Control of the Direction of Artifacts in MRI Using the Oblique Encoding Technique : Rotation of the Phase Encoding Direction within the Scan Plane

Abstract

Flow artifacts, also called ghosts or phase shift artifacts, can be caused by blood flowing fast within the image plane, due to the misregistration effect, or through the plane, because of the pulsatility of the flow. This can result in a repeated ghost signal in the phase encoding direction. Our MR unit allows the scan to be planned while viewing three images in the transverse, sagittal, and coronal directions simultaneously. This characteristic feature results in easy scan planning with complete freedom in the three dimensions. Specifically, it allows us to change the angulation in the phase encoding direction of the scan plane. We report here the clinical usefulness of the technique that controls the direction of the artifacts without having to reposition the patient. This technique consists of slanting the phase encoding direction through the combination of the three magnetic field gradient coils, similar to the double oblique. The technique allows us to have immediate freedom of the scan plan in three directions in all anatomies and sequences. This technique is useful and should be implemented in MR units, because of the easy control of artifacts depending on the phase encoding direction.