Room: Exhibit Hall
Purpose: To compare and analyze dosimetric data acquired after the addition of Varian cones in conjunction with the Interlocked Cone Verification Interface (ICVI) with previously commissioned data.
Methods: A water tank was setup to acquire PDDs, profiles, and output factors, with an A16 ion chamber, a diamond detector, and a diode. This was done for each of the cone sizes: 5, 7.5, 10, 12.5, 15, and 17.5mm. The 17.5mm cone was a new addition and hence was not compared because of a lack of prior commissioned data. Output factors and PDDâ€™s were acquired at 98.5 SSD (depth of 1.5cm for OF), and profiles were made at 92.5cm SSD at a depth of 7.5cm. A cone-based Lucy phantom end-to-end test was also performed. This involved simulation of the Lucy phantom, treatment plan creation in iPlan, and delivery to verify dosimetric and localization accuracy. A 2D gamma analysis was performed for each cone (2%/2mm).
Results: Data from the diode best agreed with previously measured data. The output factors had at most a 0.3% difference from commissioned data. The profiles all agreed with the original data (FWHM within 0.5 mm). The PDDs all matched the commissioned data to within 0.5%. The cone-based Lucy end-to-end test absolute dose measurement matched the calculation within 0.1%. The gamma indices of the 5, 7.5, 10, 12.5, 15, and 17.5 mm cones were 100%, 100%, 97.8%, 99.9%, 99.2%, 98.9% respectively.
Conclusion: The output factors and PDDs were unchanged. The 17.5mm cone data was added to the TPS. Varian cones using the ICVI dosimetrically matched the previously used BrainLab cones.