A gas scintillator detector for 2D dose profile monitoring in pencil beam scanning and pulsed beam proton radiotherapy treatments

Abstract

In order to address dosimetry demands during proton therapy treatments utilizing pencil beam scanning and/or pulsed beam accelerators, we have developed a xenon-filled Gas Scintillation Detector (GSD) that can monitor delivered dose and two-dimensional beam centroid position pulse-by-pulse in real time, with high response linearity up to high instantaneous dose rates. We present design considerations for the GSD and results of beam tests carried out at operating proton therapy clinics. In addition to demonstrating spatial resolution with σ of a few hundred microns in each transverse dimension and relative dose precision better than 1% over large treatment areas, the test beam results also reveal the dependence of the GSD dose normalization on dose rate, beam energy, and gas impurities. The results demonstrate the promise of the GSD technology to provide an important addition to dosimetry approaches for next-generation ion beam therapy.

Ultra‐high dose rate dosimetry: Challenges and opportunities for FLASH radiation therapy

“…Novel approaches based on gas scintillators are a promising alternative for beam monitoring at UHDRs, thanks to the high level of transparency and fast response. A xenon gas scintillator coupled to large photomultiplier tubes (PMTs) for real-time 2D beam monitoring for pulsed and pencil beam scanning proton RT treatments was used by Vigdor et al 103 A spatial resolution of a few hundred micrometers was achieved, with a linear response within 1% up to a dose rate of 300 Gy/s. An alternative approach was investigated using air as a medium in which fluorescence is developed.…”

Ultra‐high dose rate electron beams and the FLASH effect: From preclinical evidence to a new radiotherapy paradigm

“…29 Two-and three-dimensional measurements with luminescent technology have also been successfully implemented. [30][31][32][33][34]…”

“…recently demonstrated the successful implementation of a 10$$\ {{\mu {\text m}}}$$ thick BC‐400 film plastic scintillator coupled to a 1 mm diameter optical fiber in a synchrotron X‐ray beam, which showed excellent performance at dose rates of up to 4435 Gy/s 29 . Two‐ and three‐dimensional measurements with luminescent technology have also been successfully implemented 30–34 …”

Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

“…Due to its high spatio-temporal resolution, optical imaging has also been used for quality assurance purposes in pencil beam scanning (PBS) proton therapy; a technique which also utilizes high dose rates (up to 200 Gy/s near the Bragg Peak). For example, Vigdor et al [97] used a xenon gas scintillator coupled to large PMTs for monitoring 2D beam characteristics in real-time for pulsed and pencil beam scanning proton radiotherapy treatments. The authors demonstrated a spatial resolution of a few hundred microns.…”