| Budget Amount *help |
¥5,590,000 (Direct Cost: ¥4,300,000、Indirect Cost: ¥1,290,000)
Fiscal Year 2013: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2012: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2011: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000)
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| Research Abstract |
In passive particle radiotherapy, secondary neutrons are produced by nuclear reaction because most incident particles collide with collimators. We additionally set a fixed-aperture collimator (FC) to the upper stream in a beam delivery system to reduce neutron exposure.
This study was performed by Monte Carlo toolkit Geant4. The beam delivery system of Heavy Ion Medical Accelerator in Chiba (HIMAC) was constructed in Geant4. We calculated the neutron ambient dose equivalent at patient position with and without FC. Incident particle was carbon-ion of 290 and 400 MeV/n. The diameter of laterally uniform irradiation field was 100 and 200 mm.
The measured secondary neutron ambient dose equivalent without FC was reproduced in Geant4. The neutron dose equivalent was approximately reduced to 40% for 400 MeV/n carbon-ion beam, by inserting the FC optimized not to affect the lateral dose distribution. We can found out that the neutron exposure can be reduced by inserting the FC.
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