Season One Research Files
Episode Fourteen
1:00pm-2:00pm
ULTRASOUND
Ultrasound, or ultrasonography, is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines. The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a transducer probe. The probe can be moved along the surface of the body and angled to obtain various views. The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone). Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected. In a typical ultrasound, millions of pulses and echoes are sent and received each second.
The reflected waves are picked up by the probe and relayed to the CPU machine. The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (5,005 ft/s or1,540 m/s) and the time of the each echo's return (usually on the order of millionths of a second). The machine then displays the distances and intensities of the echoes on the screen, forming a two dimensional image.
Besides the standard two-dimensional image, other, more advanced ultrasound machines can also create 3D and moving images in a Doppler Effect.
Ultrasound has been used in medicine since World War II in a variety of clinical settings, including obstetrics and gynecology, cardiology and cancer detection. The main advantage of ultrasound is that certain structures can be observed without using radiation. Ultrasound can also be done much faster than X-rays or other radiographic techniques.
Dr. Karl Dussik, a psychiatrist at the hospital in Bad Ischl, Austria, was the first person to publish a medical use of diagnostic ultrasound in 1942. He was trying to locate brain tumors with a new method consisting of an ultrasound emitter at one end and an ultrasound receiver at the other. The patient stayed between the two devices, and the ultrasound beam transmission was measured through the patient's head.
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