Research for the characterization of brain tissue damage due to ischemia using MRI and MRS

评估缺血后脑损伤的程度对脑卒中患者的治疗具有重要意义。磁共振成像可以提供基于脑灌注和代谢变化的缺血风险脑的信息。本研究的目的是探讨MR灌注和MRS评估缺血性脑损伤的有效性。我们采用全脑再灌注动物模型和慢性闭塞性脑血管病的临床病例进行了这项研究。在动物模型中，我们观察到缺血事件后2-3周内NAA降低和Glx一过性升高（N=5）。虽然研究的大鼠数量有限，但其结果似乎反映了神经组织的丢失是一个长期的过程，并可作为缺血性损伤后组织损伤的有用指标。作为临床应用，我们在临床MR扫描仪上实现了连续动脉自旋标记（CASL）序列，提供了无创的CBF测量手段。为了验证CASL方法的有效性，我们比较了慢性闭塞性脑血管病患者的CASL和CO_2 PET的CBF值。11例患者进行了CASL和常规MRI研究。所有患者的CASL和PET的CBF值之间存在显著相关性（r=0.71±0.07，P<0.001）。使用CASL定量CBF是可行和合理的，即使在常规临床环境中使用。

It is very important to evaluate the extent of brain injury after ischemia for the management of stroke patients. MR imaging can provide the information based on brain perfusion and metabolic change about the brain at ischemic risk. The purpose of the study was to investigate the effectiveness of MR perfusion and MRS for the assessment of brain tissue damage induced by the ischemic insult. We have approached this research using both animal model with whole brain reperfusion and clinical cases with chronic occlusive cerebrovascular disease. In animal models, we have observed the decrease of NAA in 2-3 weeks and transient increase of Glx after ischemic event (N=5). Although the number of rats studied were limited, the results seemed to reflex the loss of neuronal tissue is long process and to be useful index for the tissue damage after ischemic insult. As a clinical application, we have implemented continuous arterial spin labeling (CASL) sequence on clinical MR scanner, which provide non-invasive means of CBF measurements. In order to validate the CASL method, we have compared the CBF values from CASL and CO_2 PET in patients with chronic occlusive cerebrovascular disease. Eleven patients were studied with CASL and conventional MRI. In all patients, there was a significant correlation between CBF values from CASL and PET(r=0.71±0.07, P<0.001). Quantification of CBF using CASL was feasible and reasonable, even when employed in a routine clinical setting.