Ultrasound uses high frequency sounds to construct an image based on the fact that different tissues reflect high frequency sounds differently. During an ultrasound examination, a transducer that both emits the sound and detects the returning echoes is placed on 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 (Fig BELLOW).
Ultrasound waves are reflected back at the interface of tissues having different acoustical properties. AND Ultrasound waves propagate through patient
The echoes are analyzed by a computer in the ultrasound machine and transformed into moving pictures of the anatomy being examined. Ultrasound can be used to produce excellent images of blood flow and calculate its speed in accessible vessels using the Doppler effect. This is the same principle used by a policeman's radar to catch you speeding. Scanners which produce conventional ultrasound images plus Doppler flow velocity information are called duplex scanners.
Some of the common uses of ultrasound are:
1. Echocardiography looking at the heart structure including heart valves and chambers of the heart as well as heart function.
2. Carotid arteries using Doppler ultrasound to measure blood flow.
3. Abdominal ultrasound looking at different organs such as gallbladder, liver, kidneys, pancreases, and biliary tree.
4. Pelvic ultrasound looking at structures such as the ovaries.
Its advantages include lack of ionizing radiation, relatively low cost, and real-time (moving picture) display. Disadvantages are the need for a highly-skilled operator and inability to get around bone and gas. In the last few years, methods have been developed for producing 3-D doppler ultrasound images.
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