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超声多普勒血流监测是评价血流动态的一种非损伤性检查法。理论上根据多普勒偏振频率,超声波入射角及血管直径可计算出血流速度和血流量。但当以胎儿胎盘的血管为对象时,由于超声波入射角和血管径难以测定,且往往会出现误差,故临床上除测定胎儿腹主动脉血流速度外,常根据血流速度比的各种指标,进行血流速度波形分析。对脐动脉,胎儿腹主动脉,大脑中动脉等动脉血流速度波形常采用的指标有S/D(收缩期最大血流速度/舒张末期血流速度,RI(阻抗指数即S-D/S),PI(搏动指数即S-D/平均血流速度)。还有提倡应用胎儿下腔静脉血流速度波形指标即PLI(下腔静脉逆流波/收缩期流入波)来判断胎儿心脏功能。正常胎儿的PLI与孕
Ultrasound Doppler flow monitoring is a noninvasive method of assessing blood flow dynamics. Theoretically based on Doppler polarization frequency, angle of incidence of ultrasound and vascular diameter can be calculated blood flow velocity and blood flow. However, when the fetus placental blood vessels for the object, due to the ultrasound angle of incidence and diameter difficult to measure, and often there will be errors, so in addition to the clinical determination of fetal abdominal aortic blood flow velocity, often based on blood flow velocity ratio Indicators, blood flow velocity waveform analysis. S / D (maximum systolic blood flow / end diastolic blood flow velocity, RI (impedance index, SD / S), arterial blood flow velocity waveforms such as umbilical artery, fetal abdominal aorta, middle cerebral artery, PI (pulsatile index, ie SD / mean blood flow velocity) .It also advocates the application of fetal waveform of inferior vena cava blood flow velocity index (PLI (inferior vena cava reverse flow / systolic inflow) to determine fetal heart function .Fl normal fetus And pregnancy