Midterm review Flashcards
Which best describes the elements in a linear sequential array transducer?
rectangular, 1/4 to 1/2 wavelength wide
rectangular, 1 wavelength wide
squares, 1 wavelength thick
rectangular, 1/4 wavelength thick
rectangular, 1 wavelength wide
What is the shape of the elements in an annular phased array transducer?
wedges
circles
wedges
squares
rectangles
Circles
Huygens’ Principle is based on_______
refraction
constructive indices
interference
transverse waves
Interference
Which type of transducer may produce grating lobes?
Single element
Multi-element
High frequency
Low frequency
Multi-element
In which region of a sound beam is focusing most effective?
the very shallow near zone
the end of the near zone
very deep in the far zone
throughout its entire length
The end of the near zone
Which has the greatest amount of attenuation?
muscle
water
fat
bone
Bone
Which of these intensities is the smallest?
SATP
SPTP
SATA
None of these
SATA
Which of the following will result in a minimum beam divergence deep in the far zone?
small diameter, high frequency
high frequency, large diameter
large diameter, low frequency
low frequency, small diameter
high frequency, large diameter
Two ultrasound systems produce pulses. One pulse is 0.4 µsec in duration and the other is 0.2 µsec long. Which pulse is most likely to provide the best radial resolution?
0.2µsec system
0.4 µsec system
they are the same
cannot be determined
0.2µsec system
The minimum number of active elements in a mechanical transducer is:
0
1
2
None of these choices are correct
1
All of the following describe dynamic recieve focusing except:
focusing occurs at many depths
may be used by single crystal transducers
delay pattern changes continuously throughout reception
automatically performed by the system
may be used by single crystal transducers
With regard to ALARA, what is the best way to image deeper?
increase output power
decrease PRF
decrease overall gain
decrease transducer frequency
decrease transducer frequency
What is the point or location where a beam reaches its smallest dimension?
near zone
penetration depth
focus
focal zone
focus
What is the result of decreasing the PZT thickness?
A decrease in the quality
An increase in the frequency of the transducer
An increase in the velocity of sound
A greater pulse duration
An increase in the frequency of the transducer
The focus of an ultrasound system is the location where the ______.
beam is the broadest
optimum transverse resolution is
frequency is the highest
finest depth resolution is obtained
optimum transverse resolution is
Which two controls determine a system’s temporal resolution?
frame rate and sector size
focal zones and sector depth
propagation speed and frame rate
depth of view and pulses per image
depth of view and pulses per image
Two ultrasound systems have near zone lengths of 8cm. At the focus, System G’s lateral resolution is 3.0 mm, whereas System P’s is 5.0 mm. Which system wwill produce higher quality pictures at their foci?
System G
System P
Both G and P
None of these choices are correct
System G
The average intensity across the beam’s entire cross-sectional area is termed
spatial average intensity
spatial peak intensity
temporal peak intensity
temporal average intensity
spatial average intensity
All of these decrease temporal resolution except:
lower frame rate
multi-focus imaging
deeper imaging
narrower sector
Narrower sector
What is most likely to occur if the diameter of a single, disc-shaped, unfocused transducer is increased?
The distance to the far field is reduced
The beam width in the near field is reduced
The beam width in the far field is reduced
The ultrasonic wavelength is increased
The beam width in the far field is reduced
Which of the following results in the least attenuation?
4 MHz sound, path length 2cm
4MHz sound, path length 8cm
6MHz sound, path length 8cm
6MHz sound, path length 4cm
4 MHz sound, path length 2cm
True or false
The acoustic impedance of the skin is greater than that acoustic impedances of both the matching layer and the piezoelectric element.
False
Which of the following focusing techniques is different from the others?
Phased
curved crystal
fixed
lens
Phased
While scanning in a water tank, what location in a sound beam has the highest intensity?
Focal point
focal zone
Fresnel zone
Fraunhofer zone
Focal point
-10dB means that the intensity is reduced to ________ of its original value.
one-quarter
one-half
one-tenth
cannot be determined
one- tenth
Which of the following is different from the others?
lens
mirror
phased
dynamic range
dynamic range
All of the following occur with focusing except:
lower intensity at the focus
shorter near zone length
more compact focal zone
smaller diameter beam diameter at the end of the near zone
Lower intensity at the focus
True or false?
One way for a sonographer can alter the axial resolution achieved during an exam is to adjust the maximum imaging depth.
False
With B-mode, on which axis is the strength of the reflection input?
x-axis
y-axis
z-axis
A-mode
z- axis
What is the time needed to make a single image if the frame rate of ultrasound system is 20 Hz?
1 s
0.02 s
0.05 s
15 Hz
0.05 s
Which type of transducer utilizes time delay beam steering as the primary method to direct the beam throughout the field of view?
Phased array
Annular array
Linear sequential array
Mechanical sector
Phased array
An ultrasonic pulse is traveling in soft tissue. Which of the following is most important in the determination of the frequency of sound?
the propagation speed of the ultrasound transducer’s matching layer
the thickness of the transducer’s backing material
the impedance of the transducer’s matching layer
the propagation speed of the transducer’s active element
the propagation speed of the transducer’s active element
What determines the frequency of a sound beam from a pulsed transducer?
voltage applied to the PZT
PZT thickness
frequency of the system
PRF of the pulser
PZT thickness
Two ultrasound systems are identical except for the diameter of the transducer’s piezoelectric crystal. Which system has the deepest focus?
the sytem with the smaller diameter crystal
the one with the larger diameter crystal
their foci will be at the same depth
cannot determine
the one with the larger diameter crystal
What is the process of adjusting for path length related attenuation called?
compression
compensation
time-gain compensation
reconfirmation
compensation
Which of the following results in the most attenuation?
4MHz sound, path length 2cm
4MHz sound, path length 8cm
6MHz sound, path length 8cm
6MHz sound, path length 4cm
6MHz sound, path length 8cm
The diameter of a disc-shaped, unfocused pzt crystal is 1.2cm. The near zone length is 8cm. What is the best estimate for the lateral resolution at a depth of 16cm?
16 cm
8cm
1.2 cm
0.6cm
1.2 cm
Which of the following actions will improve the signal-to-noise ratio?
increase dynamic range
increase receiver gain
increase output power
increase time-gain compensation
increase output power
Which reciever function creates an image of comparable brightness from top to bottom?
receiver gain
output power
swept-gain compensation
amplification
swept-gain compensation
Which PZT crystal would have the lowest possible frequency?
6 mm thick, 4 cm diameter, 4.0mm/µs propagation speed
8 mm thick, 2cm diameter, 2.0 mm/µs propagation speed
4mm thick, 9cm diameter, 5.0 mm/µs propagation speed
2 mm thick, 6cm diameter, 6.0 mm/µs propagation speed
8 mm thick, 2cm diameter, 2.0 mm/µs propagation speed
What is the rationale for ALARA principle?
carbon footprint
climate change
patient exposure
cavitation
Patient exposure
What is the advantage of using a 1 1/2 imensional array transducer?
improved elevational resolution
improved lateral resolution
imporved axial resolution
improved temporal resolution
improved elevational resolution
What is the thickness of the matching layer of a 2MHz pulsed wave transducer?
1.54 mm
0.77 mm
half the wavelength of the sound wave in the PZT
one-quarter the wavelength of sound in the matching layer
one-quarter the wavelength of sound in the matching layer
True or false?
The higher the frequency of the cycles within a pulse, the lower the numerical value of the axial resolution.
True
The lateral resolution of an ultrasound system is primarily determined by the _____.
width of the sound pulse
length of the ultrasound pulse
duration of the sound pulse
none of the above
Width of the sound pulse
Which of the following lists orders the impedance from highest to lowest?
skin, gel, matching layer, PZT
PZT, gel, matching layer, skin
gel, PZT, matching layer, skin
PZT, matching layer, gel, skin
PZT, matching layer, gel, skin
What is the lowest of all the temporal intensities?
temporal peak intensity
temporal average intensity
spatial peak intensity
spatial average intensity
Temporal average intensity
The lateral resolution of an ultrasound system is 4mm. Two structures are separated by 3mm and lie side by side in relation to the sound beam’s main axis. What will most likely appear on the system’s display?
two bright echoes, 7 mm apart
one echo
two bright echoes, 3 mm apart
two weak echoes, 4 mm apart
one echo
Which of the following will improve a system’s temporal resolution?
increased frequency
increased PRF
increased line density
increased sector angle
increased PRF
The sonographer reduced the sector size from 90 degrees to 30 degrees. Frame rate, however, did not change. What else happened?
imaging depth decreased
pulse duration increased
multi-focus was turned on
PRF was increased
Multi-focus was turned on
Which of the following is not considered a component of an ultrasound system?
master synchonizer
pulser
reciever
image instensifier
image intensifier
What is the actual time that an US machine is creating a pulse?
duty factor
period
pulse period
pulse duration
Pulse duration
Which of the following actions would cause a PZT crystal to lose its special properties?
breaking in pieces
exposing it to high temperatures
exposing it to electrical current
exposing it to low pressures
exposing it to high temperatures
Which of these means adjustable focusing or multi-focusing?
dynamic aperture
phased array
frequency agility
harmonics
Phased array
