Purpose/Objective(s): High-dose-rate (HDR) brachytherapy for the prostate is a widely spread and effective treatment method. A real time image guidance is perform with an ultrasound probe with the largest cross section being used as the reference view for needles insertion. The majority of institutions use a template to facilitate the insertion with a distribution so as to avoid being near organs at risk (OARs) (urethra, rectum). However, such a conservative approach may make coverage of the prostate with the prescribed dose more difficult in the central region, particularly at the base and apex. The goal of this research is to demonstrate statistically using an unpaired t-test the benefits of an insertion pattern with some needles closer to the OARs at the reference view. Materials/
Methods: A total of 40 prostate HDR brachytherapy plans have been modified by moving the needle between the urethra and rectum as close to the urethra as possible from the reference view in the axial direction. All other parameters that may influence dose distribution, whether the total number of needles, their position and the depth of insertion remained unchanged thus making it possible to isolate the impact of the difference in insertion. Then, keeping the dose received to the rectum and urethra identical to the original plan, a final optimization was performed in order to update the dose distribution. Results: The result of the paired t-test being t=5.509, the null hypothesis stating that there is no statistically significant difference is very unlikely. In addition, the new implantation allowed better coverage of the prostate for 38 of the 40 cases. Conclusion: By simply modifying the position of the needle between the urethra and the rectum so that it is as close as possible to the urethra without modifying anything else, it was possible to significantly improve the dosimetric coverage of the majority of cases of HDR prostate brachytherapy.
