0:00

Okay, so this case is mainly to talk about

0:08

sequences and how they can be useful for certain types of rectal cancer.

0:13

So I've got all four up here. Exactly. Yeah, so we've got diffusion,

0:18

ADC, coronal, and axial oblique. Okay, so I'm just going to show you

0:24

what we're looking at here. So in this particular case,

0:29

we've got a low rectal cancer, and it might be easier if I just enlarge

0:35

that for a second here. Okay, so hopefully you can see this a

0:44

little bit better. This is a challenging case. So this is the rectal

0:49

cancer here. It's this small... Again, I look for that C shape with

0:53

that raised rolled edge, and you can see that there's a central depression

0:56

here, so that's probably the ulcer. Okay, so here is the rectal cancer,

1:01

and then contrast that with the normal left side. So there's clearly some

1:04

asymmetry, but you really need to be looking sometimes for these lesions

1:11

to pop out. So here's what that lesion looks like, okay?

1:14

So that's the rectal cancer in this case.

1:18

Okay, so you know it's a low rectal cancer. So now let's put

1:20

up the first question. Which plane do you think is most useful for

1:25

the termination of T stage in this case?

1:28

So I'll give you guys a few seconds here. All right, so let's

1:33

see what people thought. Okay, so most people thought axial oblique. There

1:42

were some votes for sagittal and coronal oblique. Okay, so for low rectal

1:46

cancers, the recommendation is to use the coronal oblique image, and the

1:52

reason for that is so that we can evaluate the sphincter, okay? So

1:59

with low rectal cancers, I would suggest that you always obtain

2:04

a coronal set of images that's parallel to the sphincter mechanism.

2:09

So you would do that from your sagittal image,

2:13

and you would just create axial and coronal obliques that are parallel and

2:18

perpendicular to the sphincter respectively. And the reason is you want

2:22

to be able to assess the internal sphincter,

2:26

the intersphincteric plane, and the external sphincter here. So this gives

2:30

you that nice kind of sandwich view. So the intersphincteric plane is this

2:37

high T2 signal layer of fat here, and then the internal and external

2:41

sphincters are low T2 signal with the muscle. So

2:46

that's the critical plane to evaluate the T stage. So axial oblique is

2:52

helpful as well, but you really get a better idea of symmetry versus

2:57

asymmetry through the sphincter mechanism with the coronal oblique. Okay,

3:03

so let's see here. There's the tumor there. Okay. So let's go to the

3:06

next question. Which of the following structures are involved by tumor?

3:13

And I'll remove this here so you can get a better

3:20

look. And let me... I'm just going to put them side by side

3:27

so you guys can get a better view here.

3:31

Okay, so there's the coronal, and there's the axial. So the axial oblique

3:39

does give you another look here. And these can be quite challenging,

3:45

and sometimes it's helpful to ask a colleague as well if

3:49

you're finding it difficult to evaluate the sphincter mechanism. All right.

3:58

So let's see what people thought. And again,

4:02

I'm cognizant that you guys can't scroll through so... Okay, so we had some

4:08

votes for internal sphincter and others for all of the above.

4:11

Okay, so let's go over that. So again, I have the advantage of

4:15

being able to scroll, whereas you guys don't.

4:19

But the area of concern that we were worried about in this case

4:24

was right back here. So it was a little challenging to actually see

4:30

the fat, that it was spared. If you look at the left side,

4:35

you can see the fat is actually maintained. But on the right side, we

4:39

lose just a little bit of it here. So we were concerned that

4:42

there was intersphincteric plane extension. But the external sphincter looks

4:49

like it's probably preserved. And if you look at the coronal, you might

4:54

worry about it in here. And that's where just correlating with the axial

4:58

is helpful. So you can't see it on both planes. So we did

5:02

not think the external sphincter was involved. But we called it internal

5:06

sphincter and potentially intersphincteric plane, but we weren't quite sure

5:11

about that. So definitely internal sphincter. Sometimes in these cases,

5:15

the surgeon or referring physician might do an endorectal ultrasound to

5:20

just get a better sense. Sometimes MR has that limitation of not being

5:25

able to distinguish quite well between the lesion being confined to the

5:30

internal sphincter versus slight extension into the intersphincteric plane.

5:34

And then the other reason I wanted to show this case was

5:37

I told you at the outset that it was hard to see

5:41

this lesion initially. And then we don't... Unfortunately, the MRs don't

5:46

come with the annotation. So something else that I

5:52

like to do is I like to actually obtain the diffusion weighted images

5:57

right after the sagittal. So as you know, the sagittal is the sequence

6:02

that we use for planning the axial and coronal obliques. But I've been

6:05

caught many times with not being able to identify the lesion sometimes on

6:09

the sagittal because the rectum's collapsed or there might be a stool.

6:13

And we don't prep our patients before their rectal MR. So I like

6:17

getting the diffusion. And you can see in this case right away,

6:21

the lesion just pops out. So based on that, I can triangulate back

6:26

to the sagittal. And I don't... Sorry, I didn't actually load the sagittal

6:32

for this case, but it's really helpful to be able to triangulate back and

6:37

say, okay, this is where the lesion is, we're going to plan based

6:39

on that. So that's just a little trick that I use.

6:43

So you can definitely do that. You're going to acquire the diffusion anyway,

6:46

so you might as well just be able to use it more frequently.