k‐t BLAST and k‐t SENSE: Dynamic MRI with high frame rate exploiting spatiotemporal correlations

Abstract

Dynamic images of natural objects exhibit significant correlations in k‐space and time. Thus, it is feasible to acquire only a reduced amount of data and recover the missing portion afterwards. This leads to an improved temporal resolution, or an improved spatial resolution for a given amount of acquisition. Based on this approach, two methods were developed to significantly improve the performance of dynamic imaging, named k‐t BLAST (Broad‐use Linear Acquisition Speed‐up Technique) and k‐t SENSE (SENSitivity Encoding) for use with a single or multiple receiver coils, respectively. Signal correlations were learned from a small set of training data and the missing data were recovered using all available information in a consistent and integral manner. The general theory of k‐t BLAST and k‐t SENSE is applicable to arbitrary k‐space trajectories, time‐varying coil sensitivities, and under‐ and overdetermined reconstruction problems. Examples from ungated cardiac imaging demonstrate a 4‐fold acceleration (voxel size 2.42 × 2.52 mm 2, 38.4 fps) with either one or six receiver coils. k‐t BLAST and k‐t SENSE are applicable to many areas, especially those exhibiting quasiperiodic motion, such as imaging of the heart, the lungs, the abdomen, and the brain under periodic stimulation. Magn Reson Med 50:1031–1042, 2003. © 2003 Wiley‐Liss, Inc.