MIBG is a nuclear scan test that uses injected radioactive material (radioisotope) and a special scanner to locate or confirm the presence of pheochromocytoma and neuroblastoma, which are tumors of specific types of nervous tissue.
Alternative Names: Adrenal medullary imaging
How the test is performed:
A radioisotope (MIBG, iodine-131-meta-iodobenzylguanidine) is injected into a vein. Later that day (or the next day) you lie on a table that is positioned under the arm of the scanner. The abdomen is scanned. You may be asked to return for repeated scans for 1 - 3 days. Each scan takes 1 - 2 hours.
After injection of the radioisotope, you are given Lugol's iodine solution to block uptake into the thyroid. Because the radiation from this radioisotope is fairly high compared to most other radioisotopes, some precautions may be necessary for a few days after the test. The nuclear medicine personnel will instruct about specific precautions, which may include flushing the toilet twice after each use (to dilute radioactive material excreted in the urine) or other precautions.
How to prepare for the test:
Lugol's iodine solution may be given before the test as well as after administration of the radioisotope.
You must sign an informed consent form.
A hospital gown is usually worn during the scan, although loose-fitting clothing may be allowed. Remove jewelry or metal objects before each scan.
How the test will feel:
There is a sharp needle prick when the material is injected. The radioisotope is not felt by the body, and the scan causes no sensation, but the table may be cold or hard. You must lie still during the scan.
Why the test is performed:
To confirm the presence of pheochromocytoma or neuroblastoma.
Normal values indicate areas of increased uptake of the radioisotope.
What abnormal results mean:
Most often, this test is used to locate pheochromocytoma. It may be very useful to detect multiple tumors or tumors that are located outside the adrenal tissues.
Additional conditions under which the test may be performed include multiple endocrine neoplasia (MEN) II
What the risks are:
The risks are about the same as for x-rays (radiation) and for needle pricks.
There is some exposure to radiation from the radioisotope. The radioisotope contains iodine, so precautions such as administration of Lugol's solution will prevent excessive uptake by the thyroid. There is significant exposure of the adrenal gland to radiation.
This test should NOT be performed on pregnant women because of the danger to the fetus from radiation.
Any time the body is penetrated (such as with a needlestick), there is a risk of infection. Injection into a vein also carries a slight risk of bleeding. The risk is no greater for this scan than for intravenous injection of any sort.
The radioisotope is costly and may not be available in all medical facilities. The person must be able to return for delayed images within 1 - 3 days.