A sonogram is the image of a part of the body that is viewed during an ultrasonography (also called ultrasound) examination. Ultrasonography is an imaging technique in which high-frequency (ultrasound) sound waves are sent to a part of your body. Echoes of the ultrasound waves bouncing off the tissues of your body are displayed as images (i.e., the sonogram) on a viewing screen.
The best way to understand what an ultrasound examination (also called exam) does is to first understand what it does not do. Ultrasound exams are not a substitute for mammography (i.e., mammograms), nor are ultrasound exams recognized as a general screening tool for cancer.
Instead, an ultrasound exam is most often used in conjunction with other tests. For example, if a mammogram shows some sort of abnormality, or if a doctor has felt something unusual during a clinical exam, an ultrasound exam may be used to determine whether the abnormality is solid (such as either a benign fibroadenoma or a cancer) or fluid-filled (such as a benign cyst).
The sonogram results will help the doctor distinguish between a solid and a fluid-filled abnormality. However, the sonogram results of an ultrasound exam cannot determine whether a solid abnormality is cancerous, nor can the sonogram results of an ultrasound exam detect calcifications.
In addition, ultrasonography of the breast is a common screening technique used in women under age 30. A young woman's breast tissue tends to be very dense and full of milk glands. On a mammogram, dense breast tissue looks white, which makes it almost impossible to see any benign (non-cancerous) or cancerous growths, which also would be read as white. Many doctors say that trying to find a tumor in the midst of dense gland tissue in a mammogram can be like finding a polar bear in a snowstorm. Sonograms from ultrasonography offer a better glimpse of young patients' breast tissue.
Also, the sonogram results seen during ultrasonography are used to guide biopsy needles to exact spots in the breast where anything suspicious has been located.