Purpose: The myQA SRS device is a recently developed 2D digital detector array dedicated for patient specific quality assurance (QA) and commissioning of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). A preliminary investigation was performed to evaluate the performance of this high-resolution device for clinical use.
Methods: The myQA SRS device came with the SRS phantom and three different inserts for film and ion chamber measurements. It provided an active area of 120x140mm² and exploited complementary metal-oxide-semiconductor (CMOS) technology. Five clinically treated SRS/SBRT plans were randomly selected and evaluated. All treatment plans were originally planned in RayStation (V8.0A) treatment planning system (TPS) with VMAT using 6FFF. The QA plans were then generated on scanned CT images of the myQA SRS device within the SRS phantom and delivered on a Varian Truebeam linac equipped with HD MLCs. The same QA plans were also measured with EBT3 radiochromic film using the film insert for absolute dosimetry comparison. Gamma index analysis was performed with 1mm distance to agreement (DTA) and 3% absolute global dose difference (DD) using myQA Patient software.
Results: The large active area allowed myQA SRS to measure dose to multiple targets in one measurement. The CMOS technology provided a spatial resolution of 0.4mm. With 1mm DTA and 3% DD criteria and 10% threshold, the average gamma passing rate of TPS compared to myQA SRS and EBT3 film was 99.5% and 99.1%, respectively. The average gamma passing rate of myQA SRS measurement compared to EBT3 film was 96.0%.
Conclusion: The myQA SRS device was evaluated for patient specific QA with both SRS and SBRT treatment plans. Gamma analysis demonstrated that myQA SRS provided accurate dose measurements for small field. The large active area and high resolution improved the VMAT QA efficiency for single isocenter multiple targets SRS plans.
Funding Support, Disclosures, and Conflict of Interest: This study is supported by IBA Dosimetry GmbH