Projection reconstruction MR imaging using FOCUSS

The focal underdetermined system solver (FOCUSS) was originally designed to obtain sparse solutions by successively solving quadratic optimization problems. This article adapts FOCUSS for a projection reconstruction MR imaging problem to obtain high resolution reconstructions from angular under‐sampled radial k‐space data. We show that FOCUSS is effective for projection reconstruction MRI, since medical images are usually sparse in some sense and the center region of the undersampled radial k‐space samples still provides a low resolution, yet meaningful, image essential for the convergence of FOCUSS. The new algorithm is successfully applied for synthetic data as well as in vivo brain imaging obtained by under‐sampled radial spin echo sequence. Magn Reson Med 57:764–775, 2007. © 2007 Wiley‐Liss, Inc.