Registry Review Exam Penny Flashcards
what type of wave is sound?
mechanical, longitudinal
The frequency ranges for ultrasound are:
> 20 kHz
The speed of sound in soft tissue is:
1540 m/s
Which of the following transducers fires the elements in groups?
a. linear sequenced array
b. phased array
c. continuous-wave transducer
d. single-element transducer
a
The unit for wavelength is:
millimeters
Enhancement is caused by:
weakly attenuating structure
The wavelength in a material having a propagation speed of 1.5 mm/us employing a transducer frequency of 5.0 MHz is:
0.3 mm
An ultrasound transducer converts:
electrical energy into mechanical energy
Arrange the following media in correct order from the lowest attenuation to the highst
a. air, fat, muscle, bone
b. muscle, fat, air, blood
c. fat, muscle, bone, air
d. muscle, air, fat, bone
c
Arrange the following media in terms of propagation speed, from lowest to highest:
a. air, fat, muscle, bone
b. bone, fat, air, muscle
c. bone, muscle, fat, air
d. muscle, air, fat, bone
a
If the frequency doubles, what happens to the wavelength?
decreases by one half
What happens to intensity if the amplitude of a signal is halved?
quartered
Which of the following would be used to describe the percentage of time that sound is on?
a. intensity
b. amplitude
c. SPTA
d. Duty factor
duty factor
A 3-dB gain would indicate an increase in intensity by:
2 times
Ignoring the effects of attenuation, the intensity of the ultrasound beam is usually greater at the focal zone because of :
the smaller beam diameter
Attenuation denotes:
progressive weakening of the sound beam as it travels
Which of the following has the lowest intensity?
a. SPTP
b. SATP
c. SPTA
d. SATA
d
What is the definition of the beam uniformity ratio?
the spatial peak intensity divided by the spatial average intensity
Continuous-wave Doppler has a duty factor of:
100%
The spatial pulse length is defined as the product of the ______ and the number of _____ in a pulse.
wavelength, cycles
With phased array transducers, the transmitted sound beam is steered by:
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?
15 dB
Which of the following is true?
a. SPTA is always equal to or greater than SPTP
b. SPTP is always equal to or greater than SPTA
c. SATA is always equal to or greater than SATP
d. SPTA is always equal to or greater than SPTP
b
If the amplitude of a wave is increased threefold, the power will:
increase ninefold
Ultrasound attenuates an average of _____ dB/cm of travel for each megahertz of frequency.
0.7
If the intensity transmission coefficient is 0.74, the intensity reflection coefficient will be:
0.26
Acoustic impedance is defined as the product of:
the speed of sound in tissue and density of the tissue
Rayleigh scattering is an example of:
a reflector whose size is smaller than the wavelength
Assuming normal incidence, if medium 2 impedance is equal to medium 1 impedance:
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?
3.5 dB
The thinner the piezoelectric element:
the higher the frequency
The unit for impedance is:
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 1460 m/s, which of the following numbers most closely approximates the angle of beam transmission?
a. -90
b. 90
c. >90
d. Need the impedance to compute angle of transmission
b
ALARA stands for:
as low as reasonably achievable
A decibel (dB) describes the:
ratio of two sound intensities
The correct equation for Snell’s law is:
sin0t = (c2/c1) x sin0t
The attenuation coefficient of sound in soft tissue can be defined by which of the following equations?
a. one half the frequency times the path length
b. frequency / 6
c. frequency / 2
d. frequency x 2
c
The intensity transmission coefficient is equal to:
1 - intensity reflection coefficient
The range equation explains:
distance to reflector
The typical value for attenuation coefficient for 6-MHz ultrasound in soft tissue is:
3 dB/cm
What be known in order to calculate distance to a reflector?
travel time, propagation speed
Specular reflections:
occur when the interface is larger than the wavelength
What is the reflected intensity from a boundary between two materials if the incident intensity is 1 mW/cm^2 and the impedances are 25 and 75?
0.25 mW/cm2
The layer of material within the transducer which has an intermediate impedance between the transducer element and human tissue is known as the:
matching layer
Which of the following relates bandwidth to operating frequency?
a. near zone
b. piezoelectrical material
c. quality factor
d. far zone
c
The piezoelectric effect can best be described as:
Mechanical deformation that results from a high voltage applied to the face of the crystal that in turn generates a pressure wave
Which of the following are most commonly used in ultrasound transducers?
a. lead zirconate titanate
b. barium sulfate
c. epoxy loaded with tungsten
d. quartz
a
Differaction refers to:
Speading out of the ultrasound beam
The preferred method for sterilizing ultrasound transducers is:
Cold sterilization
A transducer with which frequency would have the thickest element(s)?
a. 2 MHz
b. 3.5 MHz
c. 5 MHz
d. 7.5 MHz
a
Which of the following is best defined as the ability to discrimnate between two closely spaced reflectors?
a. temporal resolution
b. range accuracy
c. spatial resolution
d. amplification
c
Which of the following is an effect of focusing?
a. improved lateral resolution
b. improved axial resolution
c. increased beam divergence in the near zone
d. higher frequency
a
Bandwidth is:
the range of frequencies produced by the transducer
What is the technique that permits virtual palpation of a lesion to determine the hardness or softness of tissue?
elastography
The acoustic impedance of the transducer’s matching layer:
is chosen to improve transmission into the body
If the amount of damping decreases, the bandwidth:
decreases
The region where the sound beam is the smallest is referred to as the:
focus
The near-zone length is determined by:
transducer frequency
A two-element continuous-wave transducer:
is only used for spectral Doppler
A wave’s initial intensity is 2 mW/cm2. There is an increase of 10 dB. What is the final intensity?
20 mW/cm2
Which of the following is described best as a transducer that has multiple elements in a curved shape?
a. continuous-wave transducer
b. mechanical sector
c. curvilinear
d. Linear array
c
What is the name of the control that compensates for attenuation related to path length?
time-gain compensation
The echoes are stored before final display by the:
computer memory
What portion of the ultrasound system drives the transducer?
pulser
What Doppler mode uses the amplitude of the Doppler shift in order to produce an image demonstrating flow in a vessel?
Power Doppler
How many different shades of gray can the human eye discern at one time?
100
