Evaluation of dose distribution and dose gradient in brachytherapy cylindrical applicators using a dedicated Phantom for Iridium-192 and Cobalt-60 HDR sources

Introduction: A study was performed to evaluate radiation dose distribution and dose gradient around cylindrical applicators for high-dose-rate (HDR) brachytherapy systems with 192Ir, 60Co brachytherapy source applied for rectal and vaginal cancers treatments.   Materials and Methods: Two additional computed tomography (CT) based plans were generated using a dedicated Phantom for both 60Co source and 192IridumHDR sources. The phantom contains a film and TLD-100 position on the top and peripheral areas, and a rectum cylinder with 1.5 cm insert caps into the phantom. Dose coverage of 5-mm shell surrounding the cylinder, was then evaluated for both scenarios. Results:A significant dose reduction from the expectation dose for 192Ir at the central points of the cylinder tip was observed. The results were then verified by measurements through radio- chromic film and TLDs.   Conclusion: Both 60Co and 192Ir sources were found to be suitable HDR sources for vaginal treatment using a cylindrical applicator with advantages of reducing radiation exposure to Organ At Risks (OARs) in the lower dose range, and appropriate prescribed dose to the target