What Is a PET-CT Scan — and How Does It Work?

The radioactive tracer is given in a very small amount, emits radiation at a low level, and passes out of your body through urine within a few hours. Most people feel nothing from the injection itself. If you have diabetes, kidney disease, or are pregnant, tell your team before the scan — these conditions affect how you need to be prepared. Your oncologist orders the scan when the clinical information it provides outweighs the very small radiation exposure involved.

The full appointment is usually two to three hours, though the scan itself takes less than that. After the injection you rest quietly for about an hour while the tracer distributes through your body. You then lie still inside the scanner for roughly thirty minutes. You can eat and drink normally once the scan is complete. The waiting period before scanning is the reason the appointment feels longer than a routine CT.

A CT scan shows where something is. A PET-CT also shows whether it is metabolically active, and that distinction matters for staging. A lymph node enlarged on CT may or may not be involved with cancer — the PET component can help clarify that. PET-CT is also used to assess how a tumour has responded to treatment, because a tumour can stop being active before it visibly shrinks, or shrink in size while remaining active. Your oncologist will explain what specific question the scan is intended to answer in your case.

Hypermetabolic means the area absorbed more tracer than the surrounding tissue, indicating higher metabolic activity. It does not automatically mean cancer. Infection, inflammation, healing tissue, and some normal structures — including the brain and bladder — can all appear hypermetabolic. The finding is read alongside your biopsy results if available, your clinical history, and the location and pattern of the uptake. Your oncologist interprets the result. The report alone does not give a diagnosis, and it is reasonable to ask your oncologist to walk you through the findings.

Reports are usually available within a few days of the scan, though the exact timeline depends on the centre where the scan is done and how the report is sent to your oncologist. At CION, your oncologist reviews the report before discussing the findings with you — the report is not handed over without explanation. If you have not heard back within a week of the scan, contact your team directly rather than waiting.

Yes. CION coordinates PET-CT scanning through partner imaging centres in Hyderabad. Your CION oncologist refers you to a partner centre for the scan and then reviews the report and discusses the findings with you. The scan itself takes place at the partner centre, not at a CION clinic. The team at your nearest CION centre can tell you which partner centre is closest to you and what preparation you will need beforehand.