Post on 31-Mar-2015
Understanding Doppler and its Current Uses in OB
Diana M. Strickland, BSBA, RDMS, RDCS
Continuous vs. Pulsed
Doppler – Moving structures-Red Blood Cells-
Scattered waves-low level NOISE!
Wall motion – high level NOISE!
ƒd = 2(ƒt • v • cosθ)/c
Doppler – Moving structures-Red Blood Cells-
ft ft
fr fr
f
Time
Positive shift
Negative shift
ft
f
time
Doppler – Moving structures-Red Blood Cells-
?
ft
f
time
ft
Doppler – Moving structures-Red Blood Cells-
<20o
Optimal
Doppler modes are differentiated by the way the signal is processed
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
Plug Flow - Systole
Diastole
Consider spread through sample volume
Broadening / Narrowing
Time
Frequency
S D
Envelope
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
• Gain• Scale• Baseline• Filter• Gate• Sweep
Adjusting Parameters
•Gain
•Scale
•Baseline
•Filter
•Gate
•Sweep
Size
Invert
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 ;-)
Fetal Well Being
• NST• BPP• Doppler
Fetal Well Being
S / D
RI (Resistance Index or Pourcelot Index)(S-D)S
PI (Pulsatilty Index)(S-D)A
TAMV Time-averaged mean velocity
Maximum Systole / Minimum Diastole
Middle Cerebral ArteryMCA
• Placental Insufficiency• Anemia (Isoimmunization / Parvo)
MCA – Circle of Willus
ACA
ACo
MCA
PCoAPCA
BA IC
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
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.
MCA – Placental InsufficiencyIncreased diastolic umbilical vein flow = GOOD
Increased diastolic cerebral flow - may signal placental problem
Viscosity = # of red blood cells
Anemia
Viscosity - Normal
Viscosity - Anemia
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
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)
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
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
MVLV
Uterine Artery Doppler
• Continuous Wave Doppler / Intraplacental• IUGR (Chronic Hypertension) and
Preeclampsia• High AFP
• Little change seen in doppler indices after 26 weeks
• More difficult to assess when they are abnormal
Ovarian Artery Doppler
• Tumor Angiogenesis – limited vascular tone due to absence of the muscular tunica media
• CD screening optimal in PM women• No cyclic change in ovarian volume
• RI < .40• 96.4% Sens., 98.8% Spec., 98.2 PPV in 14,317
patients• Kurjak, Fleischer, and Bourne
Ovarian Artery Doppler
• Impedance values in benign vs. malignant lesions overlap
• Studies now looking at arrangement and density of vessels
• Neural Networks and Baysian networks are being developed and tested