Nuclear medicine: PET and isotope scans, radionuclide therapy and what to expect

Nuclear medicine is a diagnostic and therapeutic specialty built on radiopharmaceuticals: medicines that carry a small amount of radioactive material to a particular tissue. A camera outside the body detects the signal and builds an image, so the scan shows activity such as blood flow, bone turnover, hormone uptake or the metabolic rate of cells.

The service is delivered by teams rather than a single type of doctor. Consultants may be nuclear medicine physicians, radiologists or others with specialist training. The British Nuclear Medicine Society describes its professional community as clinicians, scientists, physicists, radiographers, technologists, pharmacists, nurses and researchers, which reflects how many disciplines are needed to prepare tracers, run scanners and report results.

Departments are usually found in larger hospitals, as the facilities need shielded areas, a radiopharmacy and trained staff.

The NHS says a PET scan is used to diagnose and plan treatment for conditions such as cancer and also for dementia, epilepsy and after a heart attack, and that it can be combined with CT (PET-CT) or MRI (PET-MRI) when more detailed images are needed. Cancer applications include working out the size of a cancer and how far it has spread.

Some radioactive medicines are used for treatment. The NHS says radioactive iodine treatment for thyroid cancer is taken as a tablet or drink and uses radiation to kill cancer cells, given after surgery to destroy cells that may have been left behind or if cancer has come back or spread.

NICE has appraised radium-223 dichloride for treating hormone-relapsed prostate cancer with bone metastases. Other radioligand therapies, such as lutetium-177 PSMA for advanced prostate cancer or lutetium-based treatment for neuroendocrine tumours, are used in specialist centres, and funding and eligibility depend on current NHS commissioning decisions, so ask your oncologist what applies to you. Radioactive treatments often involve temporary precautions, such as limiting close contact with young children or pregnant women for a period.

The NHS says a PET scan uses a small amount of radiation. The tracer is given by injection into a vein, you then rest while it travels to the target tissue, and you lie on a bed that moves through the scanner. The scan itself is painless. Radiation exposure is kept as low as reasonably practicable, and the benefit of an accurate diagnosis is weighed against it for each referral.

Tell the department if you are pregnant or might be, if you are breastfeeding, if you have diabetes or take medicines, and if you may struggle to lie still or are claustrophobic, as the NHS advises. Staff may ask you to drink plenty of fluid and pass urine often to flush the tracer out, and may advise short-term precautions with children or pregnant people.

Scans on the NHS are requested by a hospital specialist, usually an oncologist, cardiologist, neurologist or endocrinologist, after a clinical decision and, for PET-CT, often a multidisciplinary meeting. The request needs to meet national or local criteria, which is why the scan is not generally available on direct request.

Private PET-CT and isotope scanning is offered by hospitals and imaging providers, usually with a specialist or GP referral. Check what is included, who reports the scan, whether previous imaging is compared, how the report reaches your clinician and what happens if the scan finds something unexpected. A scan without a clinician ready to act on the result adds cost without much benefit.

• Follow the written instructions for fasting and exercise exactly, since they affect image quality.

• Bring a list of medicines, details of diabetes treatment and previous scan reports.

• Wear clothing without metal and expect to change into a gown.

• Arrange childcare and transport if you will be advised to avoid contact with young children or pregnant people afterwards.

• Ask how long you will be at the department, as the tracer needs time to distribute.

Nuclear medicine departments run planned services. If you have severe breathlessness, chest pain, sudden confusion or collapse, call 999. If you feel unwell after an injection, with swelling, rash, difficulty breathing or palpitations, tell staff immediately or call 999 once you have left. Contact the department or NHS 111 for questions about precautions after radioactive treatment.