Time-dependent and anisotropic diffusion in the heart: linear and spherical tensor encoding with varying degree of motion compensation

Spherical tensor encoding (STE) can potentially shorten acquisition of mean diffusivity (MD) compared to the traditional linear tensor encoding (LTE). To avoid negative effects of motion, e.g. in the heart, motion compensation is needed. However, motion compensation requires altering diffusion gradient waveforms and their sensitivities to time-dependent diffusion. To exclude motion, we first investigated LTE and STE with different degrees of motion compensation in ex vivo pig hearts. We observed significantly different MD, which can be attributed to time-dependent diffusion and microscopic diffusion anisotropy. Our analysis suggests that time-dependent diffusion is a critical determinant of MD in the myocardium.