Errors in T2 estimation using multislice multiple-echo imaging.

Accurate T2 images calculated from multiple-echo sequences are difficult to obtain over a number of contiguous slices due to the presence of unwanted echoes that are generated at the slice edges. This problem is similar to problems encountered in single-slice imaging in the presence of rf pulse imperfections. In this paper, we use computer simulations to show that all unwanted echoes can be eliminated by defocusing them using additions to the slice-selection gradients. Accurate T2 images may then be calculated from the remaining echoes. We also present a method of experimentally displaying the slice shapes of unwanted echoes generated by a multislice imaging sequence.