CORRECTION FOR HEAD MOVEMENTS IN MULTISLICE EPI FUNCTIONAL MRI

We have investigated 2D and 3D registration techniques based on either simple rotational/translational movements or movements modeled as a f irst or second order polynomial to correct for assumed rigid and nonri gid body motion in fMRI. Data acquired with two 1.5T multi-slice echo planar imaging (EPI) MRI systems were used to develop and evaluate the registration techniques. Two sets of data were acquired with EPI. In the first set, the subjects were asked to keep their head as stationar y as possible while in the second set, subjects were asked to randomly move their herd with displacements being on the order of 1cm. Images from the second set were registered and compared to those obtained Fro m the first set. Results indicate that 2D and 3D motion corrected imag es show lower variance to mean ratio than uncorrected images and that in most cases, polynomial based nonrigid body correction produces the lowest variance to mean ratios.