0:00

What are the pulse sequences that are

0:03

utilized for the evaluation of

0:05

degenerative disease of the spine?

0:07

Well, there is some variation depending upon

0:10

whether we're dealing with the lumbar,

0:11

cervical, or thoracic spine.

0:13

All of these three areas will probably

0:17

get a sagittal T1-weighted scan with

0:20

thin sections to go basically from the

0:23

foramina to the foramina in the sagittal plane

0:26

or extend a little bit beyond that.

0:29

T2-weighted scans with fast spin echo

0:32

technique are also performed in the sagittal plane.

0:35

STIR imaging is very helpful.

0:37

It's the best sequence for us

0:39

to identify bone edema,

0:41

and that is generally performed,

0:44

however, only in the sagittal plane.

0:47

For the lumbar spine,

0:48

we combine that with axial T1-weighted scans

0:52

and axial T2-weighted scans.

0:54

Now, how you perform those axial scans

0:58

will vary from center to center.

1:00

We at Johns Hopkins do 3 mm contiguous slice scans

1:06

in the axial T1-weighted and

1:09

T2-weighted sequences,

1:10

we do not angle to the disc.

1:13

That is different.

1:15

Some other centers will perform either

1:19

the T1-weighted or the T2-weighted

1:21

scans in an oblique plane angled to the

1:23

disc in order to see the herniations

1:26

and the disc pathology better.

1:28

We at Johns Hopkins have the axial and

1:31

the T1-weighted and the T2-weighted

1:33

scans together at the same location.

1:35

So, we can look back and forth between

1:37

T1 and T2-weighted scans,

1:39

and we recreate those oblique planes,

1:43

if you will, in our heads.

1:44

Or you could do it with doing

1:46

multiplanar reconstructions.

1:48

However, with 3 mm thick slices,

1:50

there is some degradation.

1:52

So that's going to be up to you,

1:54

how you want to perform them.

1:55

In the cervical spine,

1:57

instead of T1-weighted imaging,

1:59

we add a 3dFT gradient echo scan,

2:04

usually with a five degree flip angle,

2:06

which allows the CSF to be bright.

2:09

These 3dFT gradient echo scans are

2:12

generally performed at 1 to 1.5 mm 3D volume imaging,

2:17

and that allows you, again,

2:18

to have thinner sections through the

2:20

smaller anatomy of the cervical spine

2:23

and also allows you, if you need to,

2:25

to perform multiplanar reconstructions.

2:27

We generally don't do that.

2:29

We generally just rely on the

2:31

3dFT axial scans.

2:33

Now, why are we using a gradient echo scan

2:36

as opposed to, for example,

2:37

a pulse sequence like CISS?

2:40

Here's a key factor that I find

2:43

with the gradient echo scans,

2:45

and that is that it is the best pulse

2:47

sequence to distinguish between disc and

2:51

osteophyte. On gradient echo scans,

2:54

the disc is going to be bright

2:56

in signal intensity,

2:58

and the osteophytes are going to be dark.

3:00

Unfortunately, on spin echo T2-weighted scans,

3:04

both osteophytes and usually

3:06

the disc, are both dark,

3:08

which makes it hard for you to

3:09

distinguish between a disc and an osteophyte.

3:12

And I will get into one of my pet peeves,

3:14

which is the importance of

3:16

distinguishing between disc and

3:18

osteophyte in the cervical spine and not

3:21

using the term disc osteophyte complex,

3:25

which I think is basically giving

3:29

up and using an incorrect term.

3:32

In the thoracic spine,

3:34

we do not perform these 3dFT gradient echo scans.

3:37

We just go with axial contiguous

3:39

T2-weighted scans.

3:42

The CISS sequence,

3:43

which is a highly T2-weighted pulse

3:46

sequence that can be done with very thin sections,

3:49

is sometimes performed in

3:51

the thoracic spine,

3:52

particularly if you're looking for

3:54

the potential for a CSF leak.

3:56

So that's a different indication

3:58

generally than degenerative disc disease.

4:02

In those individuals that are post op,

4:06

performing post-gadolinium enhanced

4:08

scans is very important,

4:10

and this is because when you are doing

4:13

immediate scanning after gadolinium,

4:16

the disc does not enhance,

4:19

whereas scar material

4:21

granulation tissue does enhance.

4:24

So in the setting of, particularly lumbar spine

4:28

where you have something that's up

4:29

against the nerve root and you don't

4:31

know whether it's post-op scar material

4:34

versus a new disc or a residual disc,

4:38

post-gadolinium enhanced scans

4:40

are very important. Again,

4:42

you have to scan the patient immediately

4:45

after the gadolinium because

4:46

over the course of time,

4:49

disc material will imbibe contrast.

4:53

So the initial scan shows that

4:55

the disc does not enhance,

4:57

but the granulation tissue does enhance.

4:59

Whether or not you use fat suppression

5:01

is again something that different

5:03

groups will do differently.

5:05

If you want to be able to compare

5:07

directly to your axial T1-weighted scan

5:10

that was performed without fat suppression,

5:13

then I would say do your axial post-gad

5:16

also without fat suppression so you

5:18

don't get confused by the changing dynamic range.

5:22

Some groups will use fat suppression

5:25

just on the sagittal post-gad scan, but

5:28

will do non fatsat for the axial T1-weighted

5:32

post-gadolinium enhanced scan.

5:34

The value of doing post-gadolinium

5:37

enhanced imaging for post-op cervical

5:40

spine is variable, because there's so

5:43

much enhancement that occurs in the

5:46

anterior epidural space with the venous plexus,

5:49

as well as in the neural foramina.

5:52

You often will see enhancement on

5:55

post-gad cervical spine studies,

5:57

even in the face of no presence of

6:00

granulation tissue. So again, variable...

6:03

variably performed.