Magnetic resonance spectroscopic imaging for visualization and correction of distortions in MRI: high precision applications in neurosurgery

We present a method for the quantification and correction of geometrical/intensity distortions of magnetic resonance images predominantly caused by bulk magnetic susceptibility shifts due to susceptibility heterogeneities of measured biologic tissues and shape of the object under investigation. The method includes precise and fast measurements of the static magnetic-field distribution inside the measured object and automated data processing. Magnetic-field deviations in the range ?2.4; 2.6 ppm were found in the human brain at B₀ = 1.5 T. For routinely used imaging parameters, with a read gradient strength of about 1 mT/m, the magnetic-field perturbations in the human brain can cause geometrical distortions up to ±4 mm and intensity changes up to ±50%. MR images corrected by the described method are suitable for planning high precision applications in neurosurgery.