VD-AUTO-SMASH imaging

Recently a self-calibrating SMASH technique, AUTO-SMASH, was described. Thi s technique is based on PPA with RF coil arrays using auto-calibration sign als. In AUTO-SMASH, important coil sensitivity information required for suc cessful SMASH reconstruction is obtained during the actual scan using the c orrelation between undersampled SMASH signal data and additionally sampled calibration signals with appropriate offsets in k-space. However, AUTO-SMAS H is susceptible to noise in the acquired data and to imperfect spatial har monic generation in the underlying coil array. In this work, a new modified type of internal sensitivity calibration, VD-AUTO-SMASH, is proposed. This method uses a VD k-space sampling approach and shows the ability to improv e the image quality without significantly increasing the total scan time. T his new k-space adapted calibration approach is based on a k-space-dependen t density function. In this scheme, fully sampled low-spatial frequency dat a are acquired up to a given cutoff-spatial frequency. Above this frequency , only sparse SMASH-type sampling is performed. On top of the VD approach, advanced fitting routines, which allow an improved extraction of coil-weigh ting factors in the presence of noise, are proposed. It is shown in simulat ions and in vivo cardiac images that the VD approach significantly increase s the potential and flexibility of rapid imaging with AUTO-SMASH. (C) 2001 WiIey-Liss, inc.