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A Dosimetric Comparison of ICVI Varian Cones and BrainLab Cones

R George*, D Saenz , N Kirby , K Rasmussen , S Stathakis , N Papanikolaou , Ut Health San Antonio, San Antonio, TX


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

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 PDD’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.


Stereotactic Radiosurgery, Commissioning


TH- Radiation dose measurement devices: diodes/solid state

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