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Monte Carlo-based energy response studies of diode dosimeters in radiotherapy photon beams

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Abstract

This study presents Monte Carlo-calculated absolute and normalized (relative to a 60Co beam) sensitivity values of silicon diode dosimeters for a variety of commercially available silicon diode dosimeters for radiotherapy photon beams in the energy range of 60Co–24 MV. These values were obtained at 5 cm depth along the central axis of a water-equivalent phantom of 10 cm × 10 cm field size. The Monte Carlo calculations were based on the EGSnrc code system. The diode dosimeters considered in the calculations have different buildup materials such as aluminum, brass, copper, and stainless steel + epoxy. The calculated normalized sensitivity values of the diode dosimeters were then compared to previously published measured values for photon beams at 60Co–20 MV. The comparison showed reasonable agreement for some diode dosimeters and deviations of 5–17 % (17 % for the 3.4 mm brass buildup case for a 10 MV beam) for some diode dosimeters. Larger deviations of the measurements reflect that these models of the diode dosimeter were too simple. The effect of wall materials on the absorbed dose to the diode was studied and the results are presented. Spencer–Attix and Bragg–Gray stopping power ratios (SPRs) of water-to-diode were calculated at 5 cm depth in water. The Bragg–Gray SPRs of water-to-diode compare well with Spencer–Attix SPRs for ∆ = 100 keV and above at all beam qualities.

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Acknowledgments

The authors thank Dr. Y.S. Mayya, Head, Radiological Physics and Advisory Division, Bhabha Atomic Research Centre (BARC), and Dr. A.K. Ghosh, Director, Health, Safety and Environment Group, BARC, and Dr. G. Chourasiya, BARC for their encouragement and support throughout this project.

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Correspondence to T. Palani Selvam.

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Arun, C., Palani Selvam, T., Dinkar, V. et al. Monte Carlo-based energy response studies of diode dosimeters in radiotherapy photon beams. Radiol Phys Technol 6, 151–156 (2013). https://doi.org/10.1007/s12194-012-0181-2

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  • DOI: https://doi.org/10.1007/s12194-012-0181-2

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