A PROSPECTIVE APPROACH TO CORRECT FOR INTER-IMAGE HEAD ROTATION IN FMRI

Global head motion occurring between successive image acquisitions dur ing a functional MRI time series can corrupt the signal of physiologic brain activation, potentially invalidating interpretation of the fina l activation map from that particular fMRI time series, By approximati ng the head as a rigid body, multiaxial global head motion can be deco mposed into orthogonal linear and rotational components, This paper de scribes a method using orbital navigator echoes to provide prospective correction for both through-plane and in-plane inter-image head rotat ion in functional MRI, The dynamic detection and correction of rotatio n can be performed in <100 ms, Phantom experiments demonstrate accurat e correction of rotational motion over a range of +/-0.36 degrees to /-12 degrees., Imaging studies in volunteers document the feasibility of real-time prospective correction of rotational motion in vivo., Usi ng a modified receiver operating characteristic method, motion-correct ed functional MRI sensorimotor studies incorporating deliberate head r otations are shown to be superior to functional MRI time series acquir ed under similar conditions but without motion correction.