FIG 2. Axial diffusion-weighted images (2 R-R/106/4 [TR/TE/excitations]) showing the appearance of the cervical spinal cord with the diffusion-probing gradients in the three cardinal axes, with increasing b values from left to right. R-L, A-P, and C-C indicate the direction of the diffusion gradients. The R-L and A-P directions are perpendicular to the white matter tracts. The C-C direction is parallel to 
the white matter tracts. Note the relatively greater signal attenuation with the diffusion gradients in the C-C direction, reflecting the underlying tissue anisotropy. Note also the reversal of the relative signal intensity of gray and white matter at the higher b values (640, 1000) in the C-C direction, due to the higher ADC of white matter along this axis
