0:00

This is a 51-year-old.

0:02

He actually had a prostate MRI at

0:04

another institution north of here,

0:06

an esteemed and respected institution.

0:08

But for some reason, they were not

0:10

able to get a B value on the diffusion

0:13

image of greater than 1,000.

0:15

So the diffusion image on this

0:17

case was non-complementary and not

0:20

supportive of the diagnosis of cancer.

0:23

So the patient had a rescan a week later.

0:26

His PSA is

0:27

8.5 nanograms per mL.

0:31

Let's look at his axial T2.

0:33

There is a nodule in the left,

0:36

PZP and PZM towards the midline.

0:39

It's bulging the capsule a little bit.

0:43

The peripheral zone on the right is

0:44

fairly dark but non-mass-like, very ill.

0:48

Ill-defined.

0:49

The one on the left is more nodular and mass-like.

0:53

So let's turn our attention to the

0:55

diffusion image performed at 1.5 T.

0:58

The original study a week

0:59

earlier was performed at

1:02

27 00:01:02,800 --> 00:01:04,360 5 Tesla.

1:05

And there is an area of diffusion restriction.

1:08

It's bright.

1:09

We could window it very tightly.

1:11

But it's not all that impressive.

1:12

This is a B value of 1200.

1:17

So what I want to illustrate in

1:19

this case, and let's go back a little

1:20

bit to see the lower B values.

1:22

Here's a lower B value.

1:24

This is a B0, actually.

1:26

And here is the B1200.

1:29

So there is diffusion restriction in the PZM.

1:33

But look at the ADC map.

1:36

The ADC map is so much clearer.

1:40

So when, when you have a situation where your

1:43

diffusion images are either inconsequential,

1:47

or not complementary, or not supportive,

1:50

or there's a potential technical issue, or

1:52

your B value isn't as high. The parametric

1:55

images are actually the most sensitive for

1:58

picking up areas of confluent, mass-like

2:02

diffusion restriction, these parametric maps.

2:05

And this one does so just beautifully.

2:08

Now, what are some other causes

2:11

for diffusion restriction failure?

2:14

We've talked about them in other

2:15

vignettes, but it's worth revisiting.

2:17

If your spatial resolution isn't good enough,

2:19

you're gonna, you're not gonna pick up

2:21

any tumors that are below 5, and if

2:24

your spatial resolution is really

2:25

poor, you're not going to pick up any

2:27

diffusion restriction under a centimeter.

2:30

Remember that mucinous tumors don't

2:32

restrict, but they're rare, but benign.

2:35

Very hypercellular, benign abnormalities

2:39

in the central portion of the prostate,

2:40

in the TZ, these will diffusion restrict.

2:44

So this is going to give you a false positive

2:46

if you rely on diffusion in the central gland.

2:50

But you are going to rely on diffusion

2:52

very heavily in the peripheral gland.

2:54

We've talked about abscesses.

2:56

They can give you a false positive and a

2:58

vanilla donut sign, as opposed to tumor,

3:00

which gives you the chocolate donut sign,

3:02

and that's discussed in another vignette.

3:05

And then low-grade tumors, non-aggressive

3:07

tumors, Gleason 6s and 5s, may not give

3:11

you much diffusion restriction at all.

3:13

And there are some technical factors like

3:15

hyperinflation of balloon and air in the

3:17

rectum that may affect your diffusion.

3:19

This case illustrates just how

3:21

valuable the ADC map can be.

3:24

Clearly, a left PZM, PZP lesion, well under 1.

3:29

5 centimeters in size, illustrating a

3:32

classic PI-RADS 4 with diffusion restriction,

3:36

major criteria, and supportive abnormality

3:39

on the T2-weighted images of mass.

3:42

By the way, there is absolutely no

3:44

diffusion restriction on the right.

3:47

Where we saw that charcoal-like, dark,

3:50

crescent eric area in the peripheral zone.

3:52

There it is again.

3:54

In fact, it's white on the ADC map, whereas it

3:57

should be black on the ADC map if it's a tumor.

4:00

So the ADC map really is complementary

4:03

and supportive in giving you a concrete

4:06

non-diagnosis in the right gland and a

4:08

positive diagnosis in the left gland.