Feasibility of a 64-Channel Scintillation Fiber System for Real-Time Monitoring of Dwell Positions and Dwell Times of High-Dose-Rate Brachytherapy Sources

Abstract

A 64-channel scintillation fiber-based real-time monitoring system (SFRMS) was developed and evaluated to verify the dwell position and dwell time of the radioactive source in high-dose-rate brachytherapy. The measurement system consists of 64 sensors installed around a tandem applicator. The distal end of the readout system was fiber-optically connected to the measurement system. The data readout system consisted of a photomultiplier tube and a measurement and automation explorer. The SFRMS accuracy was evaluated in terms of dwell position, output linearity, and dwell time using an afterloader with a 192Ir source. Additionally, a Gafchromic EBT3 film was inserted into the applicator to compare fiber measurements. Furthermore, a clinical treatment plan and silicon-based anthropomorphic phantom were utilized to evaluate the accuracy of the dwell positions and dwell times of the source in a situation mimicking a real treatment. The measured output signals from each sensor were fit with Gaussian and inverse-square functions to determine the exact source dwell positions. The difference in dwell position between the plans and the estimated data was −0.63 ± 0.25 mm for the Gaussian fitting and 0.72 ± 0.26 mm for the inverse-square fitting. The difference in dwell time between the plans and the estimated data was within 0.1 sec. For the measurements of the clinical plan on the silicon-based anthropomorphic phantom, the difference in dwell position between the plans and the estimated data was less than 0.88 ± 0.29 mm for the Gaussian fitting and less than 0.85 ± 0.36 mm for the inverse-square fitting. The SFRMS can accurately detect source dwell positions and dwell times and provide real-time output.

Keywords

• Index terms dwell position
• dwell time
• high-dose-rate brachytherapy
• real-time monitoring
• scintillation fiber