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Dr. P back here with a 72-year-old lady who's had a

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3 00:00:04,740 --> 00:00:07,640 left sided renal mass that's been followed for

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years and has now exceeded four centimeters in size.

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Now there's more than one way to skin a cat.

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Many of you are familiar with the in-phase, out-of-phase

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method of imaging, also known as FATSEP,

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also known as Dixon, also known as MDixon, in

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which you do basically an in-phase image, an out-of-phase

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image, you add them, and then subtract them.

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So if you just humor me for a minute, when we

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do an in-phase image, I'm gonna make things

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a little bit darker so you can see them.

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We do fat plus water.

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When we do an out-of-phase

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image, we do fat minus water.

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So this would be in-phase, IP.

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This would be out-of-phase, OOP.

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Now we're going to do a little bit of math.

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And let's see if I can get a decent color for you.

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So if we were to add these two equations

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together, the plus water and minus water

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would cancel out and you would get double fat.

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But if you were to subtract

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them, the fat would subtract out.

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You got to know a little bit about basic

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math and you would get double water.

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So that would give you four

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images with these techniques.

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That's Dixon and Dixon, et cetera.

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So you'd have an in-phase image and out-of-phase

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image, a double fat image, and a double water image.

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This could come in really handy when you want to

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see fat, whether it's micro or macroscopic fat.

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Now in microscopic fat, when you go from the IP to the

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OOP, the signal intensity of the lesion will go down,

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even though you may not see the fat with the naked eye.

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In macroscopic fat, when you look at the in-

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phase image, you'll have high signal in the

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out-of-phase image, so it'll be high signal.

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Then you'll have low signal, but then when you

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go to the double fat image, you'll have really

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high signal that you pick up very nicely.

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So now, let's perform this exercise.

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Here is our fat plus water image.

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In fact, I'll even label it for you.

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Um, we'll go fat plus water, fat plus water.

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In phase.

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Then we've got fat minus water, or out-of-phase.

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Look at the India ink sign around the

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kidney, adjacent to the fat, which tells

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you this is an OOP out-of-phase image.

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Now what's on the far right?

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The double fat image, two fat.

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And look what's happening to our lesion.

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In phase, it's got some high signals, some macroscopic

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fat, if that's truly fat in the middle there.

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It should get darker, and it does.

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It gets darker.

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But when we go to our double fat image, which is

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uber-sensitive, a lot of this lesion gets brighter.

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Now you might say, well, how

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do you know it's not blood?

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You know, blood has water in it, right?

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So if you went to the double water image, which is

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the last one I'll pull down, let's pull it down.

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Here's your double water image.

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If that was truly blood, the

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water component would stand out.

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And does it?

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Not at all.

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In fact, on the double water image, all you see

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is low signal intensity, virtually identical, not

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exactly, but very close, to the mesenteric fat.

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So using this method, this exophytic

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lesion has macroscopic fat throughout and

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even some, a little bit on the outside.

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It's got this sort of egress pattern out of the

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kidney, which is very typical of angiomyolipoma or AML.

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One of the most commonly

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encountered benign solid tumors.

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We're going to talk about that in subsequent vignettes.

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Dr. P out.