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Abstract #3367

Real-time brain masking algorithm improves motion tracking accuracy in scans with volumetric navigators (vNavs)

Malte Hoffmann1,2, Robert Frost1,2, David Salat1,2, M Dylan Tisdall3, Jonathan Polimeni1,2, and André van der Kouwe1,2
1Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Department of Radiology, Harvard Medical School, Boston, MA, United States, 3Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States

Volumetric navigators (vNavs) interleaved within longer MRI sequences are an effective method for dynamically detecting and correcting head motion during the acquisition. However, motion is estimated by registering each vNav back to the first, and bias can be introduced by non-rigid deformations of, e.g., the mouth, since the head is taken to be a rigid body. We demonstrate that this bias introduces correction-related artifacts. We present robust real-time brain extraction (0.02 s per vNav) and demonstrate offline that the bias and associated artifacts can be removed by using motion tracks from brain-masked registration.

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