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

Abstract

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. Key words: Diffusion magnetic resonance imaging; Muscle, skeletal; Ischemia; Animals, laboratory