乳猪股骨头骨骺缺血的MRI研究

目的 应用MR线性扫描弥散加权成像技术,观察乳猪模璋型股骨头骨骺缺血不同时期的表现特征及变化过程.方法 16只2周龄乳猪,手术结扎一侧股骨颈处全部供血动脉造成股骨头缺血,另一侧为正常对照.分别在术前、术后3h、72h、1周、3周、6周进行MR线性扫描弥散加权成像,计算股骨头表面弥散系数(ADC)值.6周后宰杀动物,行解剖学及组织学研究.结果 16只乳猪中7只按时间点完成了6周的观察,另9只分别于术后72h(3只)、术后第8天(3只)、术后第3周(3只)死亡.术后3h,缺血性股骨头的ADC值(1.21±0.39)x10-3mm2/s]较正常对照侧(1.74±0.31)x10-3mm2/s]低(P＜0.05),术后72h ADC值(2.15±0.33)x10-3mm2/s]较正常对照侧(1.70±0.20)x10-3mm2/s]高(P＜0.05),其后一直保持比正常对照侧高的趋势(P＜0.01).除术后第3周和第6周外,每两个连续时间点之间ADC值变化率的差异均有统计学意义(P＜0.05).组织学研究显示,缺血性股骨头骨骺首先表现为软骨细胞和骨细胞死亡,血管塌陷,随之出现不同程度的股骨头骨骺软骨异常增厚、二次骨化中心内软骨岛形成、生长板组织结构及功能受损.结论 股骨头骨骺的弥散加权成像表现特征随缺血时间延长而变化,能够用于评估缺血性骨骺的组织受损程度及缺血的时间.

MR imaging of ischemic epiphysis of femoral head in piglets

Objective To determine whether diffusion changes with ischemia of increasing duration,and whether line-acan diffusion weighted imaging(LSDWI)can provide temporal information and severity about isehemia of epiphysis.Methods Ischemia was surgically induced in one hip of each piglet(n=16)and the other hip served as a normal control.Piglets were imaged before surgery and at 3 hours,72 hours and 1,3 and 6 weeks after surgery by using LSDWI.Apparent diffusion coefficients(ADC)in epiphysis of the femoral heads were calculated.Significant differences in ADC between ischernia and control group were evaluated by using statistics.At 6 weeks after MR scan,piglets were sacrificed for histological study.Results Seven piglets were studied completely in 6 weeks period,and other nine piglets died at 72 hours (three),8 days(three),and 3 weeks after surgery(three).ADC in ischemic femoral head(1.21±0.39)x10-3mm2/s]decreased significantly at 3 hours after surgery(P＜0.05),compared to that in control(1.74±0.31)×10-3mm2/s],and increased at 72 ours(2.15±0.33)x10-3 versus(1.70±0.20)x10-3 mm2/s,P＜0.05].ADC was kept increasing until 6 weeks after surgery(＜0.01).The percentage change of the ADC value increased at 3hours,72 hours,1.and 3 week(s)after the surgery(P＜0.01),compared with that of the prior neighboring time point.No significant difference in the percentage change of ADC value was found between the 3rd week and the 6th week after the surgery(P＞0.05).Histological findings revealed abnormal epiphyseal cartilage thickening,cartilaginous islands within OSSified tissues.Growth disturbance was found iu form of regions of focal growth plate disruption.Conclusion ADC remained changed in this model of prolonged ischemia.LSDWI can be useful for evaluating duration and extent of ischemic epiphyseal disruption.