Comparison of stimulated echo, spin echo, and steady-state free precession pulse sequences for MR imaging apparent diffusion coefficient measurements

Stimulated echoes (STE), spin echoes (SE), and steady-state free precession (SSFP) have been proposed for producing MR images of the apparent diffusion coefficient (ADC). STE offers the potential advantage of smaller (T1-governed) signal losses during the diffusion evolution time compared with (T2-governed) SE losses. Calculations of the signal-to-noise ratio (S/N) normalized to imaging time were compared for SE, STE, and SSFP. In a system able to achieve 0.8 G/cm gradients, SE S/N can be as much as 50% greater than STE. STE may still be useful for observation of restricted diffusion due to the use of longer evolution times. The comparison is harder between SSFP and SE since gating is not practical for SSFP. However, SSFP can give useful diffusion images in a shorter imaging time than SE