• Looking Inside the Body—Without Surgery
    Awake!—2008 | November

    • Ultrasound Imaging

      How does it work? Also called ultrasound scanning, or sonography, this technology is essentially a form of sonar that uses sound waves above the range of human hearing. When the waves reach a boundary where there is a change in tissue density​—the surface of an organ, for example—​an echo results. A computer analyzes the echo, revealing two- or three-dimensional features of the organ, such as its depth, size, shape, and consistency. Low-frequency waves enable the imaging of deeper parts of the body; ultrahigh frequencies permit the study of surface organs such as the eyes and the layers of skin, perhaps assisting in the diagnosis of skin cancer.

      In most instances, the examiner uses a handheld device called a transducer. After applying a clear gel to the skin, he rubs the transducer over the area of interest, and the resulting image immediately shows up on a computer screen. When necessary, a small transducer can be attached to a probe and inserted into a natural opening in the body to make certain internal examinations possible.

      A technology called Doppler ultrasound is sensitive to movement and is used to reveal blood flow. This, in turn, can be helpful when making diagnoses involving organs and tumors, which tend to have an abnormally large amount of blood vessels.

      Ultrasound imaging helps physicians to diagnose an array of conditions and to discern the underlying cause of symptoms, from heart-valve disorders to lumps in the breast or the status of an unborn infant. On the other hand, because ultrasound waves are reflected by gas, the technology has limitations when applied to certain parts of the abdomen. Also, the resolution may not be as high as that of other technologies, such as radiography.

      Risks: Even though ultrasound is generally safe when used properly, it is a form of energy and can produce physical effects in tissues, including those of the unborn. Prenatal ultrasound, therefore, should not be considered risk free.

      Benefits: The technology is widely available, noninvasive, and relatively inexpensive. It also provides real-time imaging.