A novel phantom design for brachytherapy quality assurance

Background : One major challenge in brachytherapy is to verify the accuracy of dose distribuons calculated by the treatment planning system. In this project, a new phantom design has been introduced for quality assurance of dose distribuons in gynocological (GYN) brachytherapy implants using EBT GafChromic film. Materials and Methods : This phantom has been designed and fabricated from 90 slabs of 18×16×0.2 cm 3 Perspex to accommodate a tandem and ovoids assembly, which is normally used for GYN brachytherapy treatment. In addion, this phantom design is allowing the use EBT GafChromic films for dosimetric verificaon of GYN implants with Cs-137 Selectron LDR system. With this assembly, GafChromic films were exposed using a plan designed to deliver 2.5 Gy dose to point "A" in Manchester system for tandem and ovoids configuraons and to deliver 1.5 Gy of dose to 0.5 cm distance from the lateral surface of ovoids for using ovoid-pair. The measured dose distribuons with GafChromic films were compared with the TPS isodose lines both numerically and spaally. For a quantave analysis of the results, the measured doses values at several points of interest were evaluated with the treatment planning data and values obtained following the TG-43 dose calculaon formalism. Results: The results of these invesgaons have indicated that the new phantom design enables us to measure differences of greater than ±6% for LDR brachytherapy GYN treatments. Conclusion: The new phantom design could be ulized for the QA procedure of the brachytherapy remote aCer loading systems to confirm the accuracy of dose distribuon in GYN implants.