PET scans and theranostics

PET scans and imaging

PET uses a small amount of radioactive medicine called a tracer to show activity in tissues. It is usually combined with a CT scan (computed tomography), which shows the body's structures. The images help with diagnosis, assessing the extent of cancer and checking how treatment is working. A diagnostic scan does not treat the cancer.

Your team chooses the tracer that can answer the question about your care. Common scan names include:

• Fluorodeoxyglucose (FDG), which shows how tissues use a sugar called glucose.
• Prostate-specific membrane antigen (PSMA), a protein targeted by scans for prostate cancer.
• Dodecanetetraacetic acid (DOTA), which holds the radioactive label in tracers used to look for particular docking sites on tumour cells.
• Dihydroxyphenylalanine (DOPA), a substance involved in making chemical messengers, used as the basis of a tracer for selected tumours.
• Fibroblast activation protein inhibitor (FAPI), which targets a protein often found on support cells around tumours.

You only need to follow the preparation instructions for the scan you are having.

• Preparing for a PET-CT scan

  Food, medicines, diabetes, the appointment and getting your results.

• Understanding your PET scan name

  A plain-language guide to FDG, PSMA, DOTA, DOPA and FAPI.

• Having an MIBG scan

  Metaiodobenzylguanidine (MIBG) is used in a different type of nuclear medicine scan for certain tumours.

Theranostics and treatment

Theranostics connects imaging with treatment. A scan looks for a target on or around cancer cells. If the target is suitable, a related radioactive medicine may be used to deliver treatment. The scan helps select treatment; it does not guarantee that treatment will help.

Your cancer type, previous treatment, blood tests and general health also guide the decision. The aim may be to control cancer, reduce symptoms or, for some thyroid cancers, treat tissue remaining after surgery.

• Lutetium-177 PSMA treatment

  For selected people with advanced prostate cancer.

• PRRT for neuroendocrine tumours

  Peptide receptor radionuclide therapy (PRRT) targets specific docking sites on suitable neuroendocrine tumour cells. These tumours develop from cells that can make hormones.

• Radioactive iodine for thyroid cancer

  For selected thyroid cancers that take up iodine.

• FAPI scans and treatment

  Imaging and experimental treatments that target fibroblast activation protein (FAP).

• MIBG treatment

  For selected tumours that take up MIBG.

• Radioembolisation for liver tumours

  Radiation delivered through the liver’s blood vessels, also called selective internal radiation therapy (SIRT) or transarterial radioembolisation (TARE).

These treatments use different medicines and preparation plans. Liver radioembolisation also needs its own blood-vessel mapping procedure.

Planning your care together

Your oncologist and nuclear medicine specialist work together to explain the purpose of the appointment, the likely benefit and your options. Tell them about any difficulty with travel, medicines, diabetes, childcare or personal care. This helps the team make a plan you can follow.

You do not need to memorise the technical terms. Your team can explain what matters for your care.

Questions you may have