摘要：目的 在标准的动物脑梗塞模型上，对近红外光大脑地形图技术反映梗塞灶血流动力学变化进行评价。 方法 建立大鼠线栓脑中动脉梗塞模型和光敏剂诱导皮层梗塞模型，用近红外光大脑地形图(NCT),功能核磁共振成像(fMRI)和TTC染色成像技术分别对皮层进行定位测量和成像检测，并进行结果比较。 结果 光敏剂诱导模型，24 h组，NCT对梗塞灶成像面积和TTC染色样本的相关系数为0.897(P＜0.05)；对2月组，相关系数为0.906(P＜0.01)。大脑中动脉梗塞模型，常温组，NCT梗塞面积和染色样本相关系数为0.820(P＜0.05)，NCT和fMRI对梗塞灶成像面积的相关系数为0.874(P＜0.05)；亚低温组，NCT梗塞灶成像面积和样本梗塞灶染色面积的相关系数为0.851(P＜0.05)，NCT、fMRI对梗塞灶成像面积的相关系数为0.782(P＜0.05)。 结论 NCT技术能较好地反映局部脑血流的变化，该技术可望成为脑卒中趋向病人的实时预测及康复监测。

中图分类号：R319；R743文献标识码：A文章编号：1002-0832(2000)02-0084-06

Hemodynamic Assessment of Ischemic Stroke with Near-Infrared Spectroscopy

CHEN Wei-guo¹，LI Peng-cheng¹, LUO Qing-ming¹, ZENG Shao-qun¹,HU Bo²

(1.Institute of Biomedical Photonics, Huazhong University of Science & Technology, Wuhan, Hubei 430030, China；2.Xiehe Hospital, Tongji Medical University, Wuhan, Hubei 430074, China)

abstract: Objective To validate near-infrared cerebral topography (NCT) as a practical toolin tracing the regional hemodynamic changes during normal ischemic stroke model of rat. Method Middle cerebral artery occlusion (MCAO) and photosensitizer induced intracranial infarction model of rat were established. The geometric shape and infarction area were measured by NCT, functional magnetic resonance imaging (fMRI), and TTC stained anatomical imaging techniques. Result In photosensitizer induced infarction model, the correlation between anatomical infarct area and NCT image area for infarct focus were r= 0.897 for 24 h group (P＜0.05) and r=0.906 for 2 months group (P＜0.01),respectively. The correlation between anatomical infarction area and NCT image area for infarct focus were r=0.820 for normothermia group (P＜0.05) and r= 0.851 for hypothermia group (P＜0.05), respectively. The correlation between fMRI and NCT image area for infarction focus were r= 0.874 for normothermia group (P＜0.05) and r= 0.782 for hypothermia group (P＜0.05),respectively. Conclusion Measurement with NCT for infarction focus matched well with fMRI and anatomic sample in rats. NCT technique might be a practical tool for short-term prediction of stroke and the rehabilitation after stroke in real time.

Key words: near-infrared spectroscopy; cerebral blood flow; cerebral infarction; real time; prediction

Ischemic stroke is a dangerous cerebrovascular disease, which has high mortality and disability rate. The prediction and prevention are more important than treatment because the recovery of nervous system is very difficult^［1］.The prediction of stroke includes long-term and short-term prediction. The long-term prediction could be acquired from analysis of hemodynamics, cerebrovascular structure changes etc. Infact, several cerebral functional mapping techniques such as fMRI, CT, transcranial Doppler ultrasound (TCD)^［2］ have been used in prognosis of ischemic stroke. However, CT and brain MRI information concerning the extent of cerebral infarction usually come after the clinical onset, it may be helpful for the treatment,but is of little value in predicting the attack.

The short-term prediction or real-time prediction (e.g. in 5 min) could warn the patient on time to take action to protect the brain from stroke attack. But the major requirement for short-term prediction instruments is that it should be small enough to wear. It is obvious that current instruments could not meet these requirements. The short-term prediction and tracing of stroke hawe not got come true.

Near-infrared spectroscopy (NIRS), as a novel noninvasive optical technique can measure changes in concentration of oxygenated and deoxygenated hemoglobin (［oxy-Hb］, ［deoxy-Hb］) in cerebral blood. The changes in total hemoglobin concentration ［t-Hb］ reflect those in blood volume which in the optical field, are closely related to those in cerebral blood flow. Many researchers have elucidated the optical mechanism of hemoglobin state changes, which reflect the CBF and have set up non-animal models to verify the hypothesis^［3］. Even more, some mapping and spectroscopy studies on human nervous diseases and activities have been made^［4］. However, no proper animal model has been established to confirm the theory. Meanwhile, these were no consideration of the brain structure, thus localization of the focus was impossible. In fact, a certain cerebral function involves many functional areas. Without cerebral structure mapping, it is difficult to localize the functional areas involved in cerebral diseases or psychic activities. The main purpose of this study was to establish a localizing diagnostic technique of ischemic stroke and to analyze the spatial characteristics of the Near-infrared cerebral topography(NCT) images corresponding to the hemodynamic alternations during ischemia.

Method

The principle and system description of NCTThe theory of ［oxy-Hb］, ［deoxy-Hb］ absorption in near-infrared spectrum has been elucidated by many authors^［3,4］. NCT is an optical method for measuring concentration changes of oxy-Hb and deoxy-Hb in cerebral vessels by means of characteristic absorption spectra of hemoglobin in the near-infrared range. Changes in total-Hb (sum of oxy-Hb and deoxy-Hb) indicate blood volume changes and are correlated with CBF changes under condition with constant hematocrit and perfusion. Thus, NCT can measure both blood oxygenation and hemodynamics in the brain noninvasively. In our system, hemodynamic changes in cerebral cortex could be localized by the combination of the NCT signals with relative cortex points by neutrona-vigator in rats or humans.

The NCT developed by us is shown in figure 1. Two laser diodes were used as the continuous light sources; their wavelengths are 760 nm and 850 nm respectively and their intensities were modulated at 1 kHz. The distance between the end surface of incident and receiving (for reflected light) fiberoptic bundles on the rat's scalp is about 4 mm which is just the length of the path of the reflected light from the cerebral cortex, passing through the skin and the skull. We then will refer to the middle point from the incident and the received points as the measurement position. The reflected light was collected in the receiving fiberoptic bundle and transmitted to a photomultiplier tube(PMT). The PMT output was separated into two modulated signals for the corresponding wavelengths with two lock-in amplifiers. After analog-to-digital conversion, the signals were fed to a computer at a sampling rate of 1 s.

Fig.1Experimental setup of NCT

Nylon monofilament for intraluminal middle cerebral artery occlusion20 male sprague-dawley rats weighing 200～250 g were used. All processes were performing in according with institutional guidelines. Intraluminal ligature was made of 4-0 surgical nylon monofilament (Nitcho Kogyo Co,Inc).The tips of the ligatures were rounded by flame heating and coated with silicone.

Animals were initially anesthetized with 400 mg/kg IP chloral hydrate, then the anesthetic state was maintained with 0.5% to<