Further tests for thyroid cancer

CT (computerised tomography) scan Back to top

A CT scan takes a series of x-rays which builds up a three-dimensional picture of the inside of the body. This type of scan is sometimes used to help the doctors know exactly how the cancer is affecting you and can be good at detecting thyroid cancer, if it has spread to the lymph nodes or the lungs. This helps the doctors to plan the most effective treatment for you. The scan is painless and takes from 10–30 minutes. CT scans use a small amount of radiation, which will be very unlikely to harm you and will not harm anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan.

You may be given a drink or injection of a dye which allows particular areas to be seen more clearly. For a few minutes, this may make you feel hot all over. If you are allergic to iodine or have asthma you could have a more serious reaction to the injection, so it is important to let your doctor know beforehand. You’ll probably be able to go home as soon as the scan is over.

MRI (magnetic resonance imaging) scan Back to top

This test is similar to a CT scan but uses magnetism instead of x-rays to build up a detailed picture of areas of your body. Before the scan you may be asked to complete and sign a checklist. This is to make sure that it’s safe for you to have an MRI scan because the scanner is a powerful magnet. The checklist asks about any metal implants you may have, for example a pacemaker, surgical clips, bone pins, etc. You should also tell your doctor if you have ever worked with metal or in the metal industry as very tiny fragments of metal can sometimes lodge in the body. If you do have any metal in your body it’s likely that you won’t be able to have an MRI scan. In this situation another type of scan can be used.

Before having the scan, you’ll be asked to remove any metal belongings including jewellery. Some people are given an injection of dye into a vein in the arm, which doesn’t usually cause discomfort. This is called a contrast medium and can help the images from the scan to show up more clearly.

During the test you’ll be asked to lie very still on a couch inside a long cylinder (tube) for about 30 minutes. It is painless, but can be slightly uncomfortable, and some people feel a bit claustrophobic during the scan. It’s also noisy, but you’ll be given earplugs or headphones. You will be able to hear, and speak to, the person operating the scanner.

Thyroid radioisotope scan Back to top

This test uses a small amount of a slightly radioactive iodine. Thyroid cells absorb iodine more quickly than other parts of the body. The iodine will collect in the thyroid gland and the radiation can be seen on a scanner. Cancer cells don’t usually absorb the iodine as well as normal thyroid cells and can show up as areas of no radiation within the thyroid gland. These are called cold areas or cold nodules.

The radioactive iodine is injected into a vein in your arm. After about 20 minutes you will be asked to lie on a couch and a machine called a gamma camera will be positioned over your neck. The scan itself is painless and the radioactive injection has no harmful side effects.

A thyroid radioisotope scan is sometimes used after treatment with radioactive iodine|. 

PET (positron emission tomography) scan Back to top

PET scans are a specialist type of scan and you may have to travel to another centre to have one. They aren’t always necessary and are mainly used if other investigations are negative or if the thyroid cancer comes back. You can discuss with your doctor whether one would be useful in your case.

A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. A very small amount of a mildly radioactive substance is injected into a vein, usually in your arm. A scan is then taken a couple of hours later. Areas of cancer are usually more active than surrounding tissue and show up on the scan.