COIL EFFECT ON K-SPACE LINE SELECTION IN HIGHLY ACCELERATED PARALLEL IMAGING

Because the maximum acceleration factor in parallel imaging is proportional to the number of coils in the array, two phenomena are occurring as counterparts to one another: arrays are being developed with increasing numbers of (and thus smaller sized) elements while fewer k-space lines are being acquired (with the accompanying requirement that they be selected more carefully). This paper examines the inherent shift in k-space caused by the use of coils that are small relative to the field-of-view and the selection of k-space lines. The shift is easily understood as the convolution of the magnetization k-space data with the Fourier transform of the coil sensitivity pattern. Results are that the k-space shift is inherent to small coils, is in the same direction for any coil design, and has opposite signs on opposite sides of a planar coil element