Fabricated Germanium-doped optical fibres for mapping Gamma-ray doses in blood Irradiator

Blood transfusions are generally safe medical procedures; however, they can lead to Transfusion-Associated Graft-versus-Host Disease (TA-GvHD). To reduce TA-GvHD risk, blood should be irradiated at a minimum dose of 25 Gy. Dose mapping is essential for ensuring accurate and consistent dose distribution within the blood irradiator. This ensures the radiation dose falls within the prescribed range of 15 Gy and 50 Gy to mitigate the occurrence of the disease. Over the past decade, External Beam Therapy (EBT) film has been validated for blood irradiation in quality assurance (QA), while optical fibres are increasingly used as radiation dosimeters. Studies have suggested the potential of Germanium-doped optical fibres as alternative dosimeters. The objective of this study is to establish the dosimetric characteristics of optical fibre using a Gamma-ray Cobalt-60 machine, perform dose mapping in a Cesium-137 source blood irradiator using a blood-equivalent phantom, and investigate the clinical application of optical fibres as a blood dose indicator for gamma exposure of blood bags irradiated for nine minutes and 56 seconds to deliver a central dose of 25 Gy. The Thermoluminescence (TL) signals emitted by the fibres were measured using a HarshawTM 3500 TLD reader. In this study, fabricated optical fibres with a specification of 2.3 mol% Germanium-doped optical fibres were used in both cylindrical and flat shapes in comparison with the EBT-XD film. This aims to explore its feasibility as a potential dosimeter for measuring radiation dose in QA (as a dose mapper) and as a dose indicator in clinical applications in blood irradiation. From the current finding, the result revealed no significant difference in the TL responses for each type of fibre for sensitivity characteristics, with medium sensitivity batch (within ± 10%) demonstrating a decrease in Coefficient of Variation (CV) from 12.8% to 5.57% for CF and 13.8% to 5.91% for FF. For doses linearity up to 50 Gy, both CF and FF exhibit a highly linear dose response (R2 > 99%). The notable signal fading loss of 28-day storage for CF and FF were 11.5% and 9.2%, respectively. The dose mapping performed in blood irradiator using the blood-equivalent phantom revealed no significant difference (p =.654 and .073, 95% confidence level) in the mean absorbed dose of optical fibres throughout the edge and the middle of the plane when compared to the mean measured dose obtained using EBT-XD film, as analysed by the one-way analysis of variance (ANOVA) test. For the clinical trial results as dose indicator, the blood bag dosimetry also demonstrated no significant difference, with p =.285 (p > 0.05), across all dosimeters when subjected to a radiation dose of 25 Gy in the central region of the blood bags. The outcomes of this study indicate that all objectives have been successfully achieved. Germanium-doped optical fibers have exhibited excellent dosimetric characteristics in blood irradiation dosimetry. This novel Ge-doped optical fiber dosimetry reveals significant potential as an alternative passive dosimeter for mapping in QA procedures and as innovative dose indicators for clinical applications.

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