Dosimetric characteristics of the DRAXIMAGE model LS‐1 I‐125 interstitial brachytherapy source design: A Monte Carlo investigation

摘要: (Received 5 June 2001; accepted for publication 26 December published 19 March 2002) We have used Monte Carlo photon transport simulations to evaluate dosimetric characteristics of a new 125I seed, the DRAXIMAGE BrachySeed (model LS-1) source interstitial brachytherapy and calculate parameters recommended by AAPM Task Group 43 (TG-43). To eliminate thick end welds, preformed closed-ended Ti shells are welded together near transverse plane. The radioactivity is localized seed ends in order maximize isotropy at typical prescription distances. Transmission radiography reveals that its internal components can move as much 200 microm under influence gravitational forces affecting dose-rate constant relative dose distribution 5% 10%, respectively. However, clinical be well represented weighted average distributions corresponding three different orientation-dependent geometry configurations. This agrees closely (within 1% 1 cm) with derived from specified vendor model (seed uniformly spaced), which dosimetry were derived. An 0.935 cGy h(-1) U(-1) application values 0.919, 0.963, 0.920 vertical orientation, horizontal geometries, NIST wide-angle free-air chamber realization air-kerma strength primary standard, SKN99, was explicitly simulated. show output Ag characteristic x rays about half 6711 resulting between pure x-ray emitters. Finally, it demonstrated TG-43 point-source formalism more accurately estimates solid-angle small distances if one uses radial function data prepared using point-source, rather than line-source, factor.