0:01

Dr. Finazzo, we've covered high signal lesions on T2.

0:02

3 00:00:05,229 --> 00:00:06,370 We showed you some renal cell

0:06

carcinomas, or we showed the audience.

0:08

And now we're on to low signal

0:11

lesions on the T2 weighted image.

0:13

And we're going to characterize their

0:15

histopathology and use as a biomarker

0:18

their relative lack of vascularity.

0:21

So we've got a couple lesions here.

0:22

We've got, uh, at least one right there

0:24

on the T2 fat suppressed spin echo image.

0:29

We've got a second one, which I'll let you point out.

0:31

We've got a T1 spin echo in the coronal projection.

0:35

There's a bright signal lesion right there.

0:36

Then we've got an out of phase OOP gradient echo.

0:41

There's a bright signal lesion there.

0:42

And here's the in phase gradient echo.

0:45

So go ahead, take over.

0:47

So whenever I look at T2, uh, dark lesions, the three

0:51

most common things that cross my mind are: are we dealing

0:54

with a small papillary RCC, are we dealing with a lipid

0:58

poor AML, or are we dealing with a hemorrhagic cyst?

1:01

So, from there, I go right to my T1 weighted

1:05

images, and I try to characterize and

1:08

look to see if these lesions are bright.

1:10

So in this particular patient,

1:12

we have two bright lesions.

1:14

One that's really bright, and one that's not so bright.

1:18

So the question we have is,

1:20

are these both hemorrhagic lesions?

1:22

Possibly, probably.

1:24

Uh, how do we differentiate, how can we say which ones

1:27

are truly hemorrhagic benign and, and walk away from?

1:32

There's been a recent article that's written that looks

1:35

at these bright lesions and says if we can look at the

1:40

ROI of these lesions and they are more than two and a

1:44

half times background parenchyma on the T1 weighted

1:49

image, then you can be 99 percent confident that

1:53

this is just a benign hemorrhagic cyst and ignore it.

1:57

If it's not more than two and a half times background,

2:01

then we can be dealing with either a hemorrhagic

2:04

component in such as a papillary lesion, uh,

2:09

is really the other differential.

2:11

So I'm just.

2:12

Keep in mind that, um,

2:14

lipid poor AMLs will not bleed.

2:18

So if you see blood product in a lesion, you're

2:21

not dealing with a lipid poor AML and you have

2:24

to be worried about a papillary neoplasm.

2:28

So from this, I actually did the Hounsfield

2:31

field units on this and, uh, we can go

2:34

through the exercise, the signal intensity,

2:36

the signal intensity, and the ROI was.

2:39

three times higher than

2:42

the background liver parenchyma.

2:44

So we wrote this as being just a cyst.

2:47

Now, the fatty lesion is not going

2:49

to be two and a half times background.

2:50

That's

2:51

exactly, and you can even see visually

2:53

that it's not as bright as the very

2:56

bright bloody lesion that we see here.

2:58

So once I see a second lesion, the

3:01

question is, does it match background fat?

3:04

At this point, it does.

3:05

So are we

3:07

possibly dealing with an AML or are

3:11

we dealing with a papillary neoplasm?

3:15

So this is when I go to my in and out.

3:17

So on the in and out, we see the Indian

3:20

ink surrounding the lesion.

3:25

So we're highly confident that this is probably an AML.

3:29

Yeah, so right here is our lesion.

3:31

The Indian ink sign is this dark area right around it,

3:35

which is basically a chemical shift phenomenon between

3:37

the fat in the lesion, which is white, and I've just

3:39

colored over it, left the black ring in place, compared

3:43

with the water that's surrounding it in the adjacent

3:45

kidney, and that's what pretty much gives you the

3:47

the India ink sign for this fat-containing lesion.

3:50

You and I actually measured this lesion

3:52

before we gave this vignette, and it was

3:55

nowhere near two times the background,

3:57

so it's consistent with the fatty lesion.

3:59

And the other lesion turns out to be the fat

4:01

three times and is consistent with a hemorrhagic cyst.

4:04

Is that correct?

4:05

Because I struggle with this myself.

4:06

That is correct.

4:06

92 00:04:07,234 --> 00:04:08,954 And the next question is we look for

4:08

lesions for enhancement.

4:11

So we'll pull up a companion case

4:13

next to look at the enhancement

4:16

characteristics of these T2 dark lesions.

4:18

Great.

4:18

Let's do that on the next vignette.

4:20

Yes.

4:20

Okay.

4:20

Dr. P and Dr. Finazzo out.