Wobbler法と二重リングニ重散乱体法における散乱や半影の計算

概要

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The irradiation system of a heavy charged- particle radiotherapy including a proton beam should make uniform irradiation fields for target area. In order to reduce radiation dose to normal tissues, it is required to cut sharply the uniform field by a collimator. A penumbra size of the field should be as small as possible. In order to optimize the irradiation system from this point of the view, beam dynamics passing through beam modifying devices of the irradiation system should be analyzed. Analytical function, which describes statistical characteristics of the beam transversing through the irradiation system, is obtained and applied to calculate the penumbra size of the collimated beam. The analytical functions are useful for the beam wobbling system and also for the double scatterer system which are considered to be standard irradiation methods for making uniform large irradiation fields. Analytical equations for the wobbler and dual ring double scatterer methods are given and coded. From these calculations, we found that penumbra size of the irradiation system using dual-ring double scatterer was at zero depth in a water phantom twice larger than that using the wobbler method. And the difference of penumbra was kept in the deeper region of the phantom.
Japan Society of Medical Physicsの論文