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End-To-End VMAT QA Measurements- RTTs Vs Physicists

E Shekel*, D Epstein , D Levin , Department of Radiotherapy, Assuta Medical Centers, Tel Aviv, N/A


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

Room: Exhibit Hall

Purpose: As VMAT treatments become increasingly widespread, the use of image guidance to deliver treatments accurately and precisely becomes of higher importance. Independent checks of delivery accuracy allow us to determine the proficiency of the RTTs in using image guidance for accurate patient positioning and treatment delivery.

Methods: We used dedicated anthropomorphic phantoms from the MD Anderson Dosimetry lab. The phantoms contain targets and organs at risk, as well as films and TLDs. A department is required to simulate, contour, plan to given dose constraints and treat the phantoms. The irradiated phantom is sent to the lab for analysis and comparison with the department generated treatment plan.Since RTTs perform CT simulation, pre-treatment imaging and actual treatment for our patients, we wanted to compare their performance to that of the physicists. As our physicists are aware of the intent of this QA, they are highly careful in simulation and image guided delivery to ensure precision. Pass rates are always above 95% (Gamma analysis, TLD measurements). For several sets of anthropomorphic phantoms, we compared pass rates of phantoms simulated and treated by physicists to those simulated and treated by RTTs. RTTs were given no prior guidance on how to simulate, position and treat, other than to treat the phantom as they would a real patient. Contouring and planning were performed by physicists for all phantoms.

Results: Both physicists and RTT handled phantoms had high pass rates. TLD values were 0.98-1.01, and 0.96-1.02 and film gamma pass rates were 95%-98%, and 93% -99% for physicists and RTTS respectively.

Conclusion: End-to-end measurements using anthropomorphic phantoms confirm that a well-trained team of RTTs can carry out accurate simulation and treatment of patients for all sites that commonly deliver VMAT plans.


Quality Assurance, Treatment Verification


Not Applicable / None Entered.

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