ultrasound scanning

Ultrasound scan of a 12 week-old fetus showing (from right) the head, an arm, the body, and a foot. Such scans are often taken at around the twelfth week of pregnancy to determine whether any obvious developmental abnormalities have occurred.

In medicine, the use of ultrasonic pressure waves to create a diagnostic image. It is a safe, noninvasive technique that often eliminates the need for exploratory surgery.

The sound waves transmitted through the body are absorbed and reflected to different degrees by different body tissues.

By recording the returning ‘echoes’, a picture of the various structures being scanned can be built up. Free of the risks of ionizing radiation (see radioactivity), unlike X-rays and CAT scan, ultrasound scanning is especially valuable in obstetrics, where it has revolutionized fetal evaluation and diagnosis.