Nuclear medicine

Why might I need one?

Nuclear medicine covers a wide range of tests, so the reason you need one depends on which test your doctor has requested. Common reasons include investigating or monitoring:

• bone problems, such as injury, infection, or the spread of cancer to the bone
• heart conditions, including coronary heart disease and damage after a heart attack
• thyroid conditions, including unusual lumps or an overactive or underactive thyroid
• kidney function and drainage
• lung problems, such as a suspected blood clot in the lungs
• cancer, including finding, staging and monitoring the response to treatment
• digestive symptoms, such as chronic diarrhoea linked to bile acid absorption
• brain conditions, including dementia, stroke, epilepsy and Parkinson's disease.

What are the benefits of having it?

Nuclear medicine scans are less invasive than many other diagnostic procedures and can help detect disease at an early stage, sometimes before it would be visible on other types of scan. Because they show function rather than just appearance, they can help pinpoint exactly where a problem is, which may mean you avoid more invasive tests or surgery.

Nuclear medicine is also older than CT, MRI and ultrasound, having been used in patients for more than 60 years, and the techniques involved are considered very safe for patients.

Are there different types of nuclear medicine?

Nuclear medicine covers many different scans, each looking at a different part of the body. Examples include:

• bone scans
• heart scans, such as a myocardial perfusion scan (blood supply to the heart) or a cardiac blood pool scan (how well the heart pumps)
• brain scans, such as a brain perfusion scan or a DAT scan
• lung scans, looking at blood flow and airflow
• kidney tests, such as a GFR test, a renogram, or a DMSA scan
• PET scans, most commonly an FDG PET scan
• thyroid scans
• a SeHCAT scan, which checks how well your gut absorbs bile salts.

Some scans combine two techniques, such as a SPECT-CT or PET-CT scan, which merges a nuclear medicine scan with a CT scan for more detailed information.

Nuclear medicine can also be used as a treatment, not just for diagnosis. Examples include radioactive iodine treatment for an overactive thyroid or thyroid cancer, and treatments for certain cancers, bone pain or joint pain.

How do I prepare for the test?

Preparation varies considerably depending on which nuclear medicine test you're having, so it's important to follow the specific instructions you're given. This may include:

• avoiding food and drink for a few hours beforehand
• not taking, or adjusting the timing of, certain medications
• practical details, such as when to arrive and whether you'll need someone to bring you home.

Always tell your care team about any allergies you have, any medications you take, and if you're pregnant or breastfeeding, since this can affect whether the test is suitable for you.

What happens during the test?

The scan itself often takes around 30 to 60 minutes, though this doesn't include any waiting time for the tracer to travel through your body beforehand.

1. You're given the radioactive tracer, most often as an injection, though sometimes by swallowing it or breathing it in, depending on the test
2. You may need to wait while the tracer travels to the area being examined – this can take anywhere from several minutes to a few hours, or, for some bone scans, longer
3. You lie on an exam table under a special camera, sometimes called a gamma camera or a PET scanner
4. The camera detects the radiation given off by the tracer, and a computer builds detailed images – you'll need to stay still so the images are clear
5. A nuclear medicine specialist reviews the images and writes a report.

What happens after the test?

You can usually go home straight away and return to your normal activities, including eating and drinking as usual. Drinking plenty of water can help flush the tracer out of your system a little faster. The tracer is generally fully cleared from your body within about 48 hours.

A nuclear medicine specialist reviews your images and sends a report to the doctor who referred you. You'll usually discuss the results at a follow-up appointment, though sometimes they're given over the phone or made available in your health records. This can take a few days.

If anything needs a closer look, you may be offered further tests, such as an MRI or CT scan, blood tests, or a biopsy.

Contact your care team if you notice swelling, itchiness or pain at the injection site, or develop a fever, nausea or vomiting afterwards.

What are the risks or side effects?

Nuclear medicine is generally very safe and doesn't usually cause side effects. The amount of radiation involved is low, though it's typically higher than for a standard X-ray; the dose used is always kept as low as possible while still giving a clear, useful result.

Possible risks include a rare allergic reaction to the tracer, and some soreness or redness at the injection site. Nuclear medicine scans aren't usually suitable if you're pregnant, so tell your care team if you are, or think you might be, or if you're breastfeeding.