MIBG Scan

What is an MIBG scan?

An MIBG scan is an imaging test used to see certain types of tumors. MIBG stands for meta-iodobenzylguanidine. It is a radioactive substance (also called a tracer) taken up by some types of tumors. A special camera detects the tracer and takes pictures.

An MIBG scan may also be called adrenal medullary imaging, I-123 MIBG scan, I-131 MIBG scan, or MIBG scintiscan.

An MIBG scan helps locate and diagnose neuroendocrine tumors like neuroblastoma. This scan can show when this type of tumor has spread to the bone and other organs. It can also show if this type of tumor responds to therapy.

The MIBG scan happens over 2 days. It includes the injection of a tracer and a special camera taking pictures of the body. The MIBG scan does not hurt. Your child will need to stay still for the imaging part of the test.

Before the MIBG scan

• Check insurance: If you have private insurance, check with your provider to find out how much of the test’s cost will be covered. They can also tell you how much you will need to pay.
  
• Ask questions: Talk with your care team about any concerns you may have.
• Explain the test to your child: Make sure your child knows the reason for the MIBG scan. You may want to ask a child life specialist to help.
• Take prescribed medicine to protect the thyroid: The doctor will prescribe potassium iodide drops (SSKI solution) to take before the injection until the day after the scan. The drops protect your child's thyroid gland from absorbing any radioactive iodine.

Medicines and MIBG scans

A member of the pharmacy staff should contact you to review your child’s medicines. They will tell you if you need to stop giving any medicines.

Some medicines can interfere with an MIBG scan. These include:

• Certain antidepressants
  • Amitriptyline (Elavil^®)
    
  • Imipramine (Tofranil^®)
  • Desipramine (Norpramin^®)
  • Nortriptyline (Aventyl® or Pamelor^®)
• Anti-nausea medicines
  • Promethazine (Phenergan^®)
  • Prochlorperazine (Compazine^® or Compro^®)
• Blood pressure medications
  • Labetalol (Trandate^®) – Should be avoided for at least 6 weeks before an MIBG injection. Tell the staff right away if your child takes this medicine.
• Other medicines:
  • Chlorpromazine (Thorazine^® or Largactil^®)
    
  • Thioridazine (Mellaril^®)
  • Haloperidol (Haldol^®)

Your child should not take medicine with pseudoephedrine or phenylephrine. These are found in many over-the-counter cold medicines. These substances can interfere with the scan.

Do not stop giving your child any medicines on your own. Talk with your child’s doctor, nurse, or a member of the pharmacy staff if you have questions.

How to prepare for an MIBG scan

Each care center has its own procedures. Talk to your care team about what to expect and how to prepare for your appointment.

• Talk to your child about staying still: It is important that your child knows what to expect and understands they will need to lie still during the test. A child life specialist or other care team member might help your child with relaxation techniques.
• Comfort items: Most centers will allow your child to bring a comfort item, like a stuffed animal or a blanket. Ask your care team if your child can bring a comfort item to the appointment.
• Eating and drinking before the scan: Follow your care team’s instructions for what your child can eat or drink before the scan. If your child is going to have general anesthesia, they must not eat or drink for several hours before the test. Your child’s care team will give you more specific instructions.
• Check in for the appointment: Be sure to arrive a few minutes early. Check in at the registration desk with your child. You may be asked to sign a consent form. Then you will wait until your child’s name is called.
• Be sure to let the care team know if your child:
  • Is uncomfortable in small spaces
  • Has trouble staying still or has specific behavior needs 
  • Might be pregnant
  • Is allergic to contrast agents or iodine
  • Has diabetes or kidney problems
• What to wear: Be sure your child dresses in loose, comfortable clothing. Avoid clothing and accessories that contain metal. Do not wear:
  • Belts
  • Zippers
  • Snaps
  • Buttons
  • Hair accessories
  • Watch
  • Jewelry
  • A non-permanent retainer 
  • Glasses

In some cases, your child may need to change into a hospital gown.

What to expect during an MIBG scan

The test takes place over 2 days. Your child does not have to be admitted into the hospital for the test.

On the first day, your child gets an injection of a tracer that certain cells in the body will absorb. This allows the special camera to see more about what is going on inside the body.

On the second day, a special camera takes pictures that help the doctors see inside the body.

The care center may have movies that your child can watch. You may want to bring books, devices, toys, or comfort items that your child likes. If the care team says it is OK, you may also want to bring a snack or a drink for after the test.

On the first day: injection of tracer

• Your child will get a tracer injection through an IV. The injection includes MIBG combined with a small amount of radioactive iodine. Tumor cells should absorb the tracer and show up when scanned the next day.
• You and your child can return home (or to patient housing) and resume normal activities.
• You will wait 24 hours to allow time for the tracer to move to tumor sites.

Pregnant women should not have direct contact with your child for 12 hours after the MIBG injection, or until instructed by the care team.

On the second day: imaging scan

• You and your child will return to the care center for the scan.
• Your child will lie very still on a table during the test. The test can last 1–2 hours, depending on your child’s size.
• The care team may secure your child with soft safety belts.
• A special camera will take pictures of the inside of the body. The pictures show if the tumor is present. They also show if the tumor has spread or gotten smaller.
• The camera will move around close to your child’s body, but it will not touch your child.
• The scan takes pictures of areas that absorbed the tracer. Doctors look for bright spots. The bright spots may show cancer.
• An MIBG scan does not hurt. But a child who finds it hard to stay still might need sedation or general anesthesia. If your child moves during the test, the scan will blur and must be repeated.
• When the scan is complete, a care provider will unfasten safety belts and disconnect the IV, if one was used.
• After the test, your child may leave and resume normal activities if they did not have sedation or general anesthesia. If your child did receive these medicines, they will need to recover first.

After the MIBG scan

A doctor called a nuclear medicine physician or radiologist will study the images and prepare a report of the results for your child’s care team. The report may take a few days.

Your health care provider will discuss the results of the MIBG scan with you. 

Possible risks of MIBG scans

The MIBG scan is a nuclear medicine test. It uses a small amount of radioactive iodine (tracer).

Nuclear medicine specialists carefully select the amount of tracer used. They want to have an accurate test with the least possible radiation exposure.

The amount of tracer depends on:

• Body weight
• Reason for the scan
• Body part being imaged

Even with small doses, you should take precautions with radiation. Follow your care team’s instructions before, during, and after the MIBG scan. This will include your child drinking lots of water to clear out the radioactive tracer from the body.

Questions to ask your care team

• Is an MIBG scan safe for my child?
• How long does the MIBG scan take?
• What are the instructions before, during, and after the scan?
• Will the test hurt?
• Can my child use an electronic device or other distraction techniques during the scan?
• How long will it take to get scan results?