MR血氧水平依赖成像评价兔肾缺血再灌注损伤的实验研究

Experimental Study on MR BOLD for Assessment of Rabbit Renal Ischemia Reperfusion Injury

目的探讨MR血氧水平依赖成像（blood oxygen level-dependent,BOLD）对兔肾缺血再灌注损伤（IRI）的诊断价值。方法健康新西兰大白兔30只,完全随机分成IR 13组,建立左肾缺血再灌注模型,3组左肾动脉夹闭时间分别为40、60、80 min,夹闭后松开动脉夹均再灌注48 h。分别于IRI前后行双肾MR冠状位T2WI及BOLD扫描,检查完成后立即取左肾行病理学检查。分别测量双肾肾皮质（cortex,C）层、外髓（outer medulla,OM）层的R2*值,再将左肾与右肾相同区域的R2*值做比值（rR2*）,并计算IRI前后左右肾rR2*的差值（△rR2*）。IRI前后IR13组每组组内兔肾C层和OM层△rR2*比较采用配对样本t检验;IR 13组C层和OM层△rR2*组间两两比较采用LSD检验。结果肾IRI后,IR 13组OM层△rR2*分别为0.27±0.04、0.47±0.01、0.49±0.01。IR 2、3组OM层△rR2*明显高于IR 1组（P<0.01）,而IR 2组OM层△rR2*与IR 3组差异无统计学意义（P>0.05）;IR 13组C层△rR2*分别为0.12±0.02、0.10±0.02、0.11±0.03,俎间两两比较差异均无统计学意义（P>0.05）。3组OM层△rR2*均高于C层（P<0.05）。结论肾脏缺血时间越长再灌注后损伤越重;肾脏缺血时间超过60 min后,肾脏IRI的程度已经达到最大程度。BOLD通过无创地检测肾脏外髓质血氧水平,能间接地反映肾脏IRI随缺血时间变化的趋势特点,有助于肾脏IRI的检出。

Objective To investigate the diagnostic value of blood oxygen level dependent MR imaging in rabbit renal ischemia- reperfusion injury.Methods 30 healthy New Zealand rabbits were randomly divided into IR 1- 3 groups and set up the model of ischemic reperfusion injury(IRI) of the left renal artery.Each of the left renal artery occlusion time of three groups was 40,60,80 min.Coronal T_2WI and blood oxygenation sensitive sequence(BOLD MR) was performed before IRI and 48 h after releasing the artery clip on both kidneys.The left kidney was taken out immediately after the examination.Measure the R_2~* value of the both kidneys cortex(cortex,C) layer and outer medulla(outer medulla,OM) layer,and calculate the R_2~* value ratio of the left and right renal(rR_2~*) and the R_2~* value ratio of the difference between before and after IRI(△rR_2~*).The △rR_2~* values of C and OM layer of the three groups were compared using paired sample t test;LSD test was used to compare the △rR_2~* values of C and OM layer among the three groups.Results After IRI,the △rR_2~* values of OM layer of three groups were 0.27 ± 0.04,0.61 ± 0.03,0.63 ± 0.03 respectively.The△rR_2~* value of OM layer of IR2 and IR3 was significantly higher than IRI(P < 0.01),while the difference between the△rR_2~* value of OM layer of IR2 and IR3 was not statistically significant(P > 0.05).The △rR_2~* values of C layer of the three groups were 0.12 ±0.02,0.10 ±0.02,0.11 ±0.03 respectively,and the differences between each group were not statistically significant(P > 0.05).The △rR_2~* value of OM layer of each group was higher than C layer(P < 0.05).Conclusion The longer the kidney ischemia time,the heavier reperfusion injury.When renal ischemia time is over60 min,the degree of renal IRI has reached maximum level.MR BOLD imaging can noninvasively reflect the renal outer medullary blood oxygen level and can indirectly reflect the trend between renal ischemia time and IRI,which will help in the detection of renal IRI.