Radiology• Updated 21 October 2026
PET-CT Scan
A scan using a small amount of radioactive sugar to show how active tissues are, mainly used in cancer care.
Results: A few days
Quick Summary
Primary Purpose
To find cancer spread, plan treatment and check response.
What It Measures
Areas of high activity, combined with CT images.
Preparation
Fast for about 6 hours; control blood sugar; avoid strenuous exercise the day before.
Overview
Cancer cells often take up more sugar, so they show up brightly.
Inflammation and infection can also light up.
What It Measures
Metabolic activity
How active tissues are.
Anatomy
CT images.
How It's Performed
- 01
Injection
A tracer is injected; rest quietly for about an hour.
- 02
Scan
Lie still for 20–30 minutes.
- 03
Afterwards
Drink fluids; avoid close contact with babies and pregnant women for some hours.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- PET Scan(opens in a new tab) · MedlinePlus, US National Library of Medicine
- PET scan(opens in a new tab) · NHS