Multi-institution validation of a new high spatial resolution diode array for SRS & SBRT plan pretreatment QA.

PURPOSE: The SRS MapCHECK((R)) , a recently developed patient-specific quality assurance (PSQA) tool for end-to-end testing of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT), was evaluated in a multi-institution study and compared with radiochromic film. METHODS: The SRS MapCHECK was used to collect data on 84 SBRT or SRS PSQA plans/fields at 9 institutions on treatment delivery devices (TDD) manufactured by Varian and Elekta. PSQA plans from 5 different treatment planning software (TPS) were selected and executed on TDDs operating at beam energies of 6 MV and 10 MV with and without a flattening filter. The patient plans were all VMAT except for ten conformal arc therapy fields. The plans were selected to encompass a range of size and tumor sites including brain, lung, spine, abdomen, ear, pancreas, and liver. Corresponding radiochromic film data was acquired in 50 plans/fields. Results were evaluated using Gamma analysis with absolute dose criterion of 3% global dose-difference (DD) and 1 mm distance-to-agreement (DTA). RESULTS: The mean 3% DD / 1 mm DTA Gamma pass rate of SRS MapCHECK in comparison to film was 95.9%, whereas comparison of SRS MapCHECK to the treatment planning software was 94.7%. 80% of SRS MapCHECK comparisons against film exceed 95% pass rate, and about 30% of SRS MapCHECK comparisons against film exceed 99% pass rate. To maintain good agreement between SRS MapCHECK and film or TPS, authors recommend avoiding plans with a Modified Modulation Complexity Score (MMCS) 3 mu/cGy. CONCLUSIONS: SRS MapCHECK has been validated for PSQA for a variety of clinical SRS/SBRT plans in a wide range of treatment delivery conditions. The SRS MapCHECK comparison with film demonstrates near-equivalence for analysis of patient-specific QA deliveries comprised of small field measurements.