Performance of a terbium doped gadolinium oxysulphide plastic optical fiber sensor in a flattening filter free setting: Measurements and Monte Carlo simulation

Majed Alharbi, Michael Martyn, Sean Gillespie, Peter Woulfe, Sinead O'Keeffe, Mark Foley

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

This paper presents an initial investigation into the depth dependence of an inorganic optical fibre sensor (OFS) based on physical measurements and Monte Carlo (MC) simulations, using a 6 MV flattening filter free (FFF) beam. The OFS was fabricated using an inorganic scintillating material (Gd2O2S:Tb), which was embedded in a cavity of diameter 700 μm, in a 1mm plastic optical fibre. Percentage depth dose (PDD) profiles were measured in a solid water phantom for three field sizes: 10×10 cm2, 4×4 cm2 and 2×2 cm2. The OFS results were then compared to an ion chamber and the W1 plastic scintillator. A MC model of an Elekta Versa HD linear accelerator (linac) was developed using the MC software packages BEAMnrc and DOSXYZnrc and then used to simulate the Gd2O2S:Tb and polystyrene scintillators. The OFS measurements over-estimated the dose when compared to the ion chamber and the W1 measurements, across the investigated field sizes, by a maximum of 30%, 20% and 15% for 10×10 cm2, 4×4 cm2 and 2×2 cm2, respectively. The MC simulations of the Gd2O2S:Tb and polystyrene scintillators were in good agreement with the W1 and ion chamber measurements, however, the OFS measurements were found to differ across all field sizes. Our results therefore indicate the need for further investigation into the overall contribution of the stem effect to the discrepancy between the OFS physical measurements and the ion chamber and the W1 measurements.

Original languageEnglish
Title of host publicationOptical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIX
EditorsIsrael Gannot, Israel Gannot
PublisherSPIE
ISBN (Electronic)9781510623866
DOIs
Publication statusPublished - 2019
EventOptical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIX 2019 - San Francisco, United States
Duration: 2 Feb 20193 Feb 2019

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume10872
ISSN (Print)1605-7422

Conference

ConferenceOptical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIX 2019
Country/TerritoryUnited States
CitySan Francisco
Period2/02/193/02/19

Keywords

  • Inorganic Scintillator
  • Monte Carlo
  • Optical Fibre Sensor
  • Percentage Depth Dose.
  • Radiation Therapy

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