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<v ->Now are there MR imaging findings

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that allow you to predict,

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whether the findings that you are seeing are reversible

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or irreversible?

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And I wanna say, yes.

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And I'm gonna indicate three categories

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of MR imaging findings.

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Some that are usually reversible, and with the arrows,

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I'm pointing to the two that are most important.

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Some that can be reversible or irreversible,

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with two major ones where you can't be sure.

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And then those that are definitely irreversible.

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And the main one to consider, is once you have deformity

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or collapse of the subchondral bone plate.

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So let me show you examples.

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As I finish this particular lecture of some of these.

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So you're aware of

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whether they predict reversibility or irreversibility.

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A lot of the reversible MR Imaging findings

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relate to hyperemia.

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And these can be associated with linear

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or band-like alterations in the subchondral bone

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or in the metaphysis.

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Sometimes you see the vessels themselves

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as a channel-like appearance.

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The there's a particular polka dot appearance

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that generally is reversible.

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And there are some others I'm gonna throw in

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that are site specific that you can see,

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and age specific as well.

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So the first one that I wanna emphasize as being reversible

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is a linear subchondral or subcortical alteration

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in signal intensity.

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Now, this is seen especially about the knee,

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and particularly within the patella.

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And as you look at it, you can see here,

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and this is taken from an article

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of one of our previous clinical fellows in San Diego,

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Larry White and his associates.

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It occurs at the periphery of the patella.

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And it produces a bone within bone appearance.

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Related to hyper vascularity

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which is most dominant at the periphery of the patella.

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Larry White and his associates described it

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following injury in the subacute phase, but you can see it

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in other conditions associated with hyperemia.

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Here it is beneath the subchondral bone plate.

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Here it is beneath the cortex.

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Here it is beneath the cortex linear, is typical.

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So when you see this,

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you're looking at the effects of hyperemia

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and generally those effects are transit.

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And this is reversible.

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Here's another case.

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Look at, I mean, it's classic.

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You can see the linear appearance.

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It may not go all the way around the patella.

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It does in this case,

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producing a bone within bone appearance,

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and you can see how the hyperemia of the patella,

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this is from a cadaver.

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You can see here, how it is most maximum at the periphery.

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Here's another case.

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We're seeing this from Dr. Van De Berg Bruno

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he has written so much on marrow signal.

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He's a great source, so if you wanna learn about it.

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He also makes the point.

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This is evident on the fluid sensitive sequence.

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And often there's nothing or very little

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on the T1-weighted sequence.

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So that discrepancy is very, very characteristic.

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The second pattern that generally is reversible,

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is a combination of the linear pattern we just talked about

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with band-like areas of altered signal in the metaphysis

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and subchondral bone.

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So here we see that linear pattern.

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I'm showing that here with the white arrows.

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And superimposed on it,

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are band-like areas of alteration and marrow signal

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here within the distal tibia,

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here within the subchondral bone of the calcaneus.

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For those of you who read a lot of conventional radiographs

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you'll recognize those band-like areas

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because we see them in cases of osteoporosis,

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as radiolucency in these locations.

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This can occur with acute osteopenia

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or it concur with slowly develop of being osteopenia,

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but generally it is reversible.

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The third pattern that generally is reversible,

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is a channel-like pattern.

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Here, you're looking at the dilated vessels themselves.

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This is a pattern that I've seen

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particularly in the immature scale in falling injuries

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particularly around the knee.

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And you'll see alterations in marrow signal

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and you wanna call them a bone contusion,

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but as you look at them, they're channel-like

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and almost everything you're looking at, are vessels.

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This is generally reversible.

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And then one of my favorite, the 'polka dot' appearance.

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I still haven't gotten a definition

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of why it's called the polka dot, so, right?

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But hopefully we're gonna get that before too long

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but what they say is,

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are these kind of circular or kind of oval

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or elliptical areas of altered signal intensity

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often containing fat.

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So here you can see on a T-1-weighted image,

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how prominent they are.

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They disappear on the fat suppress sequence.

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Go back to the chambers that I showed you.

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When you have osteoporosis, the chamber size enlarges.

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And now you begin to see this polka dot appearance

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because you're dealing with a larger marrow chamber

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filled with fat.

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This can occur from again, rapidly onset osteoporosis,

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or as in this case, disuse.

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And generally this too, is reversible.