Ultrasound imaging uses the principles of sonar developed for ships at sea. As sound passes through the body it produces echoes, which can identify distance, size and shape of objects inside.
- During the ultrasound examination, a machine called a transducer is used to view the target organ and produce pictures for study. The transducer emits sound and detects the returning echoes when it is placed on or over the body part being studied.
- When the emitted sound encounters a border between two tissues that conduct sound differently, some of the sound waves bounce back to the transducer, creating an echo.
- The echoes are analyzed by a computer in the ultrasound machine and transformed into moving pictures of the organ or tissue being examined.
- Ultrasound waves pass easily through fluids and soft tissues, making the procedure especially useful for examining fluid-filled organs such as the uterus in pregnancy, as well as the gallbladder, and soft organs like the liver.
- Ultrasound waves are unable to penetrate bone or gas, so ultrasound is of limited use for examining regions surrounded by bone, or areas that contain gas or air. Even so, ultrasound has been used to examine most parts of the body.
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