动态对比增强磁共振成像评估兔肢体高压电烧伤后早期骨骼肌微循环灌注的可行性研究

OBJECTIVE: To explore the feasibility of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in assessing the microcirculatory perfusion of skeletal muscle in rabbit limbs in the early stage after high-voltage electric burns. METHODS: This study was an experimental study. Thirty-two male big ear white rabbits aged 6-8 months were assigned into electric burn group of 20 rabbits with high-voltage electric burns in the right lower limb and control group of 12 rabbits with sham injury in the right lower limb using the random number table method. At 0.5, 24.0, 48.0, and 72.0 h post injury, the lower limbs of rabbits in the two groups underwent axial fast spin echo T1-weighted imaging, fast spin echo T2-weighted imaging, and DCE-MRI examination. A reference region-based hemodynamic model was applied to obtain the blood perfusion parameters of skeletal muscle in the injured limbs, including the volume transfer constant K(trans) value and rate constant K(ep) value. The skeletal muscle tissue from the electric burn group of rabbits at 0.5, 24.0, 48.0, and 72.0 h post injury and the control group of rabbits at 0.5 h post injury was harvested for immunohistochemical staining to observe the microvascular changes and calculate the microvascular density (MVD). The correlation between the K(trans) and K(ep) values and the MVD of skeletal muscle tissue in electric burn group of rabbits at 0.5-72.0 h post injury was analyzed. The number of samples was 5 in the electric burn group, and the number of samples was 3 in the control burn group. RESULTS: From 0.5-72.0 h post injury, the K(trans) and K(ep) values in skeletal muscle tissue of electric burn group of rabbits exhibited the trends of increase first and decrease then, both of which reached peak values at 24.0 h post injury. The K(trans) values at 0.5, 24.0, 48.0, and 72.0 h post injury (with t values of -15.77, -14.91, -40.35, and -40.25, respectively, P < 0.05) and the K(ep) values at 0.5, 24.0, and 48.0 h post injury (with t values of -5.39, -6.82, and -6.83, respectively, P < 0.05) in skeletal muscle tissue in electric burn group of rabbits were significantly higher than those in control group. The MVD in skeletal muscle tissue in control group of rabbits at 0.5 h post injury and in electric burn group of rabbits at 0.5, 24.0, 48.0, and 72.0 h post injury was (24.7±3.5), (21.8±2.2), (40.8±9.1), (16.4±2.4), and (9.8±0.8) per mm², respectively. The MVD in skeletal muscle tissue in electric burn group of rabbits at 24.0 h post injury was significantly higher than that in control group at 0.5 h post injury (t=2.89, P < 0.05), and the MVD in skeletal muscle tissue at 48.0 and 72.0 h post injury was significantly lower than that in control group at 0.5 h post injury (with t values of 4.01 and 9.52, respectively, P < 0.05). The K(trans) and K(ep) values of skeletal muscle tissue in rabbits in electric burn group were significantly positively correlated with microvascular density at 0.5 to 72.0 h post injury (with both r values of 0.95, P < 0.05). CONCLUSIONS: The quantitative perfusion parameters K(trans) and K(ep) values of DCE-MRI can effectively reflect the microcirculatory perfusion changes of skeletal muscle in rabbit limbs in the early stage after high-voltage electric burns.