Overlapping section coverage in multisection imaging.

Abstract

A method is proposed in which the section position for two-dimensional Fourier transform multisection imaging is advanced from one phase-encoding step to the next, so that information is sampled continuously over the total volume under observation. This "ramp scan" technique allows reconstruction of images from any arbitrary position within the sampled volume. The imaging properties depend strongly on the order of distribution of phase-encoding steps to the different section positions. In practice, images are reconstructed at each nominal position of a multisection experiment, plus at each position halfway between sections. The volume under study is thus represented by overlapping sections. The gaps between sections that arise in conventional multisection imaging--even with optimized pulse shapes--are thus avoided. This approach is applicable not only to conventional spin-echo imaging but to other techniques such as RARE (rapid acquisition with relaxation enhancement) and gradient-echo and echo-planar imaging.