兔骨骼肌缺血模型扩散张量成像研究

目的 初步探讨MR DTI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3 d(12只)、10 d(10只)、28 d(7只)、56 d(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、λ_2图、λ_3图、ADC图和部分各向异性(FA)图上的表现,并测量后组肌群的λ_1、λ_2、λ_3、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3 d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λ_2和λ_3 2个特征矢量值升高明显(入_(2术侧)=1.70±0.15,入_(2健侧)=1.51±0.06,t=10.87,P<0.01;入_(3术侧)=1.17±0.12,λ_(3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_(健侧)=0.39±0.03,t=-10.61,P<0.01);术后10 d缺血骨骼肌ADC值及λ_2、λ_3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;λ_(2术侧)=1.62±0.32,λ_(2健侧)=1.48±0.31,t=5.09,P<0.01);λ_(3术侧)=1.11±0.13,λ_(3健侧)=0.85±0.09,t=6.26,P<0.01),λ_1值恢复正常(λ_(1术侧)=2.20±0.21,λ_(1健侧)=2.18±0.20,t=0.87,P=0.40);术后28 d ADC及λ_3值恢复正常(ADC_(术侧)=1.51±0.16,ADC_(健侧)=1.55±0.14,t=-1.35,P=0.23;λ_(3术侧)=0.95±0.10,λ_(3健侧)=0.92±0.06,t=1.70,P=0.14),但λ_2及FA值仍有差异(λ_(2术侧)=1.45±0.23,λ_(2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56 d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;λ_(1术侧)=2.18±0.18;λ_(1健侧)=2.24±0.14;t=-0.22,P=0.10;λ_(2术侧)=1.64±0.13,λ_(2健侧)=1.59±0.15,t=0.89,P=0.42;λ_(3术侧)=0.89±0.1,λ_(3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、10 d见肌肉损害,28 d后缺血肌肉逐渐恢复,56 d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.

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

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, λ_1,λ_2,λ_3, 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,λ_2,λ_3 values with sharply reduced FA value was observed in ligated hind-limb, which reached maximal on 3 days post-excision (ADC_(ligated)= 1.72±0.16, ADC_(unligated)= 1.53±0.16, t = 6.48, P < 0.01 ; λ_(2 ligated)= 1.70±0.15, λ_(2 unligated)= 1.51±0.06, t=10.87, P < 0.01 ; λ_(3 ligated_ =1.17±0.12, λ_(3 unligated)= 0.88±0.12, t=6.67, P < 0.01 ; FA_(ligated)= 0.24±0.04, FA_(unligated) =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 , λ_2, λ_3 values, however there was also difference of ADC,λ_2, λ_3 values between ligated and nonligated limbs except λ_1 ( ADC_(ligated) = 1.65±0. 16, ADC_(unligated)= 1.50±0.12, t =6.42, P <0.01 ; λ_(2 ligated) = 1.62±0.32, λ_(2 unligated) =1.48±0.31, t=5.09, P < 0.01) ; λ_(3 ligated)= 1.11±0.13, λ_(3 unligated)= 0.85±0.09, t=6.26, P <0. 01;λ_(1 ligated)=2.20±0.21, λ_(1 unligated) =2.18+0.20, t=0.87, P=0.40). After 28 days, ADC and λ_3 returned to normal (ADC_(ligated)= 1.51±0. 16, ADC_(unligated)= 1.55±0.14, t=-1.35, P=0.23 ; λ_(3 ligated) =0.95±0. 10, λ_(3 unligated)= 0.92±0.06, t=1.70, P=0.14), but λ_2 and FA of ligated limb were still different from those of nonligated limb (λ_(2 ligated)= 1.45±0.23, λ_(2 unligated)= 1.52±0. 95, t=-3.56, P=0.012; FA_(ligated)=0.35±0.02, FA_(unligated)=0.40±0.03, t=-3.83, P<0.01). After 56 days, all parameters retuned to normal(ADC_(ligated) =1.57±0.18, ADC_(unligated)=1.58±0.23, t=-0.71, P=0.52; λ_(1 ligated) =2.18±0.18, λ_(1 unligated)=2.24±0.14, t=-0.22, P=0.10; λ_(2 ligated)=1.64±0.13, λ_(2 unligated)=1.59±0.15, t=0.89, P=0.42; λ_(3 ligated)=0.89±0.1,λ_(3 unligated)=0.91±0.07, t=- 1.64,P= 0.18; FA_(ligated)= 0.39±0. 03, FA_(unligated)= 0.41±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 hindlimb ischemia model of rabbit.