Carotid Doppler Protocol and Top Tips - SD

Introduction

Hi, I am Cindy Owen.
I'm from Memphis, Tennessee.
Been a sonographer for about 30 years,
and currently I work with GE Healthcare
as a global luminary and research manager.
My topic today is carotid tips and protocol.
I'm gonna talk about carotid doppler protocol
and some tips for performing the exam.

Standardized Protocol

What I'm gonna start with is the standardized protocol.
That's very important that,
within each lab performing carotid doppler,
that you have a protocol that is written down
that can be followed by everyone in the laboratory.
This will standardize the procedure
and is very important for followup of patients,
because you want a patient who's coming back
to have the exam done in the same way
that it was done on the previous study.
And that way it really makes sense for,
comparing from one time to another.
So really, everyone in the lab should be doing the study in
exactly the same way.
And the interpreters should also be using the same
interpretive criteria when they're interpreting the study.

B-Mode Imaging

So what should be included in your standardized protocol?
We'll start with B mode imaging,
sometimes referred to as 2D imaging or gray scale imaging.
All of those terms mean the same thing.
I like to start with transverse imaging.
I think transverse imaging is very important
because, when you are in cross-section,
you can visualize the whole circumference of the vessel.
This gives you a good idea about the
plaque burden on the vessel.
It's also a good way to look at
where the plaque is located on the vessel so
that you can plan your sagittal approach.
You already have an idea of
how much the lumen is compromised.
It's also very helpful for differentiating
between the internal and the external carotid artery,
because in the transverse orientation, you can often
identify branches arising from the ECA,
and that's one of the best ways to differentiate
between these two vessels.

So we're gonna take be mode images or,
or transverse be mode images of the common carotid,
internal carotid, and external carotid arteries.
And I may take more than one image to demonstrate,
different features of plaque that may be present
or take images from different projections.
Once I've done the transverse images,
then I'm gonna turn the probe into a sagittal plane
and take images in a sagittal plane again,
of the common carotid,
starting at the very most proximal portion near the origin,
and then up to the internal and the external.
And again, taking images from different projections.
This image on the bottom, the sagittal view
of the internal carotid artery, you can see the plaque,
filling the bulb area
and that it is has a heterogeneous nature
and a very small residual lumen on the right hand side is
the same vessel, but just from a different projection,
and it just gives you a different look at the plaque.
So it's important to look from multiple views.

Now, as I mentioned, the transverse views can be used
to help plan the sagittal plane.
Take a look at this cine clip on the left hand side.
What you may have noticed when I started is
that in the transverse orientation here, the vessels were
diagonal to each other.
And when you see a bifurcation that looks like that
and you turn sagittal, you'll see the individual vessels,
ECA and ICA one at a time.
What's important here is
that you take the most inferior aspect of the probe,
which is the most proximal part, the foot of the probe,
and try to keep it steady over the distal
common carotid artery.
Then move the most distal portion of the probe, the top
of the probe that's cephalad to the lateral
for the internal and medial for the external.
And it's kind of like a windshield wiper blade toggling back
and forth between the internal and the external.
This isn't a large motion, it's a very tiny motion
because these vessels are actually quite close together,
just going back and forth
and then making sure that each one of them ties back
to the common carotid artery.
Why is this important? Because it ensures
that we're looking at two different vessels rather than one
vessel from two different views,
which is a mistake we might make if we pick up the probe
and simply move it between the vessels.
It's easy to actually look at the same vessel
and actually mislabel it as two different vessels.
So this will keep you from making that mistake.

Another thing you can do though, to prove
that you have both bifurcation vessels is to
line up the bifurcation by rotating the probe on the neck so
that the vessels are one on top of each other instead
of side by side or diagonal.
And watch. As I do that on the right,
I'm just rotating the probe
until the vessels are lined one on top of the other.
Now, when I turn in a sagittal projection, you can see
that I have a nice picture of the bifurcation,
and so I'm showing the tuning fork bifurcation
where I see both vessels at the same time.
Is this necessary? No, obviously not,
but it can be very helpful
because it does prove that you've seen both vessels.
Now, which vessel is on top, which is on bottom,
that depends on your plane of approach.
If I'm coming from a lateral
or posterior lateral approach, as in this case,
which you can tell by the sternal cla mastoid muscle seen on
top of the internal carotid artery,
well then the internal carotid artery, which is the lateral
or more posteriorly located vessel, will be the one
that you see on top with the external on the bottom.
On the other hand, if when I changed my approach
to line the vessels up one on top of the other, if I moved
medial,
or more anterior,
then I would likely have the external on the top
because it is more anterior or medially located.

Spectral Doppler

Okay, now when we talk further about the standardized
protocol, let's go into spectral doppler.
We wanna make sure that we sample throughout the length
of the vessels with our spectral doppler
and in the common carotid artery, that means
that we're sampling from proximal throughout the length.
And we're gonna take readings
or images of doppler samplings at proximal mid
and distal C-C-A-I-C-A, again, proximal mid and distal.
And in our lab we actually include,
a further distal reading just as far distal as we can.
This really helps in those patients
with fibromuscular dysplasia, which is seen in the mid
to distal ICA, the ECA,
we just take a single reading at the proximal ECA
unless there is stenosis.
In that case, I take at least two readings,
one within this area of stenosis, the second further distal,
to demonstrate the post stenotic turbulence.
And in the vertebral,
the area we're most interested in is the origin,
but it's okay to take a mid vertebral segment
and get a nice wave form.
And then if we see turbulence,
we'll look at the proximal segment
where stenosis is most commonly located,
and if it is abnormal with the bunny rabbit shaped wave form
or reversed, then we also wanna document the subclavian
artery because that's where the stenosis would be.
And the key there is
to look at the proximal subclavian artery
and not the mid to distal segment
because the part we wanna sample is proximal to the takeoff
of the vertebral, and that's
what would be affecting the vertebral flow
and causing it to be reversed.
In these images that you see to the right,
the one on the top shows the stenosis within,
the ICA and the one on the a normal ICA actually.
And the one on the bottom is actually showing turbulent flow
with a stenosis.

Documenting Stenosis

Now what happens when we document stenosis?
How do we alternate our
or change our protocol in those cases?
Whenever I have high velocities, I wanna make sure
that I have confidence in the
velocity value that I'm getting.
So I take two
or three samples until I really have confidence
that this is a reproducible velocity.
At that point, I take a reading there
and then I'm gonna move further distal,
just a short distance
to document the post zoonotic turbulence.
And you can see that in this, these images right here,
the top image shows a nice spec clean spectral window
because I'm within the jet of the stenosis below that you,
I have moved further distal
and now the window has been filled in with echoes indicating
that there is a lot of turbulence.
This is in the area of post stenotic turbulence demonstrated
by spectral broadening of this waveform.
And you can even appreciate some reversed flow
because of the swirling of the red blood cells
beyond the area of the stenosis.
So this is a typical wave form profile
for post stenotic turbulence.

Gray Scale Imaging Settings

Now, when we're performing the exam, it's really important
to pay attention to not only the doppler,
but also the gray scale image.
And for the gray scale
or bemo image, we want to enhance our setting so
that we can see low level gray scale.
One of the most common mistakes I see with new
sonographers performing vascular exams is
that they oftentimes want to make the image
ver a very high contrast
and even sometimes take the TGC time gain compensation
and decrease it across the vessel so that the
inside of the vessel is really black, thinking that
that's the best image they can make.
But what you realize over time is that by doing
that you've really erased some real information
and have decreased the likelihood of having the ability
to display low level gray scale,
or hypo coic plaque,
which can be very important plaque to display.
So my recommendation is to use a dynamic range
that is higher that shows the shades of gray that you need.
You wanna be able to appreciate low level gray,
choose a gray scale map that shows low level grades,
have the overall gain high enough
that you could perceive plaque
and increase the TGC within the vessel enough
that you are not eliminating any plaque that's present.
And I'd rather have a few extra echoes in there
that may be artifactual then
to not see the plaque that's present.
This is a point of, this is the point I'm trying to make.
Look at this bifurcation.
It's a nice image, but actually what's happened is the
sonographer has used the TGC on the system
to clean out the vessel and make it look nice
and black inside, in so doing, they erased this plaque.
Now, when I increased the TGC to show this plaque, yeah,
there's some artifact over beyond it or proximal to it.
I'm not really concerned about that.
I'm more concerned about having the ability
to demonstrate this pathology.
So it's much better
to have a few extra echoes in the vessel than
to make it completely black because that's artifactual.

Here's another example.
It looks like a beautiful vessel,
but actually they have not set the TGC appropriately
and this low level plaque is actually being missed.

Advanced Imaging Features

Now there's a lot of advanced imaging features
with high-end equipment that are available for us
to use today, and these have been investigated
over time and really proven to help improve the quality
of our image and should be used if you have these
capabilities on your system, which most likely you do.
One is harmonics, which helps us
to improve the contrast resolution.
There's compound imaging which steers the beam in
multiple directions at the anatomy of interest.
It combines those different steerings into
one displayed image.
This gives us better boundary detection
and closer to perpendicular incidents to multiple surfaces
of a structure or regular plaque.
We apply speckle reducing algorithms now to the image
to help reduce that salt
and pepper look that we're so familiar with,
with ultrasound, which is actually an artifact
and sometimes obscures anatomy.
And you can see that by layering these advanced imaging
features, we steadily improve the quality
of the ultrasound images.
So for example, this is a pretty decent baseline image,
but I think everyone would agree
that it's a little bit better now,
and now it's a little bit better.
And then the final image is even the best at showing all
of the boundary of that plaque and its internal composition
because we've actually layered harmonics compounding imaging
and speckle reduction.
This is another example, the base image on the left,
the improved image on the right
after using the harmonics compound against speckle reducing algorithms.
So I would just encourage you to use these features
on your equipment to really improve
the quality of the images.
Harmonics is particularly interesting
because it can sometimes be used
to actually visualize the flow,
and if we see the flow with harmonics,
it's even at a higher resolution than we can ever achieve
with color doppler or with power doppler imaging or example.
So the image on the right
that you see is not some new flow imaging technology
that's simply high frequency harmonic imaging.
And it was achieved by using the highest frequency
that would actually penetrate going into harmonics.
I steered the beam to just towards the direction
or into the direction of the flow
and then increased the gain within the vessel
and decreased my frame aging.
And by kind of making some of these adjustments, I'm able
to see the flow and really understand the hemodynamics
that's occurring and appreciate
how tiny this jet is
and this tiny residual lumen on this very short
segment stenosis.
So sometimes understanding how
to manipulate the controls on your particular ultrasound
system can really make a difference in
the image quality in certain pathological situations.

Standardized Doppler Sampling in CCA

Okay, back to our standardized protocol.
Let's talk about taking the doppler sampling in the
common carotid artery.
Remember I said sample proximal mid
and distal,
but we wanna use just one of those samplings to apply
to the I-C-A-C-C-A ratio, which is part
of our diagnostic criteria.
And the sampling that we're gonna do is,
is the distal common carotid artery.
Now, why do we care about this?
We've been using the I-C-A-C-C-A ratio for years,
but the problem was that it,
there was no standardization about whether we use the
proximal or the distal or the mid.
And so when follow up patients would come to the lab,
they may have a different ratio, maybe two
or it may be four.
And it's not due to progression
or regression of disease, it was really due
to which sonographer performed the study
and where they obtained the CCA waveform.
There's a study that was published down here in
radiology way back in 1999,
and they found that the velocity within the common carotid artery is not
uniform throughout its length.
It's higher in the proximal segment,
and it's lower in the distal segment.
So you can see that if you use different locations within
the common carotid artery to obtain the sampling
that's applied to the ratio, you'll get different results.
So we wanna standardize it. Where should we standardize it?
Probably not the proximal location
because it can be quite tortuous.
The vessel can actually be quite mobile there sometimes
because it's pulsitile.
So it may be challenging the mid segment.
It's hard to know exactly what is meant by mid.
A good way to standardize it is to go
to the distal segment about two centimeters
proximal to the bifurcation.
This is reproducible from time to time
and very easily.
Now do I actually go and take the calipers and measure?
No, we all have these scales on the screen
and I just kind of eyeball about what is two centimeters,
and then I look
and just eyeball about where two centimeters is proximal
to the bifurcation, and that's where we're going
to take our reading that's applied to the ratio,
reproducibly time after time as much as possible.

Differentiating ICA and ECA

Okay. Differentiating between the internal
and the external carotid artery, this is a key component
of the exam and actually something
that can be quite challenging.
And one of the ways that's been suggested
to help in this process is
to perform a temporal tap maneuver.
And the temporal tap is a way that we actually auscultate the temp, the temporal artery just in front
of the ear you can feel the pulsation.
And then while you're in the vessel
that you think is the ECA, you would tap on it
and while doing so, you would appreciate these
oscillations in the waveform.
But unfortunately that's really not that accurate.
There was a study that was published in radiology way back
in 1996, and what they found is that there was,
the oscillations could actually be seen in the external
and the interim carotid arteries and up to a third of cases.
And in fact, in about a third of those, the
oscillations were greater in the ICA versus the ECA
and present in the common carotid over artery
in over half of cases.
So this is an unreliable way to differentiate
between the internal and external.
Just to follow up on that, here's a couple of cases.
This is the internal carotid artery on the top.
And you can see the temporal tap maneuver shows
very prominent oscillations.
So is it mislabeled? No.
Let's look at the external carotid artery.
It has the same oscillations.
So what happens is that most of the time
we already have a good idea that we're in the external
and we perform the temporal tap and we see the oscillations
and we think it is confirming where we are.
But in actuality,
if we also did the same temporal tap maneuver while per
forming doppler in the internal carotid artery,
we would likely see the oscillations there as well.
So how do we differentiate
between the internal and the external?
It's better to look at position.
Internal is more posterior lateral.
External is more anterior medial.
It's better to look at the wave forms.
The internal is low resistant.
The external is higher resistant and look for branches.
The internal gives off no branches in the neck.
The external gives off multiple branches.
The best way to look for ECA branches is a transverse sweep
through the ECA.
This is just another case in point.
This is the internal carotid artery
with oscillations in a different patient.
And here's the ECA.
So try these other methodologies for differentiating
between the external
and the internal rather than relying on the temporal tap
is my suggestion.

Color Doppler as Roadmap

Now, we use color doppler in our studies as a roadmap.
The color doppler itself is not diagnostic,
but rather it's a roadmap to help us
place the Doppler sample volume
and help with our doppler walk through the vessel so
that we can quickly see areas of interest
where we might want to further interrogate
what the spectral doppler, such as you see here.
This is a nice example of the carotid bifurcation.
And as we're looking at the internal carotid artery,
we see the color is not filling all the way
to the posterior wall, and that's
because there's some atherosclerotic plaing there.
But not until we get just a little bit
beyond the bifurcation do we actually see a change in the
color doppler from a dark red into some focal aliasing.
And this focal aliasing is telling me that there is a higher
frequency shift at this point.
Now, a higher frequency shift could be due
to higher velocities,
or it could be that
we have a smaller angle of incidents.
So I'm gonna look at this
and assess for any changes in angulation of the vessel.
And clearly there's no change
and the vessel is straight, so that means I have
to have a higher velocity at this point.
And indeed, when we sample at that point,
we can see the velocity is about 190 centimeters per second.
So we can use color doppler in that way to help us.
We could also use power doppler just looking at the
anatomy of the residual lumen
and using that to guide our Doppler sample volume or b flow
or other flow imaging tools.
The point is that the flow imaging tools are very useful
for us, and they can provide a roadmap for placement
of the Doppler sample volume.
This is an example of using the color doppler.
Here I'm in the vertebral artery,
and it's an abnormal waveform with a very low velocity,
only 6.2 centimeters per second.
And you can see the waveform itself has a very delayed upstroke to peak systole.
This is termed to Tardis and parvus waveform.
It's tardy to get to peak systole and parvis.
It's a small pulse. Well,
whenever I see a waveform like this, I know
that it's indicative of disease proximal
to the point that I'm sampling.
So I'll look proximal,
and when I look at the proximal vertebral,
there's actually no flow.
But then with color doppler, I can actually see inflow
to the vertebral that's reconstituting it.
Without color doppler.
This could be a very confusing picture
because I would get no signal in this area.
And then here I would get a mixture of antegrade
and retrograde signals that could be very confusing.
But as you can see with color doppler, very quickly
I can tell the story of what's happening
that this vertebral is occluded approximately,
and then reconstituted right at
where it enters the spine.

Walking Spectral Doppler through Stenosis

Now we wanna walk the spectral Doppler through areas
of stenosis to obtain the peak velocity.
And what I mean by that is we're looking here
with color at the area of the stenosis.
I'm gonna place my doppler sample volume
proximal to that point.
And then in real time, I'm gonna move it slowly
through the area of the stenosis, listening with my ear
for the highest pitch sound
and watching the waveform for the highest peak.
And that's where my highest velocity is.
I may do this two
or three times until I'm satisfied
that I've really obtained the peak velocity.
Once I'm comfortable that I've obtained the peak
or maximum velocity within that stenosis,
I take a hard copy reading and document.
And here's the peak velocity.
It's nearly 400 centimeters per second in sly
and I well over a hundred centimeters per second
in diastole.
This is just another nice example of walking the Doppler sample volume
through an area of stenosis.
But in this case, one of the things
that I wanna point out is the use of a larger sample volume.
And this is something I wanna talk about a little bit
because a lot of times we have historic baggage
that we've carried along with us from the person
who taught us to do this study,
and we don't really know why we're doing some
of the things we're doing,
but just that this is the way we were taught.
And when I was first taught, I was taught
to use a very small sample volume when
performing Doppler exams.
The reason was because we tried
to evaluate small changes in the amount
of spectral broadening.
Well, now we know that that's not a very accurate way
of performing or estimating the degree of stenosis.
And in fact, with the linear ray transducers
that we have today,
small changes in spectral broadening occur even in
normal situations.
So what's better is when we get into an area of stenosis is
to open the sample volume up.
Instead of using a one millimeter sample volume size.
Here, I'm using a three millimeter sample volume size.
This helps me a lot because if I'm looking at a residual
lumen that has a diameter of only one millimeter
and a breathing patient with cardiac pulsatility,
and I have a one millimeter
or sample volume, I can't keep those
locations matched in real time
and I'll just get pieces of the stenosis
and it will be very hard for me
to get a good doppler signal.
On the other hand, in this very tough case,
if I make the sample volume larger, it improves my chances
of being able to obtain more than one wave form
to improve my diagnostic confidence
that I'm getting a real signal back from this area
and something that's measurable and reproducible.
So don't be afraid to open the Doppler sample volume.
Use one that's larger than one millimeter for most
of your carotid work, especially when you're in a
tight stenosis.

Sample Volume in Dissection

Now there are times when you wanna keep the sample volume
very small, and now an example would be
a case of a dissection.
One of the things we're trying to prove when we suspect
that there is a carotid dissection
or a dissection anywhere in the body is
that we have two different wave form patterns in two
different lumens, and we're not dealing with some kind
of artifactual echo.
So here I've made the sample volume very small
and I moved it from one lumen into the other,
and I've actually changed my sweep speed so
that I'm displaying eight seconds worth
of information rather than the typical three
or four seconds worth of information.
This gives me time to move the sample volume from one lumen
to the other and document
that indeed there is quite a difference in the waveform
profiles between the lumens that confirms
that I have a dissection.
The color doppler here is showing me
that there's two different lumens of flow and sagittal
and then also in transverse here,
this real time clip is showing you two different lumens
of flow in the transverse orientation.
And that's the other thing that we wanna watch for
and dissection is to show that there are two different lumen
that are clearly visualized in more than one imaging plane,
and with more than one flow imaging modalities such
as color doppler, and then also be mode imaging.

Comparing Waveforms Between Sides

Now another important aspect
of the carotid doppler exam is comparing the wave forms
between the right and left side,
and especially for the common carotid artery.
Here on the left side,
we see a normal appearing carotid doppler waveform.
On the right hand side on this patient,
you can see it's higher resistance with an absence
of in diastolic flow
when there's a decreased in diastolic flow on one side
compared to the contralateral side,
that tells me there's distal disease
or disease that is distal to the point where I'm sampling.
Now that could be an ICA occlusion,
which is probably the most likely event,
but it could also be that there is a stenosis
that's intracranial,
and the most likely location intracranial would be at the
carotid siphon level.
And in this particular case, it was just beyond the siphon,
and we have this high grade stenosis within the middle cerebral artery.
Now we won't see changes down at the common carotid from an
intracranial stenosis
unless the stenosis is at least 70% diameter reduced.
And of course this is much more than that.
We can also appreciate these changes in the color doppler
wave forms on the side of an occlusion
or a side where we have high resistance flow,
we'll actually see in the color doppler,
very little in diastolic flow.
And here you see some blue,
and that's the reverse component.
On the normal side, we see flow throughout the cardiac cycle
because we have a low resistant wave form
that shows flow throughout the cardiac cycle.
So this is an ICA occlusion,
and this is what we see with the gray scale imaging is a debris filled vessel
and an absence of color fill in this area.

Now, another reason we might want to compare the right
and left sides would be with proximal disease.
And here we have on the left hand side very low velocities,
a TARDIS and parvis effect to the waveform.
When you contrast that with the contralateral right side,
we have high velocities more normal upstroke
to the right common carotid artery.
And it's really quite different.
Now, you might be tempted to think
that the right side has a stenosis
because the velocity is so high,
but in actuality, this is just compensatory flow.
The real pathology lies in this case on the left hand side.
Let's look further at this case.
And if you look up into the al carotid artery, you can see
that the velocity is still low on the
left compared to the right.
There's an abnormal waveform on the left,
whereas the right has a nice normal waveform.
But look at how high the velocity is on the right,
it's about 180 centimeters per second.
Again, there is no stenosis on the right.
This is compensatory flow.
When we look at the vertebrals between sides,
both have high velocity flow, no stenosis.
This is compensatory flow.
Now, I can determine this is not stenotic number one
because I know that I have high grade pathology on the left,
which I'm gonna demonstrate to you in just a moment.
But also because there is an absence of any type
of post stenotic turbulence in these other vessels
that would have to be used to help determine
that we have a stenosis.
When there's stenosis, we see a focal acceleration coupled
with post stenotic turbulence anywhere in the body,
focal acceleration coupled with post stenotic turbulence.
That's not the case with compensatory flow,
and that's not the case in this situation.
In fact, in this situation, what happened is we even have
reverse flow in a branch of the external carotid artery
and a grade flow in the internal carotid artery.
There's a high grade stenosis at the origin
of the left common carotid artery.
That's the real culprit in this whole situation.
And if you look at the angiogram,
you can see the bifurcation is patent.
There's no stenosis here.
But if you notice that the ECA is not really filling,
and that's because it has the retrograde flow
that we've just documented here in this color Doppler image.

Attention to Detail in Complex Cases

Uh, lastly, we wanna make sure that we keep our
mind on the study paying close attention to the numbers
that we're generating throughout the study.
This can be challenging when we have tortuous vessels,
as in this case, this is a patient with a coil.
And as we doppler sample around this, we're going
to be using a variety of doppler angles.
And if we're not careful, we'll get quite a range
of velocities.
In fact, in this case, proximal to the region of the coil,
I had a velocity that was about 70 centimeters per second.
And then as I moved into the coil, all
of a sudden the velocity jumped up to 112.
This didn't really make sense to me
because there's no stenosis, no narrowing.
Actually it was just an angle correction error.
And when I lift off the probe
or update the image, I could see that I had moved slightly,
adjust the doppler angle very carefully for the area
that I'm in with within this coil.
And I have a good velocity.
So it was really closer to 79
or 80 centimeters per second in this area, not 112.
Now as I came around the coil continuing to sample, all
of a sudden I get a velocity
that's 48 centimeters per second.
Again, this makes absolutely no sense.
It's an angle correction error.
Even though the image looks like the vol the angle correction is accurate, it's not.
You update the image, double check the location
of your sample volume angle correct
to the walls as it curves around.
It's challenging to do,
but making sure that the velocity values make sense.
And sure enough, when I do this,
my velocity is 70 centimeters per second,
and that's more accurate.
So in reality in this coil,
my velocities range from about 70
to 80 centimeters per second, never from 70 to 112,
just down to 48.
That doesn't make any sense.
So keeping your head in the study
and making sure that the velocity values
that you're generating throughout the study
make sense, is very important.
We also wanna make sure it's telling the right story again,
that everything is making sense.
Beyond just taking doppler samplings in tortuous vessels
or coils, this is a case that was done
by one of my students.
And after she did the study, she asked me to help her
because she was concerned
that maybe she hadn't really told the entire correct story.
And my first input to her just on this image,
it looks like there is probably a high grade stenosis,
but there's too much aliasing.
And if you look at the velocity scale,
the numbers here are quite low, which means
that the velocity scale and or P-R-F-P-R-F
and velocity scale are two words for the same thing.
The PRF is set too low, it needs to be raised so
that we can really appreciate some of the flow without
all of the aliasing.
Next, when she sampled in the CHRO
and carotid artery,
it looked like it was a very high resistance wave form,
and low velocity, but,
and looks like the angle correction is good,
but she's sampling in the middle of the vessel,
but not in the middle of the flow.
So I really feel like the sample location is not correct.
It should be in the middle of the flow
and the image is so dark
that I really can't appreciate whether
or not there's plaque in this area, which there was.
And then the highest velocity she got as she sampled
through the internal carotid artery was 200
centimeters per second.
This could be right, but I'm suspicious
that the velocity is probably much higher than that.
Because when I have such a low velocity
common carotid artery with high resistant flow,
I would expect an even higher velocity reading
in the stenosis.
And in fact, this area of stenosis looks
to be much tighter than that.
So we brought the patient back down to look again.
And as suspected,
when we looked at the highest velocity in the internal
carotid artery, it's actually closer
to 400 centimeters per second rather than 200.
So nearly doubled.
And part of that had to do with the sampling location.
She had not walked the doppler through the entire area.
She was sampling actually just distal to the area
of maximum stenosis.
So by going back and forth
and walking through there, I was able
to pick out the highest velocity more accurately.
And you can see here an angiogram
that shows this very high grade stenosis
and consistent with the findings.

Conclusion

With that, I think the last thing that I wanted
to say is just to enjoy your work.
And I'm recognizing the staff that I've worked with
for years and years at Baptist Hospital,
at Baptist Medical Center, just right outside
of Memphis, Tennessee.
Performing carotid doppler is one.
It's a very rewarding study.
It's an important study,
but close attention to detail is key to success
and key to obtaining the proper diagnosis for our patients.
Thank you very much.