Imaging, by itself, is not a treatment but can help in making better decisions about treatments. The same imaging technique can help doctors find cancer, tell how far a cancer has spread, guide delivery of specific treatments, or find out if a treatment is working.
Here is some information about the uses of imaging:
Screening for cancer: Imaging can be used to determine if a person has any suspicious areas or abnormalities that might be cancerous. Mammograms are an example of a familiar imaging tool used to screen for breast cancer. Screening for cancer is usually recommended for people who are at increased risk (due to their family history, lifestyle, or age) for developing a particular type of cancer.
Diagnosis/staging: Imaging can be used to find out where a cancer is located in the body, if it has spread, and how much is present. Used in this way, imaging can help determine what stage (how advanced) the cancer is, and if the cancer is in, around, or near important organs and blood vessels. If a biopsy (taking a small amount of the tumor for laboratory examination) is necessary, imaging may be used to help guide doctors to the tumor and take a sample of it.
Guiding cancer treatments: Imaging can be used to make cancer treatments less invasive by narrowly focusing treatments on the tumors. For instance, ultrasound, MRI, or CT scans may be used to determine exact tumor locations so that therapy procedures can be focused on the tumor, minimizing damage to surrounding tissue.
Determining if a treatment is working: Imaging can be used to see if a tumor is shrinking or if the tumor has changed and is using less of the body's resources than before treatment. For example, in some current cancer treatment trials, X-rays, MRIs, and CT scans are done at intervals to see if a treatment is working and the tumor is shrinking. PET and other nuclear medicine techniques are used to monitor the ways the tumor uses the body's resources. Magnetic resonance spectroscopy is used to study chemical changes in the tumor.
Monitoring for cancer recurrence: Imaging can be used to see if a previously treated cancer has returned or if the cancer is spreading to other locations.