Time-resolved optically stimulated luminescence of Al₂O₃:C for ion beam therapy dosimetry

Abstract

The objective of this study was to characterize the time-resolved (TR) optically stimulated luminescence (OSL) from Al2O3:C detectors and investigate methodologies to improve the accuracy of these detectors in ion beam therapy dosimetry, addressing the reduction in relative response to high linear energy transfer (LET) particles common to solid-state detectors. Al2O3:C OSL detectors (OSLDs) were exposed to proton, (4)He, (12)C and (16)O beams in 22 particle/energy combinations and read using a custom-built TR-OSL reader. The OSL response rOSL, relative to (60)Co gamma dose to water, and the ratio between the UV and blue OSL emission bands of Al2O3:C (UV/blue ratio) were determined as a function of the LET. Monte-Carlo simulations with the multi-purpose interaction and transport code FLUKA were used to estimate the absorbed doses and particle energy spectra in the different irradiation conditions. The OSL responses rOSL varied from 0.980 (0.73 keV μm(-1)) to 0.288 (120.8 keV μm(-1)). The OSL UV/blue ratio varied by a factor of two in the investigated LET range, but the variation for (12)C beams was only 11%. OSLDs were also irradiated at different depths of carbon ion spread-out Bragg peaks (SOBPs), where it was shown that doses could be obtained with an accuracy of ± 2.0% at the entrance channel and within the SOBP using correction factors calculated based on the OSL responses obtained in this study. The UV/blue ratio did not allow accurate estimation of the dose-averaged LET for (12)C SOBPs, although the values obtained can be explained with the data obtained in this study and the additional information provided by the Monte-Carlo simulations. The results demonstrate that accurate OSLD dosimetry can be performed in ion beam therapy using appropriate corrections for the OSL response.

AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs

“…Therefore, between different proton beams, additional k Q corrections are small and likely unnecessary. However, a significant difference in k Q would be expected between a proton beam and a carbon beam, and even exist within a given carbon beam because of their greater LET variability . Heavy ion beams, in particular, pose a major challenge for luminescence dosimetry.…”

“…However, a significant difference in k Q would be expected between a proton beam and a carbon beam, and even exist within a given carbon beam because of their greater LET variability. 51,121 Heavy ion beams, in particular, pose a major challenge for luminescence dosimetry. Detector responses have been found to vary not only as a function of LET, but also as a function of the ion species at a given LET.…”

Evidence of Optically Stimulated Luminescence in Lu3Al5O12:Ce

“…Al 2 O 3 single crystals shows a significant light‐induced fading of the TSL signal, that can be exploited for producing high sensitive OSL dosimeters. Nowadays, Al 2 O 3 :C is one of the most studied OSL materials and tested in a multitude of dosimetry applications …”

Fluorescent nuclear track detectors – Review of past, present and future of the technology

“…Other two absorption bands at 230 and 255 nm with emission at 330 nm and very short lifetime of ~2 ns are assigned to transitions in single oxygen vacancies with just one electron and denoted as F + -centers (Akselrod et al, 1990;Evans and Stapelbroek, 1978). F and F + -centers have been studied in detail and play a key role in the TL and OSL mechanisms of Al 2 O 3 :C (Akselrod et al, 1990(Akselrod et al, , 1998Yukihara et al, 2015). 3c) are present.…”