Radiophotoluminescence glass dosimetry end-to-end audit of high dose rate gynaecological brachytherapy in Charlotte Maxeke Johannesburg Academic Hospital

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2020

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Ntombela, Lethukuthula Nqobizitha

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OBJECTIVES: The objective of this research was to verify the correct delivery of the treatment plans used for gynaecological brachytherapy applications in accordance with Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) clinical protocols. Different techniques were employed that included computed doses from the treatment plans, radiophotoluminescence glass dosimeter measurements and Monte Carlo simulations. The main purpose was to develop and implement an end-to-end dosimetry audit in High Dose Rate (HDR) gynaecological brachytherapy, develop an approach for gynaecological brachytherapy audits in South Africa, and improve quality in HDR brachytherapy treatment at CMJAH. MATERIALS AND METHOD: A water phantom was designed using CAD (Computer Aided Design) software and was manufactured in order to perform Ir-192 HDR brachytherapy absolute-dose measurements in the water around an applicator in a fixed geometry. The applicators were scanned using CT and reconstructed on the CT images and plans were created, using standard clinical protocols at CMJAH. The prescribed dose of 8 Gy at point “A” was used. In this work, the doses calculated by the planning system were compared with the results obtained from the RPLGD and Monte Carlo simulations. RESULTS: The doses measured by the radiophotoluminescence glass dosimeters were in good agreement with treatment planning calculated doses and Monte Carlo simulated doses. From point “A” to point “B” the overall variation between the measured, calculated and simulated doses was less than 3%. For distances greater than 6 cm from the sagittal center of the applicator shows the deterioration with under response of radiophotoluminescence glass dosimeters compared with treatment planning system. CONCLUSION: The results of this work have shown that radiophotoluminescence glass dosimeters are capable of dose distribution measurements around gynaecological applicators for the purpose of dosimetric audits in HDR brachytherapy.

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Submitted in partial fulfilment of the requirements for the degree Master of Science

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