Assessment of Vascularity andviability of the liver and liver tumors using the liver specific contrast agent in MR imaging

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Carotid occlusive disease may cause ischemic change both in the gray and white matter as a result of hemodynamic compromize. To validate proton magnetic spectroscopy (MRS) in evaluating the carotid occlusive diseases, changes in peakes of choline (Cho), the sum of creatine and phosphocreatine (Cr) and N-acetylaspartate (NAA) of the white matter were compared with the cortical oxygen metabolism measured by positron emission tomography (PET). Eleven patients with unilateral steno-occlusive carotid artery disease underwent both PET and MRS.MRS was performed in the bilateral centrum smiovale, Regional cerebral blood flow, metabolic rate of oxygen (rCMRO2) and oxygen extraction fraction (rOEF) of the crebral cortex were measured by the PET.The asymmetry index(AI) of the NAA/Cr ratio correlated positively with that of rCMRO2(r=0.809, p<0.01). as rCMRO2 is a marker of tissue viability. NAA ratio may reflect viable neuronal component. The Al of the Cho/Cr raio showed significant correlation with that of rOEF (r=0.844. P<0.01). The peak of choline contained the precursors and degradative products in the membrane metabolism, This may indicate membrane damage due to ischemia, as the centrum smiovale is the deep watershed zone. ln conclusion, the metabolic change in centrum semiovale detected by proton MRS reflects a hemodynamically compromized state and usful in evaluating the viability of brain tissue.