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[Press Release]Imaging method of monochromatic beams by measuring secondary electron bremsstrahlung for particle therapy using a pinhole X-ray camera.

Update:2018年12月26日更新
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Abstract

 A feasibility study on the imaging of monochromatic carbon-ion beams for particle therapy was performed. The evaluation was based on Monte Carlo simulations and beam-irradiation experiments, using a pinhole X-ray camera, which measured secondary electron bremsstrahlung (SEB).

 Figure (A) shows a 3-D view of the setup of the Monte Carlo simulation. The setup was symmetrical to the yz-plane. A water phantom was placed at the origin of the coordinate. The size of the phantom was 20 × 20 × 10 cubic cm. A pinhole X-ray camera was placed 98 cm apart from the phantom.

 Figure (B) shows a photograph of the experimental setup. The experiment was performed at Gunma university heavy ion medical center. The beam ion was carbon-twelve. The beam diameter was 3.52 cm. The number of the incident ions was 4.7 × 1011. The measurement duration was 300 seconds.

 The simulation results indicated that the trajectories of the carbon-ion beams with injection energies of 278, 249 and 218 MeV/u in a water phantom, were clearly imaged by measuring the SEB with energies from 30 to 60 keV (see Fig. C), using a pinhole camera. The Bragg-peak positions for these three injection energies were located at the positions where the ratios of the counts of SEB acquisitions to the maximum counts were approximately 0.23, 0.26 and 0.29, respectively.

 Moreover, we experimentally demonstrated that the trajectories of the carbon-ion beams in a water phantom, were clearly imaged (see Fig. D) and it was possible to identify the Bragg-peak positons, at the positions where the ratios coincided with the simulation results.

Image

photo of A 3-D view of the geometrical setup of the Monte Carlo simulation

(A) A 3-D view of the geometrical setup of the Monte Carlo simulation.

photo of A photograph of the experimental setup
(B) A photograph of the experimental setup.

photo of The reconstructed images for the simulations with the beam energies of (a) 278, (b) 249 and (c) 218 MeV/u. White solid lines represent the edges of the phantoms

(C) The reconstructed images for the simulations with the beam energies of (a) 278, (b) 249 and (c) 218 MeV/u. White solid lines represent the edges of the phantoms.

photo of The reconstructed images for the irradiations of the water phantom by the carbon-ion beams with the beam energies of (a) 278, (b) 249 and (c) 218 MeV/u. White solid lines represent the edges of the phantoms

(D) The reconstructed images for the irradiations of the water phantom by the carbon-ion beams with the beam energies of (a) 278, (b) 249 and (c) 218 MeV/u. White solid lines represent the edges of the phantoms.

Reference

 Physics in Medicine & Biology, in press (DOI: 10.1088/1361-6560/aaa17c)

 Imaging of monochromatic beams by measuring secondary electron bremsstrahlung for carbon-ion therapy using a pinhole X-ray camera

 Mitsutaka Yamaguchi1,*, Yuto Nagao1, Koki Ando2, Seiichi Yamamoto2, Makoto Sakai3, Raj Kumar Parajuli3, Kazuo Arakawa1,3 and Naoki Kawachi1
1Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-machi, Takasaki, Gunma, Japan
2Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, Aichi, Japan
3Gunma University Heavy Ion Medical Center, Gunma University, 3-39-22 Showa-machi, Maebashi, Gunma, Japan
*Corresponding author.

Contact

Mitsutaka Yamaguchi (mitsutaka.yamaguchi@qst.go.jp)
Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, QST