Room: AAPM ePoster Library
Electronic portal imaging device (EPIDs) have had a role in routine QA tests in clinical radiotherapy for more than a decade. These devices have been also used for animal position verification in preclinical radiotherapy. Here, we developed EPID-based suite of tests to improve accuracy of small animal image-guided radiotherapy (SA-IGRT) systems performance.
An EPID-based tests were developed to perform (i) dosimetric QA, (ii) geometric QA, and (iii) verify delivered dose to the animal on the small animal radiation research platform (SARRP; Xstrahl, Atlanta, GA) system. Dosimetric QA tests namely constancy of beam quality in terms of half-value layer (HVL) and tube peak potential (kVp), constancy of output, profile (symmetry/flatness). Geometric QA tests including accuracy and symmetry of field size, accuracy of collimator alignment, gantry rotation, stage rotation and translation. EPID was also used to estimate delivered dose to animal. Film and ion chamber were used as reference to validate EPID measurements.
HVL values measured with the EPID agreed with ion chamber measurements within 7.1%. Results showed that size of the gantry rotation isocenter was 1.45 ± 0.15 mm. The stage translational accuracies were 0.015, 0.010, and 0 mm in the X, Y, and Z directions, respectively. The size of the stage rotation runout was 2.73 ± 0.3 mm. Displacements of intended and actual delivery isocenters were 0.24 ± 0.10, 0.12 ± 0.62, and 0.12 ± 0.42 mm in the X, Y, and Z directions, respectively. Results of gamma analysis for 2D comparison between TPS-calculated and EPID-estimated exit dose distributions indicated an average of 90% passing rate with global gamma criterion of 2 mm/5%.
Conclusion: results indicate that the EPID can be utilized in preclinical kV radiotherapy as a simple, convenient device for QA of the SA-IGRT system performance, and kV dose delivery verification in small animal radiotherapy.
Funding Support, Disclosures, and Conflict of Interest: This work is support by Xstrahl.