兔严重烧伤早期脑水肿MR弥散成像的实验研究

MR diffusion imaging of brain edema in rabbits at primary stage of severe burn

目的探讨兔严重烧伤早期脑水肿发生、发展过程中MR弥散成像改变特征及其诊断价值。方法 35只健康新西兰大白兔随机数字表法分为对照组及烧伤组（烧伤后1、2、3、4、5、6 h）,烧伤组兔均制成50%总烧伤面积Ⅲ度烧伤模型。常规行MRI T1WI、T2WI、DWI、DTI颅脑检查,对各烧伤组和对照组的表观弥散系数（ADC）值、各向异性分数（FA）值,指数表观弥散系数（eADC）值进行动态观察,并用干湿质量法检测其脑含水量的变化。结果烧伤后6 h内,T1WI、T2WI像未见明显变化。与对照组相比,烧伤后4~6 h ADC值明显降低（P〈0.01）,同时eADC值明显增高（P〈0.01）,而FA值无明显改变。随着观察时间的延长,脑含水量呈逐渐增高趋势,以伤后3~6 h表现最为显著。脑含水量与ADC值（r=-0.898,P〈0.01）、eADC值（r=0.871,P〈0.01）的变化呈明显相关性,与FA值无明显相关性（r=0.135,P=0.438）。结论 MR弥散成像能够较好的反映严重烧伤后脑含水量的变化,对烧伤早期明确诊断脑水肿具有重要参考价值。

Objective To investigate the features of MR diffusion imaging for a rabbit model of severe burn with brain edema at primary stage and its diagnostic value.Methods Thirty-five healthy New Zealand white rabbits were equally randomized into 7 groups,control group and burn groups（post-burn at 1,2,3,4,5 and 6 h respectively）.Severe burn injury was inflicted by 50% total burn surface model with stage III burn.Routine MRI T1WI,T2WI,DWI and DTI with cerebral dynamic observation of apparent diffusion coefficient（ADC）,fractional anisotropy（FA） and exponential apparent diffusion coefficient（eADC） values were performed.Changes of cerebral water content were calculated by wet and dry weight method.Results No significant change was observed in T1WI and T2WI images within 6 h.Compared with control group,apparent decrease in ADC value（P0.01） was observed along with significant increase in eADC value（P0.01）,while no significant alteration was seen in FA value（r=0.1）.The water content of brain was found to increase with the elapse of time,which reached peak in 3 to 6 h post burn.Significant correlations were found between brain water content with ADC value（r=0.898,P0.01） and eADC value（r=0.871,P0.01）,however,no correlation was seen with FA value（r=0.135,P=0.438）.Conclusion MR diffusion image well reflects the change of brain water content post severe burn,and is of significant value in diagnosis of brain edema in primary stage of burn.