MEASUREMENTS OF MAGNETIC-FIELD VARIATIONS IN THE HUMAN BRAIN USING A 3D-FT MULTIPLE GRADIENT-ECHO TECHNIQUE

A magnetic resonance 3DFT multiple gradient-echo technique was used fo r measurements of the proton spectrum for each voxel in the measured s lice. Water, fat, magnetic field and T-2 distributions in the head of a normal volunteer and a patient with intracerebral hematoma were com puted. Magnetic field variations caused by the head were calculated af ter correction for the static magnetic field inhomogeneity. Large loca l magnetic field variations up to 3 ppm were found in the human brain near interfaces between air or bone and brain tissues and 0.5 ppm betw een hematoma and brain tissue. Information about magnetic field variat ions could be useful for shimming procedures in vivo and for correctin g artifacts in imaging and spectroscopy.