Diffusion sensitivity of turbo spin echo sequences

Abstract

This article introduces an effective b-factor bTSE for turbo spin echo (TSE) sequences to quantify their inherent diffusion sensitivity. bTSE is investigated for a broad variety of two-dimensional- and three-dimensional-TSE sequences using constant and varying flip angles (transitions between pseudo steady states, SPACE, VISTA, Cube, etc.). The inherent TSE diffusion sensitivity becomes important for high-resolution protocols, which can lead to subtle contrast modifications or even fluid suppressions in a clinical setting or animal imaging regime. The bTSE values obtained considerably depend on the relaxation times and diffusion coefficient and, thus, on the tissue under observation. The fractional b TSE contributions per TSE imaging encoding axis are highly anisotropic. Further noteworthy effects such as decreasing b-factors along a TSE train are pointed out and explained. The results are also discussed in combination with recent findings regarding contrast properties and possible diffusion sensitivity of TSE sequences. Identical but well more pronounced bTSE effects are observed in the animal imaging regime due to smaller field of view and higher resolutions. Copyright © 2012 Wiley Periodicals, Inc.