Sonography Equipment and Procedure
A sonography machine consists of a computer with a display screen and a hand-held transducer. After removing all your accessories and changing into a patient gown, you will be asked to lie on a bed adjacent to the sonography equipment. Your sonologist (i.e., the doctor who performs and interprets the ultrasound scan) is usually seated or standing in front of the sonography machine.
Your sonologist will apply gel on the surface of your skin overlying or adjacent to the organ of interest. For example, if you need an ultrasound scan of your liver and gallbladder, the gel will be applied on the right upper part of your abdomen. will then press the transducer against your skin, and adjust it accordingly several times to obtain different views of the organs he wishes to visualize. This is not painful. You only need to stay calm during the procedure. The sonography ends when your sonologist has obtained and reviewed all the images that he needs.
Converting sound waves to images
It is the transducer that transforms sound waves into images. When the transducer comes in contact with your skin, it sends multiple sound waves into your body. Because these sound waves have very high frequencies, you will neither be able to hear them nor feel their vibration as they go through your internal organs.
Every time a sound wave hits a structure inside your body, it bounces back, and this "echo" is subsequently detected by the transducer. By calculating the time it takes for the sound wave to echo and by measuring its intensity, the transducer is able to determine the distance of the structure that was initially hit by the sound wave. The transducer will also be able to determine if this structure is solid, filled with fluid, or full of air.
Using these mathematical data, the sonography computer reconstructs the image, which is then displayed in real time on the monitor. This process of sending and receiving sound to acquire images is similar to that used by bats and submarines for navigation.
Advantages and limitations of sonography
Sonography is widely available in health care centers. It is a fast, relatively inexpensive, and painless procedure that does not require needles or injections. Because it does not emit radiation, sonography can be repeated as often as necessary in the same patient. However, sonography is not ideal for obtaining images of internal organs filled with air such as the stomach and intestines. Sound waves are also unable to penetrate bone and demonstrate structures within it.
Obtaining images through sonography and interpreting the results require skill and practice. Make sure that your chosen sonologist is qualified before you undergo sonography.
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