0:00

What I'd like to do right now is sort of go through the

0:03

various pulse sequences that we perform for a lumbar

0:07

spine examination for DJD, and sort of give you an idea

0:11

of what I'm looking at and why I look at a particular

0:14

pulse sequence for that particular pathology.

0:18

Let's start initially with the scout image.

0:21

So the scout image is actually quite

0:23

important because in many cases,

0:27

the scout image is the only one that

0:30

is performed in the coronal plane.

0:33

I've written a paper on scoliosis and the impact of it

0:37

on degenerative change and the surgical

0:40

approach to degenerative change.

0:42

And if you're not paying attention to your sagittal

0:45

scans or your axial scans to look for scoliosis,

0:49

it's very hard to actually to identify it.

0:51

So I look at the scout image in part to look and see

0:55

whether there is scoliosis or whether there's

0:57

a straight spine in the coronal plane.

1:00

Since we do not, at Johns Hopkins, perform coronal scans

1:04

through the lumbar spine as part of our DJD protocol.

1:07

The other thing I'm looking at on the scout images,

1:11

which, as you can see, are in three planes, is I look at the kidneys.

1:14

I want to make sure that I'm not seeing any masses

1:17

in the kidneys that could be simulating

1:20

lumbar spine pain, back pain.

1:23

Certainly, for those people who have had kidney stones or

1:27

have had ureteral stones or issues with their bladder,

1:30

it can be referred to the spine.

1:32

So I look on the coronal, in particular, at the kidneys to

1:37

make sure that there are no masses associated with it.

1:39

I'm also looking down the pelvis.

1:41

This is particularly true with regard to women.

1:45

So the scout image is the only image that has the full

1:49

field of view from anterior to posterior, because we

1:54

use saturation pulses on the sagittal

1:58

lumbar spine examination.

2:00

So were you to identify a uterine

2:03

mass or an ovarian mass,

2:05

it's more likely that you will find it on the full field

2:08

of view scout images. So important to evaluate that,

2:12

as you can see here looking down in

2:15

the pelvis for pelvic pathology.

2:18

Sometimes, I also find that even on the scout images,

2:22

the bone marrow evaluation is quite nice.

2:25

And you may identify, for example,

2:28

that T8 bone met, that because the

2:33

field of view has been limited,

2:34

may not be evident on your sagittal

2:38

scans of the lumbosacral region,

2:40

where generally they're cutting it

2:42

off at around potentially T10.

2:44

So spend that extra time looking at the scout images.

2:49

So, as we said, the other pulse sequences for lumbar spine imaging

2:53

include the sagittal T1-weighted scan. I like the

2:56

sagittal T1-weighted scan to look at the bone marrow.

3:00

Most of the time the bone marrow is slightly

3:02

bright in signal intensity.

3:03

When you see something that's darker in signal intensity

3:06

in this background of bright signal intensity,

3:09

it suggests that there is a bone lesion there.

3:12

At the same time,

3:13

we know that the bright lesions on the T1-weighted

3:17

scan may be focal fat or hemangioma.

3:21

And I guess I should say that some people are now

3:25

calling hemangioma of the bone venous vascular

3:28

malformations of the bone, because

3:30

they're not really bone tumors.

3:33

The T1-weighted scan is also useful for, not only

3:37

identifying the disc pathology,

3:39

but the endplate pathology.

3:40

And we're talking a little bit about modic changes, which

3:44

are the signal intensity changes that you see associated

3:47

with degenerative change in the endplates.

3:50

So, this is our T1-weighted scan.

3:52

As you can see,

3:52

it goes pretty much from one side to the other side and

3:56

allows you a good view of the overall anatomy

4:00

of the lumbosacral region.

4:02

As you can see, 5, 4, 3, 2, 1, 12, 11,

4:05

we only go up to about T11

4:07

for our lumbosacral MRI scan.

4:10

The next pulse sequence is typically

4:12

the T2-weighted sequence.

4:14

This is a fast spin echo T2-weighted sequence.

4:17

It's quite nice in demonstrating the bright CSF around

4:20

the conus medullaris and allows you to

4:23

look at the caudaquina nerve root.

4:25

The negative about the

4:28

traditional fast spin echo T2-weighted scan is that you

4:31

have bright signal intensity fat associated with it,

4:35

both in the pelvis as well as the subcutaneous tissue.

4:39

So the dynamic range is not as broad as when we do the

4:44

STIR image. So this is the STIR sequence. Again,

4:47

bright CSF, so T2-weighted look to it.

4:51

However, the fat has been suppressed by that inversion pulse, and

4:56

that is in the subcutaneous fat, as well as in the abdominal fat.

5:02

As I mentioned previously,

5:04

the STIR image to me is the best sequence for

5:07

demonstrating bone edema. So on this sequence,

5:12

we see that there is a bright signal intensity

5:15

area in the L3 vertebra.

5:18

You also have some bright signal intensity

5:20

in the endplates at L4 and L5,

5:23

superior and inferior endplates that is

5:26

associated with degenerative changes.

5:30

And why don't we see this as well in the traditional

5:36

T2-weighted fast spin echo scan?

5:38

The reason is because predominantly

5:40

what's in the bone marrow is fat.

5:42

And since on fast spin echo T2-weighted scans,

5:44

the fat is bright,

5:46

we don't see those bone lesions nearly as well as when

5:49

we have suppressed the fat on the STIR sequence.

5:53

The next sequence to pull down is going to be

5:56

our axial T2-weighted scan.

5:59

As I said, at Johns Hopkins, these are going to be done straight

6:03

transaxial, contiguous three-millimeter slices,

6:06

and they are very good quality,

6:09

and they allow you a full range of the view from,

6:15

basically, the upper lumbar level region

6:19

down to the sacral region.

6:21

The negative of doing oblique plane T2-weighted scans is that

6:25

sometimes you will have a portion of the anatomy

6:28

that was not completely covered on the scans,

6:32

on the axial scans.

6:33

And that's why our preference is to go with straight

6:36

transaxial, contiguous slices. On these sequences,

6:41

as you can see, the disc material is generally dark.

6:45

The bone marrow, because it's a fast spin echo

6:47

T2-weighted scan with bright fat, is going

6:50

to be brighter than the disk,

6:52

and we see the thecal sac centrally with the

6:55

bright CSF sequence, pulse sequence, and

7:00

you'll also note that the facet joints are

7:03

going to be same as the bone marrow.

7:07

And you have the joint space, which I mentioned previously,

7:10

demonstrating some high signal

7:12

intensity on the right side.

7:14

So what I'm referring to is this higher signal intensity

7:17

area here in the facet joints, between the

7:20

superior and the inferior facet joint,

7:23

which is also well demonstrated

7:24

on your sagittal STIR image.

7:27

One other area that I want to highlight with regard to

7:34

discitis and osteomyelitis is paying some attention

7:38

to the psoas muscles on either side.

7:41

One of the indicators for inflammation with discitis and

7:44

osteomyelitis is bright signal intensity conversion

7:48

of the muscle on the T2-weighted scan.

7:51

And that may be something that you'll pick up

7:54

on even on a study for degenerative change.

7:58

So let's look at the final sequence of a traditional

8:03

degenerative disc disease protocol,

8:05

and that's the T1-weighted scan.

8:07

So on this T1-weighted scan,

8:09

they are performed in the exact same slice

8:12

locations as the axial T2-weighted scan,

8:15

so you can put them side by side.

8:18

Let's do a two-on-one and put the scan so you can look

8:25

back and forth between the T1-weighted scan with a dark CSF,

8:29

and the T2-weighted scans with a bright CSF

8:31

and compare them side to side for pathology.

8:36

And that is why we do ours in the same plane

8:40

for T1-weighted way and T2-weighted scan,

8:42

as opposed to doing one straight transaxial and the

8:45

other oblique to the discs.

8:48

On the T1-weighted sequences, in the axial plane,

8:52

you'll note that...

8:53

you'll see the neuroforamina fat very nicely,

8:56

which allows us to see the nerve roots coming out

9:00

of the neuroforamina and the dorsal root ganglion

9:02

highlighted very nicely. Here is the pedicle,

9:07

and therefore,

9:08

we're at the level where we're going to start seeing

9:10

the lateral recess in this axial plane.

9:15

So those are the sequences that are utilized for a

9:19

traditional non-operated back for low back pain.

9:24

Again, a sagittal scout image, sagittal T1-weighted,

9:29

sagittal T2-weighted, sagittal STIR image,

9:34

axial T2-weighted scan, and axial T1-weighted scan.