Optimization of a multipoint plastic scintillator dosimeter for high dose rate brachytherapy

TL;DR

This paper presents the design, optimization, and characterization of a multipoint plastic scintillator dosimeter for real-time dose measurement in high dose rate brachytherapy, achieving accurate in vivo dosimetry with minimized signal interference.

Contribution

The study introduces an optimized multipoint plastic scintillator design with a multispectral approach for improved in vivo dosimetry in HDR brachytherapy, including detailed configuration and performance analysis.

Findings

Optimized scintillator placement enhances light collection and reduces inter-scintillator effects.

The system accurately differentiates scintillation signals from background noise.

Dose measurements deviate less than 5% from standard TG-43 values.

Abstract

Purpose: This study aims to optimize and characterize the response of a mPSD for in vivo dosimetry in HDR brachytherapy. Methods: An exhaustive analysis was carried out in order to obtain an optimized mPSD design that maximize the scintillation light collection produced by the interaction of ionizing photons. Several mPSD prototypes were built and tested in order to determine the appropriate order of scintillators relative to the photodetector, as well as their length as a function of the scintillation light emitted. Scintillators BCF-60, BCF-12 and BCF-10 constituted the mPSD sensitive volume.Each scintillator contribution to the total spectrum was determined by irradiations in the low energy range.For the best mPSD design, a numerical optimization was done in order to select the optical components that better match the light emission profile. The optimized dosimetric system was used for HDR brachytherapy dose determination. The system performance was quantified in term of signal to noise ratio and signal to background ratio. Results: It was determined that BCF-60 should be placed at the distal position, BCF-12 in the center and BCF-10 at proximal position with respect to the photodetector.This configuration allowed for optimized light transmission through the collecting fiber, avoiding inter-scintillator excitation and self-absorption effects.The optimized luminescence system allowed for signal deconvolution using a multispectral approach, extracting the dose to each element while taking into account Cerenkov stem effect.Differences between the mPSD measurements and TG-43 remain below 5%. In all measurement conditions, the system was able to properly differentiate the produced scintillation signal from the background one. Conclusions: A mPSD was constructed and optimized for HDR brachytherapy dosimetry, enabling real time dose determination, up to 6.5cm from the 192Ir source.