Advanced Sonography of Carotid Arteries - SD

Introduction

I'm Dr. Leandro Fernandez, director of the Laboratory of Advanced Sonography at Instituto Medical Florisa in Caracas, Venezuela.

In the next minutes, I will discuss on the topic Doppler in carotid arteries.

This is a very important matter because as you all know, atherosclerosis is a major issue in western countries.

By using ultrasound, we can assess the carotid arteries looking for the presence of this disease in these very important vessels.

So let's start Doppler in carotid arteries, advanced sonography of carotid arteries.

Defining Advanced Sonography

Let's begin by defining advanced sonography.

This is a term used to refer a group of techniques, which we can include doppler in all its modalities.

Three dimensional ultrasound are ultrasound contrast agents or echo enhancement.

Real tying compound ultrasound, which is related to CT scan, extended field of view, ultrasound, speckled reduction image, or extreme resolution imaging.

And it's necessary an important technical support to perform these kind of technologies because we need proper equipment and it somehow has become some kind of new specialty amongst sonographer and sonographers to be trained and to have the capability to perform.

As I said, these techniques, advanced sonography, applications of doppler and sonography in carotid arteries.

Indications

The main indication is to look for atherosclerotic lesions.

The clinical manifestation of these disease are mainly the transitory ischemic attack or the established stroke.

And sometimes this clinical symptoms can be the Amma fu non atherosclerotic lesions are less common, but there is a big list of these conditions as kinking arthritis, aneurysms, av, fiscally extrinsic compressions, thrombosis, and others.

Another very important indication is the measurement of the edia.

It's very important to determine the edia thickening, which is very important in different medical specialty task, cardiology, internal medicine, neurology, and endocrinology and many others because it not only represents the presence or not of atherosclerotic disease, but also inflammatory diseases.

So the measurement of these specific segments of the arterial wall walls are very, very important.

Study Protocol for Performing Carotid Ultrasound

Study protocol for performing carotid ultrasound.

First of all, we must start with the anatomical position.

Normally, our patient is in supine position with a mild ext extens of the neck.

Sometimes it's good to rotate it and a slight rotation to the left or to the right part of the neck.

The transducers to be used are transducers, convicts or linear, it doesn't matter.

But the important factor here, it's the frequency of the transducers.

We need to use frequencies higher of 0.5 megahertz has higher your frequency better.

You can obtain better images because of the resolution of the system.

The approach could be anterior or posterior to the external sial muscle.

We recommend the use of anterior approach in younger, in young patients.

We can obtain a very well depiction of the vessels in elderly patients.

The posterior approach can offer better depiction of the carotid arteries.

Vascular Segments

Those are the vascular segments that can be assessed by ES in doppler or ultrasound advanced techniques of ultrasound.

This is the common carotid arteries, and we can observe the common, the common artery in the proximal me medial and distal portions.

And it's very important to evaluate the three segments of the internal carro artery, the bulb.

This is the proximal segment.

The media, the medial, and the distal segments also is important to evaluate the external carotid arteries artery.

And we can recognize or differentiate both arteries by observing this first bifurcation here in the external carotid artery.

It this article respond to the superior thyroidal artery.

Anterior and Posterior Approaches

In this slide here, we can observe how we can obtain all the orientation of the image in our screen when we do or perform the anterior or the posterior approach.

When we do the anterior approach first, the first vessel that can be observed is the external carotid artery, and the second vessel will be the internal carotid artery by using the posterior approach.

The first vessel to be observed will be the internal carotid artery here, and the second vessel will be the external carotid artery.

So anterior approach, the first vessel will be the external, and the second vessel will be the internal carotid artery.

With posterior approach.

The internal first and the external has a second vessel here, and again, here, the bifurcation.

This is the superior thyroidal artery.

Techniques Used in the Laboratory

The study protocol that we use in our laboratory is this one.

Here. We start with B mode.

We always apply or use the real time compound ultrasound because it offers a better resolution and a better image.

Then we go to Doppler.

We start with a color doppler, then we go to power doppler, then a spectral analysis.

We are very interest in three-dimensional ultrasound, so we perform vascular 3D ultrasound, and then we go to surface and MultiPlan our three dimensional ultrasound.

But really this is a matter of research at this moment.

We don't have a very clear clinical application until this moment, but we always do it, and we compare our results with the conventional ultrasound.

But in any vascular lab those are the techniques used.

Bemo real time doppler with color, power and spectral analysis.

Intima-Media Thickness Measurement

We start with evaluation of the internal the intermedia thickening thickness in this case.

We can see here the intermedia.

It's represented by this hyper hyper echogenic line here.

This is the tima, this hyper genic line.

This is the media, and again, we have an another hyper genic line or interface corresponding to the adventitia.

So in this case, we mark or place our markers or calipers here, here in order to determine the thicken the thickness of these vascular structures.

The normal measurements of the intimate media is less than 0.9 millimeters.

When you have an intimate media of 0.9 millimeters, it can be considered an abnormal.

You can see that it's enlarged in those cases by using different techniques.

In this case, we are making using some kind of color here a color display in ceia.

And using also extreme resolution and compound ultrasound, we can obtain a better definition, but always with the value under 0.9 millimeters to be considered normal.

In this case, we have an intermediate hyperplasia of 1.7 millimeters here, and even we can even see here just a small spot of a hyper cogenic area here, corresponding to a fibrotic area in this enlarged edia.

By using color doppler, we can obtain a better definition.

Of course, we can see it by using only B mode, but we when we combine the two techniques, doppler and B mode, we can observe here in this case.

And uniform hyper genic area of point 1.9 millimeters.

This is an intermedia enlarged and enlarged edia.

And in this case, it's not only hyperplasia, but only it's almost a plague here in the anterior wall o of the of the common car artery of an with an extension of 3.3 millimeter 3 3 3 0.3 millimeters here, here, and point and 2.8 millimeters.

Also, it's important the place where you make the measurements of the intimate media these measurements must be done one centimeter before the carotid bifurcation.

It is important to all the labs, and everyone makes the measurements in the same at the same place, at the same place, because we can make a proper follow up of these cases of these patients in order to see the progression of the disease, or, for example, the response to medical treatment.

Of course, if we see the president of disease in another places of the vessel, it's important to report it.

But the measurements must be done in this centimeter before the bifurcation.

And it's important to explain that information or to write this information on in our reports.

This is an example of anti media Hyperion and fibrosis.

We have three fibrotic plagues here very tiny very small very small.

And you can see here that we have and thickening of only 0.9 millimeters.

Inside this thickening, we can observe a well-defined three structures or three plagues, because we have this echoes hyper cogenic areas here without acoustic shadowing.

We will explain that with more details in the second part of the lecture.

Another case with edia hyperemia and calcification, we observe the hyper cogenic area with acoustic shadow here, with acoustic shower doing.

By combining the color doppler.

Again, we can obtain a better definition.

This is color doppler, and this is the normal edia, and this is the representation of the internal carotid artery in the proximal segment.

Doppler Analysis

Color Doppler

The bulb in the bulb we can observe by using color Doppler.

This bi directional color flow.

It is represented because we have a helical flow movement in this vascular segment.

So the flow goes up and goes down, goes up, and goes down through the bulb.

And this is the reason, because the color doppler represents these two codifications.

Up and down, up and down here, we can observe the color bar.

And this is the reason, because we can obtain this kind of image, and this is a normal image that we have to look for when we lost this image.

Something wrong is happening in the bulb.

We must in the in that case, look for a pla or any condition that is altering the normal hemodynamic of the bulb.

Power Doppler

Then we go to power doppler.

And the power doppler in this case is representing only the presence of flow, not representing the direction of flow.

And with this technique, with power doppler, we can obtain a better depiction of the flow inside the vessel.

Now we have the distal portion of the common carotid artery.

We have here the external carotid artery, and here we have the bulb, the proximal portion of the internal carotid artery.

And in fact, we are observing here a plague.

This is a soft plague that we can also named fibro lipic, play plague.

Those characteristics will be presented in the second part of the lecture.

Spectral Analysis

Spectral analysis provides a very characteristic wave behavior.

And it's very useful because by looking for alterations in these waves, we can make a proper diagnostic.

This is the normal spectral wave of the common carotid artery.

The spectral analysis shows high resistance, and we say that is high.

The resistance index is high.

When the value is equal or higher to 0.75, the wave can be dichotic, and the wave always will have the spectral window empty.

The wave can be mono by or phasic.

In this case, we are saving a wave, a monophasic wave, but with a dichotic behavior.

But this is normal.

And peak systolic velocity is always less than 125 centimeters per second.

The external carotid artery presents a very similar spectral analysis to the common carotid arteries.

If you compare both spectral analysis or spectral wave, both are very similar.

Both presents di portions, both are monophasic, but can be insist B or three faic and velocity is always less than 100, 125 centimeters per second.

So both wave are definitely similar.

The internal carotid artery has his own characteristics, also the spectral wave.

It's of low resistance.

It means that the resistant index is less than 0.75.

The wave will be always monophasic.

The measurements are done in the mid portion and the distal portion, because if you placed the sample volume here in the bulb, you will get a bidirectional spectral wave, because as I explained before, the flow in this portion is helical.

So we have a monophasic monophasic spectral wave with empty window.

It's quite important to see the spectral window empty in the internal carotid artery.

If you find some echoes inside, it means that it represents turbulence.

And if you find turbulence, it means that or you have an stenotic plague or you have any anatomical condition as a kinking for example.

But this characteristic of turbulence reflects abnormal condition.

So for a normal inter car artery, you must find an empty window.

And the peak systolic velocity is always less than 100 centimeters per second in these vessels.

With these characteristics of the spectral wave, these normal characteristics, we can if we find some alteration, we can make a proper hemodynamic diagnostic of stenosis.

We will see these abnormal characteristics in the second part of our lecture.

Correlation Between Pathologic Anatomy and Ultrasound Findings

There is a good correlation between the pathologic anatomy and the ultrasound findings of the plagues in carotid arteries.

The plagues can be soft, fibrotic, calcified, and mixed or complex plagues.

When we have any combinations of these soft fibrotic or calcified characteristics, and we also have complicated plagues when we find hemorrhage or ulcerations or even necrosis inside the plague.

Sonographic Characteristics of Plaques

Those are the sonographic characteristics of the plagues.

A soft plague looks like with low to intermediate amplitude echoes.

The fibrotic PLAs shows high amplitude echoes without acute acoustic shadow.

And the calcified pla plague present high amplitude echoes with posterior shadow.

This is very important because we can make the different differentiation bit when these two kind of plagues.

And this is important because the epigenic potential of the fibrotic plagues is different or is different of the calcified plagues.

The mixed plagues present a combination of signs.

So we can have a plague with solve with calcified portions or a fibro plague with soft soft portions.

And any kind of combination among these three conditions, the complicated plagues present, hemorrhage, ulceration, and necrosis.

And the correct the sonographic characteristics are a heterogeneous anti coic focal lesions and irregular surface, this stenosis cost.

But these PLAs can be observed mainly in the bifurcation, in the origin of the internal carotid artery, or in the initial segment of external carotid artery.

But in fact, the condition can be observed in any place of the carotid arteries, not only in the internal or sternal, but also in the common carotid artery.

So it's necessary to perform a very well detailed test in order to try to find this sonographic science.

Examples of Plaques

This is an example of a soft plague.

We here observe hyper echogenic structure.

It means that the constitution, the components of the plagues are soft, high potential of embolisms here.

Pay attention with that. And we are observing that the plague grows not only to the external portion to the advanta, and the growing will stop depending on the compliance of the advanta of the carotid artery, and then the plague will start to grow to inside the lumen.

So it is very important to determine the size of the pla, the surface of the plague.

And by using color doppler, we can observe how the flow is accelerated in this portion, and it is represented with these all in phenomenon.

Sometimes the soft plague is so hypo echogenic that we cannot observe the plague by using just B mode activating the color doppler.

Now, this pla appears very clearly here, but without the color doppler is almost impossible to detect the plague.

So it's very important to use all the technology that we can have in our system, in our equipment with not only color doppler, but also power doppler in order to obtain a better depiction of the surface of the plague.

Again, in only B mode, no pla is seen here.

And then we color doppler, and then we power doppler.

Power Doppler offers a very very clear detail of the surface of the of the plague.

In this case, this is a soft plague.

Another example of hidden plague.

In this case, we cannot observe the plague here in the posterior wall of the bulb.

Not only the bulb, the proximal segment, but only the medial segment is affected by the plague.

Here in this internal carotid artery, we can detect just a signal here, a very small signal here, more small echos corresponding to a fibrotic point in the in in in this side of the plague.

By using the color doppler, we can observe that we have a soft plague in this portion of the internal carotid artery, and also here in the anterior wall of the external carotid artery.

Another example, this is a soft plague.

The soft plague is also called fiber lippe plague.

Both expressions can be used here with beam mode.

Then the use of color doppler here with power doppler.

If we place our ultrasonic beam in this portion, in this very specific portion, and go to from longitudinal to transversal, this is the kind of image that we can obtain.

And here we are observing how the plague takes almost all the lumen of the vessel with only this residual lumen only.

Here we have patency of the flow in this segment here, and this is the transversal view, and this is very important because we have to determine the grade of obstruction, the grade of eno, of stenosis.

And I will discuss how can we perform this estimation.

Those are so fibrotic plagues.

Hyper cogenic echoes without acoustic shadowing.

This is the internal carotid artery. This is the bulb.

This is the external carotid arteries.

This is a posterior approach.

And now, by using color doppler, we can observe the surface, but in this case, the color doppler is hidden the lesions.

So we have to use, I said again, I said it again, all the techniques.

B mode, color doppler, power doppler.

In order to make a proper assessment of the vessel.

An example of calcified plague.

Here we have hyper genic, a hyper cogenic plague, and acoustic shadow.

And here the B mode shows the flow on the bulb and the median portion or segment of the car.

Internal carotid artery.

Those are mixed ather athero plates.

Better observed by using color doppler.

We have here soft component, and we have here fibrotic component.

And here we have an example of a complex plague.

This is our complicated plague. This is an ulcerated plague.

In this portion here, we have an ulcer.

We have soft plague, and here we have, we have a calcified plague.

This is a complex plague, a complex plague in the anterior wall of the this is the common artery, almost.

This is the terminal or the distal portion of the common of the common carotid artery.

But this is very dangerous because it is ulcerated and ulcerated plagues have the highest genic potential.

Here we are observing the same pla, but but now using the color doppler.

So this is the ulcer is very evident or very apparent by using both techniques.

Another complex plague this is the distal portion of the common karate artery.

This is the bulb, the proximal portion of the internal karate artery.

Here we can observe an irregular surface surface here.

This is a complicated plague with koic images, koic images inside the plague.

It can they correspond to necrosis or maybe hemorrhage inside the plague.

Internal hemorrhage inside the plague. Inside the plague.

And this is the residual lumen here, only this portion here.

So the homogenic potential of the plagues, soft, high, potential fibrotic medium, potential calcified low potential and complicated plagues.

They have very high potential to produce mli

Internal Carotid Artery Stenosis Quantification

Internal carotid, already stenosis quantification.

It is very important to quantify the grade of stenosis because with this data or with these values, we will take clinical decisions if our patients will go to medical treatment or surgical treatment in endovascular or surgical treatment.

The of the type of endarterectomy.

There are two techniques to determine the internal carotid stenosis.

Both were published many years ago at the beginnings of the nineties 92 93, the European Carotid Study trial, and the North American Study, carotid End Doctorectomy trial.

The North American method takes the residual lumen and takes the normal distal lumen of the vessel and make a relationship by applying this formula here, B minus A divided by B.

And the European study takes or make all the measurements in the place of the plague, and in the place where the residual residual lumen is take.

So this diameter here, diameter C, diameter A, so C minus A divided by C.

The problem here is sometimes when you use an acid method, you can underestimate the grade of stenosis, and sometimes when you use the European method, you can overestimate the grade of stenosis.

Examples of Stenosis Measurement Methods

Let's see some examples here.

This is a soft pla, an important soft pla located in the posterior wall of the bulb.

This is the North American method.

Here is the residual lumen.

This is the distal lumen of the vessel, the normal distal lumen of the vessel.

And here the computer offer.

The formula is not necessary to that. We calculate them.

The computer offer the offers, the results, when you place the calipers, and it says here 37%, but maybe if you make the measurements here, you can say that is more than 50%.

This is a non-significant stenosis, and more than 50% it a significant stenosis.

And here we have an example with the European method here, making all the measurements at the level of the stenosis and the level of the plague.

So we have the residual lumen here, we have the diameter of the vessel here, and the computer says 65% of stenosis.

And we have another method to do.

We can make measurements in transversal view.

In this case, we have the advantage here.

Then we have the plague.

And here we have the residual lumen, better observed observed by using the color doppler, power doppler.

And it says here that we have a reduction of 56%, again, more than 50%.

So it says that this is a significant reduction of the vessel.

Which method are we going to use?

Well, we need to make a hemodynamic correlation between the B mode in transversal on longitudinal, and the Doppler analysis, the spectral analysis.

This paper was published in 2003.

And this is a result of a consensus of experts in the matter of carotid artery.

And I think this is a very interesting and a very important material.

Many laboratories are using this method all around the world.

This is the method, or this is the the rules in somehow that we use in our laboratory.

Velocity Criteria

Those are the velocity criteria recommended by the panel of experts.

We can say that we have a normal carotid artery when there is no edia thickening or plagues, and the velocity is less than 125 centimeters per second.

This is normal if we see any plagues or any intimate media thickening.

But the velocity is less than 125 centimeters per second.

So we have stenosis and non-significant stenosis less than 50%.

This is a mild stenosis when we have the intermedia alterations, and when we have the plagues and the velocity reach 125 2 230 centimeters per second.

So this is a moderate stenosis significant but moderate in the range of 50 to 69%.

When the peak velocity, the systolic peak velocity is 230 or more.

In this case, we are we have a severe stenosis, internal carotid artery stenosis equal more or equal to 70%.

We have another condition, more condition here.

If the visible plague and we are saving lumen narrowing, we can use the expression to near occlusion occlusion, but if the lumen is really is really markedly narrowed in this case, we use the spray the expression near occlusion, and we have a total occlusion, 100% of occlusion when there is no detectable pattern lumen at degree scale ultrasound and nu flow at spectral power on colored upper ultrasound.

Very important to make these measurements.

The angle of the sample volume must be must be at 60 degrees.

Examples of Spectral Wave Behavior in Stenosis

This is an example of the behavior of the spectral wave.

In this case, we have here a very important stenosis.

This is the same patient of the complicated plague that I showed you before with the internal area of necrosis.

And here we have ine in color dopper, we placed right here the sample volume, and we have a systolic peak velocity of 350 centimeters per second.

So it corresponds to a severe stenosis more than 70%.

The velocimetry is very important, but attention, it's very useful and it's useful when our patient have a normal left ventricular ejection fraction.

But some patients with myocardiopathy or valve osis, this these patients will not will not reach that velocities I mentioned before because the ventricular ejection fraction.

And in this case, we can we must observe the spectrum and we can compare the hemodynamics of the vessel itself.

So we can observe or is necessary to observe or make the measurements in the previous segments and observe the velocity.

Then in the area of the stenosis, if the systolic peak velocity doubles, the previous velocity of the end diastolic velocity makes 2.5 times disease, a severe stenosis.

And we can say that we have a critical stenosis when the systolic peak reach four times the previous velocity or the end of d diastole reach five 5.5 times.

And here we have an example.

In this case, the previous velocity is only 48.7 centimeters per second.

But in there, exactly in the area of the stenosis, the velocity reaches here, 477 percent, so 10 times the previous velocity.

This is a critical internal carotid artery stenosis.

This is the string signs, and this is the expression that some authors use to a very very reduced lumen of the vessel.

We only can detect just a small amount of doppler signal.

Sometimes we can better observe these severe obstruction.

With power doppler, we commonly have just a string of flow in this place.

This is the internal carotid artery string sign.

In some cases, we can observe a total occlusion of the vessel.

There is an important a aroma here, occluding, total occluding, the lumen of the vessel with no color Doppler signal, no color doppler signal.

Again, no power doppler signal.

It's absolutely silent on 3D.

And here, no spectral analysis can be obtained because the total occlusion 100%.

In our laboratory, we perform first the ER study, and we make the diagnosis or the diagnostic of occlusion on the grade of stenosis only by Doppler.

And then our patient goes to arteriography, not for diagnostic, but to make an invasive procedure in this case to stent placing.

And here we have the stent placed on the area of the stenosis.

This is the previous to stenting.

And here, after placing the stent, again, the patient with the stenosis I showed you before, 350, day 30, and day 31 or 31st the next day, the patient is the problem is resolved by placing a stent.

This is the posterior or the control doppler and the velocity, previous velocity previous to the procedure was 350.

Now is 96 TERs per second doppler and an geography.

Let's compare the sensitivity and the specificity.

When we used 130 cent per second has cut off point to estimate the grade of osis 50%.

The sensitivity, the sensitivity is 98%.

The specificity 88%.

And by using two hundreds per second to estimate the grade of stenosis equal or higher than 70%.

The the sensitivity is 90% and the specificity is 94%.

We are using 125 and our practice according the panel of experts, and we are using here 230 if we increase this number, so our sensitivity t will be higher.

Conclusion

In conclusion, edia measurement is such an important, is such important, and has blood pressure values and cholesterol levels in order to estimate clinical and subclinical atherosclerosis.

And the edia measurement provides information of treatment response, for example, when the patient is undergoing treatment with statins.

Finally, carotid sonography is a unique imaging method for the investigation of carotid abnormalities, non-invasive, accurate, and cost effective.

It provides morphologic and functional information.

It is increasingly becoming the first and often the sole imaging study before endarterectomy, whereas costly and invasive procedures are reserved for special cases.

I hope this information will be useful for your practices.

Thank you for your kind attention.