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Intra-Fraction Motion Tracking of Head and Neck Patients Using Surface Image Guidance

D Christ*, A Ayan , M Weldon , N Gupta , The Ohio State University, Columbus, OH


(Sunday, 7/14/2019) 4:30 PM - 5:00 PM

Room: Exhibit Hall | Forum 5

Purpose: As an alternative to closed masks, open face masks may alleviate anxiety for patients undergoing external beam radiation therapy. The open face section inherently reduces structural integrity and contact area of the mask but also offers an opportunity to use surface based image guidance. We aim to assess the degree of intra-fraction patient motion present during head and neck treatments with open face mask immobilization.

Methods: Five patients with various head and neck cancer diagnoses were treated with QFix Fibreplast Open View masks on a Varian TrueBeam accelerator using the Optical Surface Monitoring System (OSMS) for motion tracking. These treatments ranged from 25 to 35 fractions. Each fraction, after initial setup shifts were made using cone beam computed tomography image guidance, a new OSMS reference image was captured. OSMS then monitored patient motion based on a region of interest about the patient’s face for the entirety of each fraction of treatment. Motion was recorded in six degrees: three translational axes, as well as rotation, pitch, and roll. The data is analyzed on a patient-specific basis.

Results: The translational vector magnitude of patient motion over the entire course of treatment ranged from a mean of 0.56mm±0.63mm to 0.82mm±0.74mm. Patient rotation ranged from a mean of 0.00°±0.24° to 0.24°±0.30°. Mean pitch ranged from 0.02°±0.19° to 0.21°±0.19°. Mean roll ranged from -0.02°±0.20° to 0.35°±0.58°.

Conclusion: Mean translational patient motion is sub-millimeter for the five patients treated with open face masks. The analysis of existing data as well as motion tracking of future patients with OSMS may provide guidance for clinicians opting to use open face masks.


Image-guided Therapy, Patient Movement, Immobilization


Not Applicable / None Entered.

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