J Berzanske*, D Campos, A Soldner, J Sohn, S Oh, B Coopey, M Johnson, D Pavord, B King, M Goss, Allegheny General Hospital, Gibsonia, PA

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  J Berzanske

PO-GePV-T-325 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: The opportunity to commission double-digit machines in short time span (<5 years) is unusual. In this study, we present commissioning data of 10 Elekta VersaHD linear accelerators using two methods of commissioning. The first was a comprehensive list of PDDs and profiles at various field sizes and depths per the recommendations of AAPM TG106. For the second method, an abbreviated selection of scans was utilized. The purpose of this study is to explore the question of how much data is necessary to sufficiently match an existing model. Here, we detail our abbreviated scanning technique for linear accelerator commissioning.

Methods: PDDs and profiles were obtained using PTW Beamscan water tank. Gamma analysis between the model and experimental data was performed using the accompanying Mephysto 4.2 data analysis suite to verify goodness-of-fit. Average scans for each energy and fields size were created and compared to the beam model. Sufficiency of model match for delivery was verified by examining patient-specific delivery QA results recorded in department QA log per TG-186 guidelines as well as by comparing ExpressQA results across machines to verify MLC and Jaw performance.

Results: Gamma analysis showed good agreement within 1%/1 mm between measured PDDs in the TCPE region and for profiles out to 80% of the field edge (for both photons and electrons). Patient-specific QA data showed excellent pass rates for both the comprehensive and abbreviated commissioning techniques.

Conclusion: For radiation oncology departments with an existing beam model, our abbreviated commissioning approach with respect to beam scanning for beam matching is sufficient to yield good agreement between radiation delivery and the beam model.

Keywords

Commissioning, Data Acquisition, Linear Accelerator

Taxonomy

TH- External Beam- Photons: Quality Assurance - Linear accelerator

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