory of N recoiled via C β-decay in [3-C]propionic acid and evaluated the staying probability of N in the compound, which is the glycinium (a protonated glycine) production probability from [3-C]propionic acid. The glycinium production probability was calculated to be 78.7% assuming static compound structures of [3-C]propionic acid and a glycinium C–N binding potential energy of 3.93 eV. From calculations with various binding potential parameters, a glycinium production probability of approximately 30% was expected by simulation in case of a loose C–N binding potential energy of 2-eV. Introduction The abiotic synthesis of amino acids in the first step of the chemical origin of life remains a fundam...
A New Era of Nuclear Structure Physics, 2004
In order to search for high-spin isomers in N=51 isotones, an unstable nuclear beam 17N was devel... more In order to search for high-spin isomers in N=51 isotones, an unstable nuclear beam 17N was developed using the low-energy radioisotope beam separator(CRIB) of the Center for Nuclear Study(CNS), University of Tokyo, in RIKEN. High-spin isomers in N=83 isotones have been systematically studied. These isomers are of stretch coupled configurations and oblate shape. High-spin isomers of N=51 isotones are expected
Journal of the Physical Society of Japan, 2007
Bulletin of the American Physical Society, 2005
Journal of the Physical Society of Japan, 2007
Journal of Instrumentation, 2018
The high-resolution imaging of alpha particles is required for the development of radio-compounds... more The high-resolution imaging of alpha particles is required for the development of radio-compounds for targeted alpha-particle therapy or alpha emitter detection at nuclear facilities. Therefore, we developed an ultrahighresolution, real-time alpha-particle imaging system for observing the trajectories of alpha particles in a scintillator. The developed alpha-particle imaging system is made from a 1-μm-diameter fiber-structure scintillator plate that is optically coupled with the first of two sequentially connected tapered optical fiber plates. The output of the second, larger tapered optical fiber plate was imaged by an electron-multiplied (EM) cooled CCD camera. With our developed imaging system, we observed images of alpha particles having a spatial resolution of ~11 μm. We could also observe the trajectories of alpha particles with Bragg peaks for the angled incident alpha particles. We conclude that this imaging system, which can observe the trajectory of alpha particles in a fiberstructure scintillator, is promising for research on targeted alpha-particle therapy or alpha emitter detection at nuclear facilities.
Medical physics, 2017
Positron emission tomography (PET) is a useful imaging modality that quantifies the physiological... more Positron emission tomography (PET) is a useful imaging modality that quantifies the physiological distributions of radiolabeled tracers in vivo in humans and animals. However, this technique is unsuitable for multiple-tracer imaging because the annihilation photons used for PET imaging have a fixed energy regardless of the selection of the radionuclide tracer. This study developed a multi-isotope PET (MI-PET) system and evaluated its imaging performance. Our MI-PET system is composed of a PET system and additional γ-ray detectors. The PET system consists of pixelized gadolinium orthosilicate (GSO) scintillation detectors and has a ring geometry that is 95 mm in diameter with an axial field of view of 37.5 mm. The additional detectors are eight bismuth germanium oxide (BGO) scintillation detectors, each of which is 50 × 50 × 30 mm(3) , arranged into two rings mounted on each side of the PET ring with a 92-mm-inner diameter. This system can distinguish between different tracers using ...
The Compton camera has found applications in many fields such as medical imaging, astrophysics, e... more The Compton camera has found applications in many fields such as medical imaging, astrophysics, environmental monitoring and nuclear non-proliferation. We are developing a gamma-ray Compton camera for medical use of multiple molecular imaging, which we call GREI (Gamma-Ray Emission Imaging). The GREI system consists of two double-sided orthogonal-strip high-purity germanium semiconductor detectors. Each detector can detect the interaction position and
SPIE Proceedings, 2010
ABSTRACT A prototype molecular imaging system that features wide-band imaging capability from 100... more ABSTRACT A prototype molecular imaging system that features wide-band imaging capability from 100 keV to MeV was developed based on a germanium Compton camera. In this system, radiotracer imaging is performed through the Compton imaging technique above 300 keV and through the coded mask imaging technique below 200 keV. For practical use, small animal imaging requires spatial resolution of the order of millimeters. We conducted tests with a multiple-well phantom containing 99mTc (140 keV) and 54Mn (834 keV), and confirmed the spatial resolution of better than 3.2 mm for the phantom placed 35 mm above the detector. We also report imaging results of a living mouse into which we injected 99mTc (140 keV) and 54Mn (834 keV).
2008 IEEE Nuclear Science Symposium Conference Record, 2008
In order to improve the performance of a Ge Compton camera system, γ-ray tracking technique which... more In order to improve the performance of a Ge Compton camera system, γ-ray tracking technique which determines the γ-ray multi-scattering sequence in a crystal is implemented. Using this tracking technique with optimized parameters, imaging sensitivity increases by a factor of 3.7 in the case of 1115-keV γ-ray energy.
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
We have investigated the possibility of three-dimensional (3D) tomographic imaging by semiconduct... more We have investigated the possibility of three-dimensional (3D) tomographic imaging by semiconductor Compton cameras that we have been developing for multiple molecular simultaneous imaging. As a significant feature of Compton cameras, multi-directional projection of the ¿-ray source distribution can be obtained even by a fixed-angle imaging with a single Compton camera unit. We have already implemented a 3D tomographic image
Origin of Matter & Evolution of Galaxies 2003, 2005
ABSTRACT The Mg-23+p elastic resonance scattering was observed by using a low-energy radioactive-... more ABSTRACT The Mg-23+p elastic resonance scattering was observed by using a low-energy radioactive-ion beam of Mg-23 to study resonance levels in Al-24. Resonance patterns were found in the excitation function of the elastic scattering. New information on spin-parities and widths of the Al-24 levels may help understand the stellar Mg-23(p,gamma)Mg-24 reaction rates. Another data of the Mg-24+p resonance scattering, taken simultaneously in the present experiment, confirmed the present experimental technique.
Physics Letters B, 2008
The neturon rich nucleus 13 B was studied via the proton transfer reaction 4 He(12 Be, 13 Bγ) at ... more The neturon rich nucleus 13 B was studied via the proton transfer reaction 4 He(12 Be, 13 Bγ) at 50A MeV. The known 4.83-MeV excited state was strongly populated and its spin and parity were assigned to 1/2 + by comparing the angular differential cross section data with DWBA calculations. This low-lying 1/2 + state is interpreted as a proton intruder state and indicates a deformation of the nucleus.
Physical Review C, 2005
High-spin isomers with J π = 49/2 + and 27 + have been systematically observed in a number of N =... more High-spin isomers with J π = 49/2 + and 27 + have been systematically observed in a number of N = 83 isotones with 60 Z 67 at excitation energies ∼9 MeV. Based on experimental excitation energies, an odd-even binding energy staggering has been extracted for the first time for these multi-quasiparticle states. Surprisingly, the magnitude of the odd-even effect in high-spin isomers turned out to be very close to that in ground states, thus challenging conventional wisdom that pairing correlations are reduced in highly excited states. Theoretical analysis based on mean-field theory explains the observed proton number dependence of the odd-even effect as a manifestation of strong pairing correlations in the highly excited states. Mean-field effects and the proton-neutron residual interaction on the odd-even staggering are also examined.
Physical Review C, 2006
The high-spin states of 150 Ho have been studied by the 141 Pr(16 O,7n) 150 Ho reaction at a beam... more The high-spin states of 150 Ho have been studied by the 141 Pr(16 O,7n) 150 Ho reaction at a beam energy of 165 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-γ-t coincidences were performed. Based on the coincidence relations of γ rays, a level scheme was constructed up to 11.25 MeV. The excitation energy of high-spin isomer was determined to be 8.412 MeV with a half-life of 787 ± 36 ns. The experimental results were compared with deformed independent particle model (DIPM) calculations. The excitation energy of the state with the possible configuration of the high-spin isomer in 150 Ho was discussed.
Journal of the Physical Society of Japan, 2008
ABSTRACT
Journal of the Physical Society of Japan, 2007
... Shuichi TANAKA 3, Masaki INOUE 3, Takafumi SASAKI 3, Michiya KIBE 3, Naho HOKOIWA 3, Tsutomu ... more ... Shuichi TANAKA 3, Masaki INOUE 3, Takafumi SASAKI 3, Michiya KIBE 3, Naho HOKOIWA 3, Tsutomu SHINOZUKA 4, Masahiro FUJITA 4, Akiyoshi YAMAZAKI 4, Tetsu SONODA 4, ChunSik LEE 5, Young Kwan KWON 5, Jun Young MOON 5, and Ju Hahn LEE 5 ...
Journal of Analytical Atomic Spectrometry, 2013
ABSTRACT We have constructed the second prototype of the semiconductor Compton camera GREI that e... more ABSTRACT We have constructed the second prototype of the semiconductor Compton camera GREI that enables spectroscopic imaging of wide energy-range gamma-rays. The improved imaging performance has been demonstrated by an imaging experiment with a tumor-baring live mouse, where we were able to obtain the distribution images of the 64Cu-labeled antibody to the implanted three tumor sites of different cell lines, together with that of 65Zn, which was simultaneously administered as ZnCl2 solution. The imaging performance has been compared with that of the primary prototype of GREI, and the importance of the improvement for the simultaneous imaging of multiple radiotracers has been revealed. The methodology offered by GREI is expected to make a unique contribution toward establishing a new viewpoint for understanding life phenomena.
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Papers by Tomonori Fukuchi