Preliminary research for mutual dose perturbation influence of 125I brachytherapy source

For two arrangement modes of two I-125 brachytheray sources, a homo-longitudinal axis and a homo-transverse axis, the sum of dose distributions caused by each single source and actual dose distribution of the two coexisting sources are calculated separately in a clinically interested area by Monte Carlo simulation. Comparisons between them are used to evaluate the mutual dose perturbation influence. The result shows, for the homo-longitudinal axis arrangement, obvious perturbation can be observed along the longitudinal direction when the distances between sources' centers, L, are 0.5 cm and 1.0 cm, up to 11.7 +/- 0.4% and 4.8 +/- 0.2%, respectively, but, can be negligible for the distance exceeding 2.0 cm. For the homo-transverse axis arrangement, the range of dose perturbation depends on the source length and distances between sources' centers, and an influence extent is greater than the former, e.g., 27.2 +/- 1.1%, 15.4 +/- 0.6%, and 7.0 +/- 0.3% maximum for L = 0.5 cm, 1.0 cm, and 2.0 cm, respectively. As for dose perturbation induced by the source leaning which happened in actual implant sometimes, the result indicates a dose fluctuation became more acute with obliquity increasing. The maximum dose increasing, 54.5 +/- 2.1% and 199.7 +/- 7.8%, and the maximum dose decreasing, 42.6 +/- 1.7% and 64.9 +/- 2.6%, could be observed for 10 degrees and 30 degrees obliquity with L = 1.0 cm for the two arrangement modes respectively.