Reviewed by: HU Medical Review Board | Last reviewed: May 2017.
Imaging tests may be needed to determine melanoma stage and best course of treatment. These tests are done for people with late stage melanoma (III or IV) or symptoms of cancer metastasis.1 After melanoma has been treated, you may have imaging tests to see whether treatment worked.2 Imaging tests are also used to plan radiation therapy, if this type of treatment is necessary.
Imaging is not necessary for everyone with melanoma. Imaging tests are not usually done if the tumor is entirely in the skin and you do not have symptoms of metastasis.3
Risks of unnecessary imaging tests include:3
- False-positive results, which are results indicating that cancer is present or spreading, when it truly is not. False-positive results can lead to more tests, surgery, and worry.
- Radiation exposure.
- Additional cost.
Computed tomography (CT) imaging uses x-rays to produce detailed pictures of an area inside your body.4 As the CT scanner moves around your body, it takes pictures continually. Each picture shows a “slice” of your body. A computer program puts the slices together to create a 3-dimentional picture. The picture shows your organs, bones, and other tissues.
Your doctor will look at the CT scan for suspicious spots on your lungs, liver, or other organs.2 Unusual spots might indicate that melanoma has spread. The CT scan can also reveal enlarged lymph nodes.
CT scan is painless. During the scan, you will lie very still on a table. This may be physically uncomfortable. Some people experience claustrophobia.4,5 If you have concerns about risks of radiation exposure, discuss them with your doctor. Tell your doctor if there is a chance you might be pregnant.
Positron emission tomography (PET) measures body functions, such as blood flow, oxygen use, and sugar (glucose) uptake.5 Before a PET scan, you are injected with a small amount of radioactive sugar.2 Because cancer cells grow and divide so quickly, they use more sugar than other cells. The radioactive sugar accumulates in the cancer cells. Special cameras detect the radioactivity and produce pictures of the most active areas of your body.5 The PET scan is painless, except for a needle prick when the intravenous (IV) line is inserted.5
PET scan is often done together with a CT scan.2,5 With information from these two imaging tests, your doctor can find the most active areas and evaluate them in detail.
You will be given the radioactive sugar about 1 hour before the test. Once the test starts, you will be asked to lie still while the scanner creates pictures. A PET/CT lasts about 30 minutes. You may feel discomfort from lying still or claustrophobia.5 Your doctor may recommend drinking plenty of water to flush the radioactive material out of your body after the procedure.
X-ray imaging uses electromagnetic waves to create a picture of the inside of your body.6 A chest x-ray may be done to look for melanoma that has spread to the lungs.2 The procedure is quick and painless. You are exposed to a small amount of radiation. If you have concerns about risks of radiation exposure, discuss them with your doctor. Tell your doctor if there is a chance you might be pregnant.6
Magnetic resonance imaging (MRI) uses a strong magnet and radiowaves to produce a picture of your organs and body structures.7 MRI creates better images of soft tissue than CT scans do.7 This makes MRI particularly good for finding cancer that has spread to the brain or grown into a nerve. MRI does not expose you to radiation.
MRI is a painless procedure that takes 30 to 60 minutes.7 Lying still in the machine may cause discomfort or claustrophobia. The loud noise may be bothersome, so you will be given headphones to wear.