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Dr. P here with our 72 year old lady with a

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3 00:00:03,270 --> 00:00:06,479 4 centimeter greater AML or angiomyolipoma.

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I want to talk a little bit about diffusion

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imaging and this disorder and mass.

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This is going to be a little bit of an

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opinion piece because the jury is still out.

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But let's talk just briefly about

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the causes of diffusion restriction.

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And they include, let me get something easy to

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draw with here, like yellow. We've got desmoplasia.

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Firmness can produce diffusion restriction.

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Then we've got cellularity.

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This is a very important one, so

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something like lymphoma, very tightly

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packed cells, cytoplasmic-poor lesions.

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Then we've got something like viscosity.

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Examples of that would be hemorrhage,

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an epidermoid, an abscess.

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Then you've got cell death.

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An example of that would be like an infarct.

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We see that in the brain all the time

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with loss of the cell wall.

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And then you've got something like necrotization.

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And, uh, necrotization, I won't spell

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it all out because I'm a bad speller.

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Here we go.

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Necrotization, not so good on the spelling.

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At any rate, necrotization occurs.

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Let's say somebody has, uh, heroin poisoning

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and they have a necrotizing lesion in the brain.

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That can do it as well.

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And you could also do it with destruction in the

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brain from, say, a slow acting viral infection.

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So that gives you some of the some of the

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causes of diffusion restriction, and now you

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can extrapolate and apply these into the body

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from the neural axis.

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I have on the left a series of diffusion images

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where the B value, in other words, the intensity

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of diffusion restriction, has been ramped up

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from a B value of 0 to a B value of around 1000.

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And we're going to go through the

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same locus of our angiomyolipoma.

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Here it is.

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There's the rest of the kidney.

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Here's our AML on the right, on a T1 emphasized image.

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It's got lots of fat inside it.

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And here's the rest of the kidney.

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Now let's watch as we raise the B values so

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that we're more heavily diffusion restricted.

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There's this little focus right

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here anteriorly in our AML.

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Let's keep looking.

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And it persists, but not inordinately so.

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So what does that mean?

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You know, there's some mild diffusion restriction.

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There are about three or four of

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these loci or spots about like this.

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A few of them were a little bit brighter.

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So I would say mild to moderate diffusion restriction.

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So what's the bottom line?

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Because I inferred earlier in a prior vignette that

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the absence of diffusion restriction favors an AML.

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Well, we know that AMLs can

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diffusion restrict, and why?

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Because they've got some pretty tight

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packing of smooth muscle tissue.

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You know, one cell right next to the

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other without a lot of cytoplasm.

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And there are other reasons as well.

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So AMLs can, and sometimes do,

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show diffusion restriction.

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But if I have really pronounced diffusion

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restriction in large areas of interest,

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then I go for renal cell carcinoma.

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If I have no diffusion restriction

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at all, it doesn't help you much.

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But it certainly would move you more towards a

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benign lesion and excluding some of these other

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things that we've discussed like desmoplasia,

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cellularity, viscosity, cell death, and

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necrotizing, uh, disturbance of, of tissue.

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So the bottom line is, diffusion restriction right

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now, not inordinately helpful unless you have

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extremes of large diffusion restricted areas on one

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end and no diffusion restriction on the other end.

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Let's move on, shall we?

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Dr. P out.