0:00

This next scan is atherosclerosis in the runoff

0:04

arteries, particularly in the setting of calcified

0:08

plaque. So as usual, I have one screen which has the

0:12

non-contrast images, and then the other screen which has the arterial

0:15

phase images. They're both synced up, so it's easy when I'm scrolling

0:19

on both sides to parse through calcifications as well

0:23

as to look at

0:26

the presence of calcified plaque versus contrast.

0:29

Now, this patient has had a

0:32

ligation of their

0:35

peroneal artery, and so the non-contrast images are

0:39

also going to be helpful in identifying

0:43

surgical material versus contrast.

0:47

So we're going to just kind of getting the lay of the land here,

0:51

looking at that left lower extremity artery on both sides.

0:54

You can see,

0:56

as I'm scrolling down, that these are the surgical clips in that

1:00

region of that peroneal artery on the left side.

1:03

And

1:04

as you're scrolling down,

1:07

there are some calcifications

1:10

along the

1:12

arteries, but they're not that extensive.

1:17

All right. Now we're going to focus on just that arterial phase images, and we're

1:20

going to go in our usual pattern. So all the way starting from the

1:24

aorta, there are severe aortic atherosclerosis

1:28

on both sides, as well as involving both the common

1:32

iliac arteries, the internal iliac, and the external iliac arteries,

1:36

but there's only

1:38

mild stenosis and no significant stenosis on either side.

1:43

Kind of going over

1:45

to our right side then, and scrolling all the way

1:49

from the top down,

1:52

we have mild stenosis of this common femoral and the superficial

1:56

femoral, as well as the deep femoral or the profunda femoral

1:59

arteries as we're scrolling down.

2:02

There still only remains mild stenosis of the superficial femoral

2:06

artery.

2:08

And as I'm going down here, still mild stenosis

2:12

of that

2:13

popliteal artery, and then looking at the anterior tibial artery here.

2:18

Because of the high-resolution scan, and this was done on

2:23

a photon counting scanner, we can see that looking

2:26

at just the anterior tibial

2:30

artery,

2:32

there's only mild stenosis. And even though this is a thin slice

2:35

series, so

2:37

one by 0.8 millimeter slice thickness, we're able to

2:41

kind of ascertain the degree of stenosis.

2:45

Now, if however, I was looking at both

2:48

the small field of view image reconstruction,

2:52

and this is the pure lumen, which means we've removed the

2:56

calcium out and we're only highlighting

2:59

voxels which have iodine in them,

3:03

and we're comparing 0.4 millimeter slice thickness

3:06

versus the one millimeter slice thickness, and we're going all the way

3:10

down to that level of interest and looking at that anterior

3:14

tibial artery.

3:16

We can see how once I scroll it up, that there's a

3:20

significant difference

3:23

even at similar wide window width and levels in

3:27

the appearance and the spatial resolution of these

3:31

0.4 millimeter slice thickness

3:34

recons. You can see here, because this is just a pure lumen where

3:38

only the iodine images are available,

3:41

that you can see all of this is still that contrast column, whereas this

3:45

part, which is not seen on the pure lumen images, is calcified plaque, which

3:49

has been subtracted off, or there's been material decomposition, and

3:53

it's not seen on these images. You can see that also on the bone,

3:57

that calcium is not visible. So just to kind of take another look

4:01

at the anterior tibial artery on this side

4:05

as we're scrolling down and kind of getting to that level.

4:08

So this was the area that we really kind of wanted to highlight and make

4:12

sure that this was only a mild degree of stenosis.

4:15

Looking at this in that pure lumen view, you can see that one

4:19

might be tempted to say this was moderate stenosis or up to 50%

4:22

stenosis, but acknowledging that there's blooming and that blooming can

4:26

be significantly reduced on these sharp kernel,

4:30

high-res images, that a lot of this

4:34

is just the contrast.

4:37

And so really, there's only a mild degree of stenosis.

4:41

We're now going to go back, and we're going to look at that left lower

4:44

extremity.

4:46

So looking at that left lower extremity right here,

4:50

we're going to go back, and we're going to look at both that non-con and arterial

4:54

phase scans together.

4:57

And looking at that left common iliac artery, going into that left

5:00

external iliac artery, only a mild degree of stenosis

5:05

as well. And then looking at this common femoral artery

5:09

right here. And as we come over here, I think it's really tempting to say

5:13

if one were only looking at these arterial phase images, that that

5:17

lumen is quite patent. So if someone were to just show me these images,

5:21

I would think that all of this actually could look like

5:24

just patent lumen, which means there's only a mild degree of

5:28

stenosis. However, if you look at this side by side

5:32

with the non-contrast images, I think it's easy to say that this

5:36

is a coral reef appearance, on coral reef

5:40

plaque in this vessel, which means that there's this low-density

5:44

plaque which has an isoattenuating appearance to

5:48

contrast. And so really kind of parsing this blob of

5:52

plaque, so that would be coinciding to this blob of

5:55

plaque from this adjacent contrast, is extremely

5:59

difficult And so here we can say that there's

6:02

definitely a severe amount of stenosis, because really only

6:06

this part of the lumen is what is actually

6:10

showing contrast opacification in this common

6:14

femoral artery.

6:15

Moving down and looking at the remainder of the

6:19

vessel. So as we're kind of going down and looking at the

6:23

superficial femoral artery,

6:26

we can see that there's only a mild amount of

6:30

stenosis in this superficial femoral artery as we're scrolling down.

6:34

Going down this artery here, still just a mild amount of

6:37

stenosis.

6:40

Going all the way down, and then over here, there's

6:44

quite a bit of plaque here. So you can see that there's a significant

6:48

amount of plaque

6:50

even on this non-contrast image here.

6:52

So there's severe stenosis of this superficial

6:57

femoral artery as well because you only have this much amount of

7:01

contrast that's available in that contrast column in this

7:05

distal superficial femoral artery.

7:07

Again, right here, you can see that looking at this degree of

7:10

stenosis is much easier because there's a lot of component of

7:14

non-calcified plaque here, as opposed to all of the other areas where it was

7:18

so calcified, isodense, there's blooming artifacts.

7:21

So multiple

7:22

cheeseholes of failure

7:25

that can limit your diagnostic confidence.

7:28

Again, there's severe stenosis here of this popliteal artery,

7:33

and continuous severe stenosis here with this coral reef

7:37

appearance of the popliteal artery.

7:40

And then as we're going down,

7:43

and as this artery is going to branch out,

7:48

we're going to see this tibial peroneal trunk and how much of

7:52

that tibial peroneal trunk is actually the calcified plaque suggesting

7:56

severe stenosis. And then these are clips suggesting that that peroneal artery has

8:00

been ligated. We're now going to focus on the anterior

8:04

tibial artery.

8:06

And looking at it kind of going down all the way and

8:10

following this contrast column,

8:12

you can see over here that it's significantly narrow.

8:18

And then at this point,

8:20

there's a segment that is just not visualized and

8:24

is not opacified. So

8:28

there's another one right here where you don't really see it opacifying distally,

8:32

but you can see that the rest of the arteries are opacifying.

8:35

So it's not a question of outrunning your bolus, because the bolus did reach and

8:39

the rest of the arteries in the limbs are opacified.

8:43

This is indeed

8:46

multifocal occlusions with distal kind of reconstitution

8:50

of this dorsalis pedis artery via these collaterals from

8:53

the posterior tibial artery right here.

8:56

And so that's that reconstituted dorsalis pedis artery.

9:00

I want to go back and show you those photon counting or spectral

9:05

reconstructions and real-world application in this

9:09

side of the extremity as well. So now on this side of the

9:13

screen, we're going to put the pure lumen view, whereas this

9:17

side of the screen has an arterial view image.

9:21

And everything that's suppressed here is basically calcium, and only the

9:25

iodine is supposed to be highlighted.

9:27

So as we're scrolling down,

9:29

when you compare this to the non-contrast,

9:33

so

9:35

let's put up

9:37

the non-contrast right here, the arterial phase right

9:40

here, and then just that left lower extremity right here.

9:45

And we'll scroll all of them out kind of together.

9:49

So non-contrast arterial, and then the pure lumen,

9:53

where we're only seeing the iodinated contrast right here.

9:58

So when we're doing this, we come again to this area where there's

10:02

that almost coral reefy plaque in the common femoral

10:06

artery right here. You can see that everything here that's highlighted

10:10

is just the contrast, and the rest of it was plaque.

10:13

So you can see here why you may have thought that this might be moderate or

10:17

severe,

10:19

that this was severe. In fact, this was probably just about

10:23

moderate stenosis of that common femoral artery right here.

10:26

Because all of this is still quite a bit of contrast lumen.

10:29

That's probably only about really barely

10:33

borderline moderate stenosis. So it really kind of improved my

10:37

diagnostic confidence in saying that that common femoral artery is only mildly

10:41

stenotic.

10:43

As you're going down here, looking at that superficial femoral artery, again, you

10:46

can see how well that calcified plaque

10:51

is basically subtracted out of that image, or not subtracted

10:55

out, but by material decomposition, and it's

11:00

out.

11:02

So as we're kind of going down into the distal

11:05

tie and looking at it again over here,

11:09

so comparing our arterial phase versus our

11:14

iodine lumen phase, you can see that there's a lot more confidence in

11:18

knowing how much of that plaque was actually blooming.

11:21

And even if I widen the window, then you can actually see that true extent of

11:25

how much of this was really the plaque, whereas how much of this is really that

11:29

contrast opacified vessel on the side.

11:32

All right. Moving down again, all the way down to that popliteal artery.

11:36

We had that non-calcified plaque resulting in severe stenosis right here.

11:42

So you can see that again,

11:44

where you can barely kind of see a lumen over here, and then

11:48

right here as well. So kind of multifocal occlusions of that popliteal

11:52

artery.

11:53

And then looking at the branches of the runoff.

11:57

So here again, we're going to focus on that anterior tibial artery right

12:01

here, severe stenosis, and then you're going to start losing

12:05

that vessel shortly from that known occlusion that we already know

12:09

from looking at the CTA earlier.

12:11

And then even distally right here

12:15

is when we kind of lose that vessel, and we know that it's occluded.

12:18

And then we start seeing that dorsalis pedis again, which is

12:22

reconstituted from these collateral arteries right here.

12:25

And they're really so much more easier to see the collaterals on

12:30

these high-res images, on these kind of iodine-only maps

12:34

or iodine-only images, or pure lumen images,

12:37

or iodine map images, whichever is the

12:41

platform that you're using, you could call it.

12:44

Another reconstruction that we didn't really discuss about, but if you

12:48

don't have a spectral CT acquisition and

12:52

you have a non-contrast, what you can do to increase your

12:56

diagnostic certainty, especially in areas of calcified plaque, is

13:00

subtraction imaging. So

13:03

at the scanner or at the PACS, if you have the capability, you basically

13:07

subtract out the non-contrast from the arterial phase images.

13:11

And you can see here, this is like

13:13

the calcified plaque has all been subtracted out, and what you're really seeing is

13:16

just opacified lumen. And if I was to go back to

13:20

that area of that common femoral artery, you can see right here how

13:24

this correlates pretty well to this

13:28

pure lumen imaging

13:31

in that common femoral artery plaque, which we had seen right here.

13:35

So all of these are really just to show you those different image datasets that you

13:39

can use to problem solve. And they're especially useful when the

13:43

plaque is extremely dense and extremely calcified.