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Validation of a Software Module to Verify the Fidelity of Arc Plan Delivery in Real Time

V Sarkar*, A Paxton, J Kunz, M Szegedi, G Nelson, P Rassiah-Szegedi, H Zhao, Y Huang, F Su, B Salter, University of Utah, Salt Lake City, UT


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

To evaluate the effectiveness of newly available, real-time software capability for the ScandiDos Discover transmission detector in detecting fidelity of arc-based treatment deliveries.

Non-released alpha software was used to evaluate the ability of the Discover system to detect plan delivery errors instantaneously, versus the current software’s ability to detect errors at the end of a delivered arc. Towards this end, a dynamic conformal arc plan was created as a baseline plan. This plan was imported into the ScandiDos test software as the ‘expected’ plan. In-house software was then used to systematically introduce 5 mm errors in all MLC leaf positions at different points within the arc. Errors in collimator and gantry positions were also introduced in other iterations of the plan. These altered plans were then delivered with the Discover device mounted to the linear accelerator. The ability of the new real-time software to accurately detect errors instantaneously was evaluated.

A user customizable tolerance level for leaf position accuracy was set to a requirement of at least 90% of leaves being within 1 mm of their intended position. During the measurement, a bar graph shows the percentage of leaves meeting the specified requirement. For all of the simulated known-error scenarios, the software correctly detected and accurately indicated when the leaves had been intentionally positioned out of tolerance. The system also correctly identified when the gantry and collimator were intentionally mis- positioned.

It was confirmed that this new software module can be used to provide essentially instantaneous, real-time feedback of the position of the MLC leaves, gantry and collimator during the delivery of an arc plan. This real-time feedback can allow the user to immediately interrupt treatment delivery for error prevention and further investigation.


Quality Assurance


TH- External Beam- Photons: Quality Assurance - Linear accelerator

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