Reconstruction of phase images for GRAPPA accelerated Magnetic Resonance Imaging

DOI: 10.1007/978-3-540-89208-3_192 In book: 4th European Conference of the International Federation for Medical and Biological Engineering, pp.803-806


In this work we present a method to combine complex-valued phased array MR data based on a uniform sensitivity approach, which
incorporates sensitivity profiles calculated from afore acquired data. The algorithm was implemented on a clinical 3T whole-body
MR-Scanner and embedded into the vendor-specific standard reconstruction chain.

Additionally, it was linked with the GeneRalized Autocalibrating Partial Parallel Acquisition (GRAPPA) procedure to take advantage
of partial parallel acquisition techniques as well. Thus, under-sampled data can be reconstructed with GRAPPA and subsequently
combined with the presented method. Phase images reconstructed with the proposed method were in excellent agreement with reference
data and did not suffer from errors due to incorrectly combined data.

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    ABSTRACT: A method is presented for the combination of phase images from multi-channel RF coils in the absence of a volume reference coil. It is based on the subtraction of 3D phase offset maps from the phase data from each coil. Phase offset maps are weighted combinations of phase measurements at two echo times. Multi-Channel Phase Combination using measured 3D phase offsets (MCPC-3D) offers a conceptually and computationally simple solution to the calculation of combined phase images. The dual-echo data required for the phase maps can be intrinsic to the high-resolution gradient-echo scan to be reconstructed (MCPC-3D-I). Alternatively, a separate, fast, low-resolution dual-echo scan can be used (MCPC-3D-II). Both variants are shown to give near perfect phase matching, yielding images with high SNR throughout and high GM-WM contrast. MCPC-3D is compared with other reference-free phase image combination methods; high-pass phase filtering, phase difference imaging, and matching using constant offsets (MCPC-C). Multi-Channel Phase Combination using measured 3D phase offsets method does not need an overlap between the signals from individual coils and can be used with parallel imaging, making it ideally suited to multi-channel coils with a large number of elements, and to high and ultra-high field systems.
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