Dose distribution verification in high-dose-rate brachytherapy using a highly sensitive normoxic N-vinylpyrrolidone polymer gel dosimeter.

Abstract

Rapid technological advances in high-dose-rate brachytherapy have led to a requirement for greater accuracy in treatment planning system calculations and in the verification of dose distributions. In high-dose-rate brachytherapy, it is important to measure the dose distribution in the low-dose region at a position away from the source in addition to the high-dose range in the proximity of the source. The aim of this study was to investigate the accuracy of a treatment plan designed for prostate cancer in the low-dose range using a normoxic N-vinylpyrrolidone-based polymer gel (VIPET gel) dosimeter containing inorganic salt as a sensitizer (iVIPET). The dose response was evaluated on the basis of the transverse relaxation rate (R2) measured by magnetic resonance scanning. In the verification of the treatment plan, gamma analysis showed that the dose distributions obtained from the polymer gel dosimeter were in good agreement with those calculated by the treatment planning system. The gamma passing rate according to the 2%/2 mm criterion was 97.9%. The iVIPET gel dosimeter provided better accuracy for low doses than the normal VIPET gel dosimeter, demonstrating the potential to be a useful tool for quality assurance of the dose distribution delivered by high-dose-rate brachytherapy.

• Authors: Yusuke Watanabe, Shinya Mizukami, Kou Eguchi, Takuya Maeyama, Shin-Ichiro Hayashi, Hiroshi Muraishi, Tsuyoshi Terazaki, Tsutomu Gomi
• Journal: Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) (Phys Med) Vol. 57 Pg. 72-79 (Jan 2019) ISSN: 1724-191X [Electronic] Italy
• PMID: 30738535 (Publication Type: Journal Article)
• Copyright: Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Chemical References

• Gels
• Povidone

Topics

• Brachytherapy
• Gels
• Humans
• Phantoms, Imaging
• Povidone
• Radiation Dosage
• Radiometry (instrumentation)
• Radiotherapy Dosage
• Radiotherapy Planning, Computer-Assisted