0:00

So this is a classic example of

0:02

the MR of a tongue-based carcinoma.

0:05

So here's our large mass right here

0:07

involving the right tongue base.

0:08

Now the key question is, how do we know

0:11

that this is involving the tongue base?

0:13

As I mentioned before, one of the biggest

0:14

questions I get is, well, how do I

0:16

know that's not the floor of the mouth?

0:18

Well, again, it all boils down to anatomy.

0:20

So these vertically oriented muscles

0:22

are the genioglossus muscles.

0:24

They go from the genial tubercle to the tongue base.

0:27

How do I know I'm at the tongue base?

0:28

Because the tongue base contains a

0:30

little bit of fat, as we see here in

0:31

the non-contrast T1-weighted images.

0:34

And these fibers are laterally

0:36

or horizontally oriented.

0:38

So here we can see this large mass here

0:40

that's primarily centered in the tongue base.

0:43

If we look at the T2-weighted images,

0:45

we can see the mass is high signal on T2,

0:48

and there is some anterior extension into the

0:50

posterior aspect of the floor of the mouth.

0:52

In fact, we can see that this mass

0:54

is encasing the lingual artery.

0:57

We can also see that there's involvement

0:59

of the posterior aspect of this muscle,

1:01

which is the hyoglossus muscle, and we can see

1:03

some involvement to the mylohyoid muscle.

1:06

But if I had to place an X, which I have here,

1:09

where I think that the center of the mass is,

1:11

that's gonna put us into the tongue base.

1:14

So number one, it's really important when

1:17

you perform MR to do a non-contrast T1

1:19

weighted images, because fat is our friend.

1:22

The fat forms a natural contrast

1:25

to this intermediate signal.

1:27

The T2-weighted images also help us identify

1:30

the full extent of this tongue-based carcinoma.

1:33

Now, when we give contrast, we can see that there

1:36

is enhancement of this tongue-based carcinoma.

1:39

This is hypervascularity, so there is enhancement.

1:42

But one of the challenges is that this

1:44

sequence right here is a T1-weighted

1:46

image with fat-suppressed sequences.

1:50

Now look at this sequence

1:52

here on the bottom left, compared to the bottom

1:55

right, the tumor is there, but I would suggest

1:58

that the conspicuity of the tumor is better

2:02

seen on the non-contrast T1, the T2,

2:05

or the contrast-enhanced T1-weighted images

2:08

as opposed to the fat-suppressed image.

2:10

The reason is because the tumors and the muscles

2:12

normally enhance, and when you suppress the

2:15

fat, it reduces the differentiation of enhancement

2:19

between tumor and the normally enhancing tissues.

2:22

So the bottom line is that when you are

2:24

performing MR for head and neck cancers, especially

2:27

the upper aerodigestive tract, yes, always

2:30

perform the fat-suppressed images, but make sure

2:32

you do the other sequences because that really

2:35

provides you the biggest contrast separator.

2:38

This sagittal image right here tells us

2:40

the mass is centered in the tongue base,

2:42

with a little bit of involvement of the posterior oral

2:45

tongue, and this coronal image tells us that this

2:48

tongue-based tumor goes right about to the midline.

2:52

So this is an example of a classic

2:54

example of tongue-based carcinoma.

2:56

We talked about the importance of different sequences

2:59

when looking at these, and we also emphasized the

3:02

anatomy to ensure that we can properly isolate this

3:06

in the tongue base, which is part of the oropharynx,

3:08

as opposed to primarily arising from the

3:11

floor of the mouth, which is in the oral cavity.