What type of wave is sound? - ANS mechanical and longitudinal
The frequency ranges for ultrasound are: - ANS >20,000 Hz (20 kHz)
The speed of sound in soft tissue is: - ANS 1540 m/s
Which of the following transducers fires the elements in groups? - ANS Li...
What type of wave is sound? - ANS mechanical and longitudinal
The frequency ranges for ultrasound are: - ANS >20,000 Hz (20 kHz)
The speed of sound in soft tissue is: - ANS 1540 m/s
Which of the following transducers fires the elements in groups? - ANS Linear sequenced
array
The unit for wavelength is: - ANS millimeters
Enhancement is caused by: - ANS Weakly attenuating structures
The wavelength in a material having a propagation speed of 1.5 mm/us employing a transducer
frequency of 5.0 MHz is: - ANS 0.3 mm
An ultrasound transducer converts: - ANS electrical energy into mechanical energy
Arrange the following media in correct order from the lowest attenuation to the highest: - ANS
Fat, muscle, bone, air
Arrange the following media in terms of propagation speed, from lowest to highest: - ANS
Air, fat, muscle, bone
If the frequency doubles, what happens to the wavelength? - ANS Decreases by one half
What happens to intensity if the amplitude of a signal is halved? - ANS Quartered
Which of the following would be used to describe the percentage of time that sound is on? -
ANS Duty Factor
A 3-dB gain would indicate an increase in intensity by: - ANS 2 times
Ignoring the effects of attenuation, the intensity of the ultrasound beam is usually greater at the
focal zone because of - ANS The smaller beam diameter
Attenuation denotes - ANS Progressive weakening of the sound beam as it travels
, Which of the following has the lowest intensity? - ANS SATA
What is the definition of the beam uniformity ratio? - ANS The spatial peak intensity divided
by the spatial average intensity
Continuous-wave Doppler has a duty factor of: - ANS 100%
The spatial pulse length is defined as the product of the ____ and the number of ___ in a pulse.
- ANS Wavelength, cycles
With phased array transducers, the transmitted sound beam is steered by: - ANS Varying
the timing of pulses to the individual piezoelectric elements
If the gain of an amplifier is 18 dB, what is the new gain if the power is reduced by half? - ANS
15 dB
Which of the following is true? - ANS SPTP is always equal to or greater than SPTA
If the amplitude of a wave is increased threefold, the power will: - ANS Increase ninefold
ultrasound attenuates an average of ____ dB/cm of travel for each megahertz of frequency. -
ANS 0.7
If the intensity transmission coefficient is 0.74, the intensity reflection coefficient will be: - ANS
0.26
Acoustic impedance is defined as the product of: - ANS The speed of sound in tissue and
density of the tissue.
Rayleigh scattering is an example of: - ANS A reflector whose size is smaller than the
wavelength
Assuming normal incidence, if medium 2 impedance is equal to medium 1 impedance: - ANS
100% of the intensity will be transmitted
What is the total attenuation of a 3.5-MHz pulse after passing through 2 cm of soft tissue? -
ANS 3.2 dB
The thinner the piezoelectric element, - ANS higher frequency
The unit for impedance is ________. - ANS Rayls
A sound beam encounters an interface at a 90 degree angle. If the speed of sound in the first
tissue is 1540 m/s and the speed of sound in the second tissue is 1450 m/s, which of the
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