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Quantifying the Effect of Eye Movement On Surface Guided Imaging for Stereotactic Radiosurgery

J McCulloch*, V Bry , N Papanikolaou , D Saenz , P Myers , N Kirby , S Stathakis , K Rasmussen , University of Texas HSC SA, San Antonio, TX


(Tuesday, 7/16/2019) 10:30 AM - 11:00 AM

Room: Exhibit Hall | Forum 5

Purpose: The purpose of this study was to quantify the effect of eye movement with the tracking algorithm used by a surface guided radiation therapy (SGRT) system (Catalyst, CRad) for patients undergoing stereotactic treatment in an open face mask.

Methods: A volunteer had a customized aquaplast mask (Brainlab) that was modified to simulate an open face mask extending from the eyebrows to the upper lip. The mask was painted black in order to improve skin contrast with the SGRT cameras. The individual was then placed on the treatment unit (Novalis Tx, Varian) in the open faced mask. The mask was secured to the treatment couch. The SGRT scan volume size was varied to determine whether the volume analyzed effected the accuracy (Range: 367cm^3 to 3754cm^3) . A baseline was acquired with the volunteers eyes closed. The volunteer was then asked to perform various tasks with their eyes: closed eyes, open eyes, looking to the right, looking to the left, and opening the eyes as wide as possible. During each of these tasks, the shift suggested by the SGRT system was recorded. This was repeated for several scan volumes.

Results: The 367cm^3 volume analyzed demonstrated the largest deviations overall with >2mm deviations in multiple directions from baseline with certain eye positions. All volumes demonstrated <0.3mm variation from the baseline when the volunteers eyes remained closed.

Conclusion: If using an open faced mask for SGRT treatments, the highest accuracy can be obtained by keeping the patients eyes closed. When the eyes are open and the patient is looking around, the chance for a tracking error increases.

Funding Support, Disclosures, and Conflict of Interest: Research funded in part by a vendor grant.


Surface Matching, Image Guidance, Immobilization


TH- External beam- photons: Motion management (intrafraction)

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