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Validation of Intrafraction Motion Review Using Dual Surrogate in Prospective Clinical Study

A Cetnar*, A Ayan, G Graeper, M Weldon, K Woods, N Gupta, Ohio State University - James Cancer Hospital, Columbus, OH


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

Room: AAPM ePoster Library

Our goal is to understand the accuracy of Varian's Intrafraction Motion Review (IMR) and its clinical significance. IMR was used prospectively in a cohort of patients treated for prostate cancer with Calypso beacons. This study reports the preliminary data for three questions:
•What is the difference in reported locations between IMR and Calypso data?
•What are potential limitations for the use of IMR clinically?
•What are the potential dosimetric deviations introduced by treating a patient using IMR?

Data was collected during a prospective study for patients with prostate cancer using Calypso beacon locations projected onto the imaging plane and Varian’s combined logs during treatment. The projection data was correlated to report the differences between the two systems when there was mutual information. Since IMR did not always detect the beacons, the statistics for detection and the limitations of gantry angle dependence were analyzed. Based on the uncertainty of the detection algorithm, prostate SBRT plans were recalculated to predict dosimetric impact of monitoring technology.

The data from the first five patients were analyzed for beacons detected within tolerance (N=4335) using a two-sample t-test. We fail to reject the null hypothesis that the locations for the two technologies are different at 0.05 significance level (P=0.714). The beacons were identified by the algorithm in 92% of the images. The most challenging imaging angles for detection are cardinal angles. In review of SBRT plans, the maximum dose to the rectum can increase >110% as result of 2mm variations supporting the role of intrafraction monitoring.

The data suggests IMR is a valuable tool for fiducial tracking, and the accuracy of the algorithm for detected images is comparable to Calypso for fiducial identification. Some clinical limitations to using IMR include additional imaging dose to the patient and non-continuous tracking during treatment.

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