急性兔脑微栓塞模型的CT灌注成像研究

CT Perfusion Imaging Study of Acute Cerebral Microembolic Model in Rabbits

目的:建立稳定的兔脑微栓塞模型,探讨CT灌注成像(CTPI)技术对早期脑缺血的诊断价值。方法:30只健康新西兰种大白兔,随机分成2组,其中A组5只,为假手术对照组;B组25只,为微栓塞组。分离右侧颈部血管,经颈外动脉向颈内动脉注入直径约0.5mm的SiO_2颗粒10枚,栓塞后30min行CTPI,分别测量灌注异常侧与正常对侧的CBF、CBV及MTT值。24h处死动物取脑组织行HE染色。利用SPSS11.0统计学软件进行CBF、CBV及MTT ROC曲线分析,评价各灌注参数诊断早期脑缺血的准确性。结果:A组CTPI及病理均未见明显异常。B组3只因实验意外死亡,1只因下肢静脉穿刺失败导致CTPI失败,21只行CTPI检查,其中18只CTPI异常,HE染色10只脑梗死,7只脑缺血,1只未见明显异常;3只CTPI未见明显异常,HE染色1只轻度脑缺血,2只未见明显异常。灌注异常主要表现为局部CBF降低、MTT延长、CBV无明显变化或轻度上升、下降,包括5只右侧额、颞叶片状低灌注;4只右侧额叶、颞叶、基底节及小脑片状低灌注;7只右侧颞叶小片低灌注;2只双侧额颞叶小片低灌注。灌注异常侧与正常对侧CBF值、MTT值比较差异有统计学意义,CBV值差异无统计学意义。ROC曲线分析提示CBF<67.06mI/(min·100g)、CBV<3.08ml/100g、MTT>4.58s,诊断早期脑缺血的灵敏度和特异度分别为84.6%、74.4%、87.2%。结论:CBF、MTT诊断早期脑缺血具有较高的准确性,CTPI技术可以准确、无创地反映兔脑微栓塞模型的血流动力学变化。

Purpose：To establish a stable microembolic model of brain in rabbits,and to evaluate the value of computed tomography perfusion imaging（CTPI） in acute ischemic cerebrovascular disease. Methods：Thirty New Zealand white rabbits were randomly divided into two groups：Group A（n = 5） underwent a sham operation;group B（n = 25） underwent an operation of microembolic brain injury. Right cervical vessels were separated,and about ten SiO2 grains（D = 0.5mm） were injected into internal carotid artery by external carotid artery in group B.After 30 minutes,CTPI was performed and the values of CBF,CBV,and MTT were measured in the lesions and the normal contralateral regions.After 24 hours,the brain was extracted and HE stain was performed.The analysis of receiver operating characteristic （ROC） curves of CBF,CBV and MTT were performed by SPSS 11.0 statistic software,and the accuracy of CTPI in diagnosing acute cerebral ischemia was evaluated.Results：No abnormity was seen both on CTPI and HE stain in group A.In group B,three rabbits were died during the experiment,CTPI was defeated in one rabbit because of the failure of puncture of femoral vein,and CTPI was succeeded in twenty - one rabbits,including abnormal perfusion in eighteen rabbits and normal perfusion in three rabbits.By HE stain,among the rabbits with abnormal perfusion,ten rabbits were with cerebral infarct, seven rabbits were with cerebral ischemia and one rabbit was normal.While among the rabbits with normal perfusion,one rabbit was with slightly ischemic and two rabbits were normal.Reduced CBF, prolonged MTT and slightly low or high CBV were found on CT perfusion maps.There was low perfusion in right frontal and temporal lobes in five rabbits,low perfusion in right frontal and temporal lobes,basal ganglia and cerebellum in four rabbits,local low perfusion in right temporal lobe in seven rabbits and local low perfusion in both side of frontal and temporal lobes in two rabbits.There were significant differences between abnormal side and normal side for CBF and MTT,but for CBV,there was no significant difference.By ROC analysis,when the value of CBF was set less than 67.06ml/（min·100g）,the sensitivity and specificity were all 84.6%in diagnosing cerebral ischemia.If the value of CBV was set less than 3.08 ml/100g,the sensitivity and specificity were all 74.4%.And if the value of MTT was set more than 4.58s,the sensitivity and specificity were all 87.2%.Conclusion：CBF and MTT have high accuracy in diagnosing acute cerebral ischemia and CTPI can be used as an accurate and non - invasive method in evaluating the acute ischemic cerebrovascular disease.