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

颈动脉闭塞症可导致血流动力学损害，引起灰质和白质的缺血性改变。为验证质子磁共振波谱(MRS)在评价颈动脉闭塞性疾病中的价值，将脑白质胆碱峰值(CHO)、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例单侧颈动脉狭窄闭塞症患者进行了正电子发射计算机断层扫描和磁共振成像，并对双侧大脑中动脉进行了MRS检查，测量了大脑皮质局部脑血流量、氧代谢速率(RCMRO2)和氧摄取分数(ROEF)。因为rCMRO2是组织活力的标志。NAA比率可反映神经元的活性成分。Cho/CrRAIO的Al与Roef的Al呈显著正相关(r=0.844)。P&lt；0.01)。胆碱的峰含有膜代谢的前体和降解产物，这可能是由于缺血造成的膜损伤，因为斯氏中心是深层次的分水岭。结论：质子磁共振波谱检测到的半卵圆中心代谢改变反映了脑组织的血流动力学受损状态，有助于评价脑组织的生存能力。

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.