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

颈动脉闭塞疾病可引起脑灰质和白质的缺血性改变，这是血流动力学损害的结果。为了验证质子磁谱（MRS）对颈动脉闭塞性疾病的评价，将脑白质胆碱（Cho）峰、肌酸和磷酸肌酸（Cr）和n -乙酰天冬氨酸（NAA）的变化与正电子发射断层扫描（PET）测量的皮质氧代谢进行比较。对11例单侧狭窄闭塞性颈动脉病变患者行PET和mrs检查，在双侧小叶中央行PET检查，测定脑区域血流量、脑皮质氧代谢率（rcro2）和氧提取分数（rOEF）。NAA/Cr比值的不对称指数（AI）与rCMRO2呈正相关（r=0.809, p<0.01）。因为rCMRO2是组织活力的标志。NAA比值可反映活神经元成分。Cho/Cr比值的Al与rOEF呈显著相关（r=0.844）。P < 0.01)。胆碱峰含有膜代谢的前体和降解产物，这可能是由于缺血引起的膜损伤，因为smiovale中心是深分水岭。综上所述，质子MRS检测的半囊体代谢变化反映了血流动力学受损状态，有助于评估脑组织活力。

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.