The effect of bulk susceptibility on murine snapshot imaging at 7.0 T: a comparison of snapshot imaging techniques.

The sensitivity of several single-shot imaging techniques to local field gradients (LFGs) generated by discontinuities in bulk magnetic susceptibility (BMS) were compared in mouse brain at 7.0 T. At high field, differences in BMS can cause substantial signal attenuation and image distortion. Because susceptibility effects scale with B(o), mouse brain single-shot imaging at high field is particularly susceptible to the effects of LFGs. The spin-echo techniques GRASE and RARE were found to have a decreased sensitivity to LFGs compared to echo-planar imaging (EPI). Images obtained using EPI and SE-EPI exhibit severe signal attenuation in regions of high LFGs such as near air-tissue interfaces and at the brain edges. In applications such as functional MRI and diffusion MRI, GRASE and RARE are likely to provide more comprehensive whole brain coverage in mouse brain at high field than EPI techniques, which are likely to image regions of the brain with strong LFGs with low signal to noise, reducing the probability of detecting significant physiologically based changes. Copyright 2000 Wiley-Liss, Inc.