velocity gradient短语¹⁴⁴⁹⁷²⁺² 基本例句 速度梯度 Objective To assess the feasibility of quantitative tissue velocity imaging QTVI in evaluation of myocardial velocities and myocardial velocity gradient of normal fetuses. 目的探讨超声定量组织多普勒速度成像技术 QTVI评价正常胎儿心室壁运动的临床价值。 cnki