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Collection of SRS Cone Commissioning Data Using Automated Couch Motions and a 1D Tank for Linear Accelerator-Based Radiosurgery

Y Hao*, M Schmidt , S Mutic , H Li , N Knutson , Washington University School of Medicine, St. Louis, MO


(Sunday, 7/14/2019) 2:00 PM - 3:00 PM

Room: Stars at Night Ballroom 4

Purpose: To investigate a novel approach to collect stereotactic radiosurgery (SRS) cone collimator commissioning data using automated couch motions and a 1D tank for linear accelerator-based radiosurgery.

Methods: Cone commissioning datasets were acquired using TrueBeam Developer Mode. A single Extensible Markup Language (XML) file was used to dynamically control the linear accelerator during radiation delivery for the acquisition of inline, crossline, and tissue maximum ratios (TMRs). A commercial TG-51 compliant 1D water tank was placed on the treatment couch. Several different detectors were investigated. TMR data were collected with scan towards the water surface, and detector position was maintained at isocenter by simultaneously lower couch vertical position and reduce detector depth at the same rate. Additionally, measurements were performed comparing various detectors; manufacturer provided representative data was also used for comparison.

Results: Commissioning data for each cone can be collected within 35 minutes by using our methods. Comparing to the manufacturer representative data, more than 96.4% of the measured profile points had a gamma value (0.5%/0.5mm)<1 and all data within 1%/0.5mm for all the cones (4mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm and 17.5mm) and all detectors used. More than 90.3% of the measured profile points had a distance to agreement < 0.5mm or a dose difference < 0.5%, and all data was within 0.5mm distance to agreement or 2% dose difference. All measured TMR data was acquired with less than 2% difference from representative data.

Conclusion: Our work shows the feasibility of collecting conical collimator commissioning data using automated couch motions and a 1D tank for linear accelerator-based radiosurgery. This new approach can provide a method to acquire high quality beam data while maximizing cost effectiveness and efficiency.

Funding Support, Disclosures, and Conflict of Interest: Dr. Nels Knutson receives research funding from Varian medical systems. Dr. Sasa Mutic receives income for consulting and research support from Varian Medical Systems.


Not Applicable / None Entered.


TH- External beam- photons: intracranial stereotactic/SBRT

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