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This is a case of an FDG pet that shows

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abnormal uptake in the supraclavicular area

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and along the intercostal spaces.

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And this is the typical distribution of active brown fat.

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There's two types of, uh, fat in the body.

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The most commonly is the white fat,

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which we encounter in the subcutaneous tissues

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and visceral fat.

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And then there's brown fat, which is

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most prominent when we are newborns.

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And it's, uh, very important for thermal regulation.

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And as we, uh, get older, it decreases in the amount, uh,

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that we have in the body.

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But depending on the patient,

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some might still have brown fat

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and it can get activated, for instance, in days

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that the temperatures are low, like in this case.

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So knowing the distribution

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and how to define if this is brown fat versus other is

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important because this seems to be an area

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where there's other structures that might be important

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to discern if there's malignancy, for instance, lymph nodes.

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So let's see how we can troubleshoot the situation.

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First, you are gonna look at this at the scan

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and you're gonna see that the pattern is symmetric.

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And then when we move on to the axial planes, uh,

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in the areas of uptake,

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and I'm going to triangulate here, you'll see

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that the uptake, uh, in that supraclavicular region

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corresponds to an area of fat.

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So there's really not a lesion

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or soft tissue that, uh, explains the activity.

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It's just fat. Moving down is very common

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to have brown fat also in the thoracic inlet.

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And as we go from the neck down

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to the torso, the chances

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of having brown fat decreases.

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So it's mostly seen in the area of the neck

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and supraclavicular region and mediastinum,

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and it will be less common to be seen in the perren

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and, uh, peritoneum.

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So for instance, in this case, as we mo move down, we see

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that there's bilateral foci of intense uptake that seems

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to localize in the paraspinal space.

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Let's see how it looks on Corona.

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So here you can see the symmetry,

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and when you localize the, the foy of apte, you can see

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that it's in between the ribs.

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So this is a key finding that will allow you

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to confidently say that this is brown fat.

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Same goes with, uh, mein here.

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I think the mein is a little bit trickier

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because depending on where you don't have a lot of space,

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In this case, we can see there's a little bit of fat that,

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uh, localizes to where the uptake is.

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We see the same findings in the anterior mediastinum

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and along the internal mammary vasculature

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going down, very commonly seen around the aorta,

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along the coura.

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Also, you can see in the epicardial fat

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in going down, this is a nice case of perren brown fat.

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This is not the adrenal gland.

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The uptake is behind the adrenal gland in the fat plane.

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So when I encounter something like this is something I

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always put in my report.

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It is physiologic.

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This is not a malignant finding,

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but it truly sometimes represents not a limitation,

3:50

but a challenge when you read certain cases.

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So always making a comment about these, it's helpful,

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particularly if it falls on the region

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where the malignancy is encountered.

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And unfortunately, sometimes we cannot distinguish

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or separate the uptake of brown fat from an adjacent,

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for instance, adenopathy.

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And therefore this becomes a limitation

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for the subsequent pets.

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If that is the case, I may recommend at the end

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of my impression to make sure

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that the patient appropriately prepares for the test

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to diminish the effect of the brown fat

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and applying like blankets

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or jackets during the uptake phase.