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Purpose: To determine if there is an association between the degree of prostate trauma during prostate brachytherapy and development of acute urinary toxicity., Methods and Materials: In a consecutive prospective cohort of permanent (125)I prostate brachytherapy patients, the number of times each needle was repositioned was tracked, and the dosimetry plans were used to determine the number of times needles within 1 cm of the urethra were manipulated. Additionally, prostate volume, total number of needles, number of needles/prostate volume, and the number of periurethral needle manipulations/prostate volume were determined. The need for catheterization beyond 24 hours and the Radiation Therapy Oncology Group (RTOG) urinary toxicity score at 4 weeks were recorded. The independent samples t test was used to search for a correlation between these parameters and the recorded toxicity scores., Results: Twenty-eight consecutive implant patients were evaluated in the study. Median (range) values were as follows: prostate volume 35 cc ( range, 15-51 cc), number of needles per patient 32 (range, 21-41), number of needle manipulations per patient 94.5 ( range, 55-147), and number of periurethral needle manipulations 42 (range, 17-65). The only significant association between urinary toxicity and these variables was for the number of periurethral needle manipulations (p = 0.025)., Conclusions: These data provide evidence that needle prostate trauma during brachytherapy contributes to acute urinary toxicity.

Abstract: Purpose: To investigate the feasibility of using new micro-MOSFET detectors for QA and in vivo dosimetry of the urethra during transperineal interstitial permanent prostate implants (TIPPB). Methods and materials: This study involves measurements for several patients who have undergone the implant procedure with iodine-125 seeds. A new micro-MOSFET detector is used as a tool for in vivo measurement of the initial dose rate within the urethra. MOSFETs are calibrated using a single special order calibration seed. The angular response is investigated in a 100kVp X-ray beam. Results: micro-MOSFETs are found to have a calibration factor of 0.03cGy/mV for low energy X-rays and a high isotropic response (within 2.5%). Prostate volume and shape changes during TIPPB due to edema caused by the trauma of needle insertion, making it difficult to achieve the planned implant geometry and hence the desired dose distribution. MOSFET measurements help us to evaluate the overall quality of the implant, by analyzing the maximum dose received by urethra, the prostate base coverage, the length of the prostatic urethra that is irradiated, and the apex coverage. Conclusions: We demonstrate that ease of use, quick calibration and the instantaneous reading of accumulated dose make micro-MOSFETs feasible for in vivo dosimetry during TIPPB. [Copyright &y& Elsevier]