As for any cancer, imaging of the body is necessary to determine where the cancer is located in its original site, and to determine if it has spread to other locations in the body. For thyroid cancer, there are a number of different tests that are typically used:
• Computed Tomography (CT)
• Magnetic Resonance Imaging (MRI)
• Positron Emission Tomography (PET) Scan
• Nuclear Medicine Imaging
Ultrasonography is an imaging procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echo patterns are shown on the screen of an ultrasound machine, forming a picture of body tissues called a sonogram. This type of study is typically the first study done to examine the thyroid, since images are very good at detecting nodules or other lumps within the gland. Ultrasonography can also detect abnormal lymph nodes in some parts of the neck. Because the pictures are obtained in “real time”, the ultrasound is often used to guide a fine needle biopsy of the thyroid or lymph nodes in order to obtain a specimen for cytology (see below)
Computed Tomography (CT) and Magnetic Resonance Imaging (MRI)
These are imaging tests which allow physicians to get a wider picture of differing parts of the body. CT scanning (“CAT scan”) uses X-rays to generate the images, whereas MRI images are generated with magnetic energy (no X-rays involved). These tests give slightly different levels of detail, so sometimes one study is preferable, depending on the circumstances. In thyroid cancer patients, studies may be done to look at the neck, chest or abdomen, or more rarely, the brain, in order to determine if there is evidence for spread of the abnormal cells.
Integrated PET-CT Imaging
A Computed Tomography (CT) scan can suggest the presence of cancer if lymph nodes are enlarged, but may not be conclusive. And while a Positron Emission Tomography (PET) scan is very accurate in diagnosing cancer, it may not provide good anatomic detail, making it hard for doctors to say exactly where in the body the cancer is located. An integrated PET-CT scanner, however, provides an exact picture of any suspected cancer.
Nuclear Medicine Imaging
In this method of diagnostic imaging, the patient is given a very small amount of radioactive material. The radioactive substance collects in the part of the body to be imaged, where sophisticated instruments detect it and process that information into an image. Several types of nuclear medicine imaging are used to detect tumors; each type has advantages and disadvantages, depending on the conditions and the part of the body to be imaged. For thyroid imaging, a typical study involves taking a pill or liquid containing a small amount of radioactive iodine. This agent, which is taken up only by thyroid cells (and most thyroid cancers), is then imaged by using a special camera to determine where the radioactivity (and the thyroid cells) are found in the body.