0:00

Let's look at the axial T1-weighted or fat-

0:03

weighted appearance of the prostate on MR.

0:07

I've got the axial

0:09

T2-weighted up for a comparison.

0:11

The T1-weighted image is not meant to help

0:15

you evaluate the locus or to detect cancers

0:19

and to put them in their proper zone.

0:22

Its main function is to evaluate the periprostatic

0:26

fat and the neurovascular bundles at 5 o'clock

0:30

and 7 o'clock, which should be surrounded by fat.

0:34

So, let's scroll it a little bit.

0:36

And yeah, in some locations, it may be a little

0:39

tough to, to separate or distinguish them.

0:42

But there's no mass effect.

0:43

The fat is pretty symmetric on both sides.

0:46

Now, each vessel isn't going to be

0:48

exactly identical to the other side.

0:51

So if you're very OCD, then you're

0:53

going to, you're going to tend to

0:54

overcall invasion of this area.

0:57

But, you know, if you're going to call invasion,

0:59

you should have a mass that has capsular contact.

1:03

And almost always, that mass that has

1:04

capsular contact is somewhere between

1:07

one and a half to two centimeters long.

1:10

So if you simply see a little bit of asymmetry

1:12

there, and there's no mass present, that's silly.

1:16

Don't make that mistake.

1:18

So it's not going to be exactly identical

1:20

from side to side, and you'll notice that the

1:22

signal is a little darker on the left than the

1:24

right, and perhaps the flow rates are a little

1:26

faster on the left than the right, which brings

1:29

me to another role of the T1-weighted image.

1:33

We've talked about the importance of fat,

1:36

capsular invasion, including the pre-prostatic

1:39

space of Retzius, which we'll inspect, but

1:42

also the T1-weighted image, especially

1:45

if they're, they're a little bit thinner,

1:46

can help you look for nodes just like CT.

1:51

know, I see nodules on MRI all the time."

1:54

How do I know whether something

1:56

is a nodule or a node?

1:59

That takes a little bit of experience,

2:01

but not a tremendous amount.

2:03

There are a couple of ways.

2:04

First of all, nodes are not tubular.

2:08

So if the structure you're looking at

2:10

is tubular, like that one, not a node.

2:14

Nodes are going to be gray.

2:16

So if the structure that you're looking

2:18

at is very hyperintense or white,

2:20

like that, it's not going to be a node.

2:24

You know, it's probably going to be

2:25

flow, like that flow right there.

2:28

So signal intensity is also going to help you.

2:32

Nodes that are involved by prostate

2:36

metastasis tend to be gray, round,

2:39

plump, and have no fatty hila.

2:43

Size criteria helpful, about 1 centimeter.

2:48

But morphology, plumpness,

2:51

the absence of the fatty hila.

2:54

Isolation, a node that's 1.2 centimeters

2:56

that's round and gray,

2:59

sitting all by itself in the iliac

3:02

chain, that is a worrisome thing.

3:05

Now it's very helpful to go back and

3:07

forth between, say, the T1 and the T2,

3:10

and that's why I have the T2 up here.

3:12

For instance, this structure right

3:14

here is tubular, okay, that's easy.

3:17

But let's say it wasn't tubular.

3:18

Let's say it was circuitous, like a vessel,

3:21

and it didn't have a straight course.

3:23

So it's hard to tell that it

3:24

really is a linear structure.

3:25

Well, you look over here and you see this

3:27

round on the outside and gray on the inside?

3:30

That is slow flow in a vessel with

3:34

faster flow in the center of the vessel.

3:36

So that ring-like appearance

3:38

is another method you can use

3:41

that tells you you're not dealing with a node.

3:45

Now, don't forget to look at the, the

3:47

obturator chain nodes and the obturator

3:49

canal in a patient with prostate cancer.

3:53

You, you, you do have a, a, a complement

3:56

of an artery, a vein, and a nerve in there.

3:59

Sometimes you may have some small

4:01

nodes in there that are undersized,

4:02

maybe 3 or 4 millimeters at best.

4:05

But you shouldn't have anything that

4:06

approaches a centimeter in the obturator canal.

4:10

So that's how you use the T1-weighted image

4:12

to look for neurovascular bundle invasion,

4:15

anatomic capsular crossing into the surrounding

4:18

periprostatic fat, and looking for nodes.

4:21

Don't forget, the T1-weighted image is a

4:25

very reliable, helpful sequence in prostate

4:28

cancer to look for bone mets, right?

4:31

The fat is white, and prostate cancer tends

4:35

to be sclerotic; sclerosis is dark, so dark

4:39

against the background of white, especially with

4:42

round or irregular shape, easy in most cases

4:46

of metastatic prostate carcinoma to the bone.

4:50

That concludes our discussion of the axial

4:53

T1-weighted image on MR and its role.