Midterm review Flashcards by iliana rushlow

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

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What is the shape of the elements in an annular phased array transducer?

wedges

circles

wedges

squares

rectangles

Circles

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Huygens’ Principle is based on_______

refraction

constructive indices

interference

transverse waves

Interference

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Which type of transducer may produce grating lobes?

Single element

Multi-element

High frequency

Low frequency

Multi-element

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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

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Which has the greatest amount of attenuation?

muscle

water

fat

bone

Bone

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Which of these intensities is the smallest?

SATP

SPTP

SATA

None of these

SATA

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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

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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

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The minimum number of active elements in a mechanical transducer is:

None of these choices are correct

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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

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With regard to ALARA, what is the best way to image deeper?

increase output power

decrease PRF

decrease overall gain

decrease transducer frequency

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What is the point or location where a beam reaches its smallest dimension?

near zone

penetration depth

focus

focal zone

focus

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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

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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

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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

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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

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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

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All of these decrease temporal resolution except:

lower frame rate

multi-focus imaging

deeper imaging

narrower sector

Narrower sector

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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

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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

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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