0:00

This is a display

0:02

that I personally like in which I have my NIP

0:06

projection, the maximum intensity projection,

0:09

and I start with Axis PET only CT infused.

0:14

Now remember that I mentioned that we have a

0:18

non attenuation corrected pit series

0:21

and then the attenuation corrected pit series.

0:25

In theory, you should have the attenuation corrected

0:29

images already pulled up in your display,

0:34

and sometimes you have to select that manually.

0:38

I want to briefly show you the differences between the two

0:42

of them so you can identify the differences

0:47

and use the non attenuation corrected series

0:50

to your advantage in certain scenarios

0:53

where these may be helpful.

0:55

So here I'm showing you two images of the same patient,

1:01

and you can appreciate that there's a little bit

1:03

of a difference in how things are displayed.

1:07

The organs that you're seeing

1:08

and the intensity, the non attenuation corrected the images

1:13

are the one that I'm showing you on the left side

1:18

of the screen, and the attenuation corrected image is the

1:22

one on the right side of the screen.

1:25

So notice at the periphery what the difference is,

1:30

you have higher count, higher intensity

1:35

along the periphery

1:36

of the body surface on the non attenuation corrected images,

1:41

and these decreases.

1:42

Once you have applied that CT attenuation map, this is one

1:46

of the things that may help you distinguish the tube.

1:49

This is because the photons from the periphery are barely

1:52

attenuated by the air on the original data.

1:57

And then once we have applied the ct,

2:00

they decrease in intensity.

2:02

The other organs that may present a difference is,

2:06

for instance, the liver.

2:08

We know that the liver has a moderate, uh,

2:12

diffuse uptake normally,

2:14

and in fact, we use the liver

2:16

as a point reference in the case of uh, FDG,

2:20

and look at the raw data

2:23

where you barely have activity within the liver.

2:26

The other thing would be to look at the lungs.

2:30

Lungs are showing in the raw data

2:32

or the non attenuation corrected pit as having some degree

2:36

of counts, but we, when we compare to the post correction,

2:41

you have a much lower degree of uptake in the lungs

2:45

because the majority of the photons have not been

2:49

greatly attenuated by the air within the lungs.

2:53

So these are the things to look at

2:55

to distinguish the two series.

2:59

When would you use the non attenuation corrected series?

3:04

Well, there's a couple of scenarios

3:06

that I think it's important to know.

3:07

One would be to evaluate cutaneous or superficial lesions

3:11

because they might show more prominent uptake

3:14

before you apply the attenuation correction.

3:17

And the other scenario would be to look into

3:22

artifacts, particularly metallic devices such as prosthesis

3:27

or corcas.

3:29

One of the common things is that

3:32

after applying the attenuation correction,

3:35

there is increased uptake surrounding

3:38

these metallic devices.

3:40

And to distinguish between

3:43

an artifact from the attenuation correction versus

3:46

real uptake, you would go to the raw data

3:50

and we will see a case of these shortly.

3:54

The attenuation correction of the data is necessary to

3:59

accurately quantify the standardized uptake volumes or SUV,

4:05

but also to qualitatively assess the study visually.

4:08

Right. When you place your ROI in each series,

4:13

you will notice that the non attenuation correction data

4:16

does not provide you with SUV values.

4:20

But once you've corrected the series, then you can have

4:23

the SUV values that are available for you to add

4:27

to their report.