[The application of in vivo diffusion weighted magnetic resonance imaging to intracranial disorders].
We have developed a magnetic resonance (MR) spin echo method to obtain diffusion weighted imaging using motion-probing gradient (MPG) pulses in one or three orthogonal directions before and after a 180 degree pulse. Phantom models containing water and acetone, normal volunteers and patients with brain tumors, brain edema and infarction were examined. Experimental models of brain edema including triethyltin intoxication and cold injuries were also examined in Wistar rats. MRI was performed at a 1.0-T clinical machine or a 4.7-T experimental machine using spin echo pulse sequences with or without additional MPGs on one or three orthogonal axes. The one direction method was useful to define diffusion anisotropy of myelinated axonal fibers in white matter. Faster diffusion was detected in the white matter parallel to the direction of MPGs. On the other hand, slower diffusion was detected perpendicular to the direction of MPGs because the myelin sheath restricted water diffusion. The three orthogonal gradients method was useful to demonstrate the difference in the diffusion coefficients in various diseases due to its larger total gradient strength. The clear distinction between the cytotoxic edema, which revealed slower diffusion, and the vasogenic edema, which revealed faster diffusion, was demonstrated in the experimental models using diffusion weighted image. In the clinical cases, faster diffusion was demonstrated in the brain tumor and perifocal vasogenic edema, which was in agreement with the results in the experimental models of rats. Brain tumors such as low grade astrocytoma with microcysts and perifocal vasogenic edema have very wide extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)