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All right, so let's talk about aortic anatomy and more importantly, where and how

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to take the measurements.

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So the aorta is divided into three segments, the proximal, mid, and distal portion.

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So we systematically will evaluate each one.

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We will also evaluate the more proximal iliac arteries when we look at the aorta as

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well.

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So when we measure the aorta, we always want to make sure that the technique is up

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to snuff, because if you change how you measure the technique between exams, you're

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going to have inaccurate representation of what the native looks like, and then if

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there's aneurysmal change, how that changes from study to study.

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So you always want to measure outer wall to outer wall.

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We want to get transverse and longitudinal measurements.

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The predominant measurement that you're going to use is going to be those

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longitudinal, and it's importantly perpendicular to the axis, so you're not going

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to go just straight up and down on a longitudinal image.

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However, the transverse is important because sometimes you can have asymmetric

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appearances of a aorta, especially an aneurysm.

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And so if you have a bigger transverse dimension, you want to be able to report

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that as well. So here's some examples of what that measurement technique looks

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like. This is a really well-visualized aorta where we can see the proximal and the

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mid portion. And so you can see when we are taking the measurement here, we are at

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the outer layer of the vessel. So we're at the outer wall.

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Then we go all the way down to the outer wall.

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We're not just measuring the lumen itself, we're going outer to outer, and then

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we're getting that longitudinal measurement, and in this case, it was about 1.5 and

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1.6 centimeters, so normal thresholds there.

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And so finally, the big thing that we're looking for on these imaging studies is

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we're looking for aortic and iliac aneurysms.

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So we have some typical thresholds for that.

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For the abdominal aorta, it's greater than three centimeters.

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In the common iliac artery, there can be gender differences in terms of some of the

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thresholds for that. So some criteria will use 1.8 centimeters for men and 1.5

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centimeters for women. Some sites will use over 1.5 centimeters for all adults.

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But generally, these are not considered clinically significant until you hit at

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least two centimeters or so. In terms of repair, those thresholds are about 5.5

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centimeters for the abdominal aorta and around 3.5 centimeters for an iliac

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aneurysm, obviously depending on patient factors and their suitability for surgery

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or graft repair.