Radiation Risk of Medical Imaging During Pregnancy
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A parathyroid MIBI scan is used in nuclear medicine to look at possible problems involving the parathyroid gland(s). The parathyroids are four small hormone glands lying close to or embedded in the back surface of the thyroid gland, in the front of the neck.
The parathyroid scan uses sestamibi (or MIBI for short), which is a very safe liquid radioactive material that is injected into the body and absorbed by the overactive parathyroid, but not by healthy parathyroids. An overactive (hyperactive) gland that produces excessive hormone is picked up by the scan on the pictures or images taken by a gamma camera (a type of machine or scanner used in nuclear medicine).
If you have an elevated blood calcium level and parathyroid hormone level, then finding the overactive parathyroid tissue will help the surgeon find the lesion (tumour or growth), making the surgery easier and shortening surgical time.
This allows minimally invasive surgery to be carried out rather than a larger open operation.
There is no special preparation necessary before the scan. You may eat and drink as normal.
It is important that you let staff at the hospital or radiology facility where you are having the scan know if you are (or think you could be) pregnant or are breast-feeding.
A parathyroid MIBI scan may not be suitable for pregnant women because of the radiation dose to the foetus (unborn baby). Women who are breast-feeding may need to make special preparations to stop breast-feeding for a short time after having the scan. Please discuss these with your referring doctor.
If you are a carer for small children you will need to avoid close contact with them for a short time after having the scan. This is due to the small amount of radioactivity your body may release. Talk to your referring doctor or the nuclear medicine facility where you will have the test for details (for further information see: InsideRadiology Nuclear Medicine). If you are taking thyroid medications, you may need to stop taking these before you have the scan. Your referring doctor will advise you about this.
Please tell your referring doctor or the staff carrying out the scan if you think you may not be able to stay still for a prolonged period of time while the images are being taken or if you are claustrophobic, as the camera taking the images will be quite close to your head, although it will not touch it.
When you arrive at the hospital nuclear medicine department or private radiology facility, a nuclear medicine technologist will ask you questions about your condition to obtain a medical history.
The technologist will insert a small needle into a vein on the back of your hand or in your arm to inject the MIBI material. You will then lie on a special scanning bed under a large gamma camera that will take images of your parathyroids in your neck and chest area.
The gamma camera detects the radioactive MIBI material your parathyroids will have absorbed. The camera will move around your head. It will come quite close to your head, but will not touch it. You will need to lie very still for a period of time underneath the gamma camera, as it takes the images or pictures of your neck and chest area.
In some cases, another radioactive material is given before the MIBI so that the thyroid gland alone can be picked up by the scan on the images taken by the gamma camera. This shows the position of the parathyroid glands in relation to the thyroid gland.
It can take up to 40 minutes for these images to be taken.
Once the images are completed, you will be asked to return in 2–3 hours so that further images of your neck and chest area can be taken. No further injections are given for the second session. The camera will rotate over a 360-degree arc around you, producing a series of images that include three-dimensional SPECT (single photon emission computed tomography) images. This session will take about 30 minutes.
There are no after effects from a parathyroid MIBI scan. You will feel fine and be able to drive yourself home.
You may experience a metallic taste in your mouth (but only for a few minutes) when the radioactive material is injected.
Rarely, you may have feelings of tingling, flushing (redness), nausea (sickness), erythema (redness of the skin), a diffuse (spread) rash or headache.
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.
There are two sessions, with a 2–3-hour break in between. The first session will take about 40 minutes, and the second session about 30 minutes.
There are no associated risks with having a parathyroid MIBI scan.
The parathyroid MIBI scan will determine if you have hyperactive parathyroid gland(s), and provide information as to the location.
A nuclear medicine technologist will carry out your scan.
A nuclear medicine consultant (a specialist doctor) will look at your scan images and may ask questions about your condition. If you have any other X-rays or ultrasounds of your parathyroid gland/neck at home, please take them with you when you have the scan so the consultant can compare them with your parathyroid MIBI scan.
A parathyroid MIBI scan is only carried out in a nuclear medicine department of a public or private hospital or a private radiology facility able to provide this service.
After the procedure is complete, a nuclear medicine consultant will study the images along with your medical history to interpret and make an assessment of the images. The consultant will then produce a report that will be forwarded to your referring doctor within five to seven business days.
If your referring doctor needs the results sooner, contact can be made with the nuclear medicine consultant on the day of the scan for a verbal report over the telephone.
Page last modified on 18/5/2018.
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RANZCR® intends by this statement to exclude liability for any such opinions, advices or information. The content of this publication is not intended as a substitute for medical advice. It is designed to support, not replace, the relationship that exists between a patient and his/her doctor. Some of the tests and procedures included in this publication may not be available at all radiology providers.
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