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Evaluation of distance and angular dependence of polycrystalline semiconductor dosimeters for Ir-192 brachytherapy source using experimental measurements and Monte Carlo simulations
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M.J. Han   , S.W. Kang , K.Y. Eom , I.A. Kim , J.S. Kim , B. Lee , W. Cho , J.B. Chung |
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Abstract: (23 Views) |
Background: This study evaluates the distance and angular dependence of polycrystalline semiconductor-based dosimeters (PSDs) using lead (II) iodide (PbI₂) (PbI₂ PSD) and lead (II) oxide (PbO) (PbO PSD) for Ir-192 brachytherapy source. Experimental measurements were compared with Monte Carlo (MC) simulations to verify the dosimeters' performance and accuracy. Materials and Methods: PSDs were fabricated using PbI₂ and PbO as photoconductive materials, with a thin-film deposition process ensuring uniformity. Distance dependence was assessed by measuring dosimeter responses at source-to-surface distances ranging from 1 cm to 8 cm at 0.25 cm intervals, while angular dependence was evaluated at angles from 0° to 60° in 15° increments. MC simulations using the Geant4 Application for Tomographic Emission (GATE) v9.1 were conducted under identical conditions to validate the experimental measurements. Results: The experimental and simulated data demonstrated a strong agreement with the inverse-square law, with determination coefficient (R²) exceeding 0.98 for PbI₂ and PbO PSDs. The distance at which the signal intensity dropped by 50% (D₅₀) for measurements and simulations was 1.493 cm and 1.487 cm for PbI₂ PSD, respectively, and 1.488 cm and 1.481 cm for PbO PSD. Angular dependence analysis showed a decrease in response with increasing angle, with PbO PSD exhibiting slightly larger discrepancies (maximum difference of 5.48%) compared to PbI₂ PSD (maximum difference of 4.56%) between measurements and simulations. Conclusion: PbI₂ and PbO PSDs demonstrated predictable distance and angular dependence, closely aligning with MC simulations. However, angular correction factors may be necessary to improve dosimetric accuracy in clinical applications. |
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| Keywords: Dosimeters, semiconductors, brachytherapy, iridium-192 radioisotope, Monte Carlo simulation, quality assurance. |
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Full-Text [PDF 879 kb]
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Type of Study: Original Research |
Subject:
Radiation Biology
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