The SRS MapCHECK â , 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 nine institutions on treatment delivery devices (TDD) manufactured by Varian and Elekta. PSQA plans from five different treatment planning software (TPS) were selected and executed on TDDs operating at beam energies of 6 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 distanceto-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) <0.1 arbitrary units (a.u.). In the examples presented, this coincides with avoiding plans with a mu/dose limit of >3 µ/cGy. Conclusions: Stereotactic radiosurgery 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.

Purpose: A dosimetric validation of the next‐generation 3D polymer gel dosimeter (BANG®‐3‐PRO‐2) developed for proton radiotherapy dosimetry is presented. Dose response curve is determined using both proton and electron beams. Lateral and depth profiles are compared to ion chamber measurements. 2D dose distributions are evaluated against those generated by a treatment planning system (TPS). Methods and Materials: The dosimeters were read out using a characterized optical computed tomography scanner. The calibration was performed by correlating the change in optical density along the beam axis to the depth‐dose curve from a pristine proton beam delivery (28.4 cm range, 4.5 cm circular aperture) obtained using ion‐chamber measurements. The dose range of 150–650 cGy was covered. Depth and lateral pristine‐beam and spread out Bragg peak (SOBP) dose profiles were compared to ionchamber measurements. Results: The dose response exhibited a sigmoid behavior in the studied dose range. The dose distributions read out from the dosimeters showed good agreement with ion chamber scanned profiles and were able to accurately reproduce the key features of the expected dose distributions. Planar dose along the beam axis were compared to the Eclipse TPS dose maps using the gamma metric with Dd=3 mm and DD=3% or 15 cGy, whichever is greater. Over 95% of dose points pass these criteria. For SOBP delivery (315 cGy peak dose), no response quenching in the peak region (characteristic of other dosimeter types) was observed. For a pristine beam delivery (300 cGy peak dose), the gel dosimeter demonstrated a ∼5% under‐response at the Bragg peak. Conclusion: This new polymer formulation is capable of reproducing single proton beam dose distributions with high spatial accuracy. Under dosing response in the BP or SOBP due to LET dependencies was found to be insignificant and superior to many other currently used proton‐sensitive dosimeters.

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