FIG. 1.

The effect of random subject rotation on tensor estimation. Let b_i denote the applied diffusion encoding and let p_i represent the tensor orientation, which depends on subject motion. In case of no motion, the estimated diffusion tensor (dotted line) is the same as the actual tensor (left). If there is rotational motion (right), the estimated tensor orientation will be different and the anisotropy will be lower than the actual values. The error in FA and orientation will depend on the severity of the motion and the pattern of orientation changes.