Practical implications of motion correction with motion insensitive radial k-space acquisitions in MRI

Objective: To highlight specific instances when radial k-space acquisitions in MRI result in image artifacts and how to ameliorate such artifacts. Methods: We acquired axial T-2 weighted MR images on (1) the American College of Radiology (ACR) phantom and (2) a sedated sheep with rectilinear and multiblade radial k-space filling acquisitions. Images were acquired on four (2 x 1.5T and 2 x 3T) different MRI scanners. For the radial k-space acquisitions, we acquired images with and without motion correction. All images were visually inspected for the presence of artifact. Results: Images collected via the conventional rectilinear method were of diagnostic quality and free of artifact. Both ACR and sheep images acquired with radial k-space acquisitions and motion correction suffered significant artifact at different slice locations, scan sessions and across all the four scanners. Severity of the artifact was associated with echo train length. However, the artifact was eliminated when motion correction was not employed. Conclusion: When little to no motion is present, the use of motion correction with radial k-space acquisitions can compromise image quality. However, image quality is quickly improved, and the artifact eliminated, by repeating the scan without motion correction or by using a conventional rectilinear alternative. Advances in Knowledge: By improving awareness and understanding of this artifact, MRI users will be able to adjust MRI protocols, resulting in more successful scanning sessions, better image quality, fewer call backs and increased diagnostic confidence.