Feasibility study of a plastic scintillating plate‐based treatment beam fluence monitoring system for use in pencil beam scanning proton therapy

Abstract

Purpose The purpose of this study was to describe a plastic scintillating plate‐based gantry‐attachable dosimetry system for pencil beam scanning proton therapy to monitor entrance proton beam fluence, and to evaluate the dosimetric characteristics of this system and its feasibility for clinical use. Methods The dosimetry system, consisting of a plastic scintillating plate and a CMOS camera, was attached to a dedicated scanning nozzle and scintillation during proton beam irradiation was recorded. Dose distribution was calculated from the accumulated recorded frames. The dosimetric characteristics (energy dependency, dose linearity, dose rate dependency, and reproducibility) of the gantry‐attachable dosimetry system for use with therapeutic proton beams were measured, and the feasibility of this system during clinical use was evaluated by determining selected quality assurance items at our institution. Results The scintillating plate shortened the range of the proton beam by the water‐equivalent thickness of the plate and broadened the spatial profile of the single proton spot by 11% at 70 MeV. The developed system functioned independently of the beam energy (<1.3%) and showed dose linearity, and also functioned independently of the dose rate. The feasibility of the system for clinical use was evaluated by comparing the measured quality assurance dose distribution to that of the treatment planning system. The gamma passing rate with a criterion of 3%/3 mm was 97.58%. Conclusions This study evaluated the dosimetric characteristics of a plastic scintillating plate‐based dosimetry system for use with scanning proton beams. The ability to account for the interference of the dosimetry system on the therapeutic beam enabled offline monitoring of the entrance beam fluence of the pencil beam scanning proton therapy independent of the treatment system with high resolution and in a cost‐effective manner.

Development of a real‐time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder

“…In proton therapy, the entrance dose was measured using an optical fiber and a plastic scintillator to monitor treatment beam, and perturbations induced by these devices were evaluated by measuring differences in spot sizes and ranges in their presence and absence. 47,48 Similarly, when the SC-IVD (100 mg of scintillating powder) was placed on the phantom surface, it was found that the dose at R90, usually used as the prescription depth, was reduced by 2.2% for the 6 MeV electron beam energy compared to the case without the SC-IVD. The percent dose reduction was lower at higher electron beam energy and higher at R50, which was sensitive to the measurement depth.…”

“…For example, several studies have evaluated the transmission factor for Dolphin, a commercial transmission detector, to determine the feasibility of using it online during treatment. In proton therapy, the entrance dose was measured using an optical fiber and a plastic scintillator to monitor treatment beam, and perturbations induced by these devices were evaluated by measuring differences in spot sizes and ranges in their presence and absence 47,48 . Similarly, when the SC‐IVD (100 mg of scintillating powder) was placed on the phantom surface, it was found that the dose at R90, usually used as the prescription depth, was reduced by 2.2% for the 6 MeV electron beam energy compared to the case without the SC‐IVD.…”

Two‐dimensional time‐resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations

“…Scintillation imaging has been routinely utilized for proton beams with the use of commercial scintillator‐based systems for quality assurance 4,5 or in‐house developed systems 6–11 . High temporal resolution can be obtained by using a fast camera.…”

“…Scintillation imaging has been routinely utilized for proton beams with the use of commercial scintillatorbased systems for quality assurance 4,5 or in-house developed systems. [6][7][8][9][10][11] High temporal resolution can be obtained by using a fast camera. So far, this has been employed for PBS proton irradiations at conventional dose rates from a cyclotron 12,13 and a synchrocyclotron 14,15 as well as for electron UHDR irradiations, 16 exhibiting great potential for dosimetry for FLASH radiotherapy.…”