Impacts of the composition and density of tissue on the dose distribution of implanted 125I seeds / 中华放射医学与防护杂志

ABSTRACT

Objective:To investigate the impacts of the composition and physical density of tissue on the dose distribution of implanted 125I seeds, in order to provide references for the clinical dose calculation and assessment of implanted radioactive particles. Methods:The OncoSeed 6711 physical model of 125I seeds was established using thes of twareegs_brachy and was validated through the calculation of dose rate constant and the radial dose function [ g( r)] in water. Then, based on the element composition and physical density of different types of tissue, the g( r) and absorbed dose ratein water, prostate, breast, muscle, and bone were calculated. Results:The calculated dose rate constant (0.950 cGy·h -1·U -1) and g( r)in water approached the values in related literature. The absorbed dose in bone was 6.042 times than that in water at a distance of 0.05 cm from the implanted source. The difference between the absorbed doses in breast and water was more than 10% at a distance of less than 1.7 cm from the implanted source. The difference between the absorbed doses in prostate/muscle and water was less than 5% at the same radial location. Conclusions:The dose distribution of 125I seeds in some types of human tissue is significantly different from that in water, which should be carefully considered in clinical dose calculation.