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Oliver-Canamas, L., Vijande, J., Candela-Juan, C., Gimeno-Olmos, J., Pujades-Claumarchirant, M. C., Rovira-Escutia, J. J., et al. (2023). A User-Friendly System for Mailed Dosimetric Audits of Ir-192 or Co-60 HDR Brachytherapy Sources. Cancers, 15(9), 2484–14pp.
Abstract: Nowadays, the options available to perform external dosimetric audits of the high dose rate (HDR) brachytherapy treatment process are limited. In this work, we present a methodology that allows for performing dosimetric audits in this field. A phantom was designed and manufactured for this purpose. The criteria for its design, together with the in-house measurements for its characterization, are presented. The result is a user-friendly system that can be mailed to perform dosimetric audits in HDR brachytherapy on-site for systems using either Iridium-192 (Ir-192) or Cobalt-60 (Co-60) sources. Objectives: The main goal of this work is to design and characterize a user-friendly methodology to perform mailed dosimetric audits in high dose rate (HDR) brachytherapy for systems using either Iridium-192 (Ir-192) or Cobalt-60 (Co-60) sources. Methods: A solid phantom was designed and manufactured with four catheters and a central slot to place one dosimeter. Irradiations with an Elekta MicroSelectron V2 for Ir-192, and with a BEBIG Multisource for Co-60 were performed for its characterization. For the dose measurements, nanoDots, a type of optically stimulated luminescent dosimeters (OSLDs), were characterized. Monte Carlo (MC) simulations were performed to evaluate the scatter conditions of the irradiation set-up and to study differences in the photon spectra of different Ir-192 sources (Microselectron V2, Flexisource, BEBIG Ir2.A85-2 and Varisource VS2000) reaching the dosimeter in the irradiation set-up. Results: MC simulations indicate that the surface material on which the phantom is supported during the irradiations does not affect the absorbed dose in the nanoDot. Generally, differences below 5% were found in the photon spectra reaching the detector when comparing the Microselectron V2, the Flexisource and the BEBIG models. However, differences up to 20% are observed between the V2 and the Varisource VS2000 models. The calibration coefficients and the uncertainty in the dose measurement were evaluated. Conclusions: The system described here is able to perform dosimetric audits in HDR brachytherapy for systems using either Ir-192 or Co-60 sources. No significant differences are observed between the photon spectra reaching the detector for the MicroSelectron V2, the Flexisource and the BEBIG Ir-192 sources. For the Varisource VS2000, a higher uncertainty is considered in the dose measurement to allow for the nanoDot response.
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Oliver-Cañamas, L., Vijande, J., Candela-Juan, C., & Perez-Calatayud, J. (2025). Dosimetry audits in high dose rate brachytherapy: A survey on the current scenario in Europe. Phys. Medica, 136, 105047–7pp.
Abstract: Introduction: This work aims to study the current scenario of dosimetry audits in high dose rate (HDR) brachytherapy (BT) in Europe to evaluate whether there is a need to implement more services of this type and to define the characteristics that they should meet according to users. Material and methods: A survey consisting of 30 multiple choice questions was designed and distributed among European centers. The estimated time to answer was less than 15 min. 74 HDR BT centers participated, having 192Ir, 60Co and/or electronic sources. Information about users' opinions and experience with dosimetry audits in this field, center resources and quality assurance (QA) procedures was gathered. Results: For 61 % of users, dosimetry audits in HDR BT should be recommended, but not mandatory, whereas 35 % suggested that they are necessary and should be compulsory. Only for 4 % of participants these audits are not necessary. In contrast, 86 % of users found that the current number of these services is inadequate and that more national and/or international services are needed. Most participants operate according to QA recommendations of published guidelines, with exceptions, such as the use of the Reference Air Kerma Rate provided by the manufacturer instead of the one measured by the home medical physicist. Conclusion: The number of HDR BT dosimetry audits available to users is inadequate and there is a need to implement more national and/or international services of this type. Some technical aspects that an audit of this type should fulfill are outlined in this work.
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