HOW ULTRASOUND WORKS: Ultrasound is a medical imaging technique that uses high-frequency sound waves and their echoes. It is similar to how bats navigate in the dark, and the SONAR used by submarines underwater. The machine transmits high-frequency sound pulses into the body using a probe. The sound waves travel through the body and bounce off any boundaries, such as between fluid and soft tissue, tissue and bone. Some of the sound waves are reflected back to the probe, while others travel further through until they bounce off another boundary. All the reflected waves are recorded by the machine, which then calculates the distance each sound wave traveled based on how long it took the sound wave's echo to return. This data is used to form a two-dimensional image based on the distances and intensities of those echoes.
ABOUT BREAST CANCER: Breast cancer is a type of cancer in which cells in the breast become abnormal and grow and divide uncontrollably, eventually forming a mass called a tumor. Some tumors are benign, meaning that they do not invade other types of tissue, although if they become big enough, they can interfere with some bodily functions, such as the flow of blood or urine. Malignant tumors have cells that can invade nearby tissues. When a cancer "metastasizes," cells from the original tumor break off and travel to other parts of the body via the blood or lymph systems. More than 75 percent of breast cancers begin in the milk ducts within the breast. The next most common site is in the glandular tissue that makes the milk.