Chapter 6 Kremkau Flashcards
the part of the instrument that accomplishes electronic beam scanning, apodization, steering, focusing, and aperture with arrays
beam former
the portion of a system operating on Principle 2 that acquires the echo information from the signal processor, performs the retrospective, virtual-beam computations and sends the results to the display
image former
an electronic device that rapidly performs calculations to accelerate the creation of images
Graphics processing unit (GPU)
the beam
physical beam
ultrasound waves are produced in pulses, not continuously, because the same crystals are used to generate and receive sound waves, and they cannot do both at the same time
pulse-echo principle
a line produced on a display that represents ultrasonic echoes returning from the body
scan line
an imaginary reception beam that can be thought of as determining the echo produced at each pixel location in the image
virtual reception beam
an imaginary laser-thin transmitted ultrasound beam that can be thought of as producing the excellent detail resolution throughout the image that is accomplished with retrospective, computed beam forming
virtual transmission beam
The underlying principle upon which conventional (Principle 1) sonography operates is:
the pulse-echo principle
The underlying principle upon which more recent, sophisticated (Principle 2) sonography operates is:
the virtual beam principle
Which is not needed with Principle 2 sonography?
a. transmitted beam
b. multiple-transmit focus
c. reception focus
d. TGC
multiple-transmit focus
Which is not a reason for improvement of detail resolution with Principle 2 sonography?
a. shorter transmit pulses
b. reception focus at each pixel location
c. massive postprocessing with GPUs
d. retrospective beam forming
shorter transmit pulses
Which is not a reason for improvement of temporal resolution with Principle 2 sonography?
a. shorter transmit pulses
b. fewer transmit pulses
c. no multiple focusing
d. speed of GPUs
a
Which is not significantly improved with Principle 2 sonography?
a. axial resolution
b. lateral resolution
c. temporal resolution
d. contrast resolution
a
Physical beam forming applies to ____ sonography
both principle 1 and principle 2
Virtual beam forming applies to:
principle 2
Multiple transmission focus control applies to:
principle 1
Retrospective beam forming applies to:
principle 2
Improving detail resolution sacrifices temporal resolution is true for:
principle 1
Simultaneous gray-scale, Color-doppler, and spectral-Doppler applies to:
principle 2
Principle 1 employs mostly:
focused ultrasound beams
Principle 1 yields higher frame rates than Principle 2.
false
Shear wave elastography operates on Principle 1
false
Principle 2 enables the entire image to be in focus
true
Principle 2 yields improved penetration
true
Principle 2 does not impact Doppler operations
false
Principle 2 produces laser-thin ultrasound beams
false
Multiple transmit focuses degrade temporal resolution with _____.
principle 1
Reception focus principle applies to:
both principle 1 nor principle 2
A doppler shift at 60 degrees is ____ what it would be at 0 degrees
one half
A change in doppler frequency caused by motion of a source or a reflector defines
Doppler effect
A nonsteady flow with acceleration and deceleration over the cardiac cycle is called _____
pulsatile flow
Continuous wave doppler shifts are detected within the _______
Overlapped region of the transmitting and receiving beams
Determining the direction of the doppler shift voltages is accomplished by the _______
Phase quadrature detector
Doppler measurements are not reliable at doppler angles greater than
60
Doppler shift does not depend on the
flow direction
Echoes arrive from the sample volume depth at a rate equal to
the pulse repetition frequency
for a given flow, the greater the doppler angle, the _____ the doppler shift
less
Gases, nutrients, and waste products are exchanged through the walls of
capillaries
if pressure differences in a straight vessel increase, the flow rate
increases
Motion toward the transducer demonstates
a positive Doppler shift
Poise is a unit given for ____
viscosity
Poiseuille’s equation states that, if the flow rate increases the
tube diameter has increased
Resistance to flow offered by a fluid in motion describes
viscosity
Sound reflects totally at the wall-blood boundary once the doppler angle is less than ____ degrees
30
Spectral broadening may be produced by
beam spreading in arrays
The doppler equation relates the doppler shift to the
flow speed and frequency
the amount of blood passing a point per unit of time defines
volumetric flow rate
The angle of incidence is not important with which doppler display>
power
The decreased pressure is regions of high flow speed is called
Bernoulli effect
The difference between the emitted frequency and the echo frequency returning from a moving scatter is called the
Doppler shift
The fast fourier transform derives the Doppler
spectrum
The horizontal presentation in the spectral display represents
time
The resistance of the _____ accounts for about one half of the total resistance in the systemic circulation.
arterioles
The volumetric flow rate is equal to _____
average flow rate across the vessel multiplied by the cross sectional area of the vessel
The width of the sample volume is determined by the
beam width and sample volume depth
Turbulent flow is a form of _____ flow
nonlaminar
Variance color maps demonstate a change of hues from _____
left to right
Vertical thickening of spectral tracing is called
spectral broadening
What advantage does spectral analysis have when compared to other doppler techniques
spectral analysis displays peak systolic velocities
what is required for flow to occur
pressure difference
what is the driving force behind blood flow
pressure
what type of blood flow demonstrates layers of fluid sliding over each other?
laminar
Which flow type demonstrates a flow velocity that is essentially constant across the vessel
plug
which matter is considered fluid
gases and liquids
What Doppler display cannot determine flow direction?
power
What doppler technique must be time shared
Duplex imaging
What is an advantage of pulsed Doppler
depth of sample volume can be accurately selected
What pulsed doppler technique is most likely to demonstrate slow flow velocities in deep vessels?
power doppler
Which system control eliminates low-frequency doppler shifts
wall filter
Which type of blood flow demonstrates a chaotic flow pattern?
turbulent
Which type of blood flow would demonstrate the narrowest range of doppler shift frequencies?
plug
With color doppler imaging, the priority control _____
selects which gray-scale echo strength will demonstrate color
_____ describes the volumetric flow rate as a constant
Continuity rule
An imaginary laser thin transmitted ultrasound beam that can be thought of as producing excellent detail resolution throughout the image describes a _____
virtual transmission beam
The retrospective beam forming process occurs in the
image former
What contributes to improved temporal resolution in Principle 2?
fewer pulses and broad physical beams
What type of blood flow demonstrates layers of fluid sliding over each other
laminar
resistance of the blood flow depends on the radius of the
tube to the fourth power
if pressure difference in a straight vessel increase, the flow rate
increases
Tiniest vessels in the human body
capillaries
the state of the downstream arterioles is reflected in the
arterial diastolic flow
For a given flow, the greater the doppler angle, the less the
doppler shift
The maximum normal flow speed in the circulation is
100 cm/s
Variance color maps demonstrate a change of hues from
left to right
which system control eliminates low frequency doppler shifts
wall filter
the width of the sample volume is determined by the
beam width and sample volume depth
the horizontal presentation in the spectral display represents
time
spectral broadening may be produced by
beam spreading arrays
continuous wave doppler shifts are detected within the
overlapped region of the transmitting and receiving beams
the normal adult circulatory system contains ____ of blood
5L
In a stenosis, flow speed increases and pressure
decreases
The doppler shift is proportional to the
blood flow speed
volumetric flow rate is proportional to
flow resistance
if the pressure difference between two point increases, the flow rate
also increases
Blood flows from the left and right ventricles into the _____ and _____ respectively
aorta
pulmonary artery
According to Poiseuille’s equation, if the radius of the tube increases, the flow rate
increases
If the flow speed increases, the pressure
decreases
Higher operating frequencies produce ____ doppler shifts
larger
If viscosity increases, flow rate
decreases
Increased flow speed through a stenosis can cause
distal turbulence
Multiple transmission focuses are used in
Principle 1
What contributes to improved temporal resolution in principle 2
fewer pulses
broad physical beams
The retrospective beam forming process occurs in the
image former
Physical ultrasound beam forming is required in
both principle 1 and principle 2
Weakly focused or unfocused ultrasound beams are characteristic of
principle 2
The characteristic of fluid that offers resistance to flow is called
viscosisty
Flow is a response to pressure ______ or ______
difference
gradient
If pressure difference is doubled, volumetric flow rate is _______
doubled
If flow rate is doubled, volumetric flow rate is
halved
Flow resistance in a vessel depends on
vessel length
vessel radius
blood viscosity
if operating frequency is doubled, the doppler shift is
doubled
if flow rate is doubled, the doppler shift is
doubled
Color doppler instruments use an ______ technique to yield doppler information in real time
autocorrelation
In practice, approximately _____ pulses are required to obtain one line of color-doppler information
10
color map baselines are always represented by
black
doubling the width of a color window produces a ____ frame rate
halved
Color doppler frame rates are ______ gray scale rates
less than
Doppler power imaging indicates (with color) the _____ of flow
presence
Stenosis affects
spectral broadening
Virtual beam forming applies to
Principle 2
Multiple transmission focus control applies to
Principle 1
Retrospective beam forming applies to
Principle 2
Improving a detail resolution sacrifices temporal resolution is true for
principle 1
Simultaneous gray scale, color doppler, and spectral doppler applies to
Principle 2
Principle 1 employs mostly
focused ultrasound beams
Reception focus principle applies to
both principle 1 and principle 2
