Dosimetric influence of seed spacers and end-weld thickness for permanent prostate brachytherapy

作者：Melhus Christopher S; Mikell Justin K; Frank Steven J; Mourtada Firas; Rivard Mark J^*

来源：Brachytherapy, 2014, 13(3): 304-310.

DOI：10.1016/j.brachy.2013.09.004

• Seed spacer
• Prostate brachytherapy
• Dose perturbation
• Monte Carlo

PURPOSE: The aim of this study was to analyze the dosimetric influence of conventional spacers and a, cobalt chloride complex contrast (C4) agent, a novel marker for MIRI that can also serve as a seed spacer, adjacent to (103)pd, I-125, 1 and Cs-131 sources for permanent prostate brachytherapy.
METHODS AND MATERIALS: Monte Carlo methods for radiation transport were used to estimate the dosimetric influence of brachytherapy end-weld thicknesses and spacers near the three sources. Single-source assessments and volumetric conditions simulating prior patient treatments were computed. Volume dose distributions were imported to a treatment planning system for dose volume histogram analyses.
RESULTS: Single-source assessment revealed that brachytherapy spacers primarily attenuated the dose distribution along the source long axis. The magnitude of the attenuation at 1 cm on the long axis ranged from -10% to -5% for conventional spacers and approximately -2% for C4 spacers, with the largest attenuation for Pd-103. Spacer perturbation of dose distributions was less than manufacturing tolerances for brachytherapy sources as gleaned by an analysis of end-weld thicknesses. Volumetric Monte Carlo assessment demonstrated that TG-43 techniques overestimated calculated doses by approximately -2%. Specific dose-volume histogram metrics for prostate implants were not perturbed by inclusion of conventional or C4 spacers in clinical models.
CONCLUSIONS: Dosimetric perturbations of single-seed dose distributions by brachytherapy spacers exceeded 10% along the source long axes adjacent to the spacers. However, no dosimetric impact on volumetric parameters was noted for brachytherapy spacers adjacent to Pd-103, I-125, or Cs-131 sources in the context of permanent prostate brachytherapy implants.

• 出版日期2014-6