# Standardised uptake value in PET

Hello, I have been given an article on determination of body volume by PET, to read for a job interview. There are a few concepts that i dont quite understand (not coming from a medical background) and was hoping someone may be able to help me with the understanding. (Unfortunatly it would seem I dont have access to some of the key journals on the topic)

This research is being undertaken so that in future the standardised uptake value (SUV) can be normalised to lean body mass (LBM) rather than weight. Once the volume is determined, the density can be found and, using the siri formula, the body fat calculated, which in turn can then be used to calculate the LBM.

My questions revolve around the SUV. What is the SUV? How is it used in medicine? and why is it benificial to normalise it to LBM as oposed to weight?

Also does anyone have experience of volume determination by PET? (whether it be tumor or whole body volume). This article concludes that whole body volume determination by PET is comparable to other methods - is this generally the accepted view nowadays?

Regards

## Answers and Replies

Choppy
I'm not really a PET guy, but a general description of SUV is available on Wikipedia here.

I think the general idea is that the pixel intensities in a PET image are essentially a relative measure of the concentration of radioactivity at a certain location. The SUV gives a means of normalizing this to the amount of injected radioactivity, which itself is then normalized per unit body weight. You might imagine, for example, if I put the same amount of radioactive tracer into a small person and a big person who otherwise physiologically process the tracer in an identical manner, I'll end up with brighter pixels in the smaller person - hence the body weight normalization. And I suspect that using something like lean body mass provides a better index for the body's relative ability to process radioactive sugar than overall weight. All of this then enables physicians/scientists to better compare PET images patient to patient, or in a single patient over time.

Also, I'm still getting used to the new look on the Physics Forums, but it seems this question is 9 years old. I hope the OP's job interview went well.

Greg Bernhardt
gleem