0:01

So one of the questions that often comes up is

0:03

whether to use CT or MRI to follow patients with

0:07

Crohn's disease, or when to use either of these

0:10

modalities when trying to evaluate these patients.

0:13

And so, I'm going to go over a bit of the pros

0:14

and cons as I see them for these two different

0:17

important tools in evaluating Crohn's disease.

0:20

And obviously, we didn't spend much time talking about

0:22

CT since this is an MRI course, but it does certainly

0:26

have an important role for evaluating Crohn's and UC,

0:29

and so we need to at least discuss what the differences

0:32

are and why you might choose one over the other.

0:34

So obviously the radiation is a key factor,

0:37

and that becomes more important as you

0:39

have younger and younger patients,

0:40

which can often be the case in Crohn's disease.

0:42

So really considering MRI for

0:44

younger patients may be key.

0:46

One of the advantages of MRI is the fact that

0:48

you do get multiple time points versus the

0:50

single-shot appearance that you get with CT.

0:54

So this can be helpful for cases like stricture where

0:57

you're not sure on CT if it's a consistently narrowed

1:00

segment, or if it's narrowed on multiple sequences

1:03

over the course of 30 minutes like you get with MRI.

1:06

With that, you can be a lot more

1:07

confident that there's a true stricture.

1:10

The multiple different sequences really help you

1:12

evaluate whether things are acute versus chronic.

1:15

As you saw, there's a lot of different

1:16

tools we can use to make this determination.

1:18

Whereas with CT, you're really stuck with

1:21

thickening and enhancement, which are helpful,

1:24

but oftentimes not enough to really say with

1:27

confidence whether something is acute or chronic.

1:30

The excellent soft tissue contrast of MRI can be

1:32

helpful to find things such as edema, of course.

1:36

And you can get more information with MRI.

1:40

However, there sometimes are reasons to choose CT.

1:43

So of course, CT is much faster and

1:45

it's available in emergent situations.

1:47

It's technically very

1:49

straightforward and can be performed.

1:52

And most sites are straight out of the ER,

1:55

whereas MRI is more technically challenging

1:57

and requires a lot of expertise, both with

2:01

the technologists as well as the radiologists.

2:03

So hopefully after this you guys will feel comfortable

2:06

reading MRI, but you also need to have technologists

2:08

and a system in place that allows it to be performed.

2:12

CT is certainly less expensive, although

2:15

the differences aren't major anymore.

2:17

MRI does have the high cost associated

2:20

with it, at least historically.

2:22

CT has really good spatial resolution and it's

2:25

probably better than MRI, so potentially

2:28

seeing small strictures is a little better.

2:30

However, I find that this rarely comes into play in

2:33

being an important reason to choose CT. And then CT

2:37

is easy to see air, and it also has the advantage

2:40

that you don't have the air artifacts and other

2:42

artifacts that you have to deal with with MRI.

2:46

So my recommendations generally are to

2:49

use CT or MRI for initial evaluation,

2:52

whatever you're comfortable with.

2:53

And it depends a little bit on the urgency in

2:56

urgent cases coming out of the ER. Patients and

2:59

providers don't need it or want to wait for MRI.

3:01

And so using CT is certainly

3:03

appropriate in those cases.

3:05

MRI, however, I think is much

3:07

more helpful for follow-up.

3:09

When you're trying to monitor disease,

3:10

that acute versus chronic question

3:12

becomes much, much more important.

3:14

And also, don't forget these patients

3:16

are getting serial imaging and the

3:18

radiation starts to add up over time.

3:21

And that's why MRI really is a

3:23

critical tool for follow-up exams.

3:26

This is especially true in younger patients

3:28

who certainly can and do get Crohn's disease.

3:30

And then when you're trying to

3:32

evaluate for stricture, I prefer MRI.

3:34

Some other people may disagree, but I think the

3:36

multiple time points you get with MRI really help you

3:39

to be confident whether you have a stricture or not.

3:41

And then certainly if there's a question

3:44

of perianal disease, you can detect this on

3:46

CT, but MRI is much, much better for full

3:49

characterization and much easier to detect

3:53

perianal fistulas, abscesses, and other diseases.

3:56

And then lastly, you know, we didn't talk at all

3:58

about barium, but don't forget that it is available.

4:01

For troubleshooting, particularly in situations where

4:04

dynamic real-time imaging may be helpful to do things

4:07

such as delineate the complex nature of a fistula

4:11

and what's communicating with what, or potentially

4:14

confirming whether or not a stricture is real.