MO‐D‐BRB‐02: The Radiological Physics Center's Quality Audit Program: Where Can We Improve?

Purpose: To analyze the findings of the Radiological Physics Center's (RPC) QA audits of institutions participating in NCI sponsored clinical trials. Methods: The RPC has developed an extensive Quality Assurance (QA) program over the past 44 years. This program includes on‐site dosimetry reviews where measurements on therapy machines are made, records are reviewed and personnel are interviewed. The program's remote audit tools include mailed dosimeters (OSLD/TLD) to verify output calibration, comparison of dosimetry data with RPC ‘standard’ data, evaluation of benchmark and patient calculations to verify the treatment planning algorithms, review of institution's QA procedures and records, and use of anthropomorphic phantoms to verify tumor dose delivery. The RPC endeavors to assist institutions in finding the origins of any detected discrepancies, and to resolve them. Results: Ninety percent of institutions receiving dosimetry recommendations has remained level for the past 5 years. The most frequent recommendations were for not performing TG‐40 QA tests, wedge factors, small field size output factors and off‐axis factors. Since TG‐51 was published, the number of beam calibrations audited during visits with ion chambers, that met the RPC's ±3% criterion, decreased initially but has risen to pre‐TG‐51 levels. The OSLD/TLD program shows that only ∼3% of the beams are outside our ±5% criteria, but these discrepancies are distributed over 12–20% of the institutions. The percent of institutions with ï,³l beam outside the RPC's criteria is approximately the same whether OSLD/TLD or ion chambers were used. The first time passing rate for the anthropomorphic phantoms is increasing with time. The prostate phantom has the highest pass rate while the spine phantom has the lowest. Conclusions: Numerous dosimetry errors continue to be discovered by the RPC's QA program and the RPC continues to play an important role in helping institutions resolve these errors. This work was supported by PHS grants CA10953 and CA081647 awarded by NCI.