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A Characterization of a Commercially Available Add-On Collimator with Stereotactic Cones On Rails

H Parenica

H Parenica*, C Kabat , K McConnell , A Alexandrian , K Rasmussen , N Papanikolaou , S Stathakis , University of Texas HSC SA, San Antonio, TX


SU-I-GPD-T-620 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Stereotactic radiosurgery (SRS) treatments using conical collimators have shown to be effective in delivering dose with a high degree of conformity and precision. However, conical collimators can be difficult to setup and don’t allow for multiple conical collimators to be used easily. To facilitate SRS treatments, a cone system on rails has been developed by LinaTech to allow for easier, more flexible treatment setups. Our goal is to investigate the beam characteristics and integrity of a newly developed D2SRS cone system for radiosurgery/radiotherapy.

Methods: Physical measurements for small cone profiles were taken at 100 cm SSD in a PTW MP3-M water tank using a TN60012 micro-diode and a TN31006 pinpoint (0.0016 cc) ion chamber. Beam profiles, PDDs and output factors were measured from ten cones ranging in diameter from 0.39 cm to 1.94 cm. Beam profiles were measured at depths of 1.5 cm, 5 cm, 10 cm, and 20 cm tracing both in the in-plane and cross-plane directions. All measurements were made using step sizes of 0.2 mm and integration times of 0.3s. 6 MV photons were used with a dose rate of 500 MU/min. Central cone positional accuracies were determined using EPID images.

Results: Measured field sizes were within 0.1mm from the nominal cone size. The left and right penumbras for these three cones were measured to be 1.57 mm/1.65 mm, 2.18 mm/1.96 mm, and 2.79 mm/2.20 mm, respectively, at 10cm depth. The output factors for these three cone sizes were measured 0.363, 0.702, and 0.769. EPID images showed a slight deviation in cone location with collimator rotation (up to 0.1 mm). Leakage through the cones was measured to be within 0.5%.

Conclusion: The LinaTech D2SRS cones were successfully characterized. The collected data will be used for commissioning of the beam model using the dedicated treatment planning system.

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