0:00

Let's take this 62-year-old man with a PSA of 6.4

0:04

who's had a prior negative biopsy and

0:07

elucidate the mysteries of PIRADS 2.

0:12

Now the patient has type 2 form of lobar

0:16

hyperplasia or BPH because it's the central

0:19

zone that's enlarged, pushing the urethra forward

0:22

and that's discussed in another vignette.

0:24

We could use our ellipsoid volume calculator

0:28

and give a length. A length would be

0:32

anteroposterior, times width, times height, and

0:36

multiply that by pi over 6 and get a volume.

0:39

This volume is clearly going to

0:40

be over 25 cc, so we have BPH.

0:44

We're here to discuss the PI-RADS designation,

0:48

so let's scroll up and down in the axial projection.

0:51

The peripheral zone is the wider

0:52

area around the outside, separated

0:55

from the TZ, or transitional zone,

0:57

well, by the surgical capsule.

1:00

So let's start with the TZ.

1:02

The TZ, we'll use it synonymously with

1:05

the central region of the prostate.

1:07

It contains the periurethral region

1:12

which we're going to lump together

1:14

with the TZ as part of the central zone.

1:17

And we're going to say, okay, in the

1:18

central region of the prostate,

1:21

what is the major criteria for a PI-RADS 2?

1:25

And the answer is multiple circumscribed or

1:29

slightly heterogeneous nodules but none that

1:32

deform the anatomic structures or architecture

1:36

of the central region or TZ of the prostate.

1:39

So, for instance, we've got round and bright right here,

1:43

very well circumscribed with a capsule.

1:46

Round and dark right here.

1:48

Slightly irregular, perhaps, right here.

1:50

Let's draw over this one,

1:52

because it's not perfectly round.

1:54

But it, it does have a

1:55

sharp edge to it, like that.

1:58

As opposed to, say, some charcoal smearing

2:01

that wipes away this glandular, nodular,

2:05

repetitive, redundant appearance of the TZ.

2:09

And that's gonna be the same in the

2:11

central region in the midline here.

2:14

And we're in the back of the

2:16

prostate, I believe, right here.

2:18

Let's see, yep, we're posterior.

2:20

And the same appearance is also seen here

2:22

with very little peripheral zone visualized.

2:24

So, again, repetitive, alternating areas of

2:27

hyperintensity, hypointensity, well encapsulated,

2:31

nodular, not crossing any boundaries.

2:34

These are the central region criteria,

2:36

or TZ criteria, for a score of 2,

2:40

which will leave us with a PI-RADS 2

2:42

as long as our peripheral zone is okay.

2:45

So how do we check our peripheral zone?

2:47

Pretty easy.

2:49

We look for diffusion restriction.

2:51

So rather than pull down all the diffusion

2:54

weighted images, I'm just gonna pull one

2:56

down, the one with the highest B value.

2:59

And let's look at the anatomy from apex to base.

3:04

And what we're looking for is something

3:06

really bright that corresponds to an

3:09

ugly, nodular, or aggressive mass with

3:12

mass effect in the peripheral zone.

3:14

Here's our peripheral zone.

3:16

Patient's had a biopsy, and you

3:18

can see the heterogeneity here.

3:20

From that biopsy, there's some

3:22

very faint hyperintensity on the

3:24

fusion-weighted image, but not much.

3:27

It should be really bright.

3:29

And I'll put up a B value that's a bit lower.

3:32

I'll blow it up.

3:33

You can see there was something a little

3:35

bit brighter there that faded away.

3:38

And that's exactly what benign lesions do.

3:41

Malignant lesions will get brighter

3:43

as you go to higher B values.

3:45

So this is a B value of around 50.

3:49

And In the middle, you have a B value

3:53

that is 1600, so nothing getting brighter.

3:58

Let's look at the ADC map, also at the high

4:02

B value number, and we do have an area of low

4:06

signal that implies decreased velocity, but

4:09

that is the site where our biopsy occurred.

4:15

Yes, there is some hyperintensity there,

4:17

corresponding to those loci, on the B1600

4:21

image, but it's not bright enough.

4:25

And there isn't a mass there.

4:26

If we go back to the T2, let's go back

4:29

and see the anatomic correlate of that.

4:32

Right there, nothing there.

4:34

Right there, nothing there.

4:36

So what are the things that can

4:38

produce some diffusion restriction?

4:40

Well changes in viscosity, like in an abscess.

4:43

That's clearly not the case.

4:44

Firmness, well that could be the case.

4:47

Firmness or desmoplasia from

4:49

scar tissue from a biopsy.

4:52

Hypercellularity with a paucity of cytoplasm.

4:55

That is not the case here, but that

4:57

occurs with very solid tumors, like

4:59

prostate cancer, like lymphoma.

5:02

And then necrotization, cell death,

5:05

necrosis in the brain, is another

5:07

cause of diffusion restriction.

5:10

That can occur with, say,

5:11

heroin toxicity in the brain.

5:14

So, this is an example of a prior biopsy site,

5:17

giving us a little bit of desmoplasia, a little

5:19

bit of high signal under the fusion-weighted

5:21

image in the peripheral zone, but not enough.

5:24

As you saw, it was a little

5:25

bright on the B50 image.

5:27

It's about the same brightness on the B1600 image.

5:31

Yes, it is picked up on the ADC map.

5:33

This was the site of the prior biopsy.

5:35

There's no anatomic correlate abnormality in

5:38

that locus on the axial T2-weighted image.

5:41

This is a PI-RADS 2.