A mammogram is a radiographic image of the breast. Mammograms can be used to check for breast cancer in women who have no signs or symptoms of the disease. This type of mammogram is called a screening mammogram. Screening mammograms typically involve two radiographic images of each breast. These images make it possible to detect tumors that cannot be felt. Screening mammograms can also find micro calcifications (tiny deposits of calcium) that sometimes indicate the presence of breast cancer. Mammograms can also be used to check for breast cancer after a lump or other sign or symptom of the disease has been found. This type of mammogram is called a diagnostic mammogram. A diagnostic mammogram can also be used to evaluate changes found during a screening mammogram or to view breast tissue when it is difficult to obtain a screening mammogram because of special circumstances, such as the presence of breast implants. Mammography is believed to reduce mortality from breast cancer as early detection of the disease with screening mammography means that treatment can be started possibly before it has had an opportunity to metastasize.