Real-time rigid body motion correction and shimming using cloverleaf navigators

Authors

  • André J.W. van der Kouwe,

    Corresponding author
    1. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
    2. Department of Radiology, University of California–San Diego, La Jolla, California, USA
    • Athinoula A. Martinos Center, Massachusetts General Hospital, Room 2301, Building 149, 13th St., Charlestown, MA 02129
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  • Thomas Benner,

    1. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
    2. Department of Radiology, University of California–San Diego, La Jolla, California, USA
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  • Anders M. Dale

    1. Department of Neurosciences, University of California–San Diego, La Jolla, California, USA
    2. Department of Radiology, University of California–San Diego, La Jolla, California, USA
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    • A.M.D. is a founder and holds equity in CorTech Labs, Inc., and also serves on the Scientific Advisory Board. The terms of this arrangement have been reviewed and approved by the University of California, San Diego, in accordance with its conflict of interest policy.


Abstract

Subject motion during scanning can greatly reduce MRI image quality and is a major reason for discarding data in both clinical and research scanning. The quality of the high-resolution structural data used for morphometric analysis is especially compromised by subject movement because high-resolution scans are of longer duration. A method is presented that measures and corrects rigid body motion and associated first-order shim changes in real time, using a pulse sequence with embedded cloverleaf navigators and a feedback control mechanism. The procedure requires a 12-s preliminary mapping scan. A single-path, 4.2-ms cloverleaf navigator is inserted every repetition time (TR) after the readout of a 3D fast low-angle shot (FLASH) sequence, requiring no additional RF pulses and minimally impacting scan duration. Every TR, a rigid body motion estimate is made and a correction is fed back to adjust the gradients and shim offsets. Images are corrected and reconstructed on the scanner computer for immediate access. Correction for between-scan motion can be accomplished by using the same reference map for each scan repetition. Human and phantom tests demonstrated a consistent improvement in image quality if motion occurred during the acquisition. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.

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