Program Information
Unsupervised Real-Time Verification of the Linac Machine Parameters Using the IntrEPID System
M Ahmed*, B Neal , H Nourzadeh , W Watkins , J Siebers , University of Virginia Health System, Charlottesville, VA
Presentations
MO-DE-FS1-12 (Monday, July 31, 2017) 1:45 PM - 3:45 PM Room: Four Seasons 1
Purpose: To create a real-time unsupervised linac machine parameter verification system applicable for all patient treatments.
Methods: The method takes advantage of the fact that the read-out system designed to grab EPID frames reports machine parameters independent of the EPID deployment status. The unsupervised system initiates on sending patient plan DICOM files to the record and verify system. The files are independently processed by our in-house developed real-time verification software, intrEPID. intrEPID (1) interpolates between values of the plan machine parameters to create a high-resolution trajectory of values for a specific patient delivery and (2) predicts EPID apertures for instances in which the EPID can be deployed. During treatment, the verification algorithm auto-detects the patient and field, then matches the predicted trajectory against the measured parameter stream at rates up to 10 Hz. Our current algorithm is implemented on a Varian Truebeam™, V1.5.
Results: For an IMRT and VMAT deliveries, we have found max and min deviations of various parameters are within the tolerances stated by linac manufacturer. An example delivery is presented in which the maximum deviation is the 0.3 mm EPID pitch and the minimum deviation is associated with Jaws which are nearly static during the delivery. Gantry rotation shows a maximum deviation of ±1° matching the reported tolerance by the manufacturer. Analysis time, which is ≤ 1ms, enables a fast process of elimination of false patients and fields to be matched between the 1st and 2nd points acquired.
Conclusion: A machine parameters verification algorithm was implemented which monitors linac performance in real-time. The system is capable of running in unsupervised style, eliminating the need for current post treatment machine log file quality assurance procedure.
Funding Support, Disclosures, and Conflict of Interest: The work is partially supported by Varian Medical systems.
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