A PET scan highlights areas of high activity, often called 'hot spots'. Because the tracer follows activity, cancers often light up — but so do infection, inflammation and normal busy tissues (like the brain, heart and bladder), so an active spot is not automatically cancer. A specialist reads the whole pattern alongside the CT, sometimes using a measure called SUV, and reports to your referring doctor, who explains what it means for you.
Key takeaways
- PET highlights areas of high activity ('hot spots').
- An active spot isn't always cancer — infection, inflammation and normal tissues are active too.
- Doctors read the whole pattern, sometimes using a measure called SUV.
- A specialist interprets your PET and reports to your doctor.
A PET scan works by showing activity, so the images highlight areas where the tracer has gathered — often described as “hot spots.”[1] Understanding what those mean takes a little context.
A hot spot isn’t always cancer
Because the common tracer follows the body’s most active cells, cancers often light up — but they’re not the only thing that does. Infection, inflammation, healing tissue, and normally busy organs (the brain, heart, kidneys and bladder) are active too, and take up tracer.[1] So an active area on PET is a clue, not a diagnosis — it has to be interpreted in context.
How it’s read
A specialist doctor looks at the whole pattern — where the activity is, its shape, and how it lines up with the CT anatomy in a PET-CT.[1] Sometimes a measure called SUV (standardised uptake value) is used to put a number on how much tracer an area has taken up, which helps compare a finding over time — for example, before and after treatment.
How you get your results
The specialist writes a report for the doctor who referred you, who discusses what it means and the next steps. As with all scans, the person performing it can’t give you results on the day.[2]
Frequently asked questions
Does a hot spot on my PET mean I have cancer?
Not necessarily. Active areas can be infection, inflammation, healing or normal busy tissue. The doctor interprets the pattern in context before drawing any conclusion.[1]
What does SUV mean on a PET report?
SUV (standardised uptake value) is a number describing how much tracer an area has taken up — a way to gauge activity and track changes over time, such as a tumour’s response to treatment.[1]
Why compare my PET with a previous one?
Because change matters. Comparing scans shows whether an area is becoming more or less active — often more useful than a single snapshot for judging how treatment is working.[1]
Sources
- RadiologyInfo.org (RSNA & ACR) — General Nuclear Medicine (PET) — www.radiologyinfo.org/en/info/gennuclear
- RANZCR / InsideRadiology — Nuclear medicine (Cain) — www.insideradiology.com.au/nuclear-medicine/
