Online MRI Positioning and Real-Time Motion Correction

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DESCRIPTION (provided by applicant): Automatic on-line slice positioning, on-line slice position correction and prospective real-time motion correction for magnetic resonance imaging of the human brain will be implemented. These technologies will improve the work-flow efficiency of routine clinical evaluations of the brain, and ensure accurate reproducibility of slice positioning over several scanning sessions for the evaluation of progressive illnesses such as tumors and multiple sclerosis. Motion correction will extend the usefulness of MR imaging to traditionally troublesome populations such as children, older subjects and subjects with movement disorders such as Parkinson's disease, where head movements in the scanner frequently preclude successful scanning and confound an accurate diagnosis. Automatic slice positioning obviates the need for the technologist to manually prescribe slices, thereby saving time and improving the reproducibility of scans between scanners, technologists and between sessions in longitudinal studies. The technology is based on a segmented averaged probabilistic atlas and uses a rapid gradient echo (GRE) localizer sequence with two acquisitions with differing contrasts to provide a rapid method for reliably discriminating between the various tissues in the human head and brain. The localizer is collected in approximately forty seconds at the beginning of the scanning session, and to correct for subsequent motion of the subject, two second echo-planar or segmented GRE correction localizers are interleaved between scans. These are referenced to an initial rapid correction localizer to ensure consistent positioning of every scan in the session. Test-retest reliability will be evaluated in a group of healthy volunteers. To correct for within-scan motion, a prospective real-time motion correction scheme is proposed. The scheme requires embedded "octant" navigators of less than 3 ms interleaved between the lines of a conventional 3D sequence such as GRE or 3D EPI. By comparing the navigators with an initial rapidly acquired map of k-space in the vicinity of the navigators, a full rigid body assessment can be made of the position of the object in the scanner at a rate of 50 Hz or more. Corrections to the images can be done off-line, or are made on the scanner in real-time using the rapid feedback mechanism that the Siemens platform provides. The technology will be evaluated in a group of healthy volunteers.