Distance and Angular Dependence of Polycrystalline Semiconductor Dosimeters Based on Mercury(II) Iodide (HgI2) and Tallium(I) Bromide(TlBr) for an Iridium-192 Source: Experimental Measurements and Monte Carlo Simulation Comparison
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This study evaluated the feasibility of polycrystalline semiconductor dosimeters (PSDs) fabricated from mercury (II) iodide (HgI2) and thallium (I) bromide (TlBr) for quality assurance in high-dose-rate (HDR) brachytherapy with an Iridium-192 (Ir-192) source. The PSDs were manufactured using screen-printing and annealing processes, and their performance was evaluated with respect distance and angular dependence. Experimental measurements were conducted with varying source-to-detector distances (1–8 ㎝) and angular positions (0°–60°), and the results were validated using Monte Carlo (MC) simulations with the GATE platform. Both PSDs exhibited dose responses following the inverse square law, with the HgI2-based PSD showing a slope closer to the theoretical value of -2, indicating higher sensitivity. In angular dependence, the TlBr-based PSD demonstrated superior stability, with smaller deviations over different angles compared to HgI2. The experimental data showed good agreement with MC simulations, with differences mostly generally 3–9%. These findings confirm that HgI2 and TlBr PSDs provide reliable, real-time, and high-resolution dose measurements, highlighting their potential as alternative detectors for brachytherapy quality assurance. Further investigations into long-term stability and dose-rate dependence are warranted for clinical implementation.
Abstract
This study evaluated the feasibility of polycrystalline semiconductor dosimeters (PSDs) fabricated from mercury (II) iodide (HgI2) and thallium (I) bromide (TlBr) for quality assurance in high-dose-rate (HDR) brachytherapy with an Iridium-192 (Ir-192) source. The PSDs were manufactured using screen-printing and annealing processes, and their performance was evaluated with respect distance and angular dependence. Experimental measurements were conducted with varying source-to-detector distances (1–8 ㎝) and angular positions (0°–60°), and the results were validated using Monte Carlo (MC) simulations with the GATE platform. Both PSDs exhibited dose responses following the inverse square law, with the HgI2-based PSD showing a slope closer to the theoretical value of -2, indicating higher sensitivity. In angular dependence, the TlBr-based PSD demonstrated superior stability, with smaller deviations over different angles compared to HgI2. The experimental data showed good agreement with MC simulations, with differences mostly generally 3–9%. These findings confirm that HgI2 and TlBr PSDs provide reliable, real-time, and high-resolution dose measurements, highlighting their potential as alternative detectors for brachytherapy quality assurance. Further investigations into long-term stability and dose-rate dependence are warranted for clinical implementation.