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Okay, so let's review a little bit of basic carotid anatomy, see what this looks

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like normally, and see what the normal waveforms look like.

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So as we go through this, we look at the proximal right common carotid artery, we

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move to the mid portion, and we move to the distal common carotid artery.

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You can see as we get here, we get to start to see a little bit of the branching,

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with the bulb and the ICA starting to come up.

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You can see we're nice and clean here, no significant plaque within the vessel.

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And then here we get to that branch point where we get to the proximal ICA.

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You can see again that's nice and clean with no appreciable plaque or stenosis.

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We're looking at grayscale images of the mid ICA and then the distal portion of the

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ICA. Beyond the distal ICA is when it starts to get up into the skull base, so then

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we really start to lose it beyond that point.

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So we just try to image that entire segment that we can.

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The ECA here is the additional vessel at the top, and then you can see we also are

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taking some additional images on the transverse all the way through, and we get up

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to that bifurcation. You can see here that where we have nice blood flow throughout

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that whole area. And then here's where we start to look at the waveforms.

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So here's your common carotid artery waveform.

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You have your typical intermediate look with a nice peaks of solid velocity, but

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you still have a maintained end-diastolic velocity on these.

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Similar as we get to the mid common carotid and then the distal.

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These are all representing that same principle.

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As you get to the proximal ICA, you can see once we've deviated to this deeper

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vessel, which is the ICA, the waveform changes.

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So you have a nice peak systolic velocity, but it's not quite as high, and you have

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a higher end-diastolic velocity.

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So that shows us that we are now working under the principles of a

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low-resistance waveform here. You'll see similar things as we go down to the mid

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ICA,

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and then the distal ICA.

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When we flip back to the external carotid artery, you can see again the waveform

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changes. We have now again a more significant peak systolic velocity.

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You even have a portion here where it goes below the baseline, and then the

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end-diastolic velocity is much lower.

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So that shows you that you're working with your external carotid artery.

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So this is an example of the vertebral artery's waveform.

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You can see again we are back to a low-resistance waveform.

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We have constant forward flow throughout that whole time.

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We have flow that is going towards the head, so this indicator here tells us that

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we're pointing towards the head, and we can see flow is going in that direction.

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Now here, the scale is flipped, so the away from the transducer is red in this

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context. So you can see it is flowing out in that direction.

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And so similar things will be seen on the left side.

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This has a very similar look throughout it.

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And we should see those same type of examples of the waveforms, intermediate in the

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common carotid,

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more low resistance in the internal carotid, and then higher resistance in the

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external carotid. This can show how it can be sometimes difficult to figure out

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which one is which. You can't always just show that the more deep structure is one

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and the more superficial structure is the other.

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In the previous case, the deeper structure was the ICA.

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In this case, the more superficial structure is the ICA.

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So you sometimes need some ancillary things to help figure out which is which, and

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those waveforms are critical to doing that.