Simon Robinson1, Alexander Geissler2, Siegfried Trattnig1, Roland Beisteiner2
1High Field MR Centre, Department of Radiology, Medical University of Vienna, Vienna, Austria; 2Clinical fMRI Study Group, Departments of Neurology, Neurosurgery, and Radiology, Medical University of Vienna, Austria
We assess the effectiveness of a fast MGE sequence and postprocessing steps for fieldmapping with multichannel coils in correcting for EPI distortions in presurgical planning fMRI at 7T. Complex conjugate phase combination, unwrapping, denoising and fieldmap thresholding (for maximum achievable remapping) are described. Four patients underwent multiple runs of motor area localisation. Without distortion correction, primary foci for hand activation were mislocalised by 5-7mm, which could give rise to serious postoperative impairment of function. No residual distortions were observed after distortion correction, allowing fMRI results to be reliably registered to structural images and imported into neurosurgical planning systems.