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Ultrasound imaging is a form of medical imaging which involves the use of high frequency sound waves. In ultrasonography, as ultrasound imaging is also known, sound waves are transmitted into the body from a small probe, and the probe reads the sound waves when they bounce back, generating a picture of the inside of the body. This technology is similar to that used in radar.
The sound waves used for ultrasounds vary between two and 18 megahertz, making them inaudible to humans. The frequency level can be varied depending on the level of detail and the depth of penetration desired. Modern ultrasound machines are extremely sophisticated, and capable of producing very complex and detailed images, including three dimensional ultrasound images which provide an even better visualization of the structures in the body.
This type of medical imaging is considered minimally invasive, with the transducer being used from outside the body to look in. No radiation is involved in ultrasonography, making it quite safe, although studies have indicated that high frequency sound waves can sometimes cause cavitation, in which small bubbles of gas appear in the body's tissues, and that ultrasound imaging also heats the tissue. Due to concerns about the impact of cavitation and heating on developing fetuses, some organizations recommend the minimal use of ultrasound during pregnancy, using ultrasonography solely to check on the health of the fetus.
One huge advantage of ultrasound beyond its relative safety is its ability to reflect real-time activity in the body. Using ultrasound, a doctor can see how the structures of the body move, a big improvement over static medical imaging such as x-rays, which only captures a moment in time. Doppler ultrasound, a special type of ultrasound, can be used specifically to track movements such as the movement of blood to evaluate the health of the circulatory system.
When a patient goes in for an ultrasound imaging session, he or she will be asked to remove clothing and jewelry in the area to be examined. A conductive gel will be applied to the area to improve the clarity of the image, and the transducer will be moved around on the area. The technician may need to angle the transducer or push down quite hard to get a picture, which can be momentarily uncomfortable, but the procedure should not be painful. After the ultrasound, the gel is removed, and the patient can leave.
Results of an ultrasound imaging study may be discussed with the patient immediately, or the patient may be called back at a later date by the doctor to discuss the results. In addition to being used for diagnostic purposes, ultrasound is also used in some medical procedures such as amniocentesis to guide the doctor while he or she works.