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Comprehensive Quality Assurance and Optimization of the Clinical Stereotactic Environment in a Practical Setting: A Study in Collaboration with Massachusetts General Hospital

G Shastri1*, N Battaglia2, M Kirk3, (1) (2) Radiological Imaging Technology, Inc., Colorado Springs, CO, (3) Mass General/North Shore, Danvers, MA


PO-BPC-Virtual-18 (Saturday, 4/17/2021)   [Eastern Time (GMT-4)]

Purpose: To evaluate the historical quality of a stereotactic treatment machine, and its environment, using a comprehensive isocenter optimization routine developed by Radiological Imaging Technology, Inc. (RIT).

Methods: In collaboration with Massachusetts General Hospital (MGH), five years of historical data was accumulated within a RITtrend® database. Data was collected daily for five field images, and monthly for twelve field images. In this way, 531 records were collected between 2015 and 2019 and monitored for relevant trends and specifications. The data was referenced against the 3D Maximum Measured Deviation at a nominal tolerance of 1 mm, according to AAPM TG-142 guidelines. For daily stereotactic QA, five fields were taken at the following angle configurations: (gantry = 0°, table = 0°), (g=90°, t=0°), (g=135°, t=0°), (g=230°, t=40°), and (g=330°, t=340°). These angles were deemed significant to patient treatment. For the monthly comprehensive optimization, twelve fields were taken at the recommended angle configuration provided in the RIT manual.

Results: The 3D displacement showed a rhythmic sinusoidal pattern with a mean of 0.4 mm and a mean period of 6.2 (S.D. 1.7) months. A distinct shift of about 0.6 mm in the z-axis component of the 3D displacement was also observed over the span of several days. Statistical control limits imposed on the dataset clearly alerted to numerous measurements that, though were generally within the accepted tolerance, fell out specification for the machine variance one might expect from a well-behaved system.

Conclusion: This work demonstrates the strength of monitoring machine QA with a historical perspective. The context of the data over an extended period elucidated several potentially alarming trends that may had otherwise gone unnoticed upon individual inspection of the measurements. With regards to the quality of the treatment machine and its environment, we observe this methodology’s high importance to overall machine QA procedures.

Funding Support, Disclosures, and Conflict of Interest: Mass General North Shore is a customer of Radiological Imaging Technology, Inc.


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