Purpose: The characterization of the dosimetric properties of a medical linear accelerator (linac) in radiation therapy is a critical physics task prior to the linac’s clinical use. Vendor provided application programming interface (API) access can assist in the efficient collection of validation data
Methods: Over the past year, two linear accelerators, TB1 and TB2, were commissioned with the aid of custom software assistance. The beam data validation was assisted by a software application that accesses calculated treatment planning system (TPS) percent-depth-dose (PDD) and profile data for electron and photon beam qualities. Data was also collected and analyzed for stereotactic conical collimators (SRS CC) and electronic portal imaging device images.
Results: Gamma pass rates of scanned beam commissioning data were above 94% using a 1% dose-difference (DD) and a 1mm distance-to-agreement (DTA) for PDD and 2% DD and 2mm DTA for profiles for photon beams. Electron pass rates for PDD and profile data were above 98% for TB1 and 92% for TB2 using 2%/2mm and 3%/3mm for DD/DTA for PDD and profiles, respectively. SRS CC output factors for all cone sizes were within 2% for all cone sizes and tissue maximum ratio point data were within 3% for TB1. Validation of image prediction algorithms were performed with a 2D gamma image comparison with 2%/2mm DD/DTA and an average pass rate of 99.42% for over 42 acquired images.
Conclusion: API driven analysis tools can assist commissioning physicists in the efficient and precise collection of beam scan data, calculated dose volumes, and dosimetric images. Thousands of data points and dozens of images can be analyzed while simultaneously measuring other energies and fluence modes. From the experience of commissioning two linacs throughout the past year, TPS validation scripts assist in gathering the dosimetric data needed to confidently release a linac into clinical service.
Funding Support, Disclosures, and Conflict of Interest: Washington University receives research support from Siemens, Varian Medical Systems, and ViewRay. GDH reports personal fees from Varian Medical Systems outside the scope of the present work. MCS reports personal consulting fees and honoraria with Varian Medical Systems outside of the submitted work.
Quality Assurance, Commissioning, Validation
TH- External Beam- Photons: Quality Assurance - Linear accelerator