Spectral Doppler (M3U1)

What is spectral Doppler?

- Display many simultaneous Doppler freq shifts (+ and -), corresponding to blood velocities, directions, and angles of flow

- Non scanned modality that displays a graph (x axis = time, y axis = DS freq or velocities)

What information does spectral Doppler give?

- Cardiac cycle (systole --> diastole)

- Downstream organ resistance patterns

- Pathological upstream conditions

- Estimates of blood velocity changes

- Estimates of blood volume through SV

- Presence and direction of flow

- Type of flow (laminar vs. turbulence)

What are spectral Doppler gains?

Similar to 2D, as you increase the gains, spectral trace gets brighter (inc. amplitude)

Why do spectral Doppler gains need to optimized? (HINT: 4)

- False spectral broadening

- Poor tracing (little to no flow seen)

- Over/under estimate of PSV/EDV

- Can create mirror image

What is a blossomed spectrum?

Overgaining of the spectral trace can lead to higher than true peak velocities and a decreased spectral window

TRUE or FALSE: The spectral trace should occupy only half of the graph.

FALSE: The spectral trace should occupy 2/3 or 3/4 of the graph.

If the spectral Doppler scale is too low, what artifact may occur?

Aliasing (wrapping of the trace)

- Violates the Nyquist limit so need to increase the scale

TRUE or FALSE: Adjusting the baseline can be done post-processing.

TRUE

TRUE or FALSE: Non-arterial blood flow moving into an organ is shown below the baseline.

Non-arterial blood flow moving into an organ is shown ABOVE the baseline (ex. portal veins, hepatic arteries)

What are wall filters in spectral Doppler?

- Filter out low Dopler shifts/slower moving reflectors (blood, tissue) to eliminate noise and vessel wall motion

TRUE or FALSE: For venous flow, wall filters should be set high.

FALSE: For venous and trickle flow, wall filters should be set LOW (or medium).

What is the SV box?

Sample volume box - Specific location that is sampled for Doppler shifts (and velocities)

TRUE or FALSE: You can change the size of the SVB.

TRUE:

- Small SVB = less variety of velocities = less spec broadening

- Large SVB = more velocities = more spec broadening

Name 3 things that can cause a loss of the spectral window.

- Overly large SVB

- Overgaining

- Proximity of SVB to vessel wall/Size of vessel compared to SVB

- Turbulence

TRUE or FALSE: Smaller vessels display more spectral broadening.

TRUE: Because the SVB may be larger than the vessel itself, leading to velocities from structures other than the lumen, creating spectral broadening.

TRUE or FALSE: The SVB should be placed along the walls of the artery.

FALSE: If the SVB is placed along the walls, you may miss the highest velocities in the vessel. This is because with parabolic flow, the slowest velocities are along the walls and the highest are in the middle.

TRUE or FALSE: After a stenosis, you would expect to see increased turbulence and velocities.

TRUE

What angle do you want to avoid with PW spectral Doppler?

90 degrees

What angle do you want the angle correct to be?

45-60 degrees

(anything more = directional ambiguity; anything less = too difficult to achieve)

How many pulses do you want to show in an arterial spectral trace?

3-4

What is a slow sweep speed?

Shows more time on spectral doppler graph

(thereby shows more peaks/pulses)

If there is something abnormal with the peak of a spectral trace, is there an issue proximal or distal to where the SVB was placed?

Issue is PROXIMAL or UPSTREAM

- The peak of a spectral trace relates to systole, the pumping action of the heart

If there is something abnormal with the diastole portion of a spectral trace, is there an issue proximal or distal to where the SVB was placed?

Issue is DISTAL or DOWNSTREAM

- diastole relates to the downstream resistance and organ/tissue perfusion

What is pan diastolic flow? Name an example of a vessel w/ this flow.

- Flow pattern w/ continuous forward flow in systole and especially in diastole

- Seen in low resistance vessels

- No flow reversal

Examples:

- Vertebral a.

- CCA, ICA

- Renal a., hepatic a., splenic a., ovarian a., uterine a.

- Umbilical a.

- SMA after eating

What are the features of a moderate resistance waveform? Name an example of a vessel with this flow type.

- Decreased early diastolic flow (inc. resistance)

- Early diastolic flow reversal

Examples:

- ECA

- fasting SMA

- extremity a. depending on temp. and level of exercise

What are the features of a high resistance waveform? Name a vessel that has this waveform.

Features:

- Forward systolic flow

- Early diastolic flow reversal

- Forward flow again into mid and late diastole

- Can be described as bi, tri, quadra, or quintaphasic flow

Examples:

- peripherhal extremities at rest

- infrarenal aorta

- CIA, EIA, CFA, SFA, pop a., AT, PT, peroneal a.

- Subclavian a., axillary a., brachial a., radial/ulnar a.

TRUE or FALSE: High resistance vessels display pan-diastolic flow.

FALSE: High resistance waveforms often exhibit flow reversal, which is not seen in pan-diastolic flow. Therefore, in low resistance vessels, you often see pan-diastolic flow, as there is continuous forward flow.

What influences venous waveforms? (HINT: 3)

- Respiration

- Augmentation

- Right atrium contractions

TRUE or FALSE: Venous blood flow is spontaneous.

TRUE: This means that flow is seen without provocative maneuvers.

Why is augmentation done in veins?

To check for obstruction from thrombus

- In spec trace, typically see aliasing after augmentation, displaying the acceleration of blood back to the heart

What happens to venous flow during valsalva? What venous vessels is valsalva used for?

- Flow stops due to valves (see no data on spec trace)

- Applies mostly for lower extremity veins

What venous waveforms are affected by right atrium contraction? What is their sonographic appearance?

Those close to the right atrium

- SVC

- IVC

- Brachiocephalic v.

- IJV

- Subclavian v.

- Hepatic v.

(Gives saw-tooth appearance of trace)

TRUE or FALSE: PSV is the first measurement to rise at a 50% lumen narrowing.

TRUE

What does the waveform look like for laminar flow in larger arteries?

- Pulsatile

- Clear spectral window

What does the spectral waveform look like post-stenosis?

- Chaotic, non-laminar w/ flow reversal

- Ragged edges w/ spectral broadening

Where is it normal to see flow turbulence

Carotid bulb

What does the spectral waveform of an aneurysm display?

To an fro blood flow from aneurysmal sac to the neck

If the umbilical artery displays high resistance and is more pulsatile, where is the issue?

Placenta

If the proximal hepatic artery becomes more pulsatile than normal, where is the issue? The celiac trunk or liver?

Liver - a normally low resistant vessel is now more pulsatile due to downstream issues (liver)

What is tardus parvus?

- a dampened waveform shape with a delayed peak systolic upstroke that indicates proximal obstruction

- Loss of inertial energy after a stenosis makes blood go slower (slower rise to systole and smaller waveform)

Velocity measurements are highly dependent on ________ ____________

angle correct

Where is EDV measured on spec tracing?

Just before systole

How are velocity ratios taken?

Velocity taken at the stenosis/ velocity before stenosis

(if 3 or 4x faster = probably a hemodynamically significant stenosis)

What does a PI of 0-2 indicate? Name a vessel that would have this PI?

Low resistance (pan-diastolic flow)

Examples:

- Uterine a., ovarian a.

- ICA

- Renal a.

- Umb a.

What does a PI of over 4 indicate?

High resistance (more pulsatile)

What is the resistive index (RI)? Name an example of when it is used.

Measure of downstream resistance level = (PSV - EDV)/PSV

Examples:

- Intracranial adult arterial assessment (MCA, ACA, PCA)

- Neoplasms (low RI = more flow to neoplasm = neoplasm growth)

- Trophoblastic neoplasia (RI less than 0.5)

- Retained products

- Ectopic pregnancy

- Transplanted kidney (RI over 0.7 = rejection)

What does an RI of 0 mean?

No resistance at all (ex. venous flow)

What does an RI of 0.1-0.7 mean?

Low resistance diastolic forward flow

What does an RI of 0.7-0.9 mean?

Progressive resistance to higher resistance

What does an RI of 1.0 mean?

Full resistance (no end diastolic flow at all)

What is systolic acceleration time (SAT) or AT?

- Time it takes to reach peak systole (onset of contraction)

- Normal = rapid increase to PSV = smaller amount of time

- Abnormal = slow increase to PSV = longer time

(look for dampened waveform = tardus parvus to indicate proximal disease)

TRUE or FALSE: With PW spectral Doppler, you should always avoid aliasing.

TRUE: Aliasing should be avoided b/c it inhibits you to find the PSV. However, aliasing is useful information in colour Doppler.