final III Flashcards by Valery Dzev

How is blood flow related to resistance?

directly
inversely
indirectly
unrelated

inversely

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Which of the following types of flow would be seen due to cardiac contraction?

phasic
pulsatile
steady

pulsatile

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Which of the following would demonstrate the highest resistance waveform?

a large artery
a small artery
a large vein
a small vein

a small artery

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Which of the following is not a force that opposes blood flow and is not a major source of resistance?

friction
vessel diameter
vessel length
blood viscosity
oxygen content

oxygen content

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Which of the following is a correct statement in regards to pressure gradient?

pressure gradient increases when flow or resistance increases
pressure gradient increases when flow increases or resistance decreases
pressure gradient increases when flow decreases or resistance increases
pressure gradient increases when flow or resistance decreases

pressure gradient increases when flow or resistance increases

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Which of the following is a form of potential energy that provides flow by overcoming resistance?

pressure energy
kinetic energy
gravitational energy

pressure energy

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During expiration when the diaphragm moves upwards, the venous flow in the lower extremities would…

increase
decrease

increase

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You would expect to find less resistance to flow in which of the following?

in long narrow segments
in short large segments
at bifurcation
in smaller vessels

in short large segments

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During inspiration, pressure in the thoracic cavity ____ while abdominal pressure ____.

increases; increases
increases; decreases
decreases; decreases
decreases; increases

decreases; increases

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T/F: The diaphragm movement during respiration causes variations in arterial flow away from the heart.

false

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A received frequency that is less than the transmitted frequency is which of the following.

positive Doppler shift
negative Doppler shift
flow away from the transducer
flow toward the transducer
antegrade flow
retrograde flow

negative Doppler shift
flow away from the transducer
retrograde flow

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The major reflector for Doppler ultrasound is…

blood vessels
fluid
red blood cells
tissue

RBCs

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The doppler shift is dependent of all of the following except…

frequency
velocity of moving blood
thickness of the vessel wall
angle between sound beam and moving bloodd

thickness of the vessel wall

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The cosine of 180 is which of the following?

1
0
-1
none

-1

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The extracting of lower Doppler frequencies from higher transducer frequencies is called…

compression
demodulation
rectification
thresholding

demodulation

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Which of the following information is recorded by spectral Doppler?

speed of the reflector
velocity of the reflector
both speed and velocity of the reflector
neither speed and velocity of the reflector

velocity of the reflector

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T/F: Inaccurate angle correction may result in spurious velocity determinations which may lead to misdiagnosis.

true

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Velocity refers to:

speed of red blood cells
direction of flow of red blood cells
both
neither

both speed and direction

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This form of Doppler is used in a clinical setting to simply identify the presence of flow when direction of flow is of no consequence.

nondirectional Doppler

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Simultaneous imaging and Doppler is termed..

duplex immaging

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When discussing laminar flow within a vessel, blood velocities are…

turbulent/chaotic
equal throughout the entire vessel cross-section
highest in the center and decrease to zero at the walls
at an angle to the vessel

highest in the center and decrease to zero at the walls

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Which of the following may be present in pulsed Doppler but not in continuous wave Doppler?

aliasing
wall filter control
directional detection capabilities
spectral analysis of the Doppler signal

aliasing

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The purpose of the fast fourier transform program (FFT) is to…

eliminate aliasing
automatically limit system gain
display the Doppler frequency spectrum
filter out low frequency Doppler shifts

display the Doppler frequency spectrum

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Aliasing in pulsed Doppler occurs when:

the sample gate is too large
the signal doesn’t reach the nyquist limit
the Doppler frequency shift exceeds 1/2 the PRF
velocities are too low
the sampling rate is less than 2x the frequency of the signal

the Doppler frequency shift exceeds 1/2 the PRF
the sampling rate is less than 2x the frequency of the signal

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T/F: A patient who has anemia should not have a Doppler exam performed due to the low concentration of RBCs.

false

The strength of the Doppler signal from flowing blood is most closely related to... the area of the ultrasound beam the shape of the red blood cells the speed at which the blood is moving the number of red blood cells in the beam

the number of red blood cells in the beam

T/F: Absence of color on a color Doppler image always indicates no flow is present.

false

T/F: on color Doppler image, red always indicates flow toward the transducer and blue always indicated flow away from the transducer.

false

T/F: color Doppler reports peak velocities.

false

T/F: Power Doppler can identify direction of flow, but not velocity.

false

The Doppler shift produces information about which of the following? velocity speed direction distance

velocity

What is the current method of processing spectral Doppler signals? chirp z transform autocorrelation zero crossing detector fast fourier transform time interval histograms

fast fourier transform

When high velocities appear negative of the spectral tracing, it is termed... aliasing crosstalk spectral broadening overgain

aliasing

The science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing bioeffects is which of the following? dosimetry risk-benefit ratio radiation force epidemiology

dosimetry

What is related to the likelihood of harmful bioeffects form cavitation?

mechanical index

Research performed within the living body is known as...

in vivo

What are the letters that stand for the thermal index of soft tissue?

TIS

A high MI will cause less/more cavitation.

Which of the following is generally true of diagnostic ultrasound? only 3D and intravascular ultrasound need to be evaluated for bioeffects harmful bioeffects are often seen but the benefit to the patient outweighs the risk harmful bioeffects do not occur but it would be irresponsible to ignore the possibility they may in the future harmful bioeffects do not occur so it is unnecessary to discuss themm

harmful bioeffects do not occur but it would be irresponsible to ignore the possibility they may in the future

Which of the following is the correct intensity for an unfocused beam? 100 mW/cm sq 10 mW/cm sq 0.1 W/cm sq 1 W/cm sq

100 mW/cm sq

Which of the following is the correct intensity for a focused beam? 100 mW/cm sq 10 mW/cm sq 0.1 W/cm sq 1 W/cm sq

1 W/cm sq

What is the unit for impedance?

Rayls

What is the unit for pressure?

Pascals (Pa)

Which of the following is the processor used to analyze spectral Doppler? autocorrelation fast fourier transform zero crossing detector bidirectional Doppler histogram

fast fourier transform

Which of the following will give the most accurate spectral Doppler information? 60 degrees 90 degrees 45 degrees 180 degrees

180 degrees

Adding more focal zones will do which of the following? increase frame rate increase sweep speed decrease temporal resolution decrease imaging depth

decrease temporal resolution

You're using spectral Doppler to evaluate heart pressure and need to know exactly where the velocities are coming from. What kind of Doppler would you use?

Pulsed wave Doppler

T/F: Adding too much filter or decreasing the filter too much will lead to a loss of information of spectral Doppler waveform.

true

Which of the following is the half value layer thickness of a 7 mHz transducer? 1cm 0.65cm 0.85cm 1.1cm

0.85cm

What is the attenuation in dB using a 2.5 MHz transducer and imaging to a depth of 16 cm? 35.2 dB 16 dB 10 dB 20 dB

20 dB

When does a positive vs negative Doppler shift occur? Which vessels give these shifts?

+ = when the reflector is moving towards the transducer, arteries - = when the reflector is moving away from the transducer, veins (except for portal vein and pulmonary veins)

What increases the Doppler shift?

an increase in velocity, frequency, and cosine

What is the Doppler shift measured in and then converted to?

frequency aka Hz then converted to velocity (m/s)

T/F: the closer you get to 0 or 180 degrees, the more accurate the velocity obtained.

true

At which angle do we not experience Doppler shift?

90 degrees. perpendicular incidence

What are the cosines of 0, 60, 90, and 180 degrees?

0 = 1 180 - -1 90 = 0 60 = 0.5

Blood cells traveling at 60 degrees that are evaluated with doppler reports ___________.

1 m/s

The measured velocity is _______ of the true velocity.

1/2

What are the advantages of a sample gate?

range resolution, specificity, and lack of range ambiguity artifact

T/F: a sample volume box will only calculate reflectors within the gate.

true

What are the 3 characteristics of a stenosis?

1. elevated velocities 2. aliasing 3. spectral broadening

Differentiate non-directional vs directional Doppler.

non-directional aka non-coherent/power doppler: only measures presence of blood flow (comparative to "speed") directional aka color doppler: measures velocity, requires speakers (one listens to away sound, other listens to towards sound), display above and below baseline, requires processing signals (phase quadrature)

What are the upper limits of PSV and EDV?

PSV <125 cm/s EDV <40 cm/s

What is phase quadrature/qudarature detection?

signal processing technique that separates signals into 2 components (in phase and quadrature/ I/Q) US signal multiplied by a sine wave and cosine wave, then demodulated into in-phase (cosine product) and quadrature (sine product)

What are the main differences and pros/cons of CW and PW?

CW: two crystals, one transmitting and other receives -more sensitive, good temporal resolution, no aliasing, peak velocity measured - range ambiguity con PW: one crystal sends out pulse and waiting for returning signal before next one - range specificity - cons: inaccurate high velocity signal measurements, high velocity signals incorrectly display direction, aliasing

When does aliasing occur?

when the nyquist limit reached

How do you calculate nyquist limit?

PRF/2

Differentiate what happens when the sample gate is shallow vs deeper.

shallow: high prf (aka frequency), high nyquist limit, more accurate high velocities deep: low prf (aka frequency), low nyquist limit, inaccurate velocities recorded and aliasing occurs

Higher frequency transducers create _____ aliasing due to the creation of a ______ doppler shift, while lower frequency transducers create _____ aliasing due to the creation of a ______ doppler shift.

more; higher; less; lower

Does aliasing exist in CW ultrasound?

no only PW

What are two methods of spectral analysis?

fast fourier transform and autocorrelation

What does autocorrelation analyze and do?

color doppler; processes a large amount of data digitally

What is the advantages vs disadvantage of autocorrelation compared to FFT?

less accurate, but faster

PW and CW are bother able to record what velocities?

peak velocities

What do Doppler Packets refer to?

the number of pulses sent down each scan line in a color sector

What are the advantages vs disadvantages of larger packet size?

advantage: more accurate velocity measurement and sensitive the low flow disadvantage: reduced frame rate and temporal resolution since more time taken to acquire data

What is a Doppler artifact and why does it happen? What is a way to reduce this artifact?

ghosting: color bleeding from doppler shifts from moving anatomy wall filter: serves as a reject of low frequency doppler shifts from moving anatomy rather than moving cells (no effect on higher shifts from RBC motion)

What is resistive vs pulsatility index?

resistive : calculates vascular resistance to help grade severity of a stenosis RI = velocity max - min / max pulsatility: also calculates stenosis severity, but requires the mean over entire cardiac cycle PI = velocity max - min / mean

What are the similarities of RI and PI along with their advantages?

mathematically derived, depend of waveform shape, and unaffected by Doppler angle

When are quality assurance checks done?

routinely and periodically

What are the 4 quality assurance requirements?

assessment of system components repairs preventative maintenance record keeping

Where is ultrasound information the most unreliable and why?

region closest to the transducer due to a lot of artifact from different propagation speeds

Define registration accuracy and its 2 subcategories.

placement of echoes at correct depths range accuracy: place echoes at correct depths parallel to sound beam Horizontal calibration: place echoes at correct depths perpendicular to sound beam

define vertical depth accuracy

accuracy of depth assessment of structures within phantom

A lower contrast indicates a ______ dynamic range with more ______, while high contrast indicates a ______ dynamic range with more _______ imagery.

higher; grayscale; lower; B&W

What is operating and output testing?

operating: takes entire ultrasound system into account for evaluation output: only considers pulser and transducer in evaluation, performed by the manufacturer.

what are the 3 methods of evaluating operation?

AIUM 100mm test object tissue equivalent phantom doppler phantom

What is the AIUM 100 test object made of and what can it not evaluate?

0.75 mm stainless steel rods in a mixture with 1540 m/s no tissue properties; cannot evaluation gray scale, penetration, motion, compression/dynamic range

What is a tissue equivalent phantom?

includes soft tissue, solid, and cystic properties fibers used to detect avial + lateral resolution similar to soft tissue and can eval speed of sound, attenuation, scattering, echogenicity

what is a doppler phantom?

uses blood-mimicking fluid with a moving string inside with known velocity, pulse rate, and duration can produce pulsatile and retrograde motion

What are the 2 methods for evaluating acoustic output?

force-balance system: evaluates intensity or power of sound beam hydrophone: evaluates acoustic pressure at specific locations along the beam

What is the difference between preventative maintenance vs in-house QA?

PM done by trained professional, taking voltage measurements, assess image quality, done 2-3x yearly in house QA done by sonographers with tissue equivalent phantoms

What are the sensitivity and specificity formulas?

sensitivity: tp / tp+fn specificity: tn / tn+fp

How are sensitivity and specificity determined?

sensitivity: refers to true positive ratio that measures ability of test to find disease when its present specificity: refers to true negative ratio that measures ability of test to indicate no disease when no disease is present

What is the positive and negative predictive value?

positive: tp / total positive tests negative: tn / total negative tests

How is accuracy calculated?

tp + tn / total tests performed

Define energy

the capacity to do work

define power

a measurement of amount of energy / rate at which energy is transmitted)

define voltage

electrical pulses that drives the transducer

What determines the frequency of the ultrasound pulse?

the frequency of the voltage pulse

What are the limits to unfocused and focused beam intensities?

unfocused: SPTA below 100mmW/cm^2 focused: SPTA below 1W/cm^2

What image settings rank lowest to highest in intensity?

gray scale m mode color flow pulsed wave

What should the MI and TI be under?

MI: 1 TI: 2

T/F: Heat does not disperse with unfocused sound beams.

false

What is the relationship between area and intensity?

inversely proportional

what are two other ways to measure intensity?

via calorimeter (measuring total power in relation to heat generated) or thermocouple (electronic thermometer that is more precise in location)

Which measure of intensity is related most closely to tissue heating? A Im B SATA C SPPA D SPTA E SPTP

D SPTA

What is stable and transient cavitation?

stable: gaseous bubbles that expand + contract, but do not burst (lower MI) transient: gaseous bubbles expand + contract, but burst (high MI/power)

Which component of a US system is most likely to expose a patient to danger? A. monitor b. transducer c. scan converter d. pusler

b or d accepted

What is the matching layer?

in front of crystals; increases transmitted signals by reducing acoustic mismatch/reflection prior to sound beam entering patient

What happens to an image with a large difference in impedance levels?

artifacts, strong reflections, refraction

List the lowest to highest impedance values with the transudcer/skin.

skin (1.7 Mrayls) < gel < matching layer (2.6 Mrayls) < PZT (5.4 Mrayls)

What acts as an additional matching layer?

ultrasound gel

What is activation of the PZT element?

polarization, which happens bc of heating from strong electrical field

When does depolarization of the PZT element occur?

when the crystal overheats at its curie point

Thickness and frequency are _______ related.

inversely thicker = lower frequency thinner = higher frequency

Crystal diameter determines _______ ________.

beam width

Narrow crystal diameter = _____ focal length. Wide crystal diameter = _____ focal length.

short; long

What does the backing material / damping layer do? What kind of ultrasound is it found in?

decreases ringing of the crystal ; pulsed wave

Why does the amping layer not exist in continuous wave ultrasound?

there is no listening time, only talking time

Which characteristics of the sound beam does the backing material affect?

decreases SPL + PD + DF, increases QF + axial resolution

The less damping material, the _____ the pulse and the _______ the axial resolution

longer ; poorer

What does variance mode refer to on the screen?

the color on the PRF scale that represents turbulent or stable flow

What happens to the Doppler shift when a more vascular area is being scanned?

becomes higher

What happens to frame rate and temporal resolution if sector size was changed fro narrow to wider?

decreases

Which degrees of incidence will give us the truest velocities?

0 and 180

Once we reach above 90 degrees incidence angle, the doppler shift becomes ______ and the waveform appears ______ baseline.

negative; below

What are the typical doppler shift ranges?

45-60 degrees

final III Flashcards

(130 cards)