J Xue*, H Wang, J Teruel, D Barbee, P Galavis, A Mccarthy, T Chen, New York University, New York, NY

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  J Xue

PO-GePV-T-305 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Commissioning Acuros XB (AXB) in Eclipse (Varian Medical Systems) involves multi-step validation processes. We performed a thorough tests based on and extended beyond AAPM MPPG 5.A. to evaluate the performance of the algorithm. This work summarizes our experience and findings.

Methods: AXB verification process started with tests described in MPPG 5.A including ion chamber measurements in water phantom for off axis dose, small field, oblique angle beam, and composite MLC shape beams. Ion chamber measurements are done at multiple locations inside heterogeneity phantoms generated by sandwiching acrylic and cork layers with solid water slabs, followed by End-to-End (E2E) tests performed using CIRS IMRT thoracic phantom and CIRS ATOM dosimetry verification phantom (head and neck only).

Results: Validation passed all tests in MPPG 5.A. Heterogeneity phantom measurements demonstrated the accuracy of AXB in different mediums and at the interfaces between the materials of varied densities. AXB outperformed AAA in cork-made heterogeneity phantoms by an average of 2.9% higher (2.5% for small targets, 3.3 % for large targets) (p< 0.01) in agreement with ion chamber measurements for all energies; and had a comparable performance against AAA in acrylic heterogeneity phantoms. E2E tests on thoracic phantom had <3% difference between AXB calculation and ion chamber measurement in multiple plans. E2E tests on head and neck phantom using radiochromic film demonstrated AXB have better Gamma index passing rate than AAA calculated dose.

Conclusion: We performed a comprehensive testing to evaluate the performance of AXB in homogeneous and heterogeneity medium and the results showed AXB outperformed AAA in most clinical scenarios.

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