An optimized pulse sequence for isotropically weighted diffusion imaging

Single-shot echo-planar imaging is becoming the most widely used technique for magnetic resonance diffusion imaging, since it enables measurement of d iffusion coefficients in human brain without motion artifacts. However, its reliability is limited by geometrical distortions due to eddy currents. In this report, an isotropically weighted echo-planar pulse sequence, optimiz ed to give the maximum signal-to-noise ratio in the computed trace image an d designed to produce inherently low distortions, is presented. It is also shown how the residual translational distortion can be easily characterized and removed by postprocessing. A full characterization of the distortion a rtifact involves a few measurements on a phantom, in order to estimate the distortion as a function of slice orientation, which can then be used to co rrect any slice orientation. Results of applying the image translation corr ection to data collected from a patient are presented. (C) 1999 Academic Pr ess.