Author: James L. Giltz, Michael J. Merrick π¨βπ¬
Affiliation: Alyzen Medical Physics, University of Kentucky π
Purpose: To evaluate the capability of MyQA SRS in performing high-resolution machine QA to verify multileaf collimator (MLC) behavior and integrity for adaptive radiotherapy (ART). This study demonstrates how comprehensive MLC assessments can provide clinicians with greater confidence in machine performance, ensuring MLC functionality meets expectations and enabling trust in ART delivery without requiring additional patient-specific QA.
Methods: MyQA SRS was utilized with its 0.4 mm Γ 0.4 mm detector resolution to assess key MLC performance parameters: positional accuracy, edge detection, delivery repeatability, and dosimetric consistency. Tests included (1) MLC edge detection and leaf positioning analysis for HDMLC leaves, (2) MLC positioning, gap stability and variance detection, and (3) transmission analysis. MLC accuracy and functionality were evaluated through a series of specifically designed delivery patterns as well as the commonly used βchair testβ which encompasses several of MLC parameters within one test.
Results: Through the exceptional resolution of the MyQA SRS, least count edge detection enables accurate leaf edge detection of 0.6 Β± 0.2 mm, as well as indicates individual MLCβs position accurately under various dosimetric conditions. However, with derivative gradient analysis that detection can be refined to a sub-detector element effective resolution. MLC positioning, gap stability and transmission measurements showed deviations consistent with TPS expected variance. Variance detection indicated very high level of dosimetric quantification of MLC movement down to sub-millimeter shifts, confirming MyQA SRSβs suitability for dynamic ART QA.
Conclusion: This study highlights the value of MyQA SRS in providing precise verification of MLC behavior and performance through high-resolution dosimetry and provides possible evaluation metrics for online-ART. MyQA SRS provides an effective solution to verify MLC behavior, preventing errors rather than identifying them post-treatment, thus enhancing the safety and accuracy of ART.