Program Information
Monthly Quality Assurance in External Beam Radiation Therapy Using a Single System
K Ding1*, T Ji1,2 , I Iordachita3 , E Velarde4 , J Hyatt5 , J Wong6 , (1)Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, (2) Department of Radiation Oncology, The First Hospital, China Medical University, Shenyang, Liaoning, (3)Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MARYLAND
Presentations
SU-F-T-232 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:
Monthly quality assurance (QA) is time consuming for external beam radiation therapy, taking as long as 6-8 hours for each machine. It is due to the use and setup of multiple devices for different QA procedures. We have developed a single system with rotational capability for the measurement of both optical light and radiation which significantly reduces the time spent on Monthly QA.
Methods:
A single system using mirrors, a phosphor screen and a CCD camera is housed on a cylindrical motor so that it can rotate 360 degrees. For monthly QA, the system is placed on the patient couch of the medical accelerator with the plane of the phosphor screen at isocenter for all measurements. For optical QA such as optical distance indicator, room laser and light field, the optical image is collected directly with the camera. For radiation QA such as beam profile, MLC speed, picket-fence test, collimator rotation, table rotation and gantry rotation, a brass build-up plate is attached to the top of the phosphor screen. Two brass plates with islands of different thickness were designed for photon energy and electron energy constancy checks. Flex map, distortion map and uniformity map were developed to calibrate the motor bearing, camera/lens distortion, and the phosphor screen’s measured response across the field.
Results:
Following the TG142 guidelines for monthly QA with our system, the overall run time is reduced from 6-8 hours to 1.5 hours. Our system’s rotating design allows for quick testing of the gantry radiation isocenter test that is also independent of the sag of the gantry and the EPID.
Conclusion:
Our system significantly shortens the time needed for monthly QA by unifying the tests with a single system. Future work will be focused on extending the technology to Brachytherapy, IMRT and proton therapy QAs.
Funding Support, Disclosures, and Conflict of Interest: This work is funded in part by a sponsor research grant from JPLC who owns the Raven technology. John Wong is a co-founder of JPLC.
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