The Physics
Factbook
An encyclopedia of scientific essays

Frequency Used in Ultrasonic Imaging

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Cutnell, Johnson. Physics, 3rd Edition. New York: Wiley, 1995. "high frequencies in the range from 1 to 15 MHz are the norm, so the wavelengths are small." 1–15 MHz
World Book Encyclopedia. Chicago: World Book, 1995. "Ultrasound is sound waves with a frequency over 20,000 Hz." > 0.02 MHz
Samuels, Mike. The New Well Pregnancy Book. New York: Farside, 1996. "In medical ultrasound a sound wave of 2 million cycles per second is produced." 2.0 MHz
Joseph C. Segen. The Patient's Guide to Medical Tests. New York: Facts On File, 1998. "Electricity applied to a crystal in a transducer causes a high frequency (2.25–5.0 MHz) mechanical vibration." 2.25–5.0 MHz
Ultrasound Transducers. Department of Electrical Measurements. Lunds Tekniska Högskola. "Ultrasound frequency: 200 KHz–15 MHz (in water/tissue)." 0.2–15 MHz

Ultrasonic waves are used in medicine in many diagnostic procedures. These waves are produced by a rapidly oscillating crystal, and are inaudible to humans. They are directed toward a patient's body and are then reflected when they reach the boundaries between tissues of different densities. These reflected waves are detected as echoes by the transducer and displayed on a monitor. Using ultrasonic waves doctors can obtain sonograms of their patient's inner anatomy. Ultrasound can also be used to detect malignancies and hemorrhaging in various organs. It is also used to monitor real-time movement of heart valves and large blood vessels. Air, bone, and other calcified tissues absorb most of the ultrasound beam; therefore this technique cannot be used to examine the bones or the lungs.

Boris Zolotaryov -- 1999

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
ter Haar, Gail. "Acoustic Surgery." Physics Today. December 2001: 31.
 
Frequency
(MHz)
Source
area
(cm2)

Power
(W)
Maximum
intensity
(W cm-2)

Pulse
length
Diagnostic imaging          
Pulse-Echo 1-20 1-30 0.05 1.75 0.2-1 µs
Pulsed Doppler 1-20 1 0.15 15.7 0.3-10 µs
Physiotherapy 0.5-3 3 < 3 2.5 2-8 ms or
          continuous
Surgery 0.5-10 50 ~200 1.5 × 103 1-16 s
1–20 MHz

Editor's Supplement -- 2001