0:00

Moving on to anatomy. So once we get the images, it's important to know what

0:05

really constitutes a CTA runoff and what the patterns of

0:09

diseases can be

0:11

before we go into pathology.

0:13

Now the main vascular supply of the body is the aorta, and we start

0:17

off there. So the abdominal aortic branches include

0:22

the celiac artery branch in the abdomen,

0:25

which then divides into the common hepatic artery, the

0:29

splenic artery, and gives rise to the left gastric artery.

0:32

The next branch of the aorta is the superior mesenteric artery,

0:36

which provides vascular supply to majority of the bowel.

0:40

Then you have bilateral renal arteries, and then you have the inferior

0:44

mesenteric artery, which provides supply to the large bowel.

0:48

Now in addition, the aorta has more branches, such as the lumbar

0:52

arteries, the intercostal arteries, and the subcostal arteries, which we

0:56

don't particularly look at in detail when we're routinely interpreting these scans,

1:00

but they do play an important role when there's an occlusion, and they provide

1:03

collateral pathway.

1:05

I like to think of the

1:07

vascular supply to the lower extremity in terms of inflow,

1:11

outflow, and runoff. And so when we think about an inflow,

1:15

it's what brings in blood into the thigh.

1:19

So starting at the aorta at the level of the pelvis, the aorta then

1:22

bifurcates and gives rise to the common iliac artery.

1:26

The common iliac artery then again bifurcates to give rise to an internal iliac

1:30

artery, the branches of which we won't discuss today because for the

1:34

purpose of runoff, it's really the external iliac artery, which

1:37

is the artery of interest.

1:41

So once the common iliac artery has divided into the internal iliac and the

1:44

external iliac artery, the external iliac artery also gives

1:48

rise to the branches, such as the inferior epigastric

1:52

artery and the circumflex iliac artery.

1:55

The circumflex iliac runs along the iliac crest, whereas

1:59

the inferior epigastric artery runs across the rectal

2:03

sheath.

2:04

At the level of the inguinal ligament, which really is a line when you draw

2:08

between the pubic tubercle and the anterosuperior iliac spine,

2:13

the external iliac artery then continues and is called as the common

2:17

femoral artery. Another way to think of this transition, other than

2:21

the inguinal ligament, is after the takeoff of the inferior

2:24

epigastric and the circumflex arteries from the external iliac

2:28

artery.

2:30

Next, coming into the outflow.

2:33

Now the outflow consists of vessels that take the blood out of the

2:37

thighs, and so it includes the common femoral artery,

2:41

which then divides into the deep femoral artery.

2:44

Branches of the deep femoral artery include muscular perforators.

2:48

The other branch is the superficial femoral artery, which

2:52

then continues down all along the thigh.

2:55

The superficial femoral artery courses through the upper thigh in the adductor

2:59

compartment,

3:01

and the deep femoral artery forms an

3:05

important pathway of collaterals when there is occlusion of the superficial

3:09

femoral artery.

3:11

The next is outflow and runoff. And so while the

3:14

outflow includes the femoral popliteal arteries, the runoff includes all

3:18

of the calf arteries.

3:20

So at the level of the adductor hiatus, the superficial femoral artery

3:25

then becomes the popliteal artery, and it gives rise to the genicular

3:29

arteries, muscular, as well as cutaneous branches.

3:33

The popliteal artery then gives rise to the anterior tibial

3:36

artery, and then a short tibioperoneal trunk.

3:40

The tibioperoneal trunk then divides into a more medial posterior

3:44

tibial artery and peroneal artery, which runs between

3:48

the anterior and the posterior tibial arteries.

3:53

The popliteal artery is divided into three segments, the

3:57

P1, the P2, and the P3. The P1 extends from

4:01

the adductor hiatus to the proximal pole of the patella.

4:04

The P2 extends from the proximal pole of patella in the knee joint, and

4:08

then the P3 extends from the knee joint to the level of the

4:12

takeoff of the anterior tibial artery.

4:16

Some diseases have a predilection for certain vascular segments, and that's why

4:20

thinking of it in terms of inflow, outflow, and runoff is helpful.

4:24

For example, in diabetes with infrainguinal

4:27

involvement, in smoking, there's inflow involvement.

4:31

At the level of the ankle, the anterior tibial artery then continues as the

4:35

dorsalis pedis artery, and it dips down between the first two metacarpal

4:39

heads.

4:41

Most commonly, the posterior tibial artery continues as the

4:44

plantar artery and gives rise to the collateral pathway

4:48

to the feet when it anastomoses with branches of the

4:52

dorsalis pedis artery.

4:55

All right, so we're going to start off by looking at the normal anatomy of the

4:58

lower extremity. Now the vascular supply routinely imaged with

5:02

an aortofemoral runoff CT angiogram

5:06

begins with the abdominal aorta. And so as we're scrolling

5:10

down on this axial series of arterial phase images in

5:14

the thin slices, you can see right in the center here is the aorta, and it

5:18

gives off many branches. The first branch is the

5:22

celiac artery branch that then gives rise to this left

5:25

gastric artery that goes all the way up top, supplies the stomach.

5:30

Coming back down to the celiac artery, it

5:33

bifurcates, and it gives rise to this common hepatic artery and

5:37

the splenic artery. The splenic artery goes.

5:39

This one is a tortuous splenic artery, and it supplies the spleen.

5:44

The common hepatic artery then divides and gives rise to the

5:47

gastroduodenal artery that runs between the duodenum

5:51

and along the pancreas. And then the other

5:55

branch of it is the proper hepatic artery, which then

5:59

divides as well

6:02

Now here there's a little bit of a variation because instead of a

6:06

proper hepatic artery, this continues as just the right hepatic artery

6:10

and gives rise to the right hepatic arterial branches, whereas

6:14

the left hepatic artery is actually arising at the ostium of

6:18

that gastroduodenal artery and supplies that left hepatic

6:21

lobe.

6:23

After the celiac artery, as we're scrolling down, the next branch that

6:26

comes off is the superior mesenteric artery, which

6:30

supplies majority of the intestines.

6:33

The next set of arteries that arise from the aorta are bilateral renal arteries.

6:38

This patient has accessory arteries, so there are one and two left

6:42

renal arteries, and then an additional one and two right

6:45

renal arteries as well.

6:48

We need to look at these arterial vessels carefully because they

6:52

may be a clue to vascular disease elsewhere, or they may be

6:56

enlarged in the setting of a collateral

6:58

pathway. The last branch of the

7:02

aorta that comes off is the inferior mesenteric

7:06

artery above the bifurcation.

7:09

The additional smaller branches that we've discussed earlier include the

7:13

lumbar arteries, which form important collateral pathways.

7:17

As we're going down the abdominal aorta then bifurcates

7:20

into the common iliac arteries on both sides.

7:24

We're going to focus on one side, but know that there's a mirror

7:28

imaging and the same anatomy on the contralateral side.

7:31

So the common iliac artery then courses

7:35

down and gives rise to the internal iliac artery and the

7:39

external iliac artery.

7:41

Again, we're not going to discuss branches of the internal iliac artery.

7:44

It's beyond the scope of this, but we're going to focus on the external iliac

7:48

artery, which really provides the sole supply to the lower

7:51

extremity arteries.

7:53

The external iliac artery then courses down through the

7:57

pelvis, and its branches include this

8:01

inferior epigastric artery, which runs in the rectus sheath

8:04

right here as we're going up. The other branch of the

8:08

external iliac artery is this circumflex iliac artery

8:13

right here,

8:14

and that courses along the iliac crest.

8:18

Now, the transition point of the external iliac

8:22

artery is really the inguinal ligament.

8:26

And so right after it gives rise to the inferior epigastric and the

8:30

circumflex artery, it then continues as the common femoral

8:34

artery.

8:35

The common femoral artery then bifurcates, and it gives rise

8:39

to the deep or the profunda femoral artery, and then

8:43

the common femoral artery continues down in the thigh as the superficial

8:47

femoral artery. The deep femoral artery is

8:51

an important collateral pathway formation whenever there is

8:55

a significant stenosis of the superficial femoral artery.

8:59

The superficial femoral artery then courses through the upper

9:03

thigh

9:04

and courses all along the thigh

9:08

in the adductor compartment

9:11

all the way down.

9:13

And at the level of the adductor

9:17

hiatus in the mid to distal thigh, this then

9:20

continues as the popliteal artery.

9:24

The popliteal artery then continues behind the knee

9:28

joint

9:29

and between the segment between the adductor

9:34

hiatus to that proximal patellar pole.

9:37

So right here is the P1 segment of the popliteal artery.

9:41

Beyond the knee joint, it is the P2 segment,

9:45

and then it's the P3 segment. And so continuing

9:49

down this popliteal artery,

9:51

one of the more common branching patterns is that the anterior tibial

9:55

artery takes off. It courses laterally along the lateral

9:59

aspect of the thigh. And then we have the

10:02

tibioperoneal trunk,

10:05

which courses through the interosseous

10:09

membrane.

10:11

And then this tibial peroneal trunk then bifurcates

10:15

into the peroneal artery and then the posterior tibial artery.

10:19

So we have the anterior tibial artery, the peroneal

10:23

artery, and then the posterior tibial artery.

10:26

The anterior tibial artery courses along the lateral aspect

10:30

all along the calf and continues down to the ankle,

10:34

whereupon it continues as the dorsalis pedis artery as it

10:38

crosses the ankle into the foot

10:42

right here. That's the dorsalis pedis artery.

10:45

And then this dips down

10:48

and forms the collateral pathway to the feet between the first and second

10:51

metatarsal head. Going back more proximally

10:55

and looking at the arterial branches, we're not going to focus on pathology

10:59

right now, but just kind of looking at the anatomy in this section.

11:02

So you have the posterior tibial artery and the peroneal artery.

11:06

The peroneal artery has varying degrees of opacificaiton up until the foot,

11:11

and depending on if there are any variations.

11:13

And then the posterior tibial artery, as we course

11:17

down, it then gives rise

11:20

to at the level of the foot, continues

11:24

onwards and gives rise to the plantar arteries.

11:27

You have the medial and the lateral plantar arteries, and it forms a plantar

11:31

arch along with the dorsalis pedis artery and gives a collateral supply

11:35

to the feet. Now, we looked at all of this on an axial plane, and

11:39

just to show you on a coronal plane what this would look like.

11:43

So we have the aorta that then bifurcates into the common

11:47

iliac arteries on both sides. Then the common iliac artery bifurcates into the

11:51

external iliac and the internal iliac artery.

11:54

The external iliac artery courses in the front, kind of goes

11:58

over that inguinal canal, gives rise to the

12:01

superficial and the deep femoral arteries.

12:04

The superficial femoral artery then kind of goes down all the way in the

12:08

thigh and knee. When we're kind of describing pathologies, we say whether it's

12:12

in the proximal thigh, the mid-thigh, or the distal thigh

12:17

right here. And then as it's exiting that adductor hiatus, it becomes

12:21

the popliteal artery.

12:24

That's the popliteal artery right here.

12:29

And now we're going to use the different capabilities

12:32

of our PACS system and our reconstructions,

12:36

and we can make this into a maximum intensity projection.

12:40

So this is a coronal maximum intensity projection of that same

12:44

data set, and we can see that takeoff of that anterior tibial artery

12:48

and then the tibioperoneal trunk, which then divides into the peroneal artery and

12:52

the posterior tibial artery all the way down through the calf,

12:56

going down into the plantar arteries as an extension of the

13:00

posterior tibial artery. Whereas the anterior tibial

13:04

artery continues here,

13:08

flows to that tibia right here, and then becomes the dorsalis pedis

13:12

artery. The other reconstructions that we discussed were just

13:16

having a volume rendered image like this, which lays out the anatomy

13:20

really well, and you can see that whole aortofemoral branching pattern

13:24

in this rotating volume rendered image with bone

13:27

suppression.