0:01

Let's talk about the actual protocol that

0:03

we're using for prostate MRI, and we're

0:06

going to have a diagnostic protocol

0:09

and screening protocol.

0:10

But before we get to that, let's begin

0:12

with the sensitive subject of preparation.

0:17

First, most people do not want to have an

0:21

endorectal coil placed into their buttocks,

0:24

and it is absolutely, positively unnecessary.

0:28

It is also unnecessary for a 3T

0:33

magnet to perform your prostate MRI.

0:36

In fact, there are some disadvantages.

0:39

Contrast resolution is not

0:41

as good at 3T as it is at 1.

0:44

5T, but the most important reason that

0:47

3T may not be as practical as the 1.

0:52

5T, besides the cost and the siting, etc.,

0:55

is that the artifacts from motion and pulsation

0:58

mismapping and susceptibility effects from air

1:01

in the rectum are worse at 3T than they are at 1.

1:04

5T.

1:06

Now granted, you might be able to get

1:07

a little bit better spatial resolution,

1:09

but it's not statistically relevant.

1:12

So a 1.5 Tesla

1:14

scanner is going to do a perfectly

1:15

fine job as long as you have the right

1:18

coil technology and you can do high

1:21

quality T2 fast spin echo 2D and 3D.

1:25

And you can do diffusion-weighted imaging

1:27

with B values going all the way up to 1600.

1:31

So the prep.

1:32

I like to have the patients NPO

1:34

with a soft diet for 24 hours.

1:38

I like to have them screened for

1:40

claustrophobia so I don't waste my

1:42

time trying to get them on the machine.

1:44

That is usually done by our ancillary personnel.

1:47

They go in feet first wherever possible.

1:50

That averts the possibility of

1:52

claustrophobia in many cases.

1:55

We use a Fleet's enema one to

1:56

three hours before arrival.

1:58

And then we ask them to go into the

2:00

bathroom and manually cleanse the rectum

2:02

in the restroom right before the exam.

2:07

Now, let's take a look at an axial

2:11

T2-weighted image, which is one

2:13

of the stalwarts of MR scanning.

2:17

And there'll be, there's a

2:18

five-point scoring system.

2:21

With T2 beginning at the top, the simple

2:23

T2 FASP and ECHO, which can be done with

2:26

either 2D technique, but if you're planning

2:29

on biopsy, with biopsy localization,

2:33

using some of these new software

2:34

algorithms, then you'll have to perform 3D.

2:38

Axial, T2, Fast Men Echo, with thin

2:42

section, and a 50 percent overlap.

2:45

Now right away on this T2-weighted image,

2:48

you see the anterior fibromuscular zone, and

2:50

we're going to get into anatomy separately,

2:52

so have no fear, but it illustrates an area,

2:55

an advantage of MRI, over ultrasound, and

2:59

over biopsy, and over physical examination.

3:02

Your finger's over here, right?

3:03

You got a tumor over here?

3:04

Not going to feel it.

3:06

Got a tumor over here?

3:07

Not going to see it.

3:08

You're not going to see it visually,

3:10

you're not going to see it with ultrasound.

3:12

So, visualizing apical tumors, which by the

3:14

way, not uncommon, huge advantage of MRI.

3:19

What's a potential disadvantage

3:21

on a T2-weighted image?

3:22

Or even on a T1-weighted image?

3:24

Well, bleeding.

3:26

If the patient has had a prior biopsy,

3:28

then bleeding can convolute the

3:30

image, but there are some techniques.

3:33

that will help you avert this pitfall,

3:35

and we'll talk about them separately.

3:39

Artifacts are another potential issue.

3:42

Now, artifacts can be eliminated, for the most

3:45

part, if you get rid of all the air in the rectum.

3:49

And the best way to do that is with

3:51

the prep I've given you previously.

3:54

Another potential pitfall

3:57

is the slices are too thick.

3:59

What slice thickness do I like to have?

4:01

Three or less, for 2D,

4:03

and 1.

4:04

2 or less for 3D.

4:09

Another potential pitfall, lower grades of

4:11

tumor that are less aggressive, Gleason's

4:15

2s, 3s, 4s, 5s, and tumors that are 2 or

4:18

maybe even 3 millimeters in size may not

4:21

be visualized with MRI, and especially

4:24

the ones that are small and aggressive.

4:27

Which, fortunately, are few and

4:29

far between, may only be seen with

4:32

DCE, Dynamic Contrast-Enhanced MRI.

4:37

And then finally, there are certain therapies

4:40

that may diminish the conspicuity of abnormalities

4:44

on contrast-enhanced MRI, which, by the way,

4:47

is the least important part of the exam.

4:50

One example of that would be hormone therapy.

4:53

The patient's on a testosterone-blocking therapy.

4:56

Then the intensity of enhancement on dynamic

5:00

contrast-enhanced MRI is going to be diminished.

5:03

So now that we have demonstrated the

5:06

very basic, easy to perform, any scanner

5:10

can do it with a high-quality coil.

5:12

This is a cardiac wraparound coil in this patient

5:15

showing the prostate in the axial projection

5:18

with, by the way, a tumor seen posteriorly.

5:22

Let's talk about the five-point

5:24

scoring system, and then in the next vignette, if

5:27

you have time, we'll actually show you the images.

5:30

So that includes the T2 fast bin echo, 2D or

5:33

3D, the diffusion-weighted image, and we're

5:37

going to look at the severity of diffusion by

5:40

comparing the signal on different B values all

5:43

the way from 0 to 1600, the ADC parametric map,

5:49

which is derived from the diffusion-weighted

5:52

image. And in most, but not all cases, the

5:55

dynamic contrast-enhanced MRI, we're going

5:58

to look at the intensity of enhancement, how

6:01

early it shows up, and whether it washes out.

6:05

And each slice, at each location, will

6:07

occur somewhere between 7 and 12 seconds.

6:11

So 7, 14, 21, 28, 35, and

6:15

you're going to keep going.

6:16

At the same locus throughout the prostate gland.

6:19

So you'll have different points on the time

6:21

activity curve just as you do in DCE MRI

6:25

elsewhere in the body, including the breast.

6:28

Then the fifth part of the scoring

6:30

system, which is hardly ever used, the

6:33

least valuable is spectroscopy, looking

6:36

for the absence of a citrate peak.

6:38

We're going to set that aside right

6:39

now because that's really, uh, a

6:41

separate discussion altogether.

6:43

So if you have time, tune in to the

6:45

vignette where we actually show you

6:48

the images from this scoring system.