团注法与再灌注法超声造影评估兔肾皮质血流灌注的对比研究

Comparison of bolus infusion and replenishment in contrast-enhanced ultrasound in assessing renal cortical blood perfusion

目的探讨团注-实时低机械指数法与连续注射-爆破再灌注-实时低机械指数法超声造影评估。肾皮质血流灌注的准确性与可操作性，进一步分析时间-强度曲线（TIC）参数的意义。方法健康新西兰大白兔20只，先后以剂量0．5、2．0、5．0ug·kg-1·min-1持续滴注多巴胺，用团注-实时低机械指数法与连续注射-爆破再灌注-实时低机械指数法行肾超声造影检查，分析TIC得到造影剂峰值强度（A）、达峰时间（TTP）及拟合曲线得曲线上升支斜率（k），行给药前后各参数配对样本t检验，同时分析各参数与肾有效血浆流量（ERPF）的相关性。结果团注方法的时间-强度曲线上升支近似为直线，再灌注法曲线上升支近似两条直线组成；两种方法得出的A值与ERPF显著正相关（r团注=0．85，r再灌注=0．66），TTP与ERPF显著负相关（r团注=-0．92，r再灌注=-0．76），伽玛函数公式拟合团注曲线得出的k与ERPF无相关性（r团注=-0．13），指数曲线给出的连续注射-爆破再灌注法的k与ERPF显著正相关（r再灌注=0．77）。结论团注-实时低机械指数法和连续注射-爆破再灌注-实时低机械指数法均可较准确地估肾皮质血流灌注，A与TTP分别反映部血流灌注容积与速度；团注方法较连续-再灌注方法更准确、方便；与k相比，TTP更能反映肾皮质微小血管平均灌注速度。

Objective To compare bolus infusion and replenishment using real low mechanical index contrast enhanced ultrasound in assessing the change of renal cortical perfusion. Methods Using dopamine （i. v. ） at the dose of 0.5,2.0,5.0 ug . kg-1 . min-1 to change renal blood perfusion of 20 rabbits, then during bolus or contant injection of SonoVue, at coded pulse inversion mode, real-time contrast ultrasound was performed, the latter method needed destroying microbubble at a high MI when amplitude reach a steady state,then recording the replenishment, peak intensity（A） and time to peak（PPT） were obtained through raw time-intensity curve, and slope rate of TIC（k） was acquired by curve fitting, standard effective renal plasma flow（ERPF） was measured through 4-aminohippuric acid clearancerate method, meanwhile correlations between ERPF and parameters were analyzed, as well as the paired samples t test for each parameter before and after dopamine administration. Results The ascending branchs of raw TIC of bolus infusion increased sharply and were approximately straight, then descended gradually, while that of replenishment looked like two straightlines with different slopes,then stayed horizontal. Both the value of A of two methods were positively correlated with ERPF（ r b = 0.85, r re = 0. 66）, and were different at the same ERPF, meanwhile the value of TTP were negatively correlated with ERPF（ r b = -0.92, r re = - 0.76） ,and there were no statistically difference between the two methods, k from Gamma fitting was far from correct, while k from exponential fitting was apparently correlated with ERPF （r re= 0.77）. Conclusions Both bolus injection and constant injection-replenishment method can assess renal cortical blood perfusion, TIC parameters A and TTP represent regional blood volume fraction and microbubble velocity respectively. Bolus-infusion with real low mechanical index is more precise and available. Comparing with k,TTP is more appropriate to reflect perfusion velocity.