LAUSR

Patient specific quality assurance (PSQA) is a critical element of routine service in a radiotherapy department for verification of complex treatment delivery, particularly during the introduction of new techniques, equipment or treatment sites. There are traditional or recommended guidelines for passing criteria for PSQA, however, they may not continue to be appropriate for the current generation of techniques/QA equipment. We have undertaken a review of our PSQA to determine what is the most appropriate criteria and if it should vary based on equipment or treatment site. Additionally, we aim to streamline our PSQA by reducing the number of physical measurements and needed to determine what equipment is best suited to be used as a single form of measurement. The ideal PSQA system would have independent from the Linac, high resolution and sensitivity, resource efficiency. PSQA measurement data was collected for breast, prostate and palliative treatment sites using the ArcCheck,PerFraction and Portal Dosimetry and analysed against Eclipse using gamma scoring criteria. We determined we would expect to see a failure rate of 10% and various sensitivities of the gamma score were evaluated to find a passing criteria meeting this failure rate. It was found that 10% of all prostate plans fail at 97.2% for gamma analysis at 2%/2 mm. 10% of breast plans fail at 91% at 3%/3 mm gamma analysis. The pass threshold was found to vary between treatment sites and measurement technique. PerFraction is the likely solution for ongoing streamlined PSQA.