Single-Shot T1 Mapping Using Simultaneous Acquisitions of Spin- and Stimulated-Echo-Planar Imaging (2D ss-SESTEPI)

The conventional stimulated-echo NMR sequence only measures the longitudinal component while discarding the transverse component, after tipping up the prepared magnetization. This transverse magnetization can be used to measure a spin echo, in addition to the stimulated echo. Two-dimensional single-shot spin- and stimulated-echo-planar imaging (ss-SESTEPI) is an echo-planar-imaging-based single-shot imaging technique that simultaneously acquires a spin-echo-planar image and a stimulated-echo-planar image after a single radio-frequency excitation. The magnitudes of the spin-echo-planar image and stimulated-echo-planar image differ by T-1 decay and diffusion weighting for perfect 90 degrees radiofrequency and thus can be used to rapidly measure T-1. However, the spatial variation of amplitude of radiofrequency field induces uneven splitting of the transverse magnetization for the spin-echo-planar image and stimulated-echo-planar image within the imaging field of view. Correction for amplitude of radiofrequency field inhomogeneity is therefore critical for two-dimensional ss-SESTEPI to be used for T-1 measurement. We developed a method for amplitude of radiofrequency field inhomogeneity correction by acquiring an additional stimulated-echo-planar image with minimal mixing time, calculating the difference between the spin echo and the stimulated echo and multiplying the stimulated-echo-planar image by the inverse functional map. Diffusion-induced decay is corrected by measuring the average diffusivity during the prescanning. Rapid single-shot T-1 mapping may be useful for various applications, such as dynamic T-1 mapping for real-time estimation of the concentration of contrast agent in dynamic contrast enhancement MRI. Magn Reson Med 64:734-742,2010. (C) 2010 Wiley-Liss, Inc.