0:00

Our initial focus will be on techniques for MR Imaging

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MR is the primary modality for evaluating patients

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who have a demyelinating disorder,

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and so we're going to dispense with discussion of CT.

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With respect to the MR Technique,

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the most commonly performed pulse sequences are

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going to be sagittal T1-weighted and sagittal

0:26

FLAIR scans, axial FLAIR scans,

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axial T2-weighted scans,

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as well as pre and post-gadolinium

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T1-weighted scans.

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I'll talk a little bit about the role of

0:38

susceptibility-weighted imaging in the evaluation

0:41

of patients with white matter disease.

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So here, we have a sagittal T1-weighted scan,

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axial T2-weighted scans.

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axial FLAIR scan.

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Remember that the axial FLAIR scan is demarcated

0:53

by dark CSF and bright signal intensity

0:58

in the abnormal white matter.

1:00

In addition,

1:01

as opposed to other ways of evaluating the brain,

1:05

sagittal scanning is utilized most effectively

1:09

with multiple sclerosis evaluation.

1:12

And because of the sagittal orientation,

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allows us to see the corpus callosum very well,

1:19

as well as off-midline images

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to see the white matter and the location of

1:23

white matter disease is very important.

1:26

In this off-midline sagittal FLAIR scan,

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one can see white matter lesions that

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are within the deep white matter,

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as well as in the subcortical

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regions of the brain,

1:39

an example of 7T FLAIR imaging.

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And with 7T FLAIR imaging,

1:46

we're able to understand multiple sclerosis

1:48

a little bit better in that it is indeed

1:51

a perivenular demyelinating disorder.

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The example to the right here shows areas

1:58

where the veins are present,

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and the demyelination is occurring

2:03

around those veins.

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This is in contradistinction from other

2:09

causes of white matter lesions,

2:11

such as migraines or neuromyelitis optica spectrum disorder,

2:17

which we'll talk about shortly.

2:18

So these perivenular techniques

2:21

in the FLAIR scan,

2:23

as well as what we'll see with

2:24

susceptibility weighted scan,

2:25

are very important for understanding both the

2:29

pathophysiology of multiple sclerosis,

2:31

as well as distinguishing it from other demyelinating disorders.

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While this is an example at 7T,

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you may also be able to see this at high

2:40

resolution on 3 Tesla imaging.

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This is an example of three-dimensional FLAIR imaging.

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These are usually performed in the

2:49

sagittal plane through the brain,

2:50

and then reconstructed either in an axial plane

2:53

or a coronal plane, or off-midline plane.

2:57

In this example, one sees

2:59

again, multiple sclerosis,

3:01

as opposed to the differential diagnosis

3:04

of multiple sclerosis,

3:05

which includes Sjögren's disease as well as lupus

3:09

as well as antiphospholipid syndrome.

3:12

Once again, with multiple sclerosis,

3:15

we see that perivenular demyelination.

3:19

You see a linear area on the axial scan with the

3:21

white matter abnormality seen around it.

3:24

If you reconstruct in a sagittal plane,

3:27

once again, you see the blood vessel,

3:28

the vein in the center,

3:31

with the demyelination around it.

3:36

And this is a coronal plane where,

3:38

once again,

3:39

the vein is in the center and the demyelination,

3:42

shown as the bright signal intensity,

3:45

is seen around that vein.

3:47

Contrast that with the differential diagnosis

3:50

where there is no vein in these other entities,

3:53

and that, again,

3:54

is helpful in the differential diagnosis.

3:58

Some people are

3:59

employing post-gadolinium FLAIR imaging

4:02

in order to detect enhancement of the leptomeninges,

4:07

superficial to cortical white matter lesions.

4:11

So, it's a little bit of a paradox that I'm talking

4:14

about cortical white matter lesions,

4:16

but we now know that multiple sclerosis is

4:20

a disease not just of the white matter,

4:22

but also of the gray matter.

4:23

When one has superficial lesions in the cortex,

4:27

you may see leptomeningeal enhancement

4:30

superficial to the cortical lesion.

4:33

In this example,

4:34

one can see that on the post-gadolinium FLAIR imaging,

4:39

you see this bright area in the cortex,

4:42

which extends to this superficial layer of the Pia.

4:46

And in the subarachnoid space and subpial

4:49

cortex you see below here,

4:51

there is indeed inflammatory process going on in

4:54

the superficial meninges in the subarachnoid

4:57

space adjacent to the cortex,

4:59

where demyelination has occurred,

5:01

and all of these darker cells are the inflammatory

5:04

cells that are occurring in the leptomeninges.

5:08

There have been recommended protocols that one can

5:12

follow from various large multiple sclerosis

5:16

societies, and this is one of them,

5:19

from the consortium of MS Center Task force

5:22

for a standardized MRI protocol.

5:24

And this is largely what is utilized

5:28

in the United States.

5:29

So, the field strength should

5:31

be of adequate quality.

5:32

We usually use 1.5 or 3 Tesla scanning,

5:36

and we're usually using axial oblique sections,

5:39

and we cover the entire brain with

5:43

sections that are 3 mm or less.

5:46

And the core sequences that are described here

5:50

include 3D sagittal FLAIR imaging,

5:54

3D T2-weighted scans in an axial plane, generally,

5:58

2D axial diffusion-weighted imaging.

6:00

Now, diffusion-weighted imaging is interesting

6:02

in multiple sclerosis.

6:04

We use diffusion-weighted imaging as another

6:07

attempt to determine the activity of disease.

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Because multiple sclerosis is a polyphasic disease,

6:14

it has different aged plaques,

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and one way of determining an acute plaque is by

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whether or not it is showing restricted diffusion.

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We then have pre and post-gadolinium enhanced scans,

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sometimes with the FLAIR,

6:29

sometimes with T1-weighted scans.

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You see here, 3D flash T1-weighted

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post-gadolinium enhanced scans.

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Again, this is because in order to determine the

6:39

activity of a multiple sclerosis plaque,

6:41

we also look at whether or not it is

6:43

showing gadolinium enhancement,

6:45

active blood-brain barrier breakdown.

6:49

Optional sequences include proton

6:53

density signal intensity sequences

6:58

or doing the pre-gadolinium

7:00

in a T1-weighted scan, instead of sagittal FLAIR

7:03

and the susceptibility-weighted imaging,

7:05

which I'll talk about shortly.

7:07

This is another group of multiple sclerosis centers,

7:10

and these are follow-up of MS plaques.

7:13

And you can see, once again, that the core sequences

7:16

that are recommended generally

7:19

are 3D sequences with FLAIR,

7:22

2D T2-weighted scans,

7:27

or 3D sequences,

7:29

the DWI,

7:30

and then your gradient echo scans before

7:35

and / or after contrast-enhanced images.

7:40

So, if you look at the MS partners' technique

7:44

and look at all the sequences

7:46

that they're recommending,

7:47

they include the 3D sagittal T1,

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axial T1 to look at pre and post-gadolinium,

7:53

diffusion-weighted scans,

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FLAIR scans,

7:55

axial proton density,

7:58

and T2-weighted scans.

7:59

This if for the volumetric evaluation of plaque volume,

8:04

post-gadolinium enhanced scans,

8:06

and then you have your various 3D

8:08

and reconstructed 2D FLAIR scans.

8:12

The key ones are the 3D FLAIR that can be

8:17

reconstructed in any plane,

8:18

the T2-weighted scan,

8:21

and the pre and post-gadolinium enhanced scans

8:23

in order to see enhancing plaques.

8:27

With regard to scanning of the spine,

8:31

most sequences include sagittal T1-weighted,

8:34

sagittal T2-weighted, and sagittal STIR sequences

8:38

with thin section images through the spinal cord,

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followed by axial T2-weighted scans

8:44

and gradient echo scans.

8:47

And I want to highlight this,

8:48

that although the MS

8:49

partner's Advanced technology and Health Solutions

8:53

MS path spine sequences has gradient echo scan

8:57

as an option, I want to highly recommend

8:59

that you utilize this because on some cases,

9:02

the gradient echo scan shows the demyelination in

9:05

the spinal cord in a superior fashion

9:08

to the T2-weighted scan.

9:09

And of course,

9:10

we do post-gadolinium T1-weighted scans

9:13

to look for enhancing plaques.

9:15

Here is the gradient echo sequence on the right

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hand side and the fast spin echo T2-weighted sequence

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on the left-hand side.

9:23

And this is a nice example sample of how sometimes

9:26

the gradient echo scan shows the plaques in a more

9:31

elegant way than the regular fast spin echo

9:34

T2-weighted sequence.

9:36

So just to make sure we're all

9:37

looking at the same thing,

9:38

here is a plaque along the lateral right side of

9:42

the spinal cord on the T2-weighted

9:44

fast spin echo scan.

9:45

Notice how well you see that or how much better

9:48

you see that on the gradient echo.

9:49

And the same is true in this posterior column

9:52

plaque on the left side,

9:54

compared to the fast spin echo sequence.

9:57

So this is gradient echo here.

10:00

And these are the fast spin echo.

10:04

And in my opinion,

10:05

gradient echo sometimes is very valuable.