Slice profile correction for transmit sensitivity mapping using actual flip angle imaging

Authors

  • Shaihan J. Malik,

    Corresponding author
    1. Robert Steiner MRI unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital campus, Imperial College London, London, United Kingdom
    • Robert Steiner MRI Unit, Hammersmith hospital, Du cane Road, London W12 0HS, UK===

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  • Gavin D. Kenny,

    1. Metabolic and Molecular Imaging Group, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital campus, Imperial College London, London, United Kingdom
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  • Joseph V. Hajnal

    1. Robert Steiner MRI unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital campus, Imperial College London, London, United Kingdom
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Abstract

To enable clinical use of parallel transmission technology, it is necessary to rapidly produce transmit sensitivity (σ) maps. Actual flip angle imaging is an efficient mapping technique, which is accurate when used with 3D encoding and nonselective RF pulses. Mapping single slices is quicker, but 2D encoding leads to systematic errors due to slice profile effects. By simulating steady-state slice profiles, we computed the relationship between σ and the signals received from the actual flip angle imaging sequence for arbitrarily chosen slice selective RF pulses. Pulse specific lookup tables were then used for reconstruction. The resulting σ-maps are sensitive to T1 in a manner that depends strongly on the specific pulse, for example a precision of ±3% can be achieved by using a 3-lobe sinc pulse. The method is applicable to any RF pulse; simulations must be performed once and thereafter fast reconstruction of σ-maps is possible. Magn Reson Med, 2011. © 2010 Wiley-Liss, Inc.

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