Enhancing the performance of accelerated MRI through preservation of acquisition SNR: An "aliased" k-space approach

A method for preserving acquisition SNR through simultaneous acquisitions of distinct k-space phase encodes to enhance the performance of accelerated MRI is presented.

An excitation module comprising RF pulses and gradients is inserted into a sequence of choice to overlap and acquire distinct k-space phase encodes. This accelerates a scan as all phase encodes can now be acquired in a duration shorter than that of a typical scan. Next, this "aliased k-space" is restored during reconstruction using receiver sensitivity profiles. When the aliased k-space is also sub-sampled for additional acceleration, Parallel Imaging (PMRI) is applied first to synthesize the unacquired aliased samples. The synthesized samples are then used with the acquired samples in an iterative reconstruction to obtain the output.

Depending on the sequence, acquisition SNR increased by 18-25% relative to PMRI or by 5% relative to the unaccelerated scan. This compensates for the SNR loss when the aliased k-space is sub-sampled for additional acceleration. With PMRI, the method could enable acceleration factors as high as 12 in 2D cartesian scans.

A method for accelerating MRI scans through aliased k-space acquisitions and the feasibility of combining the same with PMRI for greater acceleration has been demonstrated. Magn Reson Med 74:150-161, 2015. © 2014 Wiley Periodicals, Inc.