Ultrasound, Ultrasound Scan
Sound waves of a very high frequency, higher than the human ear can hear. Ultrasound can be used to examine structures within the body by using an ultrasound scan. If ultrasound is directed at the body, it is reflected back differently by different types of tissue. In an ultrasound scan, these differences are measured and used to build up pictures of structures inside the body. Ultrasound scans are useful in diagnosing cancer.