PET Scan

A PET scan (positron emission tomography), almost always combined with CT as a PET-CT, is a nuclear medicine test that shows how active tissues are rather than just how they look. A small amount of a radioactive tracer is used to highlight areas of high biological activity. In spinal care it is not a routine test; its main roles are in investigating cancer — detecting tumour, seeing whether it has spread to the spine, and monitoring treatment — and sometimes in difficult cases of infection.

The most common tracer is a form of glucose (sugar) labelled with a tiny amount of radioactivity. Cells that are very active — such as many cancer cells, and areas of infection or inflammation — take up more glucose, so they accumulate more tracer and light up on the scan. The PET part detects these active "hot spots," while the CT part provides the detailed anatomy to show exactly where they are. Combining the two pinpoints active disease and locates it precisely within the body and spine.

You are given the tracer through a small injection into a vein and then rest quietly for a period — often around an hour — while it distributes and concentrates in active tissues. You may be asked to avoid strenuous activity and, for a glucose tracer, to prepare with regard to food and blood sugar beforehand. The scan itself involves lying still while the PET-CT machine captures the images. It is painless. Because it uses radioactivity, you will be given advice about the low dose and about brief contact precautions afterwards.

When the question is whether a spinal problem is a tumour, whether a known cancer has spread to the spine, or how active a lesion or infection is, a PET-CT can provide answers that structural scans alone cannot, by showing biological activity across the whole body in one test. It is a specialised, selectively used investigation, chosen for these specific questions rather than for common mechanical back pain.

• —Royal College of Radiologists — iRefer: Making the Best Use of Clinical Radiology
• —Royal College of Radiologists / British Nuclear Medicine Society — Guidance on PET-CT
• —UK Health Security Agency — Ionising Radiation: Patient Dose Information

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.