EFFECT OF MOTION OUTSIDE THE FIELD-OF-VIEW ON FUNCTIONAL MR

PURPOSE: To evaluate the effect of objects moving outside the field of view on functional MR imaging. METHODS: Echo-planar image sequences w ere acquired in the sagittal plane of a stationary phantom or of the h ead of a volunteer subject while a second phantom was moved periodical ly outside the field of view. The signal intensity changes in each pix el within the field of view were measured, RESULTS: Movement of the ph antom outside the field of view produced signal intensity changes in t he field of view that equaled or exceeded typical functional activatio n without the latency that characterizes activation. The greatest chan ges occurred at the bottom and top edges in the phantom and at the int erfaces in the head. CONCLUSION: If temporally correlated with the per formance of a task, movement of objects or tissues outside the field o f view may produce artifactual changes in signal intensity. The artifa ctual signal intensity changes were characterized by their location, g reater magnitude, and more rapid rise to maximum than seen with typica l ''activation.''