Figure 1. Multiple-gradient echo EPI images of four-tube phantom in severe field non-uniformity. Above, EPI images from Multiple-Echo EPI sequence (TE = 22.3, 66.8, 96.4 and 124.2 msec). Left, profile of frequency through the central (water only) portion of the phantom (by SS-PARSE frequency estimate). Note the combination of dropout and distortion in multiple-gradient-echo EPI suppresses signal from most locations, precluding estimation of net relaxation rate R2* or frequency in most of the phantom.

Figure 2. SS-PARSE parameter maps of magnitude, relaxation rate R2*, and frequency, and computed T2*-weighted image, acquired from same phantom in same severe field inhomogeneity. Frequency and R2* are estimated throughout the phantom.