final II Flashcards by Valery Dzev

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time?

13 microseconds
1.3 microseconds
65 microseconds
130 microseconds

130 microseconds

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A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 39 microseconds. What is the total distance that the pulse traveled?

1 cm
2 cm
3 cm
6 cm

6 cm

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How long does it take for sound to make a round trip to and from the skin’s surface to a reflector 1 cm depth in soft tissue?
13 microseconds
150 ms
15 microseconds
2 seconds

13 microseconds

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One reflector is 5 times deeper than another. The time of flight of sound to the deeper structure is ______the time of flight of the shallower reflector.
One fifth as much as
Equal to
Less than
Five times more than

Five times more than

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The depth of view is set to 20 cm, What is the PRP?
130 microseconds
520 microseconds
260 microseconds
260 mm

260 microseconds

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When the depth of view is set to 30.8 cm, PRF is ______
5000 Hz
10000 Hz
400 microseconds
2500 Hz

2500 Hz

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T/F: When the depth of view is shallow, PRP is long.

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Axial resolution may also be referred to as all of the following EXCEPT:
Longitudinal
Parallel
Range
Radial
Depth

Parallel

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T/F: Axial resolution measures the ability of a system to display two structures that are very close together when the structures are perpendicular to the sound beam’s main axis.

False

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Two ultrasound systems produce acoustic pulses. One pulse is 0.4 microseconds in duration and the other is 0.2 microseconds. Which pulse will most likely provide the best lateral resolution?
0.4 microsecond pulse
0.2 microsecond pulse
they are the same
cannot be determined

cannot be determined

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A short pulse is created in two ways (two answers).
less ringing
higher frequency
more ringing
lower frequency

less ringing
higher frequency

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Which transducer has the best axial resolution?
2 cycles/pulse, 4 MHz
4 cycles/pulse, 4 MHz
4 cycles/pulse, 2 MHz
2 cycles/pulse, 2 MHz

2 cycles/pulse, 4 MHz

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T/F: The more cycles there are in a pulse, the greater the detail that will be visualized in the ultrasound scan.

False

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An ultrasonic pulse has a pulse repetition period of 1.2 msec, a spatial pulse length of 2.0 mm and a wavelength of 0.4 mm. What is the axial resolution of the system?

2.0 mm
1.0 mm
0.4 mm
1.8 mm

1.0 mm

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The axial resolution of an imaging system is reported to be .80 mm at the beam’s focus. What is the closest estimate of the system’s radial resolution at a location that is 6 cm deeper than the focus?

less than .80 mm
equal to .80 mm
greater than .80 mm

equal to .80 mm

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T/F: A wide bandwidth has a low quality factor and is not good for imaging.

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What component of the transducer is made of lead zirconate titanate?
matching layer
active element
damping material
scan converter

active element

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What is the thickness of the matching layer of a 2MHz pulsed wave transducer?
0.77 mm
1.54 mm
1/2 wavelength of PZT
1/4 wavelength of matching layer

1/4 wavelength of matching layer

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Define the range equation.

depth (mm) = 1.54 mm/microseconds X go-return time / 2

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If the impedance of the transducers matching layer is 2.6 MRayls and the impedance of the transducers PZT crystal is 3.4 MRayls, what is the best estimate for the impedance of the skin?
3.8 MRayls
2.8 MRayls
1.5 MRayls
3.4 MRayls

1.5 MRayls

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T/F: The purpose of the backing material is to shorten the pulses creating better image quality.

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T/F: A narrow bandwidth gives better image quality with superb resolution.

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T/F: More backing material makes the transducer less sensitive during both transmission and reception.

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How are PRF and depth related?

Inversely

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How is Q factor related to bandwidth? directly inversely unrelated directly proportional

inversely

How is pulse length related to pulse duration? directly inversely unrelated

Directly

All of the following correctly describe an imaging transducer except... low Q factor wide bandwidth high sensitivity damped

high sensitivity

What is axial resolution vs. lateral resolution?

Axial: ability to discriminate two objects in PARALLEL to the beam Lateral: ability to discriminate two objects PERPENDICULAR to the beam

How are depth and go-return time related?

Directly

How does the range equation relate to PRF? (equation)

PRF (Hz) = 77,000 cm/s / imaging depth (cm)

How are PRP and depth related?

Directly

How does the range equation relate to PRP? (equation)

PRP (microseconds) = imaging depth (cm) x 13 microseconds/cm

How many cycles are there in a pulse for ultrasound transducers?

Usually 2-3

What is the 13 microsecond rule?

Every 13 microseconds of go-return time, the object creating a reflection is 1cm deeper in the body

Less ringing means....

there are fewer cycles in the pulse

The higher the frequency, the _______ the axial resolution.

Better

What are the other terms to describe axial resolution?

Longitudinal Axial Radial Range Depth

Define axial resolution in equation format.

axial resolution = SPL/2 ar = wavelength x #cycles in pulse / 2 ar = 0.77 x # cycles in pulse / frequency

Shorter wavelengths are characteristic of ________ frequency sounds.

High

Does shorter SPL improve or degrade axial resolution?

improve

What is axial resolution determined by?

Pulse duration and SPL

What is the greatest depth of penetration?

3.5. MHz (the lowest Hz allows greater depth of penetration)

What are the alternate terms for lateral resolution?

Lateral Angular Transverse Azimuthal

With an unfocused transducer, there is/is not a focal zone.

is not

Lateral resolution =...

the width of the beam

What are the 3 methods of focusing? What are they named? What type of focus do they exhibit?

Lens (EXTERNAL): fixed, conventional, or mechanical Curved active element (INTERNAL): fixed, conventional, or mechanical Electronic (PHASED ARRAY): adjustable

Is axial or lateral resolution most affected by the focal zone?

Lateral

How does adding additional focal zones affect resolution?

Lateral resolution improves, while temporal resolution degrades

What is PZT?

Lead zirconate titanate

What is the near zone also called?

Fresnel zone

What does Huygens principle describe?

The idea of sound wavelets interacting with one another, participating in constructive/destructive interference

What is the far field also called?

Fraunhofer zone

Is there more or less divergence in the far field with a small diameter transducer?

When a sound beam reaches the focal zone, what does the beam eventually do?

It diverges wider than how it was originally

The longer the near zone, the better/worse the lateral resolution.

worse

How is lateral resolution affected by a small diameter transducer?

It improves

As a beam approaches the focal zone, what happens to it?

it begins to narrow

With a wider element diameter, how it the near field affected?

it becomes longer

What kind of transducers have the deepest natural focus?

High frequency and wide diameter

Is the focal zone in near or far field?

Both; half of it is in both

The greater the element frequency, the more/less beam divergence.

less

Axial resolution ________ with decreased PD and SPL.

improves

What is the most common form of fixed focus? How does it work?

Curved PZT material, which concentrates sound energy into a narrower sound beam

T/F: Many active elements fire at almost the same time in a mechanical scanner.

Diffraction is _______ law while refraction is _________ law. Huygen's, Boyles Snell's, Huyerns Boyles, Huygens Huygens, Snell's

Huygens, Snell's

As the sound beam narrows, how is resolution impacted?

axial and lateral resolution improves

What is phased focusing used on?

multi-element transducers

If the transducer diameter is 9 millimeters (mm) what is the lateral resolution at the end of one near zone length? 1 mm 4.5 mm 1 cm 9 mm

4.5 mm

How does the addition of focal carats affect frame rate?

Decreases frame rate

What are the 3 ways focusing helps image quality?

1. focus is moved closer to the transducer, decreasing the length of near field 2. beam diameter beyond the focal zone widens, improving lateral resolution in near + focal zones 3. size of the focal zone is reduced

T/F: A machine that displays A mode and 2 D imaging is called a Duplex scanner.

If the diameter of the transducer is 9 mm, what is the lateral resolution at two near zone lengths? 06 cm 4.5 mm 9 mm cannot be determined

9 mm

The ability to distinguish two structures lying close together side by side is called? axial resolution range resolution depth resolution lateral resolution longitudinal resolution

lateral resolution

In which region of the sound beam is focusing most effective? very shallow near zone end of the near zone deep in the far zone throughout the entire length

end of the near zone

All of the following are examples of conventional focusing EXCEPT? lens phased curved crystal mirror

phased

Which of the following types of focusing is external? lens curved crystal electronic

lens

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 end of near zone

lower intensity at the focus

Huygen's principle is based on which of the following? refraction constructive indices transverse waves interference

interference

All of the following terms describe the shape of a sound wave created by a tiny fragment of PZT crystal EXCEPT? spherical Huygen's wavelets V-shaped wedge shaped shaped

wedge shaped

When two reflectors are closer side by side than the beam width, only one reflection is observed on the image. When this occurs the lateral resolution is said to be? sub-optimal accurate the appropriate beam width narrower than it should be

sub-optimal

What is another term for "shadowing by refraction"? comet tail clean shadow edge shadow dirty shadow

edge shadow

Which of the following waves whose periods listed below has the highest frequency? 6 s 60 microseconds 6 Ms 600 ks

60 microseconds

Which of the following artifacts serve a diagnostic purpose? posterior shadowing rib shadow mirror image Posterior enhancement corsstalk speckle

posterior shadow and enhancement

Which artifact displays the correct number of reflectors at improper depths. posterior enhancement speed error reverberation comet tail side lobes

speed error

A hyperechoic region beneath tissues with abnormally low attenuation is called? edge shadow enhancement shadowing speckle dead zone

enhancement

T/F: Axial resolution is related to beam diameter.

false

An ultrasound pulse has a width of 4mm, and a length of 2 mm. what is the best estimate of the systems axial resolution? 2 mm 4 mm 1 mm 2 kHz

1 mm

All of the following result in too many echoes on the image EXCEPT? mirror image comet tail grating lobes shadowing

shadowing

Which artifact does not result from multiple reflectors? reverberations ring down comet tail enhancement

enhancement

Which of the following is an amplitude mode where the height of the spike is related to the strength of the returning echo? A mode B mode C mode M mode

A mode

Which of the following statements is correct for power and amplitude? power and amplitude are reciprocals power is proportional to the waves amplitude squared power and amplitude are unrelated when power increases amplitude increases equally

power is proportional to the waves amplitude squared

If the sonographer increases the amplitude of the wave by a factor of 3, which of the following best describes what happened to the power. increases by 3 dB decreases by 3 dB increases 9 fold decreases 9 fold

increases 9 fold

What is reverberation?

Parallel echogenic lines reflect off a strong reflector

T/F: Decreasing the imaging depth also decreases the transmit time.

The actual amount of time that the US system is actually emitting a pulse if known as:

duty factor

What does A mode measure?

Distances that are close together

T/F: When the imaging depth is increased the spatial pulse length is also increased.

When applying pulsed/spectral Doppler, we want the sample gate to be _____ of the diameter of the vessel

1/3

What does continuous wave Doppler measure?

It can accurately measure the highest velocities of blood flow, but we don't. know where they're located

What is a propagation speed error artifact?

The speed of sound in the media is being recording slower/faster than whats actually showing

What are comet tail artifacts? Where are they usually seen?

type of reverberation, usually seen with gallbladder polyps

2D imaging average range is between ...

0.1 - 300 mW/cm^2

What is a refraction artifact?

The bending of a sound beam, causing incorrect location of the object

What is a multipath artifact? Where is it common?

echoes from a strong reflector bounce back and forth, causing shadowing that mimics an anechoic structure; bladder

What is the grating lobe artifact?

something anechoic fills in with low-level echoes, decreasing lateral resolution

What part of the reverberation artifact is actually real?

The first 2 reflectors generally then the rest is reverberation

What is ring down artifact?

type of reverberation that is caused by air/sometimes seen with an abscess

What is range ambiguity artifact?

misconnect in near field that fills something anechoic with low-level echoes

What is mirror artifact?

when we hit a very strong reflector and the structures populate on the opposite side

Average range Doppler intensities is...

0.2 - 400 mW/cm^2

What is the side lobe artifact?

A reflection arises from the side lobe, placing the original reflector along the main beam basically a minor duplication

If a structure exhibits posterior enhancement, the structure is _____ in attenuation.

low

When do we see speckle/noise artifact most commonly?

lower frequency transducers

Describe volume averaging/beam width artifact.

a superficial and anechoic lesion fills in with echoes

What has the slowest to fastest speed of sound?

lung --> soft tissue --> blood-->muscle --> bone

What is the speed of sound in bone?

3-5 mm/microseconds

What are the typical values for frequency?

2-15 MHz

What is the typical percentage. value for duty factor?

0.2% - 0.5 %

Shorter PD or SPL will improve/degrade axial resolution.

improve

What are the typical values for SPL?

0.1-1.0mm

What are the typical values for pulse duration?

0.3-2.0 microseconds

What are the typical values for amplitude?

1MPa - 3 MPa

What are the typical values for wavelength?

0.1mm - 0.8mm

What are the typical values for period?

0.06 - 0.05 microseconds

What are the typical values for propagation speed?

500 m/s - 4000 m/s

What are the typical values for PRP?

100 microseconds - 1 microsecond

When a sound beam hits a tissue interface, some sound is reflected and other sound is transmitted. If only 90% of sound is transmitted, what is the refraction coefficient?

10%

What are the typical values for PRF?

1000 Hz - 10000 Hz

Attenuation is determined by 2 factors:

path length and frequency of sound

What does the thickness of the matching layer measure?

1/4 of the wavelength in matching layer material

The higher the frequency, the ______ the fresnel zone.

longer

What are the 3 reasons for attenuation?

reflection, absorption, and scattering (specular vs diffuse)

The smaller the transducer diameter, the _______ the fresnel zone

shorter

The thickness of the piezoelectrical element equates to _____ of the wavelength of sound produced.

1/2

The thinner the crystal element, the ______ the frequency. The thicker the element, the ______ the frequency.

Higher; lower think wine glass to beer mug

What are the other names for perpendicular incidence?

90 degree, right angle, orthogonal

How does the backing material/damping layer affect PD and SPL?

shortens it, which improves axial resolution

The more damping material, the _____ the pulse and ______ the axial resolution.

shorter; better

The width of the beam affects ____

lateral resolution

As bandwidth widens, what happens to the quality factor, axial resolution, and image quality?

QF decreases, AR and image quality improves

What portion of the transducer determines bandwidth?

Damping material

What determines beam width?

the diameter of the crystal

Edge shadowing artifact can be appreciated with imaging what kind of structures?

rounded/curved such as testicle or cyst

What is crosstalk?

mirroring of spectral waveform

What is the matching layer?

increases efficacy of sound transmission into the body and protects the element

Where is the matching layer generally located?

in front of the piezoelectric element

How is propagation speed related to frequency?

Directly

Frequency is _____ related to the element thickness.

inversely

What is not usually seen in continuous wave transducers?

backing material/damping layer

What is the quality factor?

The pureness of the signal

How is quality factor related to bandwidth and axial resolution?

The wider the bandwidth, the lower the QF, the better AR

final II Flashcards

(151 cards)