The influence of flow and motion in MRI of diffusion using a modified CE-FAST sequence.
Severe motion and flow artifacts are a problem in MRI of diffusion in vivo due to the application of strong magnetic field gradients. Here it is shown that image artifacts can be removed by using a modified fast-scan MRI sequence (CE-FAST) in conjunction with averaging of diffusion-weighted images. In phantom studies slow (coherent) flow (less than 1 mm s-1) in the presence of strong diffusion gradients is shown to cause signal losses in diffusion-weighted images that depend on the relative orientations of the flow direction and the diffusion gradient. On the other hand, pulsatile motions of macroscopic dimensions (e.g., 1 mm, 1 Hz, in-plane) lead to smearing and ghosting of signal intensities along the phase-encoding direction of the images. In both phantoms and rabbit brains in vivo motion artifacts were found to be reducible by averaging 8-16 images. Unfortunately, the resulting image contrast no longer represents a "true" diffusion contrast but is affected by additional signal losses due to motion averaging. All experiments were performed on a 40-cm-bore 2.35-T Bruker Medspec system.
Merboldt
K D
KD
Max-Planck-Institute für biophysikalische Chemie, Göttingen, Federal Republic of Germany.
Hänicke
W
W
Gyngell
M L
ML
Frahm
J
J
Bruhn
H
H
D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D004058:Diffusion; D006801:Humans; D008279:Magnetic Resonance Imaging; D011817:Rabbits