实验性缺氧缺血性脑损伤的表观扩散系数和氢质子MR波谱与病理学的对照研究

Experimental hypoxic-ischemic brain damage comparison research of apparent diffusion coefficients,proton MR-spectroscopy and pathologic study

目的结合病理学,对照研究MR表观扩散系数(ADC)和氢质子波谱(1H-MRS)在评价急性期缺氧缺血性脑损伤(HIBD)中的价值。方法出生后7d的新生猪30头,分成假手术对照组5头和缺氧缺血组25头。缺氧缺血组分成5组,分别于缺氧缺血(HI)后即刻、3、6、12、和24h测量皮层下白质、侧脑室旁白质及基底节区平均ADC值和脑内代谢物N-乙酰天冬氨酸(NAA)、乳酸(Lac)、肌酸(Cr)、胆碱复合物(Cho)的峰高比率,并作脑组织病理学检查。结果缺氧缺血组HI后即刻,ADC值(3.69±1.45)、NAA/Cho(0.712±0.080)和NAA/Cr(1.040±0.137)明显下降,Lac/NAA(1.798±0.139)、Lac/Cho(1.280±0.167)和Lac/Cr(1.876±0.357)明显增高。HI后3～12h,ADC值、Lac/NAA、Lac/Cho和Lac/Cr出现一过性恢复,NAA/Cho相邻组间比较差异均有统计学意义(P<0.05),而NAA/Cr相邻组间比较差异均无统计学意义(P>0.05)。HI后24h,ADC值再次明显下降(4.06±1.25),Lac/NAA(1.221±0.128)、Lac/Cho(0.716±0.088)和Lac/Cr(1.212±0.177)再次明显增高。各时间点病理结果进行性加重,以胶质细胞水肿的逐级加重、崩解为主要改变,神经元病变相对较轻。对照组ADC值、MRS和病理学检查均未见异常。结论ADC值和1H-MRS均能敏感地反映HIBD早期病灶;NAA/Cho的演变与HIBD早期病理学的动态变化最相一致,其准确性优于ADC值和其他代谢物比率。

Objective To compare the apparent diffusion coefficients （ADC）, proton MR spectroscopy （1^H-MRS） and pathologic changes in young pigs subjected to acute hypoxic-ischemic brain damage （ HIBD ）. Methods Thirty 7-day-old neonatal pigs were divided into sham-operation group （ n = 5 ） and hypoxic-ischemic group （n = 25 ）. HI group was divided into five small groups. ADC value, NAA/Cho, NAA/Cr, Lac/NAA, Lac/Cho and Lac/Cr were calculated on cessation of the insult, 3, 6, 12 and 24 h after resuscitation in subcortical white matter, periventricular white matter and basal ganglia. Immediately after MR examinations, injury of the brains was evaluated by hematoxylin-eosin-stained and histopathologic study. Results The hypoxic-ischemic piglets showed ADC（3.69 ± 1.45）reduction, NAA/Cho（0. 712 ± 0. 080） and NAA/Cr（ 1. 040 ±0. 137） decrease, Lac/NAA（ 1. 798 ±0. 139） , Lac/Cho（ 1. 280 ±0. 167） and Lac/Cr（ 1. 876 ± 0. 357 ） increase on cessation of the insult; transient ADC, Lac/NAA, Lac/Cho and Lac/Cr recovery, NAA/Cho progressive decrease （P 〈 0. 05） and NAA/Cr reduction （P 〉 0. 05 ） from 3 h to 12 h after resuscitation; secondary ADC （4. 06 ± 1.25 ）reduction, Lac/NAA （ 1. 221 ±0. 128 ）, Lac/Cho （0.716±0.088）and Lac/Cr （ 1.212 ± 0. 177 ） increase 24 hours after resuscitation. Corresponding pathologic study revealed astrocytes gradually swelled and collapsed after resuscitation, while neurons changed mildly. The control piglets showed normal ADC, 1^H-MRS and pathologic investigations. Conclusions ADC value and 1^H-MRS can sensitively detect lesions of early HIBD. NAA/Cho has the highest correlation with the pathological changes of early HIBD and is superior to ADC value and the other metabolite ratios in evaluating early HIBD.