This publication is designed to provide you, the patient, with an understanding of the diagnostic procedure commonly known as sonography and also known as ultrasonography. Extensions and applications of sonography include Doppler ultrasonography and echocardiograms, the use of sonography to scan the heart.
A HARMLESS, PAINLESS, QUICK PROCEDURE: The first thing that you should know about sonography is that it is a technique that is easy on the patient. It can be performed in an outpatient setting; it takes only 15 to 60 minutes to complete; it can be performed by a technician as well as a doctor; it is usually non-invasive; it usually causes no pain; it carries no risks of complications. Since sound is used instead of potentially harmful x-rays, there is no danger of long term damage to the chromosomes. You cannot get cancer from sonography.
PRINCIPLES OF SONOGRAPHY: Sound travels in waves. The higher the frequency (number of wave crests passing a given point per unit of time) of the sound wave, the higher the pitch. The unit of frequency is the hertz, one wave crest per second. The human ear can generally hear things in the range of 20-20,000 hertz. What it cannot hear in the higher frequencies, the range above 20,000 herz, is termed ultrasound.
Ultrasound has a number of medical applications and it is also used by animals. Bats, who can hear sounds as high pitched as 100,000 herz, use ultrasound to guide them in flight, to locate prey, and in courtship . The usefulness of ultrasound for animals, and for diagnostic imagining, rests on two facts: 1] when a sound is generated it travels through different materials at different speeds; 2] when sound waves encounter solid material they “bounce,” that is, they are reflected off it. Thus, if a wave of high pitched sound is sent into tissue, the reflections which come back from organ boundaries, and from areas within organs, contain a great deal of data about the density and structure of the things which lie within the area being studied. A computer can be used to convert this data into two dimensional pictures of the area . In certain types of applications a series of images can be generated in a short period of time; these show the organs in motion and thus give valuable clues as to how well they are functioning.