Ultrasound Physics Review Flashcards
When you change the transmit frequency, which of the following is altered?
a. displacement amplitude of the particles in the medium
b. speed at which the sound wave propagates through the medium
c. Number of cycles per second
d. pulses transmitted per second
e. number of electric impulses applied to the transducer per second
c
While performed a Doppler ultrasound examination, you adjust the pulse repetition frequency to 12 kHz. This can also be expressed as:
12,000 Hz
When you switch from a 2.5 MHz to a 5.0 MHz transducer, the sound wavelength:
halves
Which of the following factors does NOT affect impedance?
a. stiffness
b. density
c. propagation speed
d. frequency
e. all of the above
d
What is the purpose of the gel coupling between the transducer and the skin?
to provide a medium for sound transmission, since ultrasound does not propagate through air
An example of a specular reflector is:
a. pericardium
b. liver parenchyma
c. red blood cells
d. ascites
e. hematoma
a
Which phenomenon is associated with a pattern produced by a sound beam after passing through a small aperture?
a. scattering
b. absorption
c. diffraction
d. interference
e. diffuse reflection
c
As a general observation about media in diagnostic sonography, sound propagates faster in materials with greater:
a. compressibility
b. acoustic impedance
c. stiffness
d. refractive index
e. all of the above
c
You may observe sound attenuation by all of the following EXCEPT:
a. reflection
b. scattering
c. conversion of sound to heat
d. absorption
e. compression
e
What is the relationship of frequency to absorption?
a. if frequency is halved, absorption is doubled
b. if frequency is doubled, absorption is doubled
c. if frequency is doubled, absorption is halved
d. if frequency is halved,absorption is quartered
e. The rate of sound absorption is not frequency-dependent
b
Another term for nonspecular reflection is:
a, destructive interference
b. refraction
c. diffraction
d. scattering
e. absorption
d
As you perform a sonographic exam, you switch from a 3.5 MHz transducer to a 7.o MHz transducer to image a superficial structure. Compared to the 3.5 MHz transducer, what will the 7.0 MHz attenuation rate and wavelength be?
a. double the attenuation rate, one-half the wavelength
b. double the attenuation rate, double the wavelength
c. one-fourth the attenuation rate, one half the wavelenth
d. one half the attenuation rate, double the wavelength
e. one half the attenuation rate, one fourth the wavelength
a
You are scanning a large mass that is composed primarily of fat. Which of the following are you most likely to encounter?
a. posterior acoustic shadowing caused by increased attenuation through the fat
b. axial misregistration of objects distal to the mass on the screen due to the slower propagation speed through fat
c. Lateral misregistration of the mass on the screen because of refraction
d. total reflection of the sound beam caused by a large acoustic impedance mismatch
e. diffraction of the sound beam due to a virtual small aperture through the mass
b
The transducer you are using transmits wide-bandwidth pulses whose frequency content is 2-5 MHz. Which of the following most correctly describes the reflected echo signals after they have traversed the tissue?
a. the echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies
b. the echo signals will be of reduced intensity but will have the same frequency content as the transmitted beam
c. the echo signals will be shifted upward in frequency due to the increased absorption of the lower frequencies
d. only the center frequency component of the bandwidth will be reflected back to the transducer
e. the echo signal frequency content will be identical to that of the transmitted beam
a
What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?
a. specular reflection
b. refraction
c. diffraction
d. destructive interference
e. scattering
e
Attenuation of the sound beam increases with increasing:
a. path length
b. absorption
c. frequency
d. scattering and reflection
e. all of the above
e
You are imaging a rounded mass with irregular borders. The mass has a much lower propagation speed than surrounding tissue. What sound-tissue interaction will be encountered as the ultrasound propagates through this interface?
a. refraction
b. reflection
c. absorption
d. scattering
e. all of the above
e
You are imaging a structure that is highly attenuating. Which imaging effect do you expect to encounter?
a. enhancement
b. increased penetration
c. shadowing
d. refraction
e. increased acoustic speckle
c
If sound waves of 3 MHz, 5 MHz, and 10 MHz are transmitted through the same section of an anatomy, reflections from which frequency would reach the transducer first?
a. 3 MHz
b. 5 MHz
c. 10 MHz
d. reflections from all three frequencies would have nearly identical transit times
e. it is not possible to predict which will arrive first
d
For pulsed ultrasound, which of the following factors determines the frequency of the sound wave?
a. PRF
b. transmitter frequency
c. area of the transducer elements
d. pressure applied to the transducer
e. all of the above
b
Wavelength is ______ proportional to frequency.
inversely
Impedance increases if density or propagation speed _____/
increases
a large smooth interface such as the renal capsule, diaphragm, or pericardium. Primarily responsible for the bright interfaces seen at organ boundaries
specular reflector
the general term for various phenomena in which waves from different parts of a source add or subtract
diffraction
includes all sound interactions that result in a weakening of the beam. These include reflection, scattering, absorption, and, to a lesser extent, refraction.
attenuation
the conversion of sound to heat in tissue
absorption
results in a bending of the beam
refraction
Because of the large acoustic impedance mismatch between soft tissue and calcium, most of the sound is _______ at the stone-tissue interface
reflected
Results from decreased attenuation through a fluid-filled structure compared to the adjacent tissue
acoustic enhancement
There is a ______ relation between absorption and frequency.
direct
______ reflection occurs when the interface is large and smooth
specular
Nonspecular reflection is also known as:
scattering
occurs when the interface is small, less than several wavelengths across
nonspecular reflection
If frequency is doubled, the rated of attenuation is ____.
doubled
If frequency is doubled, and the rate of attenuation is doubled, then wavelength _____
halved
If sound travels more slowly through a medium, the round trip travel time will be longer and the system will place the structure _____ on the image
deeper
If sound travels through a medium with a propagation speed faster than that of soft tissue, the round trip travel time will be shorter and the structure will be placed _____ on the iamge
shallower
Higher frequencies are absorbed ____ quickly than lower frequencies
more
the degree of attenuation for each centimeter of sound propagation.
attenuation coefficient
occurs because of the oblique incidence (round surface) and different propagation speeds of the insonated media
refraction
occurs because the acoustic impedance is different (different densities and propagation speeds)
reflection
occurs as sound propagates through tissue
absorption
occurs as a result of the irregular margins of the mass
scattering
With _______ attenuation, there will be loss of sound energy through reflection, scattering, and absorption.
increased
occurs when the sound strikes an irregular or rough surface that is small compared to the wavelength
scattering
occurs when the surface is smooth and large compared to the wavelength
specular reflection
requires the sound to pass through a small aperture
diffraction
occurs will oblique incidence and a change in propagation speeds at the interface
refraction
The speed of sound does not vary appreciably with _____
frequency
the number of cycles that occur in one second
frequency
The speed of sound is determined by:
the medium, not the sound source
Frequency is determined by:
the sound source (the transducer)
The number of electric pulses delivered to the active element per second
PRF
The PRF does not affect the _____ frequenc
imaging
determined by the propagation speed and the thickness of the piezoelectric material in the transducer, and by the center frequency of the drive signal applied to the transducer
frequency
What conditions below are most likely to result in turbulent flow?
a. 5 mm vessel with 300 cm/s flow velocity
b. 2 mm vessel with 300 cm/s flow velocity
c. 2 mm vessel with 30 cm/s flow velocity
d. 1 mm vessel for with 30 cm/s flow velocity
e. 4 mm vessel with 30 cm/s flow velocity
a
What is the maximum velocity limit for a 3 MHz CW Doppler unit operating at a depth of 4cm?
a. 40 cm/s
b. 200 cm/s
c. 2.5 m/s
d. 4 m/s
e. none of the above
e
Which of the following statements about formation of the color Doppler image is TRUE?
a. the color and B-mode images are generally derived from the same pulse
b. the color image is superimposes on the existing B-mode image.
c. the color and B-mode images are generally formed using the same frequency sound wave
d. The B-mode is usually obtained at a lower frequency than he coor image
b
What error will occur if the angle correct cursor is NOT adjusted parallel to the vessel wall?
a. the frequency shift will be underestimated
b. No Doppler frequency shift will be detected
c. mirror imaging of the Doppler spectrum wiii occur
d. the velocity estimation will be inaccurate
e. Aliasing if the Doppler spectrum will occur
d
Which of the following actions would decrease color Doppler frame rate?
a. decreasing frequency
b. increasing line density
c. decreasing packet size
d. decrease color box size
e. increasing gain
b
What is the result of increasing the wall filter during Doppler sampling?
a. increased visibility of low-velocity signals
b. increased spectral broadening
c. decreased bandwidth
d. reduced display of low frequency Doppler signals
e. reduction of aliasing
d
You have increased the packet size while using color Doppler to evaluate flow. What negative result will occur from this action?
a. decreased penetration
b. decreased flow sensitivity
c. decreased frame rate
d. increased variance
e. increased spectral broadening
c
You have increased the packet size while using color Doppler to evaluate flow. What positive result will occur from this action?
a. improved signal-to-noise ratio
b. reduced aliasing
c. improved axial resolution
d. improved lateral resolution
e. improved temporal resolution
a
What system control on Doppler adjusts PRF?
a. dynamic range
b. packet size
c. ensemble length
d. gain
e. spectral velocity scale
e
If you increase the Doppler transmit frequency, which of the following will result?
a. the velocity will increase
b. the Doppler frequency shift will increase
c. the penetration will increase
d. the frame rate will increase
e. the Nyquist limit will increase
b
What aspect of the Doppler spectrum is color-encoded with color Doppler?
a. amplitude
b. frequency shift
c. power
d. velocity
e. bandwidth
b
According to the Doppler equation, for any given velocity, the frequency shift will increase by increasing the:
a. Doppler angle
b. Transmit frequency
c. pulse length
d. pulse repetition frequency
e. all of the above
b
Parabolic flow is most likely to occur:
a. distal to a stenosis
b. in small veins
c. in laminar flow states
d. in disturbed flow states
e. when aliasing is present
c
A flow condition in which parallel streamlines of flow are present within a tube is termed:
a. parabolic flow
b. laminar flow
c. aliased flow
d. disturbed flow
e. turbulent flow
b
According to Poiseuille’s equation, what will happen to flow if pressure difference increases?
a. flow rate will increase
b. flow will stagnate
c. flow will become pulsatile
d. flow velocity will decrease
e. flow will become turbulent
a
Which of the following best describes the Doppler frequency shift when you encounter high velocities within a vessel?
a. amplitude is increased
b. power is increased
c. frequency shift is increased
d. bandwidth is increased
e. all of the above
c
