Doppler Index S-D Ratio (Systolic / Diastolic); key measurement in obstetric ultrasound скачать в хорошем качестве

Doppler Index S-D Ratio (Systolic / Diastolic); key measurement in obstetric ultrasound

The Systolic/Diastolic (S/D) ratio is a key Doppler ultrasound index used in obstetric imaging, especially for assessing umbilical artery blood flow during pregnancy. Here's a clear breakdown: 🧠 What Is the S/D Ratio? It’s the ratio of peak systolic velocity to end-diastolic velocity in the umbilical artery. Reflects resistance to blood flow in the placenta. A higher S/D ratio suggests increased resistance, which may indicate placental insufficiency or fetal compromise. 📈 Normal Reference Values by Gestational Age Gestational Age 50th Percentile S/D Ratio 20 weeks ~4.0 30 weeks ~2.83 40 weeks ~2.18 The S/D ratio normally decreases as pregnancy progresses due to improved placental perfusion. ⚠️ Clinical Significance Elevated S/D ratio may be seen in: Intrauterine growth restriction (IUGR) Preeclampsia Placental insufficiency Absent or reversed end-diastolic flow is a critical finding and may warrant early delivery3. 🛠️ Related Doppler Indices Index Formula Interpretation S/D Ratio Systolic / Diastolic ↑ = ↑ resistance Resistance Index (RI) (S - D) / S ↑ = ↑ resistance Pulsatility Index (PI) (S - D) / Mean ↑ = ↑ resistance #Doppler #dopplerultrasound