0:01

Our next section is positioning

0:02

technique and protocol.

0:06

Positioning is really important for breast MRI.

0:10

The positioning is prone, so the patient is

0:13

lying face down with her face in a face holder.

0:16

We use a dedicated breast coil.

0:19

The breasts are centered from

0:20

top to bottom and side to side.

0:23

The nipples should be straight

0:24

down and the breast pulled down.

0:27

So this is going to require some

0:30

cooperation between the patient and

0:32

the technologist to get it right.

0:34

The breast should not touch the coil,

0:36

if possible. Sometimes it's difficult

0:39

if the patient has larger breasts.

0:41

The arms can be positioned up or

0:43

down, depending on patient's comfort.

0:46

And we really want to try and make the patient

0:48

as comfortable as possible because it's

0:50

going to be really important that the patient

0:52

doesn't move at all during this exam.

0:57

This is a typical position, a diagram

0:59

of a patient positioned for the exam.

1:02

Or she's clothed for this model, but...

1:07

You can see that her face is in the face holder,

1:10

and she's in a relatively relaxed position.

1:13

There's a support

1:15

in the center of the chest that

1:16

sort of rests against the sternum.

1:18

It's padded, but it is somewhat uncomfortable.

1:22

And in this case, that patient's arms are

1:24

down, but they can also be up over her

1:26

head in the sort of Superman position.

1:30

We use a 1.5 or 3 Tesla MRI scanner, and

1:32

we do bilateral axial imaging.

1:35

And I think it's very important to

1:40

use an appropriate field of view.

1:42

And I just want to show you an example of...

1:46

appropriate and inappropriate field of view.

1:49

So this is one of our cases from our

1:53

institution, and you can see that the

1:55

majority of the field is occupied by the

1:59

breasts, right breast and left breast.

2:03

We can see that pectoralis muscle is included,

2:06

sternum is there, part of the heart, anterior

2:10

chest, and we know that as we would scroll

2:14

up and down through this exam, we'd be

2:17

able to see the axillary lymph nodes.

2:19

So that's important.

2:21

And internal mammary lymph nodes would be

2:23

here in the anterior portion of the chest.

2:25

We want to be able to see those

2:27

as well, but really we don't want

2:29

to include the rest of the chest.

2:31

And this is an example that we looked

2:34

at as an outside interpretation.

2:36

And you can see in this study, the

2:40

field of view includes the entire chest.

2:43

And we really don't want to be

2:45

looking at the vertebral bodies

2:47

or descending aorta for this exam.

2:49

It's not really part of the exam, and

2:51

we want the focus to be on the breasts.

2:53

And it does affect pixel size when

2:58

you have a larger field of view.

3:00

So we want to have an appropriate field

3:03

of view for best practice imaging.

3:06

This is our protocol at Hopkins.

3:09

We do a three-plane localizer:

3:12

axial, sagittal, and coronal,

3:17

and then the technologist uses the

3:19

localizer to prescribe the slices.

3:25

And then we do a T1-weighted

3:27

sequence with no fat saturation.

3:31

Then we run a STIR sequence, and

3:34

then a T1-weighted sequence with fat

3:37

saturation, and that's pre-contrast.

3:40

Then we give gadolinium-based IV contrast.

3:44

The power injector amount of contrast

3:47

we give is weight-based, and then we do

3:51

the same T1-weighted fat-saturated images

3:55

in a dynamic fashion after contrast.

3:58

We use three time points.

4:00

After we give the contrast, we

4:03

have a 30-second delay before we start

4:06

imaging, and then those three sets of

4:09

images are just performed consecutively.

4:13

Our post-processing includes subtraction images

4:16

and a maximum intensity projection image,

4:19

and that maximum intensity projection image

4:21

is based off of the first subtracted series.

4:26

I put diffusion-weighted imaging in

4:28

parentheses here because we don't, uh,

4:31

perform this as part of our routine protocol,

4:36

but I know a lot of other institutions do.

4:38

So I'm just adding that, but the images that

4:41

I'm going to be showing today, or the cases that

4:43

I'm going to be showing today do not include

4:46

DWI because it's not part of our protocol.

4:50

I wanted to run through this protocol

4:53

with you, and the images that I'm going

4:55

to be showing you are from the same slice,

4:59

just from different series.

5:01

So this is our T1 non-fat-saturated sequence.

5:05

You can see on this series, here's

5:08

the right breast and the left breast.

5:11

Our fatty tissue is quite bright, so high

5:17

signal intensity, whereas the breast tissue

5:20

itself is of relatively low signal intensity,

5:25

as are some of the other structures,

5:26

including the pectoralis muscle

5:29

sternum, and other muscular tissue.

5:33

This patient has some cysts, fluid-filled cysts,

5:36

and they are of low signal intensity on T1.

5:42

This is our STIR sequence, and you

5:44

can see that the fatty tissue is

5:46

suppressed, so it is dark on STIR.

5:49

And the things that are bright on STIR

5:52

images would be things that contain fluid.

5:57

So the fluid in the cysts is bright.

6:01

If we had edema in the breast tissue

6:03

or the skin, that would also be bright.

6:05

And this patient happens to have some

6:07

physiologic fluid, pleural fluid in the

6:10

right hemithorax, and that layers anteriorly

6:13

because the patient is lying prone.

6:15

And, uh, we can see that as bright on the STIR.

6:19

This is our T1-weighted fat-saturated image,

6:22

and you can see that the fat becomes darker.

6:25

The tissue is a little bit brighter than what

6:27

we were seeing on the T1 with no fat saturation.

6:31

Muscles are also a little bit bright.

6:34

And then this sequence is useful for looking

6:38

at areas that are intrinsically T1 bright.

6:42

So if we have proteinaceous fluid in the

6:45

ducts, and there's a little bit of that

6:48

here, you can see these little white dots.

6:51

Or proteinaceous fluid in a cyst.

6:54

Sometimes hematomas at certain

6:56

stages will be bright on T1 as well.

6:59

This is after administration of contrast,

7:01

our first post-contrast administration,

7:04

and you can see that some of the

7:06

background tissue is starting to enhance.

7:09

There are little foci of enhancement throughout.

7:13

And you can also see the blood vessels

7:15

are enhancing, and the heart is enhancing.

7:18

And you can see internal mammary

7:21

artery and vein well on these images.

7:26

This is the second post-contrast sequence,

7:29

and you can see the breast tissue is starting

7:31

to enhance a little bit more as we go along.

7:35

The blood vessels are still enhancing.

7:37

The heart is still bright.

7:39

And our third post-contrast sequence,

7:44

tissue enhancing a little bit more

7:47

and blood vessels are still bright.

7:50

In post-processing, we're going

7:51

to do some subtraction imaging.

7:54

So we're subtracting the pre

7:57

from the post-contrast images.

7:59

And what should be enhancing at this point are

8:03

just the areas that are enhancing with contrast.

8:05

So you can see all of these little

8:07

foci of enhancement in the background,

8:10

as well as the blood vessels.

8:14

Second post-contrast subtraction series,

8:19

and third post-contrast subtraction series.

8:22

And you can just see that the breast tissue

8:24

is filling in more and more with time.

8:28

This is the MIP or maximum

8:31

intensity projection image.

8:33

And this is a nice overview

8:34

of the entire breast.

8:36

Usually this can be turned or tumbled so that

8:40

you can look at it in different projections.

8:43

But this is the, you know,

8:44

sort of true axial projection.

8:46

You can see that there's a lot of

8:48

background parenchymal enhancement here.

8:51

All of this tissue is enhancing.

8:53

You get a nice overview of all the vessels and

8:57

some imaging of the axillary nodes as well.