Ultrasound (or sonogram) technology allows doctors to "see" inside a patient without resorting to surgery. A transmitter sends high-frequency sound waves into the body, where they bounce off the different tissues and organs to produce a distinctive pattern of echoes. A receiver "hears" the returning echo pattern and forwards it to a special computer, which translates the data into an image on a television screen. Ultrasound is better than x rays at distinguishing subtle variations between soft, fluid-filled tissues, so it is particularly useful in providing diagnostic images of the abdomen, breast, eye, pelvis, scrotum, and thyroid. Unlike x rays, it does not damage tissues with ionizing radiation. Improvements in the technology, application, and interpretation of ultrasound continue. Its low cost, portability, versatility, safety, and speed have made it a popular medical imaging technique. Ultrasound remains faster and less expensive than computed tomography scans (CT), its...