INHOMOGENEITY CORRECTION USING AN ESTIMATED LINEAR FIELD MAP

A fast and robust method for correcting magnetic resonance image disto rtion due to field inhomogeneity is proposed and applied to spiral k-s pace scanning. The method consists of acquiring a local field map, fin ding the best fit to a linear map, and using it to deblur the image di stortions due to local frequency variations. The linear field map is d etermined using a maximum likelihood estimator with weights proportion al to the pixel intensity, The method requires little additional compu tation and is robust in low signal regions and near abrupt field chang es. Additionally, it can be used in combination with other deblurring methods. The application of this method is illustrated in conjunction with a multislice, T-2-weighted, breath-held spiral scan of the liver.