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Understanding Doppler and its Current Uses in OB

Understanding Doppler and its Current Uses in OB. Diana M. Strickland, BSBA, RDMS, RDCS. Continuous vs. Pulsed. Doppler – Moving structures - Red Blood Cells-. Wall motion – high level NOISE!. Scattered waves- low level NOISE!. ƒd = 2( ƒt • v • cos θ)/c.

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Understanding Doppler and its Current Uses in OB

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  1. Understanding Doppler and its Current Uses in OB Diana M. Strickland, BSBA, RDMS, RDCS

  2. Continuous vs. Pulsed

  3. Doppler – Moving structures-Red Blood Cells- Wall motion – high level NOISE! Scattered waves- low level NOISE! ƒd = 2(ƒt • v • cosθ)/c

  4. Doppler – Moving structures-Red Blood Cells- fr fr ft ft Positive shift f Negative shift Time

  5. Doppler – Moving structures-Red Blood Cells- ft ? f time

  6. ft f time

  7. Doppler – Moving structures-Red Blood Cells- Optimal ft <20o

  8. Doppler modes are differentiated by the way the signal is processed

  9. FFT – Fast Fourier Transform • Algorithm to display multiple frequencies in a single time frame – Spectral Doppler • Think of a single note versus a chord • Color Doppler is an average of the spectral doppler – it can’t show each frequency in a specific time unit • Standard display is BART – Blue away, Red towards • Density of blood cells displayed as an intensity of gray • High density (power) – bright • Low density (power) – less bright • Is power useful in Spectral Doppler – NO, but it is in Power Doppler • Color tone determined by density (#) of cells

  10. Diastole Plug Flow - Systole Consider spread through sample volume

  11. Broadening / Narrowing Frequency S D Envelope Time

  12. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  13. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  14. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  15. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  16. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  17. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  18. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  19. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  20. Adjusting Parameters • Gain • Scale • Baseline • Filter • Gate • Sweep

  21. Invert Size

  22. Other causes for poor Doppler signal… • Frequency of transducer too high for vessel depth • Lower frequency • Receiver gain too low • Increase gain • Focal zone not optimized to area of interest – the vessel • Move it ;-)

  23. Fetal Well Being • NST • BPP • Doppler

  24. Fetal Well Being Maximum Systole / Minimum Diastole S / D (S-D) RI (Resistance Index or Pourcelot Index) S (S-D) PI (Pulsatilty Index) A TAMV Time-averaged mean velocity

  25. Middle Cerebral ArteryMCA • Placental Insufficiency • Anemia (Isoimmunization / Parvo)

  26. MCA – Circle of Willus ACo BA IC ACA PCA PCoA MCA

  27. MCA – Placental Insufficiency • CerebroPlacental Ratio – CPR • Originally used the anterior cerebral artery • Wladimiroff, et al. • RI c / RI u • >1 Normal, <1 Redistribution • MCA RI • <70 Indicative of Redistribution • Others • Umb Artery RI • Umb Artery PI • MCA PI • MCA TAMV • Thoracic Aorta PI • Thoracic artery TAMV • UA/MCA PI ratio • MCA/Thoracic Aorta PI ratio • MCA PI x Thoracic TAMV

  28. MCA – Placental Insufficiency • Valuable when fetus is reacting to hypoxia • When physiological responses to hypoxia become exhausted, fetus cannot adapt further • Decline of forward cardiac function (increase venous doppler indices) • Deregulation of cardiovascular homeostasis may be seen and arterial circulation indices become less reliable.

  29. MCA – Placental Insufficiency Increased diastolic umbilical vein flow = GOOD Increased diastolic cerebral flow - may signal placental problem

  30. Anemia Viscosity = # of red blood cells

  31. Viscosity - Normal

  32. Viscosity - Anemia

  33. MCA – Anemia • Fetuses healthy and w/ anemia mild, moderate, and severe. • Linear models fitted to data for individual fetuses – slope was determined • Average rate of change as a function of GA • MCA-PSV – expressed as MoM • Healthy vs. Mild anemic – NS • Healthy vs. Severely anemic (P=.01) • Conclusion – excellent tool to predict which fetuses will become severely anemic Detti, Mari, Moise et al, AJOG Oct 2002

  34. MCA - Anemia • Peak Velocity (w/fetal blood sampling) • Sensitivity for moderate or severe anemia 100% FPR 12% fetuses w/o hydrops (Mari, et al, NEJM Jan 2000) • Fetuses w/Parvo B19 Sens /Spec 100/100% slightly less in alloimmune group (included post transfusion follow-up) (Delle Chiaie, et al, USOG Sep 2001) • Correlation between Hemoglobin and MCA-PSV becomes more accurate as severity of anemia increases. (Mari, et al, OG Apr 2002) • TAMV (Abdel-Fattah, et al, BJR Sep 2002)

  35. IVC/SVC doppler • Influenced by heart rate, RH hemodynamics and function, and AMOUNT of blood flowing through veins • Reciprocal shift observed between IVC and SVC velocity waveforms (Smin) • Changes another manifestation of blood flow redistribution toward the brain • May be good to use prior to 30 weeks when doppler findings more difficult to interpret

  36. Fetal Echo • Critical to evaluate flow an GV anomalies • Quantitate flow – Artery size, volume, VTI • Direction of flow • Presence of flow • Quality of flow – turbulence • Tei Index – (TI) MV & LV flow in one waveform • Tissue Doppler MV LV

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