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.