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Positioning, Technique, Protocol for Breast MRI

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Our next section is positioning

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technique and protocol.

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Positioning is really important for breast MRI.

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The positioning is prone, so the patient is

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lying face down with her face in a face holder.

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We use a dedicated breast coil.

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The breasts are centered from

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top to bottom and side to side.

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The nipples should be straight

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down and the breast pulled down.

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So this is going to require some

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cooperation between the patient and

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the technologist to get it right.

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The breast should not touch the coil,

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if possible. Sometimes it's difficult

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if the patient has larger breasts.

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The arms can be positioned up or

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down, depending on patient's comfort.

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And we really want to try and make the patient

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as comfortable as possible because it's

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going to be really important that the patient

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doesn't move at all during this exam.

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This is a typical position, a diagram

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of a patient positioned for the exam.

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

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

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and she's in a relatively relaxed position.

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There's a support

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in the center of the chest that

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sort of rests against the sternum.

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It's padded, but it is somewhat uncomfortable.

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And in this case, that patient's arms are

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down, but they can also be up over her

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head in the sort of Superman position.

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We use a 1.5 or 3 Tesla MRI scanner, and

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we do bilateral axial imaging.

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And I think it's very important to

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use an appropriate field of view.

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

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appropriate and inappropriate field of view.

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So this is one of our cases from our

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institution, and you can see that the

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majority of the field is occupied by the

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breasts, right breast and left breast.

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We can see that pectoralis muscle is included,

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sternum is there, part of the heart, anterior

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chest, and we know that as we would scroll

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up and down through this exam, we'd be

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able to see the axillary lymph nodes.

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So that's important.

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And internal mammary lymph nodes would be

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here in the anterior portion of the chest.

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We want to be able to see those

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as well, but really we don't want

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to include the rest of the chest.

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And this is an example that we looked

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at as an outside interpretation.

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And you can see in this study, the

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field of view includes the entire chest.

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And we really don't want to be

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looking at the vertebral bodies

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or descending aorta for this exam.

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It's not really part of the exam, and

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we want the focus to be on the breasts.

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And it does affect pixel size when

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you have a larger field of view.

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So we want to have an appropriate field

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of view for best practice imaging.

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This is our protocol at Hopkins.

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We do a three-plane localizer:

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axial, sagittal, and coronal,

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and then the technologist uses the

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localizer to prescribe the slices.

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And then we do a T1-weighted

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sequence with no fat saturation.

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Then we run a STIR sequence, and

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then a T1-weighted sequence with fat

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saturation, and that's pre-contrast.

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Then we give gadolinium-based IV contrast.

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The power injector amount of contrast

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we give is weight-based, and then we do

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the same T1-weighted fat-saturated images

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in a dynamic fashion after contrast.

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We use three time points.

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After we give the contrast, we

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have a 30-second delay before we start

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imaging, and then those three sets of

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images are just performed consecutively.

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Our post-processing includes subtraction images

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and a maximum intensity projection image,

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and that maximum intensity projection image

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is based off of the first subtracted series.

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I put diffusion-weighted imaging in

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parentheses here because we don't, uh,

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perform this as part of our routine protocol,

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but I know a lot of other institutions do.

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

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

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I'm going to be showing today do not include

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DWI because it's not part of our protocol.

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I wanted to run through this protocol

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with you, and the images that I'm going

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to be showing you are from the same slice,

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just from different series.

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

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You can see on this series, here's

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the right breast and the left breast.

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Our fatty tissue is quite bright, so high

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signal intensity, whereas the breast tissue

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itself is of relatively low signal intensity,

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as are some of the other structures,

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including the pectoralis muscle

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sternum, and other muscular tissue.

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This patient has some cysts, fluid-filled cysts,

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and they are of low signal intensity on T1.

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This is our STIR sequence, and you

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can see that the fatty tissue is

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suppressed, so it is dark on STIR.

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And the things that are bright on STIR

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images would be things that contain fluid.

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So the fluid in the cysts is bright.

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If we had edema in the breast tissue

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or the skin, that would also be bright.

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And this patient happens to have some

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physiologic fluid, pleural fluid in the

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right hemithorax, and that layers anteriorly

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because the patient is lying prone.

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

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This is our T1-weighted fat-saturated image,

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and you can see that the fat becomes darker.

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The tissue is a little bit brighter than what

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we were seeing on the T1 with no fat saturation.

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Muscles are also a little bit bright.

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And then this sequence is useful for looking

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at areas that are intrinsically T1 bright.

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So if we have proteinaceous fluid in the

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ducts, and there's a little bit of that

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here, you can see these little white dots.

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Or proteinaceous fluid in a cyst.

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Sometimes hematomas at certain

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stages will be bright on T1 as well.

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This is after administration of contrast,

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our first post-contrast administration,

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and you can see that some of the

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background tissue is starting to enhance.

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There are little foci of enhancement throughout.

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And you can also see the blood vessels

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are enhancing, and the heart is enhancing.

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And you can see internal mammary

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artery and vein well on these images.

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This is the second post-contrast sequence,

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and you can see the breast tissue is starting

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to enhance a little bit more as we go along.

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The blood vessels are still enhancing.

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The heart is still bright.

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And our third post-contrast sequence,

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tissue enhancing a little bit more

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and blood vessels are still bright.

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In post-processing, we're going

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to do some subtraction imaging.

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So we're subtracting the pre

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from the post-contrast images.

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And what should be enhancing at this point are

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just the areas that are enhancing with contrast.

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So you can see all of these little

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foci of enhancement in the background,

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as well as the blood vessels.

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Second post-contrast subtraction series,

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and third post-contrast subtraction series.

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And you can just see that the breast tissue

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is filling in more and more with time.

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This is the MIP or maximum

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intensity projection image.

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And this is a nice overview

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of the entire breast.

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Usually this can be turned or tumbled so that

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you can look at it in different projections.

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But this is the, you know,

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sort of true axial projection.

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You can see that there's a lot of

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background parenchymal enhancement here.

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All of this tissue is enhancing.

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You get a nice overview of all the vessels and

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some imaging of the axillary nodes as well.

Report

Description

Faculty

Lisa Ann Mullen, MD

Assistant Professor; Breast Imaging Fellowship Director

Johns Hopkins Medicine

Tags

Women's Health

MRI

Breast

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