Optimizing the Vascular Exam - SD

Introduction

Hi, I am Cindy Owen.

I'm the General Imaging research and luminary manager for GE Healthcare.

I'm a sonographer and I've been in the field for about 30 years, and previously worked at Baptist Medical Center in Memphis, Tennessee.

My topic today is optimizing the vascular exam.

Importance of Optimizing the Vascular Exam

Optimizing the vascular exam is very important.

It involves the B mode, the color doppler, and the spectral doppler, all important aspects of a vascular exam.

Optimizing is a challenge because in today's world, we're asked to do more patients faster and faster.

But it's still very important because when we optimize, we are creating the best possible images for whoever is interpreting the exams.

And then for the physician who is actually performing the interpretation, the more you understand about how the image is optimized, the better you can help guiding the sonographer when things are not to the optimal level that for your interpretation.

Finding the Best Acoustic Window

So to begin with, we all know that ultrasound is very window dependent.

So that's one of the things that separates a sonographer from someone else just picking up the probe and putting it on the body, is that we have to help find the best acoustic window for the anatomy that we're going to be interrogating.

So for example, for a kidney, if I just want to look at the B mode aspects of the kidney, compare its echogenicity to the liver, measure the length of the kidney, then the image that you see on the bottom is perfect for that.

On the other hand, if I want to interrogate the intravascular aspects of the kidney, if I want to evaluate the inter lobar, the arcuate, the interlobular vessels within the kidney in a patient's suspicious for renal artery stenosis, then I want to change my plane of approach, perhaps roll the patient up and get the kidney closer to the surface of the abdomen.

This is going to give me a better angle towards those and vessels within the kidney.

It's also going to give me the capability of having a higher frequency transducer and using settings that will be more optimal for visualizing that intravascular area within the kidney.

Now another example is in the abdomen.

If I want to look at a small vessel such as the coronary vein, what I have to do is find the left lobe of the liver and try to, as much as possible, get it on top of the splenic vein so that I can identify this tiny coronary vein.

This is a vessel that can be important in patients with portal hypertension, and we want to assess the direction of flow.

Well, some patients have a very long left lobe of the liver, and they're just ideal for this just as they lie on the scanning table.

But many other patients, we have to make some adjustments in order to get that left lobe to hang down low enough so that it creates that window for visualizing the splenic vein.

In the coronary vein, I might have them sit up or lean back.

I might have them take in a deep breath.

Sometimes I even have them make a big Santa Claus belly or just stick their belly out, and that will push the organ down to create a sonographic window.

So keep in mind whatever study you're doing, there is an optimal window and sometimes more than one optimal window for finding that anatomy.

Avoiding Artifacts in Sonography

Now, the other thing that we have to be aware of in sonography is that there are a lot of artifacts and some of the artifacts can be helpful, but others are not, and some we really want to avoid.

So I use different techniques to try to avoid artifacts.

In the upper example, you can see that I'm actually have a very narrow field of view, and what I'm doing is trying to cone in the image or reduce my sector width so that you're not seeing the rib shadows.

Those kinds of artifacts can be distracting to whoever is actually interpreting the study.

If I have clutter artifact or a grating lobe or a side lobe, I might actually reduce my sector width or try a different plan of approach just to avoid that artifact.

In the bottom image, I'm actually using harmonics and in this case a very high frequency harmonics to visualize the blood flow.

So this is not a new flow imaging tool, but rather I'm using high frequency harmonics, and it's just showing me the flow through this high grade stenosis.

And one of the reasons I can see this with harmonics is that harmonics improves contrast resolution, and it actually allows me to see more clearly the low level echoes that come from comprise the blood flow.

Choosing the Right Probe and Frequency

Choosing the right probe and frequency is also key to optimizing the vascular exam.

In my upper example here, I'm looking at the liver, and here is a paraumbilical vein that's showing flow exiting the liver in this patient with portal hypertension.

So here I'm using a lower frequency abdominal probe in order to display this, but we all know that once that flow exits the liver, then it courses up to the surface of the abdomen and moves towards the umbilicus.

And at that point it's very superficial.

So a better transducer would be for me to choose a linear array transducer that has a higher frequency.

That way my focus is closer to the surface and I have a higher resolution.

So I'm choosing, I'm changing probes to optimize my exam.

In this example, you see the carotid, the in the internal carotid artery and a plaque in this area right here.

And what I'm using is a higher frequency transducer.

Because this is a small patient, we all get in the habit, I think of when we have an abdominal exam, we choose a three and a half.

If we have a carotid exam, we choose our linear array transducer that has a frequency in the range of five to seven megahertz.

But there are plenty of times when going to the higher frequency will actually give us much better results if we just make the effort to use a more appropriate probe.

So the hint is that we should really pick up the highest frequency probe that will do the job, because that's going to optimize our spatial and contrast resolution.

Compound Imaging

Now, another tool that we have at our disposal is compound imaging.

It goes by different names on various pieces of equipment, but basically on all pieces of equipment, what it does is steer the beam in multiple directions and then average those together to create one image.

The advantage of doing this is that it gives us closer to perpendicular incidence.

Now, what, in this example you see of a Schering camera, that's allowing us to actually visualize the sound beam towards a perpendicular interface, and you can see that the reflection comes directly back to the transducer.

But many times when we're scanning, we don't have perpendicular incidence.

We have a vessel that's curving across the interface or the image, or we have something that is oblique.

And you can see what happens is that the sound beam comes down and it strikes that oblique interface and the reflection is going off and never actually reaching the transducer.

So what would happen is that's really invisible to us on sonography.

If we turn on compounding, we're actually steering the beam in multiple angles and then averaging those steers of at least three different steering directions together to create one image.

When we do that, as you can see here, one of the angled beams happens to be striking that oblique interface at perpendicular incidence.

And now the reflection from that interface is coming directly back to the transducer.

Hence, we're gonna be able to see it so that invisible object has now become visible.

So you can see that the advantage of using compound imaging is that it then allows us to have better border detection and we can see the edges of structures much more clearly.

Now with compound imaging, there are definitely times when it's very helpful to use and times when it's not helpful to use.

As I mentioned before, I think we should really use it almost all the time, but occasionally, if you're imaging a structure that's moving very rapidly and you're firing at it from multiple angles, averaging all of those together, you can end up with something that's a little bit blurry like this, where I have a thrombus in the subclavian vein and it's moving a lot, but it's just giving me a blurry image.

If you look over at the right hand side, I've actually turned compounding off now and here I have a much clearer image because I'm not doing all of that averaging.

So my recommendation is that use compounding most of the time.

If you have a structure that's moving rapidly, then that's a time when you might just turn it off for that image and then turn it back on when you're done.

Virtual Convex

Here I've added a feature called virtual convex, which allows me to just have a larger field of view and many transducers support this type of a feature and just very handy with the linear array transducer to turn this trapezoidal view on and give you a larger field of view and enable you to see more structures that are around your main area of interest and put it into perspective.

Optimizing Gray Scale for Plaque Detection

Now, one of my pet peeves in sonography, especially vascular sonography, is when we set up our system in a very high contrast fashion, because we're looking at vessels and we want to see that the inside of the vessel is completely black or empty.

And what happens with that is that we actually throw away real information and real information that can be valid and useful.

And I call this the myth of the invisible plaque because we often hear at conferences or see images where there was a plaque that was not imaged on gray scale, but clearly is present when we turn on the color and it's turning writing around something.

But actually the plaque could be visible on our gray scale image if we optimized the image to see the low level grays that comprise such hypo echoic plaques.

We don't, and this is the difference that we would see just between optimizing and not optimizing the image.

And you can see the difference right there.

So my recommendation is, whenever we're performing vascular sonography, I like to use all the shades of gray in the system.

I don't go to a very high contrast map.

I don't go to a very low dynamic range.

I don't want a black and white image.

I wanna be able to appreciate the low level gray that would comprise a hypo echoic plaque.

And in fact, I even encourage the sonographers that I work with to increase the TGC or the gain within the vessel so that there are some extraneous echoes.

I'd rather see that than to have a completely black vessel.

So we can see these low level plaques.

This is another example here on the left hand side, it looks like a normal common carotid artery, but on the right hand side, when I increased the gain, you can see that there's a dissection and right here's the dissection, and we just totally didn't see it when the TGC was decreased and it just wasn't visible.

So the better setting is on the right hand side to be able to appreciate these structures.

Doppler Hints

Well, let's move to Doppler and I've got a few Doppler hints to share with you.

Size Matters

Number one is that size really matters.

If you look at my top image over here, there's a little bitty wave form.

I don't want to show a very tiny wave form.

I'd rather change my PRF or scale, which are two words for the same thing, or increase my frequency so that the waveform really fills the entire spectral display as much as possible.

When the waveform is larger, I can be more accurate in placing the calipers.

I can more accurately see the anatomy of the waveform, so I'm gonna adjust my scanning parameters so that the waveform is really much larger.

Now, occasionally you have a very tough case and this is the best you can do, but that's uncommon.

It's better to take the time and really optimize the doppler so that you have a nice large waveform.

Wall Filter Setting

Another thing to watch is the wall filter setting.

When we change the PRF, the wall filter on most pieces of equipment will automatically track, but occasionally it's not just perfect for the waveform that you're looking at.

And this is such a case where we have this dark area, this black line underneath the waveform, and that's an indication to me that the spectral doppler wall filter is set too high and it's obliterating the low velocity flow that's associated with in diastole.

And in fact, if I were to put a caliper and try to measure in diastole here, I really couldn't do it.

So I want to make sure that I decrease the wall filter so that we can see all parts of the wave form.

So that's something to pay attention to and watch.

Spectral Doppler Aliasing

Whenever you have spectral doppler aliasing, you wanna make sure that you reduce the baseline, increase the PRF as much as possible.

If neither of those will get rid of the aliasing, then a couple of other things you could do would be to decrease the frequency, either by a frequency control of the spectral doppler or change your probe to a lower frequency probe that then might support a lower frequency Doppler.

As a last resort, I might increase the angle, but keeping in mind that we really never want the Doppler angle to be greater than 60 degrees.

Doppler Auto Calcs

Something else to watch for is Doppler auto calcs.

Most of the equipment nowadays has a method that automatically will place the Doppler calipers on the areas that you have defined that you're interested in.

And in this case, I'm interested in peak systole and in diastole.

So when I freeze the image, the calipers appear automatically at peak systole and in diastole, and that's all well and good, but it's my job as the sonographer or the physician who's interpreting this to make sure that those are really set appropriately.

Doppler, as you know, is very noisy.

We're trying to get a doppler signal from moving red blood cells, which are very tiny and send back a weak reflected signal, much weaker than the surrounding tissue signal.

So with doppler, a lot of times, and especially when we're in a stenosis where we have a high PRF setting, there's a lot of noise and the automatic calipers may not be placed appropriately, and in those cases, we just have to make sure that we're paying attention and that we edit them to make sure that they are represented correctly on peak systole and in diastole.

Colorizing the Spectrum

And the last one is really just a matter of personal preference, but I do like to colorize the spectrum.

I think sometimes it enables me to see smaller parts of it.

It enables me to see the weaker range of the frequency shifts that are present in the spectrum.

And besides for that, it just looks pretty.

So colorizing the spectrum can be helpful but also just can aid in the aesthetics as well.

Choosing the Optimal Doppler Frequency

Other doppler hints, choosing the optimal doppler frequency, we're probably more used to choosing the optimal B mode frequency or color frequency, and perhaps often don't think about choosing the spectral doppler frequency, but that can be very important too.

For example, here in this image on the left hand side, this is a high grade ICA stenosis and look at the velocities over 600 centimeters per second in systole.

Well, I've had to lower my baseline and increase my PRF up to a very high level in order to unwrap this waveform.

But sometimes, especially in the deeper parts, I may not be able to unwrap the waveform, may not be able to get the pulse repetition frequency up high enough.

And in such a case as that, I might actually lower the Doppler frequency or use a different transducer that has a lower spectral Doppler frequency.

And what that will do is give me a smaller frequency shift from the red blood cells even though they're going the same velocity.

And then that may allow me to show the waveform without spectral aliasing.

Keep in mind too, that the higher the frequency, not only the higher the frequency shift, but the greater the amount of Rayleigh scattering from the red blood cells.

Remember they were tiny, they're smaller than the wavelength of the sound beam and they're given a special name Rayleigh scatterers.

So we actually get more scattering at higher frequencies and it increases to the fourth power the frequencies.

So here in the kidney, I'm looking with two different frequencies at the inter lobar artery at 1.8 and at 2.1, and you can see the 2.1 frequency is actually much stronger compared to the 1.8.

And in fact, not only that, I have a higher resolution signal.

So there is an optimal frequency for different parts of the body and different types of flow velocities.

Sweep Speed

Another thing to think about is how long to sweep typically our sweep speed or rather the amount of display that we're showing here, from zero to eight seconds and in this case from zero to three seconds, is usually about three and a half or four seconds.

So depending upon what I want to show, I may adjust that sweep speed on the right hand image.

I've actually lengthened it to show eight seconds of time.

And the reason I've done that is because I want the interpreter to quickly be able to see that there is a portal vein stenosis, and if I move the sample volume from this point into the stenotic area, by doing this, they can quickly determine that.

Yeah, the there's a big jump in velocity, and we really do have a stenosis.

It's just a quick way to grab their attention and show the pathology.

And that's the goal of a sonographer is to create images that tell the story of the pathology that this particular patient has.

And this is gonna tell the story more quickly.

When I'm looking at a renal doppler within the kidney, then I want to make the sweep speed so that I'm only showing about three seconds of information.

That way I'm gonna have a larger waveform and I can better depict the anatomy of the waveform because I'm looking for very small parts such as this early systolic peak that I'm circling right here.

I wanna be able to demonstrate that.

So I want the waveform as large as possible.

Angle Correction

Now, angle correction is a very important aspect to the exam.

If we don't angle correct accurately, the velocities that we obtained from our doppler studies are gonna be inadequate.

So in this example, I have purposefully given you the wrong doppler angle and it's actually overestimated the angle.

And by doing that, it's showing that the angle is measured at 74 degrees and it's estimating the velocity at 150 centimeters per second.

Now I've underestimated the angle and it's telling me the velocity is 58 centimeters per second.

Neither one of those calculations is even close to correct though, because I didn't have the correct angle measured when I actually placed the angle correction cursor so that it's parallel to the walls of the vessel at the point of sampling.

Now I've got a 60 degree angle and the velocity is 84 centimeters per second, so I have to be very particular and pay close attention to really setting that doppler angle appropriately.

Now, some labs have in their protocol that they want to do all doppler at 60 degree angle and that's perfectly fine, but it's not correct unless that angle correction cursor is 60 degrees and parallel to the walls of the vessel.

So in this case, it's clearly not parallel to the walls of the vessel.

So this is not truly a 60 degree angle and hence this velocity value is incorrect.

What I wanna do is actually heel toe the probe so that now I do have a 60 degree angle and it is parallel to the walls of the vessel.

So very important.

So these are just some examples here of some good quality doppler wave forms and some ways of how we would want to perform the spectral doppler by having it completely fill the window colorizing the spectrum when we desire to placing the calipers correctly and so on and so forth.

Color Doppler Hints

So let's move to color doppler from here with color doppler.

I have several hints that I want to share.

Filling the Vessel and Adjusting PRF/Scale

And the first one is just basically filling the vessel and adjusting the PRF or scale the same way.

And remember, PRF and scale are two different words for the same thing.

The PRF is the pulse repetition frequency or the how many pulses are emitted by the transducer within a second timeframe.

One second timeframe.

So this is a pseudo aneurysm.

And in the top example I have a very high PRF setting, and so we're visualizing the fast flows really well.

It's a great way to show just the jet, but it's not showing me the slow flow filling the rest of the pseudo aneurysm, and I don't have any clue here whether or not it's thrombosis or whether there is really flow.

And the bottom example though, you can see that there's flow completely filling the lumen because I've lowered the PRF increasing my sensitivity to the slow flow.

I don't see just the jet as clearly now, but that's not as important in this particular case.

I wanna show where the flow is.

Another example would be a carotid body tumor In this case, I've got the carotid body tumor displayed very nicely on gray scale, but as we all know, carotid body tumors are highly vascular tumors.

And to make the diagnosis one must demonstrate that there is high vascularity within the mass, but within a tumor the velocity is much slower than the velocity in the carotid system.

So in order to demonstrate the flow in the carotid body tumor, I have to lower the PRF so that I can really appreciate that slower flow.

And once I've done that, now you can see in the bottom example that yes, indeed there is flow within the carotid body tumor and we've made that aspect of the diagnosis by adjusting our controls appropriately.

Many times when I visit labs all over the world and I watch sonographers or physicians scan, I see them turn on the color and just look at an area to determine whether or not flow is present.

And oftentimes they're not touching a single button, they just turn on the color, don't see flow and say, oh, there's no flow there.

And obviously that's not a good way of doing it because our ability to see the flow depends on the parameters that we're using and the type of flow that we're trying to assess.

So if we're looking for slow flow, such as in a tumor, like the carotid body tumor, or as in this case this is a pancreatic tumor, I'm not gonna appreciate much flow in that at a high PRF.

But when I lower the PRF, there's more time between the pulses and I have a better chance of actually demonstrating the flow that's there.

Threshold or Priority Key

Another important control on the system is the threshold or priority key.

This is the color decision circuit.

It controls the level of gray that the color's allowed to write on top of, and that level of gray is indicated by this bar that you can see this green bar on the gray scale bar.

Now to understand the color Doppler threshold, you need to first know how the color Doppler image is created.

And in actuality the B mode images are fired across the transducer face and the B mode or gray scale image is created first and the color is actually fired second, and then superimposed upon the existing gray scale image.

And the problem occurs when for the same pixel location, the system actually receives both gray scale and color information and it has to decide which is going to demonstrate in that particular pixel location.

So that is done by the gray scale decision circuit or the threshold or sometimes called priority button.

If you have a case like this where you're looking at echogenic flow that is quite visible in the image, if we don't have the threshold set appropriately, we won't be able to write color doppler on top of that.

So for example, if the threshold is set to a low level, as you see here, the color doppler is being told by the system operator who set this control, don't write over the gray scale that's any brighter than this shade of gray.

So hence we're not seeing the color completely right over the gray scale.

When I turn the threshold up, now I can see that the color is indeed writing over all of the gray scale tissue and I can see where the flow is.

Here's an example of a chronic thrombus in the great saphenous vein.

In this case, if I have a high threshold, then the color is tending to write on top of the chronic thrombus.

Keep in mind remember the B mode image created first, the color is written on top of that the B mode and the color resolution are not equal.

The axial resolution for the gray scale is very good.

It's a short pulse.

The axial resolution for the color is not as good.

It's a longer pulse because we have more energy in that pulse.

We're trying to get information from red blood cells that are weaker.

So one of the ways we compensate for that is having a longer pulse train.

The result of having a longer pulse is poorer axial resolution.

So the color tends to ride over the walls of the vessel and bleed out of the vessel.

And one of the ways we help control that is with our threshold setting control.

So in this case, I've actually lowered the threshold so the color doesn't write over the parts of the thrombus and outside of the wall of the vessel.

And this is a much better image on the top.

Just another couple of examples of the same thing here.

I have an anomaly of the left gastric vein arising directly from the abdominal aorta.

On the bottom example, I have a high threshold and the left gastric vein is actually kind of smearing into the abdominal aorta and I don't see it very clearly, but on the top where I've lowered the threshold, I can clearly see the tissue in between and it helps me to visualize that a little bit better.

One last example in the carotid system on the bottom with the high threshold, the color, because of the different resolution settings that we just spoke about is writing over the wall of the vessel.

But by setting the threshold more appropriately for that particular exam type, I can have the color, even though it's a lower resolution contained more accurately within the lumen of the vessel.

So this ends up being a better image.

Packet Size or Ensemble Length

Let's move on to a different control and talk about the packet size or ensemble length.

Also sometimes called the dwell time.

This control is the number of pulses on each line of sight that makes up the color box.

It actually affects our frame rate and our signal to noise ratio.

When we have a packet size of eight, as you can see up here, it means that I'm only pulsing eight times on each line of sight and I end up with an image that has a high frame rate, but maybe a little bit noisy.

On the bottom example, I have a packet size of 16 with 16 pulses on each line of sight.

And you can see that it's a much more pleasing image, less noisy, but overall has a lower frame rate, which I'm not concerned about because really what I wanna show here is just that there is vascularity within this lymph node.

So having the higher packet size gives me a better image and I'm not too worried about the loss in the frame rate.

Line Density

What about line density?

Line density is the closeness or sparseness of the scan lines that are creating the B mode and or the color Doppler image.

We have different line density settings for both the B mode and the color doppler.

And in general it's lower for color doppler compared to B mode.

We actually take the information from each of the scan lines and average them together to fill in the blanks in between so that we have a smooth looking image.

When I have a high line density setting, which is displayed here, then I'm gonna have good lateral resolution.

If I take half of those lines away, I've degraded the lateral resolution, but the thing that's improved is the frame rate.

So like everything in ultrasound, it's a compromise.

And depending upon the clinical situation, I may desire to have higher frame rate or higher lateral resolution.

When you choose the presets that come with your system, in general, the manufacturers have optimized all of these controls for the specific exam that you choose.

So for example, if you choose a carotid exam, it will probably come set up with a low line density because we're not too concerned about lateral resolution, we're more concerned about high frame rates.

So but if I choose an exam such as small parts, I'm not as concerned about frame rates.

So I am more concerned about having good lateral resolution and it will come set with a higher line density, but the operator always has control so that they can vary this.

Now the control again, has different names on different machines.

It may be called line density, it may be called space time or simply resolution.

You need to learn your particular system so that you understand what control to vary, to affect the line density.

Now here's an example of what would happen if you evaluated a structure that has a lot of fine vessels with a low line density setting.

This is that same lymph node that we looked at a little bit earlier and with low line density, a lot of those individual vessels are actually smeared together.

We don't have adequate lateral resolution to resolve them as individual vessels, but if I increase the number of scan lines within the color, now you can see many more vessels within that lymph node because I have actually improved the lateral resolution.

But you're also noticing that there's been a hit to the frame rate.

The frame rate is much faster on the top example and slower on the bottom example.

So it's a compromise.

And the operator of the unit, the sonographer or sonologist performing the study must choose the appropriate line density for each exam type.

But remember, if you choose the preset that came from the manufacturer, you're gonna be at a very good ballpark setting for most of your studies.

And you're probably only gonna vary this when you find pathology or something else that's different from the expected anatomy.

Frame Averaging or Persistence

Let's talk a little bit about frame averaging or persistence.

Frame averaging is another way that we can fight noise in the image and we're actually gonna take a whole picture or frame and average it in with the next frame or maybe the preceding frame or all three, so that we can get rid of some of the noise and show the color without as much of the background noise that we had talked about earlier, that is so pervasive with doppler.

But the downside of having a high frame averaging is that I lose some of the hemodynamic information because I've averaged in multiple frames together.

In this example of the pseudo aneurysm, I have very low frame averaging and you can really see the hemodynamic situation and the pulsatility in real time.

On the bottom, I've turned the frame averaging really up just to make a point, turned it up very high and you can see how you're losing the hemodynamic information.

So depending upon the hemodynamics that you're evaluating, you may adjust the frame averaging to better suit the particular image that you're looking at.

For example, here I'm looking at a venous thrombus.

This is an acute DVT in the femoral vein.

And my goal here is not really to show something that's rapidly moving, but rather to show the flow going around the thrombus tip.

And that's best done by having a little higher frame averaging setting so that I'm not getting any noise and just really getting a nice smooth image.

But in this example of a carotid dissection, just the opposite is my need.

I have rapidly moving hemodynamics and I want to show the difference between the true and the false lumen.

So when I have a high frame averaging, as you're seeing here, some of that information is lost.

If I turn the frame averaging down on the right hand side.

Now you can clearly see that there's flow during different parts of the cardiac cycle in the two lumens.

Choosing the Right Color Mode

Another color hint is to choose the right color mode.

Now we've talked about, actually, I should say they're the right flow imaging mode.

We've mostly been focusing on color doppler, but there are other modes that are available to help us image the blood flow.

It could be power doppler, it could be B flow, it could be harmonics or other different flow imaging modes that are available.

You have to learn what's available on your particular system that you're using.

In this particular case, I'm looking at a dialysis fistula and I have a very high PRF because the flow in the fistula is very fast and I wanna reduce the amount of aliasing, but I'm suspicious that there's something abnormal going on just below the fistula and I can see some little fingers of flow down there.

So I'm suspicious for perhaps a pseudo aneurysm, but I'm not filling it well.

And so I'm gonna reduce the PRF so that I can show flow in this area.

And sure enough, I can see that there is a lot of flow in that area, but by once I reduce the PRF, now the artery or the fistula itself is alias because of the high velocities that are present.

So perhaps in a case like this, a different flow imaging mode might be more ideal, such as just turning on harmonics or B flow or something else.

That allows me then just to see the fistula.

And in this case I can see that there's actually three different pseudo aneurysm jets going into this area.

Or in this particular case, I've got color doppler.

This is a thrombus in the SFA.

And I can see with color doppler very clearly where it looks like the jet may be and a little bit of the turbulence beyond that.

But when I go to a B flow, I can really appreciate a little bit better some of the anatomy of the flow and this irregularity there.

So choosing the right mode for the right type of flow can be very helpful.

Conclusion

And with that, I'm finished.

I wanna thank you for your attention and I wish you happy scanning and have fun optimizing your vascular images.

I hope this was helpful to you. Thank you.