3D TOF ANGIOGRAPHY USING REAL TIME OPTICAL MOTION CORRECTION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Correction of motion artifacts is an ongoing challenge in MRI. Sadly, motion is often worst in patients that are acutely ill and in which time cannot be afforded to repeat failed exams. This is the case, for example, in children or in patients suffering from acute ischemic stroke or intracranial hemorrhages. In these patients 3D Time of Flight (TOF) angiograms are often performed, but their image quality is often technically borderline or even inadequate due to profound patient motion. We proposed an approach in which external pose information is used that allows one to keep the short-TR features of the TOF intact. MATERIALS & METHODS: A MR-compatible camera was mounted on a head coil and combined with a 2D geometric marker, which was placed on the subject's forehead to allow tracking of head motion. The external tracking processor was running a motion detection software which analyzed the camera's video stream and fed the updated pose data back to the scanner's sequencer. This allows one to adjust in quasi-real time the prescribed slab. Experiment: A healthy volunteer underwent three consecutive scans each consisting of a single 7.7cm 3D slab that covers the Circle of Willis whereby for each acquisition instructions were given to perform a specific motion pattern: to remain still, and to perform head motion as much as permitted by the coil. To read about other projects ongoing at the Lucas Center, please visit http://rsl.stanford.edu/ (Lucas Annual Report and ISMRM 2011 Abstracts)