0:01

Let's synthesize the American College

0:03

of Radiology's PI-RADS scoring system

0:06

1 through 5 using 3 parameters: diffusion

0:11

weighted imaging, T2, fast spin echo

0:13

imaging, and dynamic contrast-enhanced MRI.

0:17

It's no coincidence that DWI is first

0:21

because it trumps these other categories.

0:25

The PI-RADS 1 and the PI-RADS 5 are easy.

0:30

A PI-RADS 1 has no abnormality on any B

0:35

value, especially on the high B-value images.

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It doesn't really matter what the T2 and the DCE

0:43

MRI show, although typically there is no mass

0:47

like rounded lesion on the T2-weighted image.

0:51

Some enhancement in the peripheral zone will

0:53

be allowed as long as there is no B-value.

0:57

Diffusion restriction.

0:59

And the ADC map will also show

1:02

no hypointense mass like foci.

1:06

Now, Pirates 5, that's also easy.

1:10

You're going to have diffusion

1:12

restriction of a mass that is over 1.

1:17

5 centimeters, closer to 2 centimeters in size.

1:23

On the ADC map, you're going to have

1:25

a focal hypointensity that is over 1.

1:29

5 centimeters.

1:30

And on the DWI, you're going to have

1:33

hyperintensity on the high B-value numbers

1:37

that ascends greatly as the B-value starts

1:41

to go up and its size is also over 1.

1:45

5 centimeters.

1:46

So a PI-RADS 4 is also quite easy.

1:50

It's the exact same as a PI-RADS 5,

1:52

irrespective of what happens on the T2 or

1:55

the DCE MRI, except the lesion's smaller.

1:59

It's Under 1.5 centimeters

2:03

or 1.5 centimeters or less.

2:06

So it's a size criteria between a four and a five.

2:10

Let's go to a Pi-RADS two and a Pi-RADS two.

2:14

Once again, the DWI trumps everything.

2:17

You might see some indistinct hypointensity

2:20

on the parametric ADC map, however.

2:25

The high b-value DWI-acquired image is negative.

2:31

The T2-weighted image may show some linear

2:35

areas, or wedge-like areas, or non-mass-like

2:38

areas of signal hypointensity, but any

2:42

signal intensity here, and any mass-like

2:45

signal intensity, is trumped by a negative

2:50

DWI, as described here, a DWI score of 2.

2:54

And even the dynamic contrast-enhanced

2:56

image doesn't add a tremendous amount.

3:00

So you really have to have some substantive

3:04

DWI restriction and ADC map abnormalities to

3:09

start moving up into the higher categories.

3:13

PI-RADS 3, the tweener.

3:17

The PI-RADS 3 is when you

3:19

have an indeterminate DWI

3:23

or diffusion-weighted series of sequences.

3:26

What that means is that you have mild or

3:29

moderate hypointensity on the ADC map and iso-

3:33

intensity to mild hyperintensity as you go

3:37

from a b-value of 0 to 4 to 800 to 1200 to 1600.

3:43

So it goes up, but not as much as it goes up here.

3:46

It doesn't smack you right in the nose.

3:49

The T2-weighted peripheral

3:51

zone appearance can be any.

3:54

But if you are going to read a PI-RADS 4 in

3:57

this scenario, so let's say you have an

4:00

ill-defined mass, a DWI criteria of 3, if you get

4:04

early enhancement on the DCE MRI, it's now a 4.

4:09

So the tweener becomes a 4 based

4:11

on the DCE MRI and gets biopsy.

4:17

Early enhancement before anything

4:19

else, with or without a washout.

4:22

On the other hand, if it's non-enhancing, then

4:27

it's categorized as a 3 or minimally enhancing.

4:30

It's categorized as a 3, and now

4:33

you've got a challenging situation.

4:35

You've got a tweener lesion.

4:37

Fortunately, that doesn't happen very often.

4:39

Less than 5 to 10 percent of the time,

4:42

and you'll be reading PIRADS 3s.

4:44

Less and less frequently, as you

4:46

see more and more prostate MRI and

4:50

get comfortable with the modality.

4:52

So that's the synthesis of the PI-RADS

4:55

assessment using these three parameters

4:58

in the peripheral zone, the prostate.