MIBG scan

Author: Dr Dee Nandurkar*

What is an MIBG scan?

An MIBG scan is a nuclear medicine scan that involves an injection of a radioactive medication (radiopharmaceutical) called iodine-123 meta-iodobenzylguanidine – MIBG for short. The radiopharmaceutical is injected into a vein usually on the inside of the elbow.

A special gamma camera (a type of scanner) takes images or pictures to confirm if there are tumours (a lump or growth) called neuroendocrine tumours. These tumours involve specific types of nerve tissues and most commonly include pheochromocytomas (a rare tumour of the adrenal gland – which is located above and on the surface of the kidneys) and neuroblastomas (cancers that affect nerve tissue). Neuroblastomas usually begin in the adrenal gland, but might also be found elsewhere in the body.

Why would my doctor refer me to have this procedure?

Your doctor might suspect the presence of a neuroendocrine (nerve-related) tumour. If so, your doctor may request this test for diagnosis and to detect the presence, absence, or spread of a known or new tumour.

How do I prepare for an MIBG scan?

Some medicines may need to be stopped for around 3 days before the test is carried out.
These medications include:

• tricyclic antidepressants;
• antihypertensives;
• cocaine;
• sympathomimetics
• decongestants containing pseudoephedrine, phenylpropanolamine and phenylephrine.

Talk to your referring doctor or the nuclear medicine staff where you are having your MIBG scan as to whether you need to stop any medications you are taking and for how many days before the scan.

Before having the scan, you will have to take potassium iodide tablets or Lugol’s iodine solution to prevent the thyroid gland from absorbing too much radioactivity. The thyroid gland is more susceptible to attracting radioactivity than other parts of the body, and it can lead to malfunction of the thyroid gland. The nuclear medicine facility where you are having the scan will advise you about when you need to take this medication and the dose.

It is important that you tell the staff where you are having the scan done if you are (or think you could be) pregnant or are breast-feeding.

This study may not be suitable for pregnant women because of the radiation dose to the growing foetus (unborn baby). Please discuss this with your referring doctor.

Women who are breast-feeding and people who are the primary or sole carer for small children may need to make special preparations for after the scan. This is due to the small amount of radioactivity your body may release for a while afterwards. Talk to your referring doctor or the nuclear medicine facility where you will have the scan for details and instructions as to how to manage your breast-feeding. The Australian Radiation Protection and Nuclear Safety Agency has recommendations about breast-feeding and close contact with children after nuclear medicine tests. For further information: see InsideRadiology: Nuclear Medicine.

What happens during an MIBG scan?

A MIBG scan is carried out over 2 days

On the first day: You will be given an injection of radiopharmaceutical usually on the inside of the elbow. Your blood pressure will be monitored during and after this injection.

Four hours later, after the radiopharmaceutical has spread around your body, you will be given the scan. A special gamma camera (a type of scanner) will take images while you are lying on a bed. The camera will move over your body, but not touch it.

On the second day: You will return to have the images taken again. You will not have another injection

Are there any other after effects of an MIBG scan?

The initial injection may cause an increase in your blood pressure. If it does, you will need to stay in the radiology facility for about 30 minutes after the scan so that your blood pressure can be monitored. The chance of this happening is less than 10%.

No other side-effects are expected.

How long does an MIBG scan take?

The scanned images will be taken over 2 days. On the first day there will be two visits. The first visit involves receiving an injection of a small dose of radiopharmaceutical and monitoring of blood pressure for 15–30 minutes. You will then be able to leave, and return 4 hours later for your first set of images, which will take around an hour.

The following day you will need to return for the second set of images, which will take from 60 to 90 minutes.

What are the risks of an MIBG scan?

Apart from the possibility of an increase in blood pressure, which is a relatively rare side-effect, there are no significant risks. Any increase in blood pressure usually resolves within 48 hours after the injection and rarely requires treatment.

There is a small dose of ionising radiation that is similar to other routine medical imaging tests (see InsideRadiology: Radiation risk of medical imaging for adults and children).

The dose of the radiopharmaceutical is relatively small, approximately twice the normal annual background radiation from the environment.

If you are breast-feeding or caring for young children, see the “How do I prepare” section for more information about special precautions you may need to take.

What are the benefits of a MIBG scan?

It will help your doctor to find or confirm the presence of a tumour (a lump or growth) found on a specific type of nerve tissue. This could be a rare tumour of the adrenal gland (which is located above and on the surface of the kidneys) or a cancer that affects nerve tissue. An MIBG scan examines the whole body, so it will also help determine if the cancer has spread anywhere else within the body.

Who does the MIBG scan?

A nuclear medicine technologist will give you the injection of radioactive medication and take the images. A nuclear medicine physician (a specialist doctor) will assess and interpret the images and provide a report of the MIBG scan to your referring doctor.

Where is an MIBG scan done?

MIBG scans are carried out in the nuclear medicine department of a public or private hospital or in a private radiology practice.

When can I expect the results of my MIBG scan?

A report is written by the nuclear medicine physician after reviewing your images and taking into account your medical details provided by your referring doctor.

The radiology facility where you are having the scan will be able to tell you when your doctor is likely to receive the written report.

It is important that you discuss the results with the doctor who referred you, so that they can explain what the results mean for you.

*The author has no conflict of interest with this topic.

Page last modified on 18/5/2018.