# Shared Flashcard Set

## Details

Understanding Ultrasound Physics Ch.3
Ultrasound Physics Ch. 3 Chapter Questions
20
Physics
Not Applicable
05/04/2016

Term
 How did ultrasound get its name?
Definition
 Sound is classified based on the ability of humans to hear it.  Sound with frequencies so high that humans cannot hear it is called ultrasonic or ultrasound.
Term
 Why is frequency important in diagnostic sonography?
Definition
 It affects penetration & image quality.
Term
 What is the relationship between frequency & period?
Definition
 Inversely related.  ↑ F = ↓ P    &    ↑ P = ↓ F
Term
 What is the difference between amplitude & peak-to-peak amplitude?
Definition
 Amplitude is measured from the midline to the max or min of the wavelength.          Peak-to-peak is measured from the top of the wavelength to the bottom.  It is twice the value of the amplitude.
Term
 How are amplitude & power related?
Definition
 Directly related.  ↑ Power = ↑ Amplitude.  Both are parameters that describe the size or magnitude of a wave.  Power is ȣ to Amplitude2.
Term
 How is intensity related to power & amplitude?
Definition
 Intensity ȣ Power ȣ Amplitude 2.  They are all proportional to each other.
Term
 What is the difference between wavelength & period?
Definition
 Both are a single cycle in a sound wave, but a period is the time it takes to complete a single cycle & a wavelength is the length of a single cycle.
Term
 What is the relationship between wavelength and frequency?
Definition
 Inversely related.  ↓ F = ↑ λ The lower the frequency the longer the wavelength.
Term
 What is the wavelength of 1 MHz sound in soft tissue?
Definition
 1.54mm
Term
 What is the wavelength of other frequency sound waves in soft tissue?
Definition
 Sound with a frequency of 2 MHz has a wavelength of 0.77mm in soft tissue.                                       1.54mm = 0.77mm                                      2
Term
 What is the rule that defines the relationship btween frequency & wavelength of sound in soft tissue?
Definition
 Divide 1.54mm by the frequency in MHz.                                     λ  (mm) = 1.54mm/us                                                  F (MHz)
Term
 Why is wavelength important in diagnostic ultrasound?
Definition
 Short wave = high frequency = better picture.
Term
 What is the speed of sound in soft tissue?
Definition
 1,540 m/s  (or 1.54 mm/us)
Term
 What is the speed of sound in biologic tissues other than soft tissue?
Definition
 Lung = 500 m/s             Fat = 1,450 m/s             Liver = 1,560 m/s             Blood = 1,560 m/s             Muscle = 1,600 m/s             Tendon = 1,700 m/s             Bone = 3,500 m/s
Term
 What is the speed of sound in other media?
Definition
 Air = 330 m/s              Water = 1,480 m/s              Metals = 2,000 – 7,000 m/s                                        C (m/s) = F (Hz) x λ (m)
Term
 What characteristics of a medium determine the speed of sound in that medium?
Definition
 Density & Stiffness
Term
 How does stiffness affect speed?
Definition
 Directly related. ↑ Stiffness = ↑ Speed The stiffer the media, the faster the sound.
Term
 How does density affect speed?
Definition
 Inversely related.  ↑ Density = ↓ Speed The denser the media, the slower the sound.  If 2 media are equally stiff, the denser medium will have a lower speed.
Term
 What other terms describe stiffness?
Definition
 Elasticity & Compressibility
Term
 Which has the greater influence on speed, density or stiffness?
Definition
 Stiffness.
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