0:01

So in this video we are going

0:03

to review the different patterns of muscle uptake, uh,

0:07

that can happen with FDG.

0:10

So normal uptake in the muscle should be mild

0:15

and should be homogeneous in a resting state.

0:20

Muscle undergoes fatty acid oxidation

0:24

and that would be the major source

0:25

of energy in the skeletal muscles when there's

0:30

insulin in the blood.

0:32

That induces a rapid increase in the glucose uptake in this

0:36

muscles and induces the translocation

0:40

of the transporters,

0:42

specifically the glute four transporters

0:45

from the intracellular vesicles to the plasma membrane.

0:50

And therefore there is an increase of transporters

0:53

that will take up the FDG.

0:56

When we exercise,

0:59

there's basically also an increase in the expression

1:03

of these transporters at the level of the membrane.

1:06

And so there is increased glucose metabolism

1:09

just from consumption.

1:11

Normally when we exercise, uh, the skeletal muscle cells

1:16

undergo, um, stress and they they need extra glucose.

1:21

So this is, uh, what we see on, on P CT as well.

1:27

So things that we have to make sure that we do well, uh,

1:31

prior to the injection of FDG is that, uh,

1:36

we should avoid injecting FDG in a post pan state.

1:41

We discussed earlier the importance of preparation.

1:44

We ask the patients to fast for four to six hours,

1:47

so the insulin levels decrease when there is insulin use

1:52

because the patient is diabetic.

1:55

We should know what insulin has been injected.

1:59

If it's a short acting versus a long acting.

2:02

There's different guidelines for each.

2:04

And these are all in the S-N-M-M-I guidelines

2:09

for FDG pet

2:10

and we should follow those to make sure

2:13

that the scan is diagnostic.

2:16

It is common that during the uptake phase or even just

2:20

before the study, there's some muscle tension.

2:23

And so, uh, these muscles that are being used

2:26

and contracted will also increase the tracer uptake and

2:29

therefore we could see those.

2:30

So talk, uh, to the patient about trying to relax

2:36

and, uh, breathe normally are things that we can do

2:39

to decrease the uptake in muscles.

2:44

So for instance, in this case, you can see

2:47

that there is intense muscle uptake in the area of the jaw.

2:52

And this is because, uh,

2:53

patient was probably biting really hard while the scan

2:58

Was, um, happening either during the haptic phase

3:02

or during the, the scan.

3:04

And you can see that in the fusion image it corresponds

3:08

to the masseter muscles.

3:10

This is another example, for instance, of a patient that

3:14

exercised just prior to the pet,

3:17

and you can see how there's intense uptake in all these, uh,

3:21

muscles throughout the body, upper extremities,

3:24

lower extremities, and,

3:26

and also in the torso, in the fused images, you know,

3:29

they are very nicely correlated to the entire muscle used.

3:33

This indicates not only the use,

3:36

but probably with this degree

3:37

of uptake indicates some underlying injury, which is

3:41

what happens normally when we go to the gym and exercise.

3:46

These are for examples of the different muscle uptake

3:50

that we can encounter.

3:52

Uh, and we'll go through the three abnormal ones, uh,

3:57

on axial images as well.

3:59

But because you are gonna see those, uh, mid images,

4:02

it's important that you familiarize yourself with how

4:07

the abnormal distribution is in each case.

4:10

Uh, when you have an overview of the patient.

4:14

So the first image is the normal distribution

4:17

and you can see that there's very little uptake,

4:19

very mild uptake in the muscles.

4:22

The second case is a case

4:24

of hyperinsulinemia in which the patient didn't follow the

4:27

instructions and so there was a peak of insulin

4:30

by the time we injected the FDG

4:33

and then all that FDG went into the musculature

4:36

by the mechanism that I just uh,

4:38

mentioned a few minutes ago.

4:40

The second case is a patient that had gone

4:44

to the gym, but look at how it is symmetric

4:48

and intense uptake in the muscles of the lower legs,

4:52

but not so much on the rest of the body.

4:54

So this patient had gone to the gym and had done, uh, squads

4:59

and this was not within the 24 hours prior to the scan.

5:04

This was two weeks before the scan.

5:07

So, uh, you can imagine the degree of muscle injury.

5:12

Um, she reported that she was unable to walk, uh,

5:16

for at least a week after going to the gym.

5:19

The last case, uh, it's a case

5:21

of infectious myositis in this case.

5:24

We do have uptake in the cough muscle

5:26

but is fu it's asymmetric.

5:29

We don't have it on the right, it's only on the left

5:32

and it's diffused

5:33

and we'll see it better on the axial beers.