Interactive Transcript
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Dr. Finazzo, we've covered high signal lesions on T2.
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3 00:00:05,229 --> 00:00:06,370 We showed you some renal cell
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carcinomas, or we showed the audience.
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And now we're on to low signal
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lesions on the T2 weighted image.
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And we're going to characterize their
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histopathology and use as a biomarker
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their relative lack of vascularity.
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So we've got a couple lesions here.
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We've got, uh, at least one right there
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on the T2 fat suppressed spin echo image.
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We've got a second one, which I'll let you point out.
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We've got a T1 spin echo in the coronal projection.
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There's a bright signal lesion right there.
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Then we've got an out of phase OOP gradient echo.
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There's a bright signal lesion there.
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And here's the in phase gradient echo.
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So go ahead, take over.
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So whenever I look at T2, uh, dark lesions, the three
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most common things that cross my mind are: are we dealing
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with a small papillary RCC, are we dealing with a lipid
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poor AML, or are we dealing with a hemorrhagic cyst?
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So, from there, I go right to my T1 weighted
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images, and I try to characterize and
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look to see if these lesions are bright.
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So in this particular patient,
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we have two bright lesions.
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One that's really bright, and one that's not so bright.
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So the question we have is,
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are these both hemorrhagic lesions?
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Possibly, probably.
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Uh, how do we differentiate, how can we say which ones
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are truly hemorrhagic benign and, and walk away from?
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There's been a recent article that's written that looks
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at these bright lesions and says if we can look at the
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ROI of these lesions and they are more than two and a
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half times background parenchyma on the T1 weighted
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image, then you can be 99 percent confident that
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this is just a benign hemorrhagic cyst and ignore it.
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If it's not more than two and a half times background,
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then we can be dealing with either a hemorrhagic
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component in such as a papillary lesion, uh,
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is really the other differential.
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So I'm just.
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Keep in mind that, um,
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lipid poor AMLs will not bleed.
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So if you see blood product in a lesion, you're
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not dealing with a lipid poor AML and you have
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to be worried about a papillary neoplasm.
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So from this, I actually did the Hounsfield
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field units on this and, uh, we can go
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through the exercise, the signal intensity,
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the signal intensity, and the ROI was.
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three times higher than
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the background liver parenchyma.
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So we wrote this as being just a cyst.
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Now, the fatty lesion is not going
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to be two and a half times background.
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That's
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exactly, and you can even see visually
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that it's not as bright as the very
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bright bloody lesion that we see here.
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So once I see a second lesion, the
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question is, does it match background fat?
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At this point, it does.
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So are we
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possibly dealing with an AML or are
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we dealing with a papillary neoplasm?
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So this is when I go to my in and out.
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So on the in and out, we see the Indian
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ink surrounding the lesion.
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So we're highly confident that this is probably an AML.
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Yeah, so right here is our lesion.
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The Indian ink sign is this dark area right around it,
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which is basically a chemical shift phenomenon between
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the fat in the lesion, which is white, and I've just
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colored over it, left the black ring in place, compared
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with the water that's surrounding it in the adjacent
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kidney, and that's what pretty much gives you the
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the India ink sign for this fat-containing lesion.
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You and I actually measured this lesion
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before we gave this vignette, and it was
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nowhere near two times the background,
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so it's consistent with the fatty lesion.
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And the other lesion turns out to be the fat
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three times and is consistent with a hemorrhagic cyst.
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Is that correct?
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Because I struggle with this myself.
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That is correct.
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92 00:04:07,234 --> 00:04:08,954 And the next question is we look for
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lesions for enhancement.
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So we'll pull up a companion case
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next to look at the enhancement
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characteristics of these T2 dark lesions.
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Great.
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Let's do that on the next vignette.
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Yes.
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Okay.
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Dr. P and Dr. Finazzo out.
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