Room: Room 202
Purpose: A feasibility study on an imaging of a monochromatic carbon-ion beam for carbon-ion therapy using a pinhole camera for X-rays by measuring secondary electron bremsstrahlung (SEB) was performed by means of a Monte Carlo simulation and a beam-irradiation experiment.
Methods: A beam-irradiation experiment was performed at Gunma University Heavy Ion Medical Center. A horizontal carbon-ion beam having the energy of 290 MeV/u was perpendicularly incident onto a water phantom and SEB photons from the beam trajectory in the phantom were measured by a pinhole camera. We also performed a Monte Carlo simulation to evaluate the image acquired by the pinhole camera by utilizing a simulation code PHITS.
Results: From the simulation, it was found that the trajectory of the carbon-ion beam having the injection energies of 290 MeV/u in a water phantom were clearly imaged by measuring the SEB having energies from 30 to 60 keV by the pinhole camera. The range position was found to be coincident with the position where the ratio of the count of SEB acquisition to the maximum count was 0.231. For the experimental result, we evaluated whether the expected range position coincide with the estimated range position where the ratio of the count to the maximum count coincided with the ratio 0.231, which was deduced from the simulation. As a result, the estimated range from the experimental result was 15.54 Â± 0.12 cm and slightly shorter than the expected range, 14.87 cm.
Conclusion: We showed that the beam trajectories were clearly imaged measuring SEB. In the simulation result, the range positions were able to be pinpointed by the position where the ratio was 0.231. For the experimental result, the position which was pinpointed by the ratio of 0.231 slanted 0.67 cm to the positive direction of x-coordinate from the expected range position.