兔肝缺血再灌注损伤的表观扩散系数量化分析与病理生化对照研究

目的 探讨DWI及ADC值对兔肝缺血再灌注损伤（IRI）的诊断价值及通过与肝酶、病理对照研究探讨其病理生理机制。方法 新西兰大白兔42只，用数字表法随机分成7组，每组6只。按照IRI后行MR扫描时间分为0.5、2.0、6.0、12.0、24.0和48.0 h IRI组及假手术（Sham）组。IRI组阻断肝左叶血供60 min后，恢复血供。Sham组未作缺血处理。采用3.0 T DWI，梯度因子(b)＝20、50、100、200、300、400、500、600 s/mm2，同时行T2WI、T1WI和T1WI增强扫描，并行组织病理学和肝酶学丙氨酸转氨酶(ALT)和天冬氨酸转氨酶(AST)检查。不同b值下多组ADC值、各IRI与Sham组的AST、ALT值的比较采用单因素方差分析，组间均数差异的比较采用LSD-t法。结果 ADC值的总体变化趋势是在复氧后0.5h明显下降，然后在2.0h组急剧上升，经过6.0～12.0h缓慢上升后，24.0h组再次下降，于48.0 h组ADC明显升高。B值分别为20、50、100、200、300 s/mm2时，Sham组ADC值分别为(3.47±0.53)×10-3、(3.11±0.39) ×10-3、(2.87±0.19)×10-3、(2.56±0.37)×10-3和(1.95±0.33)×10-3mm2/s，0.5 h IRI组ADC值分别为(2.63±0.31) ×10-3、(2.47±0.32)×10-3、(2.12±0.38)×10-3、(2.01±0.51) ×10-3和(1.61±0.17)×10-3mm2/s,24.0 h IRI 组ADC值分别为(2.72±0.09) ×10-3、(2.51±0.11) ×10-3、(2.28±0.30)×10-3、(1.96 ±0.14)×10-3和( 1.58 ±0.17)×10-3mm2/s。当b≤300 s/mm2时，0.5h与24.0 h IRI组ADC值均低于Sham组，差异均有统计学意义(P＜0.05)。Sham组、0.5 h IRI组、2.0 h IRI组、6.0 h IRI组、12.0 h IRI组、24.0 h IRI组和48.0 h IRI组ALT分别为(80±8)、(181 ±34)、(413±62)、(474±83)、( 424±41)、(332±41)和(302±39) U/L，AST分别为(79±10)、(454±55)、(547±72)、(607±31)、(649±79)、(785±49)和(1526±167) U/L，各IRI组与Sham组比较差异均有统计学意义(P＜0.01)。病理表现在IRI早期肝窦内、汇管区、中央静脉及小动脉内充血淤积，随着损伤加重，肝窦肿胀，肝细胞核同缩凋亡，肝窦解离，最后发展为凝同性坏死。结论 3.0T DWI能够动态监测肝IRI的病理发展过程，为临床诊断和治疗提供了一种可行性的评价方法。

Quantitative study of rabbit hepatic ischemia reperfusion injury with apparent diffusion coefficient values: comparison with pathology and biochemistry

Objective To explore the value of DWI ADC in the diagnosis of hepatic ischemia reperfusion injury (IRI) at 3.0 T and investigate the mechanism by comparison with liver enzyme and pathological findings. Methods Forty-two New Zealand white rabbits were divided randomly into ( n ＝ 6,each) six IRI groups by rank sum test. The IRI animals underwent left lobar ischemia for 60 min and were reperfused 0. 5 h, 2. 0 h, 6. 0 h, 12. 0 h, 24. 0 h and 48. 0 h later. One Sham operative group underwent laparotomy without liver ischemia. T2 WI, T1 WI, DWI and contrast-enhanced T, WI were performed with 3.0 T magnetic resonance imaging scanner in each group respectively. For DWI, b-values of 20, 50, 100,200,300,400,500 and 600 s/mm2 were used respectively. Blood samples were taken to detect the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) at different time points. Liver samples were examined histologically after MRI scanning. One-way analysis of variance (ANOVA) was used to determine differences, followed by LSD-t test for multiple comparisons. Results Overall, ADC decreased markedly at the early IRI phase ( 0. 5 h), drastically increased in the 2.0 h group, and then ascended slightly from 6. 0 h to 48.0 h after reperfusion, except for a transient decrease at the time point of 24. 0 h. When b values were 20, 50, 100,200 and 300 s/mm2, the ADC values in the Sham group were (3.47 ±0.53) × 10-3, (3.11 ±0.39) ×10-3, (2.87 ±0.19) ×10-3, (2.56 ±0.37) × 10-3 and (1.95 ±0.33) ×10-3mm2/s, (2.63±0.31)±10-3, (2.47±0.32) ×10-3, (2.12±0.38) ×10-3, (2.01±0.51) ×10-3and (1.61 ±0.17) ×10-3mm2/s in the 0.5 h group, (2.72 ±0.09) ×10-3, (2.51±0. 11) ×10-3, (2.28 ±0.30) ± 10-3, (1.96 ±0. 14) × 10-3 and (1.58 ±0. 17) × 10-3mm2/s in the 24.0 h group, respectively. ADC of 0. 5 h and 24. 0 h groups were significantly lower than that of Sham group (P＜0.05) when b value was under 300 mm2/s. In the Sham, 0.5 h, 2.0 h, 6.0 h, 12.0 h,24.0 h and 48. 0 h IRI groups, they were (80±8), (181 ±34), (413 ±62), (474 ±83), (424 ±41 ),(332 ±41 )and(302 ±39) U/L for the levels of ALT,and (79 ± 10), (454 ±55), (547 ±72), (607±31 ), (649 ±79), (785 ±49) and ( 1526 ± 167) U/L for the AST respectively. The levels of AST and ALT in IRI groups were significantly higher than those in the Sham group ( P ＜ 0. 01 ). Histological findings showed diffuse hepatocytes swelling and erythrocytes depositing in the hepatic sinusoids, portal area, central venous and arterials at the initial phase. With the injury aggravated, inflammatory cell infiltration,hepatocyte nuclear condensation of apoptosis, sinusoidal dissociation and coagulation necrosis developed eventually. Conclusion 3.0 T DWI can monitor the pathological process of rabbit liver ischemia reperfusion injury dynamically, and provides a feasible imaging modality for clinical diagnosis and treatment.