[Diffusion-weighted imaging of brain death: study of apparent diffusion coefficient].

DWI(Diffusion-weighted images) of the brain has been revealed to be useful in diagnosis of several clinical conditions. However, little is known about DWI with regard to brain death. We had opportunities to study patients with brain death. Case 1. A 34-year-old woman experienced cardiopulmonary arrest due to severe ventricular fibrillation, and resuscitated after about 120 minutes. After brain death, DWI showed high signals in the cerebral cortex, putamen, thalamus, brain stem and cerebellum, and ADC(apparent diffusion coefficient) values were 30-40% lower than those of normal volunteers. Case 2. A 45-year-old woman experienced cardiopulmonary arrest due to pontine hemorrhage, and was resuscitated after about 20 minutes. Before brain death, DWI showed high signals in the cerebral cortex, putamen, thalamus, brain stem and cerebellum, and ADC values were the same as those of normal volunteers. After brain death, DWI showed more clearly defined in these areas, but ADC values were 30-40% lower than the first values. DWI and ADC mapping shows areas corresponding to edema of a cytotoxic nature and to ischemic tissue. The characteristic views of high signals in the whole area of the brain were present, and an objective evaluation was possible with DWI after the brain death diagnosis by measuring ADC values.