兔骨骼肌缺血模型扩散张量成像研究

Diffusion tensor imaging study of hind-limb ischemia model on rabbit

目的初步探讨MRDTI在定量评估兔后肢缺血模型骨骼肌缺血中的应用价值。方法对14只新西兰大白兔进行结扎并切除一侧后肢股动脉，成功建立兔后肢缺血模型共12只，分别于术后3d（12只）、10d（10只）、28d（7只）、56d（5只）对两侧小腿行DTI检查，并在每个时间点留取病理组织。观察两侧肌组织在DWI、本征向量（λ）1图、λ2图、λ3图、ADC图和部分各向异性（FA）图上的表现，并测量后组肌群的λ1、λ2、λ3、ADC值和FA值，采用配对t检验比较两侧小腿的差异，并与病理组织对照。结果术后3d手术侧ADC值升高（ADC术侧=1．72±0．16，ADC健侧=1．53±0．16，t=6．48，P〈0．01），其中λ2和λ32个特征矢量值升高明显（λ2术测=1．7±0．15，λ2健侧=1．51±0．06，t=10．87，P〈0．01；λ3芳侧：1．17±0．12，λ3健侧=0．88±0．12，t=6．67，P〈0．01），FA值急骤下降（FA术侧=0．24±0．04，FA健便=0．39±0．03，t=-10．61，P〈0．01）；术后10d缺血骨骼肌ADC值及λ2、b值下降，但两侧仍有差异（ADC术侧=1．65±0．16，ADC健侧=1．50±0．12，t=6．42，P〈0．01；λ2术侧=1．62±0．32，λ2健侧=1．48±0．31，t=5．09，P〈0．01）；λ3术侧=1．11±0．13，λ3健侧=0．85±0．09，t=6．26，P〈0．01），λ1值恢复正常（λ1术侧=2．20±0．21，λ1健侧：2．18±0．20，t=0．87，P：0．40）；术后28dADC及k值恢复正常（ADC术侧=1．51±0．16，ADC健侧=1．55±0．14，z=-1．35，P=0．23；λ3术侧=0．95±0．10，λ健侧=0．92±0．06，t=1．70，P=0．14），但λ2及FA值仍有差异（λ2术侧=1．45±0．23，λ2健侧=1．52±0．95，t=-3．56，P=0．012；FA术侧=0．35±0．02，FA健侧=0．40±0．03，t=-3．83，P〈0．01）；术后56d各观测指标均恢复正常（ADC术侧：1．57±0．18，ADC健侧=1．58±0．23，t=-0．71，P=0．52；λ1术侧=2．18±0．18；λ1健侧=2．24±0．14；t=-0．22，P=0．10；λ2术侧=1．64±0．13，λ2健侧=1．59±0．15，t=0．89，P=0．42；λ3术侧=0．89±0．1，λ3健侧=0．91±0．07，t=-1．64，P=0．18；FA术侧=0．39±0．03，FA健侧=0．41±0．02，t=-0．83，P=0．47）。组织学观察，在缺血后3、10d见肌肉损害，28d后缺血肌肉逐渐恢复，56d恢复正常形态。结论DTI可以定量且较准确地评估动物后肢缺血模型随时间推移发生的肌肉组织损伤及修复过程。

Objective To explore the application of diffusion tensor imaging in the assessment of ischemic muscle in hind-limb ischemia model of rabbit. Methods Excision of femoral artery in unilateral hind limb was done in 14 New Zealand white rabbits and ischemic model were established in 12 rabbits. Three （12 rabbits）, 10（ 10 rabbits） ,28（7 rabbits） ,56（5 rabbits） days after the model establishment, DTI scan was performed on bilateral hind limbs in each of the models, respectively and, λ1, λ2, λ3, ADC and FA values were measured. Histological analysis was also performed at these time points. Pared t test was used to compare the differences of these indexes in bilateral hind limbs. Results Following femoral artery excision, a rapid ascending of ADC , λ2, λ3 values with sharply reduced FA value was observed in ligated hind-limb, which reached maximal on 3 days post-excision （ ADCligated = 1.72 ± 0. 16, ADCunligated = 1.53 ± 0. 16, t =6.48, P 〈0. 01 ;λ2ligated =1.70 ±0. 15,λ2ligated =1.51±0.06, t =10.87, P 〈0. 01 ;λ3ligated = 1.17 ±0. 12, λ3unligated=0. 88 ±0. 12, t =6. 67, P 〈0. 01 ;FAligated =0. 24 ±0. 04,FAunligated =0. 39 ±0. 03, t = -10. 61 ,P 〈 0. 01 ） and histologic analysis revealed the severest muscle damag at that time. Ischemic muscle recovered very slowly during the first 10 day post-excision accompanied with reduction of ADC , λ2, λ3 values, however there was also difference of ADC, λ2, λ3 values between ligated and nonligated limbs except λ1 （ ADCligated = 1. 65 ± 0. 16, ADCunligated = 1.50 ± 0. 12, t = 6.42, P 〈 0. 01 ;λ2ligated= 1.62 ±0. 32, λ2unligated = 1. 48 4± 0. 31, t = 5. 09, P 〈 0. 01 ） ; λ3 ligated= 1. 11 ± 0. 13,λ3unligated = 0. 85 ± 0. 09, t = 6. 26, P 〈 0. 01 λ1unligated = 2.20 ＋ 0. 21, λ1unligated = 2. 18 ＋ 0. 20, t = 0. 87, P = 0. 40）. After 28 days, ADC and k3 returned to normal（ ADCligated = 1.51 ± 0. 16, ADCunligated = 1.55 ±0. 14, t = - 1.35, P = 0. 23 ; λ3unligated = 0. 95 4± 0. 10, λ.unligated = 0. 92 ＋ 0. 06, t = 1. 70, P = 0. 14）, but λ2 and FA of ligated limb were still different from those of nonligated limb （λ2 lighted = 1.45 4± 0. 23, λ2 ligated= 1.52 4± 0. 95, t = - 3.56, P = 0. 012; FAligated = 0. 35 ±0. 02, FAligated = 0. 40 4± 0. 03, t = - 3.83, P 〈 0. 01 ）. After 56 days, all parameters retuned to normal（ADCligated = 1.57 4±0. 18, ADCunligated = 1.58 4±0. 23, t = -0. 71, P =0. 52; λ1igated =2. 18 ±0. 18, λ1 unligated =2. 24 ±0. 14, t = -0. 22, P =0. 10; λ2 ligated = 1.64 ±0. 13, λ2unligated = 1.59 4± 0. 15, t = 0. 89, P = 0. 42 ; λ3 lighted = 0. 89± 0. 1, λ3unligated = 0. 91 4± 0. 07, t = - 1. 64, P = 0. 18 ; FAligated = 0. 39 ± 0. 03, FAunligated = 0. 41 4± 0. 02, t = - 0. 83, P = 0. 47 ） . Conclusion DTI is a quantitative and relatively accurate technique to assess time-dependent changes of ischemic muscle in hind- limb ischemia model of rabbit.