Cancer Tests Overview See All Understanding Cancer Tests in Cancer Tests Overview Doctors use tests like mammography, MRI) and CT scans to help them screen for, diagnose, treat, and monitor cancer. Read on to learn more about them. ...more Cancer Diagnostic Imaging in Cancer Tests Overview Imaging—X-rays, CT scans, MRIs—is a process that makes pictures of body structures and organs. It is used to find tumors and other abnormalities, to determine the extent of disease, and to evaluate the effectiveness of treatment.