Worm hole

Diffusion Weighted Echo Planar Imaging uses partial k-space acquisition combined with homodyne reconstruction. When there is rotational motion in conjunction with the diffusion lobe, the k-space data is shifted by a large amount. This is the root cause of the wormhole-like artifact. The frequency in which the artifact appears increases at high b-values due to the use of higher and/or longer diffusion gradient lobes.

Head scan tip: To prevent the in-plane rotational motion, use non-conductive padding to support the sides of the patient's head and restraints to prevent rotational motion in the A/P direction.