How To: The Cerebrovascular Examination - SD

Introduction

Hi, my name is George Bjo
and I am the Director
of Vascular Ultrasound Services at Montefiore Medical
Center in New York City.
I'm a registered vascular technologist.
I'm also a fellow for the Society of Vascular Ultrasound,
and today I'm gonna be going over carotid artery ultrasound
techniques and some pitfalls and pearls
and other techniques to help you
or sort of guide you through the performance
of carotid artery ultrasound.
So let's get started here.

Evaluating the Common Carotid Artery Origin

What we're doing here is using a
an L nine three transducer.
Really the workhorse for carotid artery testing.
And we're gonna start out the evaluation
by starting at the base of the neck as far down
as you can go, and identifying the origin
of the common carotid artery.
Now, the anatomy is a little bit different on the right
than it is on the left
and on the right you can almost always identify the origin
of the common carotid artery.
If you look at the screen here
and my pointer right now,
I'm outlining the common carotid artery.
Here's the jugular vein as I point the transducer,
what you're seeing here is the common carotid artery
as it joins with the subclavian.
This is the innominate.
Here's the carotid, and I'm gonna turn long axis here.
And here we have the origin of the common
carotid artery.
Now this is important
because you always wanna be able to evaluate the carotid
as far proximal as you can.
The reason for that is
because evaluation of the waveform at this portion will tell
you about the potential for disease proximal
to that level.
So what I like to do here is put the color flow on
and make the appropriate adjustments.
I'm just gonna increase the color gain a little bit.
And then what I like to do is just put a sample volume in at
that level and take a quick look at the waveform.
Now, there are two things that we
should be looking for here.
It's the velocity itself
and also the shape of the waveform.
Just steering the color flow box there
to optimize the color flow image.
And let's just take a quick look at the spectral waveform and see what it looks like.
Now what we're looking at here is a velocity
of about 120 centimeters per second,
but really what's important is to note the upstroke here.
And you see how very quickly the waveform
gets from the onset of systole to its peak.
I'm just gonna update a second, make sure I'm in that vessel.
And let's just freeze this quickly
and just take a quick look.
Here's my pointer.
Here is the onset asystole and this is a peak.
All vessels in the carotid artery circulation should really
have a rapid upstroke.
The other important thing to do at this point would be
to compare this waveform to the contralateral side.
Keep in mind that all studies should be bilateral,
always comparing the correspondent waveforms
to the contralateral side at the same level.
And all studies really should be bilateral.

Scanning to the Carotid Bifurcation

What I'm gonna do is go back to the 2D image then.
And what I like to do is to put the color on
and just very quickly scan through the carotid artery
to the level of the bifurcation,
making the appropriate adjustments.
As I do that, I'm just steering the color box
now to the other side.
I'm gonna decrease the color gain just a little bit
and work my way up to the bifurcation.
Now I'm allowing the color flow image to tell me whether
or not I need to sample at any point between the origin
of the common carotid artery and the carotid bifurcation.
This is a very nice normal image.
So what I'll do at this point then is go back
and obtain my second velocity.
And where I do typically is find the
bifurcation, which is right here.
Here's one vessel, this is the other.
And then go back about two to three centimeters proximal to
that level in the common carotid artery, somewhere
where the vessel is disease free and where it's straight.
Now this is important especially in labs
who use an ICA to CCA ratio
to determine the percent stenosis within a vessel
gonna make the appropriate adjustments angle wise.
Now, if you look at this image closely, what you see is
that the doppler angle cursor is parallel to the vessel wall
and that the doppler angle has been adjusted to 60 degrees.
And that's the appropriate angle we will then update
to get the second flow of velocity
within the common carotid artery at its midpoint.
Now this is an important measurement, again, as I noted,
'cause this is the one that you use for calculation
of your ICA to CA ratio.
So I'll just freeze that
and then acquire the velocity information
so we can hit calc
And here's your first caliber.
We'll set that at the peak
and then we can get a second caliber up.
And we set that right here
to get your diastolic flow velocity.
In this case, the peak systolic velocity in the mid portion
of the common carotid artery is 107 centimeters per second.
The end diastolic flow velocity is 33.4.
The other thing I want you to note is that,
I'm just gonna put a pointer around here.
The end diastolic flow velocity is calculated at 100
milliseconds prior to the start
of the systolic upstroke,
which should be somewhere in this area.
You don't necessarily have to get a caliber out to make
that measurement, but you have to be sure
to get your diastolic velocity measurement somewhere in this
area shouldn't be anywhere else.
I've seen some texts make the mistake
of measuring it here or in other places.
Should always be measured somewhere in this area right here.
Then unfreeze, I'm gonna go back to the 2D image, excuse me,
put the color back on.
And again, allowing the color to determine
where within the carotid artery circulation,
I'll be obtaining flow velocities.
Now in this case, the carotid artery is normal.
However, in some patients you will have disease.
Now, in the old days when we didn't have color, we used
to have to stop and sample all the various areas
where we suspected that there was disease.
But with an appropriately set color flow image,
we can allow the color flow image to tell us
where to stop and sample.
Now in the absence of disease, the next stop
in the carotid system would be the carotid bifurcation.
And again, here we have one vessel
and this is the other.
So what I'll do here is then identify the carotid
bifurcation, get it in the center of the image.
Typically I like to turn the color off,
we don't need that anymore.
Get the sample volume up again,
make the appropriate adjustments.
Make sure the doppler angle cursor is parallel
to the vessel wall somewhere just proximal
to the carotid bifurcation
and get that second waveform
within the common carotid artery.
Again, just proximal to the carotid bifurcation,
we see a nice normal waveform here, good sharp upstroke,
nice acoustic window.
Get four samples that are representative four so
that are representative of
the vessel that you're looking at.
Freeze and then acquire the velocity measurements.
By the way, don't forget to label as you go along.
For documentation purposes,
that's the peak systolic velocity.
And then the end diastolic flow velocity.
In this case, the peak velocity is 90 centimeters per second
and diastolic flow of 33 0.4, no plaque in this vessel.
Again, this is a normal study. Go back to the 2D image.

Identifying Internal and External Carotid Arteries

Now the next important thing is to be able to identify
beyond the bifurcation the two bifurcation vessels,
the internal and the external carotid artery.
And there are a couple of ways to do that.
I immediately see two vessels here. This is the intern.
Well my guess would be without any other parameters.
Just looking at the size of the vessel, my guess would be
that this is the internal,
let's just get the pointer up here.
This would be my internal.
Now I'm pointing the transducer toward the face.
This is the second vessel.
My guess based on anatomic location
and transducer position is toward the face
external away from the face.
And because of the larger size
and the location of the bulb internal.
But you really should confirm that by placing
a sample volume in the vessel.
And just taking a quick look at
the doppler spectral away from.
So what I do typically is I like to get
that sample volume out a little bit distal into the vessel
that I'm evaluating.
And let's just take a quick look at the flow waveform.
So we have a flow waveform here that
is yielding continuous forward flow throughout the cardiac
cycle with what looks like good amount of diastolic flow.
Let's take a quick look at that other vessel
and see what that looks and sounds like.
Let's make the appropriate adjustments here.
Let's update and get a much sharper peak here,
but still good amounts of diastolic flow.
So based on the anatomic information,
I would've guessed this was
external and the other was internal.
This, another thing that we can do
is we can do a temporal tap.
So let's take a quick look.
My guess right now is that this is external.
So what I do is I locate the superficial temporal artery
around the heat the ear.
And what I'm gonna do is some light tapping
and look for oscillation of the spectral waveform
and see if there's any response.
And you can see that as I tap the temporal artery,
let's just freeze that image.
We see some oscillation in the spectral waveform here.
Now, one of the other important things to do is
that if you do see oscillation,
let's just very quickly go back to that other vessel
and make sure that there's no oscillation in this vessel.
Because if you see that oscillation in both vessels,
then this technique really doesn't work well in terms
of identifying the internal versus the external carotid art.
I wanna put up the volume a little bit, so I wanna be able
to hear the sound as well.
Let's take a quick look. Let's tap,
you can see there's really no response
here to temporal tapping.
So now my guess based on the shape of the waveform,
the anatomic location, the sound
and the amount of diastolic flows that I'm looking at,
the internal in this case
and that other smaller vessel is the external.
Now once I've, oh, here's the other thing you can do.
By the way, let's take the pulse wave off for a second.
Let's put the color flow on
and see if we can identify branches.
You can see here in this vessel we have a couple
of branches that are easily seen.
Here's one, here's two.
And again, it's just more confirmation.
This is the other vessel. Don't really see
any branches here.
This turn transverse, sometimes transversely,
you can determine based on size
and the presence of branches.
Again, here are some branches in this vessel.
This is the external carotid artery
based on all those parameters.
And it's a good idea to use all the parameters
that are available to you when determining
or when they're trying to distinguish the internal from the
external carotid artery.

Evaluating the Internal Carotid Artery

So now once we've made that determination,
we can go back now and start to evaluate those vessels.
This is a nice image of the internal carotid artery.
Just put the color on very quickly.
I'm gonna steer that to optimize the color flow image.
I'm gonna decrease the color scale a little bit as well.
And what I like to do is then just follow this
internal carotid artery.
As far out as I can get with the color flow image,
it's gonna increase the gain a little bit.
And this is a very nice image here of the distal
internal carotid artery, which is gonna invert the color
'cause we like to keep the arteries in red
and the veins in blue.
And I'm way out here now almost to her, to her ear.
If you just take a good look at this,
and this is pretty far, this about as far as you can get
with the internal carotid artery.
And it all looks normal based on the color flow image.
Of course, we always have to go back
and get the doppler information to confirm that.
But once I've determined based on the color flow
that it looks normal, what I'll do now is I'll just take the
color flow image off
and start to get some of that spectral information.
So we'll first optimize the 2D image.
We use a little bit of a more posterior approach here.
Great image. So let's first optimize the 2D image,
go back to that origin and a steer
to get the appropriate angle.
And let's listen to what's going on at the origin here.
Now, one thing to be aware of, especially in bulbous vessels
and may not happen here, but let's take a quick look.
This is the near wall or by the flow divider.
Let's just take a quick look at the waveform.
Very characteristic of an internal carotid artery,
but let's move it out further away from the flow divider
and see what happens in many cases.
And you see it here, you get this flow separation pheno
phenomenon, which is not unusual, especially in patients
with very bulbous ICA origins.
So my recommendation is
that when you're acquiring the proximal ICA velocity,
get as close to the flow divider as possible.
Lemme just update this and optimize the image.
Again, get as close to the flow divider as possible so
that you're displaying a waveform that's representative
of the vessel that you're looking at.
And also representative of the pathologic condition in this case, normal.
So a few waveforms. Now we can freeze them.
I'm gonna turn the gain down a little bit,
do a little bit over gained here.
And what happened there was my patient just swallowed
and that's okay, not a big deal.
Just update the image,
Get a couple of representative waveforms freeze,
and then again, acquire your velocity measurements,
your peak systolic velocity,
and then the end diastolic flow velocity.
And here the velocity are 82 for a peak
and lifestyle velocity of 27.
Well within normal limits.
And again, you'll be documenting all this.
In some cases the machine will do it for you.
You may be acquiring hard copy images.
You may have a PAC system,
but all this information should be documented and then
provided to the interpreting physician for
his interpretation.
So again, once we're done with the proximal portion
of the internal carotid artery,
what I do is put the pulse wave back on and update.
And what I'd like to do is step
through the carotid system.
I'm gonna steer this now so that we're parallel to the wall
and then look for any areas of flow disturbance.
Again, by the color flow image, we've determined
that this vessel is normal, but I'll just step through
as far distal as I can in this vessel.
Again, optimizing the image first,
placing the sample volume.
Gonna increase the gain here a little bit,
Maybe a little bit less than that.
And now in the distal internal carotid artery will freeze
again, acquire the measurements here
in my peak and the end diastolic flow velocity, again,
well within normal limits, a peak velocity
of 70 centimeters per second within diastolic flow of 29
centimeters per second.

Evaluating the External Carotid Artery

Now, once we're done evaluating the internal carotid artery,
we can then turn our attention to the external.
And our protocol calls for evaluation
of the external and again, internal away from the face,
and a very subtle movement of the transduced.
So you may not have noticed any movement at all will reveal
the external carotid artery.
Again, internal, very subtle movement,
and we can visualize the external carotid artery.
Let's optimize the 2D image, hit our
sample volume up, steer that so that again,
we're parallel to the vessel wall.
And let's see what the waveform looks like. Now.
See, it sounds different, much sharper peak.
We've done the temporal tap for the oscillation.
We can do that again. I just decreased the scale
and again, we can see the oscillations there.
And once we get a few waveforms
that we think are representative of the vessel,
I'm gonna update actually, see I wasn't in the
vessel there, and that's okay.
Every now and then you'll move and no problem.
We can update, Fix that image
and you can hear the difference in the waveform.
So you, your ear is an important tool in the process of scanning.
You need to listen to that waveform.
If it doesn't sound like what a difference, just update,
fix your image and get that waveform.
Okay, we can get our measurements.
Here's the peak and the end diastolic flow velocity
71 and 23 respectively.
Waveform looks normal. Don't see any evidence of plaque.
We can unfreeze take the pulse wave off at this point.

Vertebral Artery Assessment

Now what we have to do is evaluate the vertebral artery,
and if you have trouble finding your vertebral, one
of the tricks is we'll turn the patient's head back just a
little bit and use a very anterior approach
to identify the common carotid.
Typically, we would scan the carotid artery from a more
posterior medial approach, a lateral approach.
This time we're gonna go anterior
and then just point the transducer laterally.
And typically what you get is
this type of image here.
So here is the common carotid artery,
Move that transducer laterally.
And this is the classic image of a vertebral artery.
What we have here is the vertebral artery
and the boning process artery
and bone casting a shadow.
And this is a classic image.
And the best way to find the vertebral is to do it this way.
Once I've identified this image,
what I do now is put the color on.
And the primary reason to look at the vertebral is
to assess it for flow direction.
What I'll do now, again,
remember we said we keep all arteries in red.
The flow right now is moving away from the transducer.
The head is oriented or the brain is oriented so that,
or the image is oriented so that the brain is to the left
and the heart is to the right.
So in this case, the flow should be moving from the right
to the left or away from the transducer,
and we've coated that flow as red, so
it's moving in the appropriate direction.
I'll put the pulse wave on
place, the sample volume, and then update.
And this is again, a very classic
vertebral artery waveform.
It should look very similar to that
of the internal carotid artery.
Lots of diastolic flow
because it peruses the brain directly to through the
basilar artery.
Just wanna optimize that just a little bit,
Just Sample right here
and take a quick look at what that looks like.
And there you go. Good sharp upstroke.
Lots of diastolic flow can freeze that and do our calcs.
Here's your peak velocity
and your end diastolic flow velocity.
Now, the vertebral arteries a little
bit different than the carotid.
This would probably the be the only part of the carotid circulation
where you don't have symmetry everywhere else within the
carotid artery examination.
You should have symmetry.
The vertebrals will be a little bit different.
Often the velocities in the right will be greater than those
on the left, so you shouldn't be surprised about that.
I'm gonna just unfreeze and go back
to the image here.
Now, if you have to evaluate the vertebral artery
for atherosclerosis, it's unlikely that you're gonna see
atherosclerotic disease anywhere in the mid portion
of vertebral artery.
Most often that would happen at the origin.
So what we do is identify the vertebral artery in it's mid
portion and just work your way back using the color
flow image as a guide.
We're gonna work our way back all the way
to the origin here, and here is the vertebral artery.
And again, using the color as a guide.
Here's your vertebral, I'm gonna take
that all the way back to its origin.
Now you can see there are multiple vessels here.
If I had just gone to the origin, I might have mistaken this
for a vertebral artery or any other branch.
In fact, this is the origin of the vertebral artery.
If you wanted to evaluate it for atherosclerosis
or stenosis, you take it to the origin, identify that,
turn the color off place, the sample volume.
Let's just steer this to create the right angle
and let's update and get a velocity here.
You see the velocity is about 80
centimeters per second or so.
I just wanna update then see if we can optimize that signal,
and that's much better turn the gain down
to eliminate some of that background noise.
And this is a way forming a velocity
that's well within normal limits.
So that's the way, that's the technique
for evaluating the origin of the vertebral artery.

Transverse Sweep Technique

Now, there was one thing that I didn't mention at the onset.
We wanna start off every evaluation again
with a transverse sweep.
And I did mention the transverse orientation
for identifying the origin of the common carotid artery.
Again, here's the origin.
You wanna work your way up to the bifurcation.
Here is your common carotid artery,
and this is your internal jugular vein.
What you wanna do is just follow that up transversely
all the way up to the level of the bifurcation.
And we can see here, here is the carotid artery bifurcation.
Here's one vessel, and this is the other.
Again, we've already identified this as the
external carotid artery,
and this is the internal carotid artery.
The nice thing about the transverse scoop is it allows you
to get a preview of the carotid system, allows you
to know plaque if there's any present, the level
of the bifurcation and the amount
of plaque burden within the arteries.
Within the first 30 seconds
or so of the beginning of the examination,
you pretty much have a good idea about how long it will take
and how difficult the examination will be.
So it's a good idea to start off every examination
with a nice transverse sweep with the carotid artery system.

Subclavian Artery Evaluation

So I've demonstrated the techniques that you can use
to evaluate the carotid arteries.
Of course, you would repeat the same steps on
the contralateral side.
Keep in mind that every examination should be bilateral
and include examination of the common carotid,
the carotid bifurcation, the internal
and external carotid arteries, as well
as the vertebral artery.
Now, in some cases you may also want
to evaluate the subclavian arteries,
and I'll show you how to do that right now.
Just put a little bit of gel in the transducer
and take a quick look at the subclavians.
Now, a good indication
for looking at the subclavian would be in a patient
who presents with posterior circulation symptoms
or who has abnormal flow changes,
waveform changes in the vertebral artery.
Now in this case, what we can do is again,
identify the common carotid artery
and work your way down to its origin in this image.
Again, here is your common carotid artery.
This is your subclavian,
right here is the origin of the subclavian.
Here is your denominate.
So working your way out toward the shoulder,
here's a subclavian,
and this is of course the infraclavicular portion
of the subclavian artery.
And typically what you wanna do is again,
optimize your image in this case
proximal on this end
and distal on this end, once you've optimized your image,
we can put your pulse wave on.
Let's steer that to get a good angle.
Again, we're at 60 degrees
and parallel to the vessel
wall update.
Now in this case, we should be expecting a
multiphasic waveform
because the subclavian artery is in fact profusing the arm.
In many cases it'll be phasic.
In this case, we actually, we have four phases of flow
and this is absolutely normal.
This just freeze that
and I'll show you the four phases
of the spectral waveform, forward flow, a reverse flow component,
a second forward flow component,
and then a second reverse flow components in this case
four phases of flow.
And that's absolutely normal for the subclavian artery.
In the presence of stenosis, you should expect
to see the flow changes that are consistent
with the various degrees of disease.
Probably the first thing you'd see is a loss of the reverse flow component.
You can take this examination out into the periphery
and into the chest and shoulder.
Keep in mind that the first impediment
to the imaging will be this huge bone here,
which is the clavicle.
So you'll have problems seeing the subclavian vein here,
but you can take it out at least
to the level of the clavicle.
And then further out, I'm gonna just gonna add some gel here
and let's just image the quickly the infraclavicular portion of the subclavian artery.
Again, access is important. Here's the clavicle.
We just imaged it scl
and I'm gonna take it out here into the infraclavicular
portion of the subclavian artery.
And let's take a quick look at that.
There is the subclavian vein.
Superior to that you would find the subclavian artery
and you can see a couple of branches there.
But that's a very nice image of the subclavian artery.
And again, let's just put the pulse wave on
and take a quick look at the subclavian at this level.
Now, it's important also to note
that when you're looking at the subclavian artery in a
patient who has a suspected subclavian artery stenosis based
on changes in the vertebral artery waveform,
you really wanna do a comparison of the right subclavian
to the left subclavian.
Again, looking for asymmetric changes.
Again, in this patient, she's absolutely normal
and we don't see any of those changes.
But in my opinion,
it's probably a little bit easier
to identify the subclavian artery infraclavicular,
but if you're going to make those comparisons,
always make sure to look at the contralateral subclavian
artery at the same level, look at the waveforms,
and look at the velocities before rendering a diagnosis.

Conclusion

So that's the carotid artery evaluation,
including the subclavians.
I hope it's been helpful
and good luck to you
and your carotid artery imaging.
Thanks a lot.