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So, Dr. Farnazo, we're introducing some

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3 00:00:02,340 --> 00:00:04,489 of the basic concepts of using MRI.

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We've got an in-phase gradient echo, not so pretty.

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A patient moved a little bit and is a huge patient.

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And an out-of-phase gradient echo.

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And the point is, are we dealing with

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microscopic fat or macroscopic bulk phase fat?

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Now, when you're dealing with microscopic fat,

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which you can get in some AMLs, although the

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classic fat-containing AML has macroscopic fat,

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but when it has microscopic fat, it's tougher.

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It's tougher.

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A renal cell carcinoma and Wilm's

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tumor also contain microscopic fat.

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And this is a renal cell carcinoma.

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I want to draw over it so the viewing audience

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can see, our colleagues can see where the lesion is.

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It's right here.

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On the outer face, it's a little bit clearer.

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It's right here.

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And while there are some dark lines around

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the lesion, I'm going to take them away.

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Those dark lines are compressed tissue.

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They're not this very smooth, etched India ink sign

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that you see between the kidney, which has water in it,

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and the surrounding fat,

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which is the retroperitoneal fat.

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So this would be a sign of macroscopic fat.

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In other words, macroscopic fat in the

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retroperitoneum, not in the kidney.

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Now if we look at water in the kidney versus

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microscopic fat in the lesion, what do we see?

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What's happening?

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So, basically, this is very difficult to

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look at, but you're looking for a very subtle

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drop between the in-phase and out-of-phase images.

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And why is that important?

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As we mentioned, hypervascular

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lesions in the kidneys can be AMLs.

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Clear cell renal cell carcinomas

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and chromophobe carcinomas.

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Renal cell has fat in it as

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opposed to chromophobe cancers.

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And because our goal today is to do some

1:59

histologic subtyping to evaluate which tumors

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are aggressive, we're trying to look for fat.

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Now, clear cell renal cancer has glycogen

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cells in it, which is why they have dropout,

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but the amount of glycogen that they have is very little.

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So you're looking for very subtle dropout changes.

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But when we do identify that and the lesion is

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hypervascular, we know and we can tell our urologist

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that we're probably dealing with a renal cell cancer.

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And this is a perfect example

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where there's very subtle

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dropout in the in-phase, out-of-phase,

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telling us we're dealing with microscopic fat.

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So just to summarize, here's the in-phase image.

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You've got this gray lesion right here.

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Then we go out of phase.

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It's just a little bit darker.

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Yet, because it doesn't have macroscopic fat,

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but rather microscopic fat in the glycogen

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component, we don't see the circumferential India

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ink sign that we would expect in macroscopic

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fat, like we've shown you in other vignettes.

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So this is an example of microscopic fat

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in a hypervascular renal cell carcinoma.

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And we're going to talk about vascularity

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and enhancement on MRI in renal cell

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carcinomas in a separate vignette.

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Pomeranz and Farnazo out.