コリメータ散乱係数(S_C)およびファントム散乱係数(S_P)を用いた4MV X線不整形照射野線量評価法

概要

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Calculation of in-air or in-water dose for 4 MV X-ray irregular fields could be accurately performed using the collimator scatter factor (S_c) and phantom scatter factor (S_p) concepts. It has been revealed that the equivalent square field for a multi-leaf collimator (MLC) irregular field can be evaluated accurately by using the S_p-Clarkson or S_c-Clarkson integration method; however, the S_c-Clarkson integration method is more straightforward because the S_c factor expresses the in-air X-ray output factor. It has been found that when the MLC field is relatively much smaller than the main collimator field, the S_c factor can be accurately evaluated by introducing the small segment correction (SSC) factor (except for the case in which the MLC field is less than 1×1 cm^2). It has also been found that both the 5P factor and the tissue-phantom ratio (TPR) can be precisely evaluated by introducing the FMLC factor in cases in which the ratio of the MLC equivalent square field side to the main collimator equivalent square field side is less than about 0.7.
社団法人日本放射線技術学会の論文
2004-11-20