Abstract

An optical fiber sensor for monitoring low dose radiation is presented. The sensor, based on radiation sensitive scintillation material, terbium doped gadolinium oxysulphide (Gd2O2S:Tb), is embedded in a cavity of 700µm diameter within a 1mm plastic optical fiber. The sensor is compared with the treatment planning system for repeatability, angular dependency, distance and accumulated radiation activity. The sensor demonstrates a high sensitivity of 152 photon counts/Gy with a temporal resolution of 0.1 seconds, with the largest repeatability error of 4.1%, to 0.361mCi of Iodine-125 the radioactive source most commonly used in LDR brachytherapy for treating prostate cancer.

Highlights

  • Prostate brachytherapy (BT) refers to the implantation of radioactive sources into the prostate under image guidance

  • This paper presents a radiotherapy dosimeter based on optical fiber sensor technology, offering the unique ability to directly measure the radiation dose administered to the tumour and surrounding tissues

  • The optical fiber sensor was fixed within a novel prostate phantom, developed in-house using water equivalent RW3 material, to allow for comparison of results with the Task Group (TG)-43 Dose Calculation [21]

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Summary

Introduction

Prostate brachytherapy (BT) refers to the implantation of radioactive sources (or “seeds”) into the prostate under image guidance. The patient undergoes a transrectal ultrasound or Computed Tomography (CT)/ Magnetic Resonance Imaging (MRI) based volume study This information allows the radiation oncologist to pre-plan the 3D seed distribution required to deliver the prescribed dose to the prostate. Real-time treatment planning guides the radiation oncologist on where is best to locate the seeds in terms of proximity to organs at risk (OARs) [1] These seeds are usually Iodine-125, with apparent activities of the individual seeds typically ranging from 0.357mCi to 0.42mCi, and have a half-life of 59.43 days. Human errors contribute to the majority of mistakes and accidents reported from brachytherapy, a few are related to technical issues [8] This can be typically incorrect patient demographics, seed radiation activity, prescribed total dose or simple software issues [8]. This work has expanded on the verification methods used to validate the sensor and its potential clinical application in brachytherapy

Sensor fabrication
Results and discussion
Repeatability
Angular dependency
Distance
Accumulated radiation activity
Discussion and conclusion
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