PET-CT Scans — When You Cannot Lie Flat

Back pain is one of the most common reasons patients worry about a PET-CT, and it is routinely managed. The scanning team can place foam wedges under your knees and lower back to reduce spinal strain. In some cases the table itself can be angled slightly. Tell the centre in advance what position is most comfortable and how long you can hold it — they will plan the session around that.

Breathlessness when lying flat — orthopnoea — is seen often in oncology patients and many centres accommodate it. The scan can be performed semi-recumbent, with the head of the table elevated. The radiologist is told about the modified position so the images are read correctly. If your breathlessness is currently severe, ask your oncologist whether it is worth timing the scan for a more stable period.

PET-CT scanners vary in their bore width and weight capacity. If you are concerned, ask the imaging centre directly about their machine's specifications before your appointment. This is a routine question. If one centre cannot accommodate you, another with a wider-bore scanner may be able to — your care coordinator can help identify the right one.

The PET-CT scanner is open at both ends — it is not a closed tunnel — which many patients find less distressing than they expected. If anxiety or pain makes staying still difficult, tell the team before your appointment. Your oncologist can sometimes prescribe a short-acting medication for the day. A brief walk-through of the scanning room beforehand can also help.

PET-CT uses ionising radiation and a radioactive tracer. It is not performed during pregnancy. If you are pregnant, or think you may be, tell your oncologist and the imaging centre immediately. Your team will use alternative imaging — MRI, which avoids ionising radiation, is often appropriate — to answer the clinical question safely without delay to your care.

A small number of patients cannot have the scan in any position — because of acute pain, severe breathlessness, or inability to stay still. Your oncologist will then consider which other imaging answers the same clinical question: MRI in a modified position, CT alone, a bone scan, or ultrasound, depending on your cancer type and what is being assessed.