Sensitivity of diffusion weighted steady state free precession to anisotropic diffusion

Diffusion‐weighted steady‐state free precession (DW‐SSFP) accumulates signal from multiple echoes over several TRs yielding a strong sensitivity to diffusion with short gradient durations and imaging times. Although the DW‐SSFP signal is well characterized for isotropic, Gaussian diffusion, it is unclear how the DW‐SSFP signal propagates in inhomogeneous media such as brain tissue. This article presents a more general analytical expression for the DW‐SSFP signal which accommodates Gaussian and non‐Gaussian spin displacement probability density functions. This new framework for calculating the DW‐SSFP signal is used to investigate signal behavior for a single fiber, crossing fibers, and reflective barriers. DW‐SSFP measurements in the corpus callosum of a fixed brain are shown to be in good agreement with theoretical predictions. Further measurements in fixed brain tissue also demonstrate that 3D DW‐SSFP out‐performs 3D diffusion weighted spin echo in both SNR and CNR efficiency providing a compelling example of its potential to be used for high resolution diffusion tensor imaging. Magn Reson Med 60:405–413, 2008. © 2008 Wiley‐Liss, Inc.