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  4. A Verification of High-Dose-Rate Brachytherapy Dose Distributions for Prostate Cancer with a VIPET Polymer Gel Dosimeter

A Verification of High-Dose-Rate Brachytherapy Dose Distributions for Prostate Cancer with a VIPET Polymer Gel Dosimeter

K Eguchi1*, Y Watanabe2 , S Mizukami2 , T Maeyama3 , S Hayashi4 , T Gomi2 , (1) Kitasato University Graduate School of Medical Sciences, Sagamihara, Kanagawa, Japan, (2) School of Allied Health Sciences, Kitasato University, Sagamihara, Kanagawa, Japan, (3) School of Science, Kitasato University, Sagamihara, Kanagawa, Japan, (4) Faculty of Health Sciences, Hiroshima International University, Higashihiroshima, Hiroshima, Japan,

Presentations

(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The purpose of this study was to evaluate the accuracy of a three-dimensional dose distribution measurement using a normoxic N-vinylpyrrolidone-based polymer gel dosimeter (VIPET) in a clinical application of high-dose-rate (HDR) prostate brachytherapy.

Methods: A cylindrical glass vessel with a diameter of 120 mm and a height of 125 mm was used as a gel container. An iridium-192 source was transported into a VIPET gel dosimeter with 18 flexible catheters to simulate a clinical case. For all catheters, nine source positions within 40 mm of each other were used. Moreover, a dwell time of 4 s was used all source positions. This approach corresponded to delivering an absorbed dose of 10 Gy to a planning target volume (PTV). A 1.5 T MR scan of the gel produced Râ‚‚ (= 1/Tâ‚‚) maps. The dose distribution in the VIPET gel dosimeter and treatment planning system (TPS) calculations were compared using a gamma analysis.

Results: The VIPET gel dose response was linear up to 30 Gy. A dose rate dependence was not observed in the range of 3.1−18.9 Gy/min. The dose distribution of the VIPET gel dosimeter and the TPS calculations showed a good agreement. A gamma passing rate was 93.2%, within 3%/2 mm criteria and 30% threshold dose. The magnetic susceptibility artifact due to air in the catheters was observed in a region less than 5 mm from the source center.

Conclusion: In this study, we measured the dose distribution of a plan with multiple catheters and source positions that simulated HDR prostate brachytherapy using a VIPET polymer gel dosimeter. The dose distribution measured with the VIPET gel dosimeter was in a good agreement with TPS calculations in simulation. Therefore, VIPET gel dosimeters have the potential to be useful for quality assurance in HDR brachytherapy.

Keywords

HDR, Brachytherapy, Gel Dosimeter

Taxonomy

TH- Radiation dose measurement devices: 3D solid gel/plastic

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