The accuracy of single‐seed dose superposition for I‐125 implants

Abstract

The Monte Carlo method was used to study perturbations of single I-125 seed dose distributions created by the presence of one or three neighboring seeds for the case of seeds immersed in a water phantom. Perturbation factors were determined within the geometric shadow of neighboring seeds for two-seed designs, four-seed spacings, and several choices of dose point. The results were compared to dose estimates obtained by the simple superposition of single-seed data for one- and two-plane implants. Some significant differences were found.

Code of practice for brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task Group No. 56

“…Similarly, in computer dose calculations for interstitial implants, interseed effects are ignored. Measurements 45 and Monte Carlo calculations 46 for 125 I implants show that for the specific geometries investigated the actual peripheral dose is about 6% lower than that obtained from summing single source doses. Unlike the situation with colpostats, there are as yet insufficient data to recommend incorporating interseed effects into treatment planning systems.…”

Preliminary Research of Tissue Heterogeneity Correction for Dose Distribution of125I Brachytherapy Source

“…By considering Eqs. (2), (6), and (7) together, we can find that dose calculation under tissue heterogeneity conditions is transformed to a process of determining the dose calculation parameters of the source in some homogeneous medium. The method to determine these parameters has been discussed in many articles.…”

“…Nevertheless, this calculation model has ignored several important factors: namely (a) seed anisotropy introduced by the real 3-D line source, (b) interseed effect caused by numerous sources that are available simultaneously, and (c) tissue heterogeneity which is substantial in actual clinical implants. Although there have been numerous detailed works [4][5][6][7][8][9][10] available focusing on (a) and (b), studies on the tissue heterogeneous effect are not common and detailed. 11,12) Here, we conduct research and discuss the tissue heterogeneous effect on dose distribution for a single source.…”

High-resolution mapping of 1D and 2D dose distributions using X-band electron paramagnetic resonance imaging

“…In brachytherapy the need of validation is high; in interstitial brachytherapy, the effects of source-to-source shielding (1,2) should be considered and shielded applicators in intracavitary brachytherapy are used the dose distributions should be validated (3). Several dosimetry systems have been used to perform accurate dose measurements.…”