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Parallel MR imaging

Choosing a reconstruction algorithm

Denis Hoa

In the present commercially available parallel MR techniques, image domain is the most widespread reconstruction technique: SENSE (Philips), mSENSE (Siemens), ASSET (GE), SPEEDER (Toshiba). Among the frequency domain reconstruction algorithms, GRAPPA is the only one used in routine clinical practice.
Both types of algorithm offer similar reconstruction quality and are globally equivalent. In cases where it is difficult to make a reliable sensitivity map (heterogeneous zone explored: thoracic or abdominal imaging) or when differences exist between acquisition for sensitivity mapping and the imaging sequence (echo-planar type, more sensitive to magnetic susceptibility artifacts), algorithms of the GRAPPA type are preferred. The acquisition of central k-space lines effectively provides both image contrast data and mapping of the entire field.
Image-domain reconstruction techniques perform better when the phase encoding direction is perpendicular to the plane of the coil elements, positioned face-to-face. In other cases, namely when phase encoding direction is parallel to the coils, frequency-domain reconstruction techniques are better suited.