MIBG scan

Author: Dr Dee Nandurkar*

What is a MIBG scan?

An MIBG scan is a nuclear medicine scan that uses iodine-123 meta-iodobenzylguanidine – MIBG for short. An MIBG scan is commonly used for detection of neuroendocrine tumours, such as neuroblastoma and phaeochromocytoma. It can also aid in the detection of carcinoid and medullary thyroid carcinoma.

What are the generally accepted indications for an MIBG scan?

• Diagnosis of a suspected neuroendocrine tumour (phaeochromocytoma and neuroblastoma) when there is hormonal indication of one.
• Determine staging of a known neuroendocrine tumour.
• Determine suitability for MIBG therapy.

What are the prerequisites for having an MIBG scan done?

Results of serum and urinary catecholamines are necessary at initial presentation before approval of the scan by the nuclear medicine department. A history of previous neuroendocrine tumour is required for follow-up MIBG scans.

What are the absolute contraindications for an MIBG scan?

This study may not be suitable for pregnant women because of potential harm to the developing foetus. In pregnancy, the timing of the scan needs to be considered in relation to the benefit versus risk to the foetus: this should be discussed with the nuclear medicine specialist.

What are the relative contraindications for an MIBG scan?

Women who are breast-feeding may need to make special preparations after the test to stop breast-feeding for a short time. Expressing and storing breast milk before the scan, followed by expressing and discarding the breast milk for 22 hours after the injection of the radiopharmaceutical should be considered to avoid unnecessary radiation to the infant.

See InsideRadiology: Nuclear Medicine for further information about the precautions to take with nuclear medicine studies for breast-feeding patients and those in close contact with children.

What are the adverse effects of an MIBG scan?

There is a relatively small risk of a transient increase in blood pressure at the time of the initial injection. The patient is generally monitored in the nuclear medicine department for this over the initial 30 minutes. Any hypertension usually resolves within 48 hours after injection and rarely requires medical therapy.

Is there any specific post procedural care required following an MIBG scan?

As I-123 is excreted in breast milk, if used in nursing mothers, formula feeds will need to be replaced for breast milk for at least 22 hours. For further details, please see InsideRadiology Nuclear Medicine: Referrer information.

Are there alternative imaging tests, interventions or surgical procedures to an MIBG scan?

Although the MIBG scan is the test of choice for detection of a phaeochromocytoma and neuroblastoma, at times poorly differentiated tumours can be MIBG-negative. In this case, detection is better achieved with positron-emission tomography (PET) scans. By contrast, PET scans can yield false negative results in well-differentiated, slow-growing tumours.

MIBG imaging performs better with a benign phaeochromocytoma, whereas octreotide and PET scans are more sensitive for detection of a malignant phaeochromocytoma.
Generally, MIBG imaging is superior to PET imaging for detecting well-differentiated neuroblastomas. However, PET is beneficial in tumours with aggressive or de-differentiated histology, that fail to concentrate MIBG or are weakly MIBG-positive.

Some neuroendocrine tumours, such as paragangliomas, can be MIBG-negative, but may be detected with indium 111-pentetreotide (octreotide scan) or DOTA-TATE (PET) scans.

If you require more information, please contact your nuclear medicine specialist to determine which nuclear medicine study would be the most appropriate for your patient.

Anatomic imaging with computed tomography and magnetic resonance imaging is often complimentary, as it is sensitive, but not specific for tumour type.

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

Page last modified on 18/5/2018.