| Summary: | 碩士 === 元培科學技術學院 === 影像醫學研究所 === 95 === Abstract
Clinically, the issue of air cavity interface dose is the major concern of radiation oncologists and medical physicists. Underdosing of the treatment target in radiation therapy can occur when tumors are situated near natural air cavities due to charged particle disequilibrium around air-tissue interfaces.
The measurement is performed using a Siemens Primus linear accelerator equipped with 6 MV and 15 MV photons. The study use CVD diamond thermoluminescent dosimeter to measure the interface dose. The variables of the problem included x-ray energy, cavity shape and dimension, and depth of the cavity in water. The study results indicate that the dose perturbation is strongly dependent on x-ray energy, field size, depth and size of cavity in water. Results, the CVD diamond films measurement show dose reductions of 77% at 3×3cm2 .respectively, beyond the air–water interface distal to the radiation source for a 4cm thick air slab irradiated will increase 20% Dose. When used difference cavity shape, in square air cavity will finding interface dose increase 18%. In triangular form air cavity will finding interface dose increase 6% and circular form air cavity interface dose increase 8%。In order to reduce air cavity interface dose effect. The study adding the water balloon in air cavity to reduce air cavity content should improving electron disequilibrium effect.
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