Chapter 10 Kremkau... To conclude final review Flashcards
Which of the following frequencies is in the ultrasound range?
a. 15Hz
b. 15 kHz
c. 15 MHz
d. 17,000 Hz
e. 17 km
c
The average propagation speed in soft tissue is _____.
1.54 mm/us
The propagation speed is greatest in ____.
bone
Which of the following has a significant dependence on frequency in soft tissues?
a. propagation speed
b. density
c. stiffness
d. attenuation
e. impedance
d
The frequencies used in diagnostic ultrasound imaging _____.
determine imaging depth in tissue and determine detail resolution
An echo from a 5-cm deep reflector arrives at the transducer _____ us after pulse emission.
65
A small (relative to the wavelength) reflector is said to _____ an incident sound beam.
scatter
Which of the following determines the operating frequency of an ultrasound transducer?
a. element diameter
b. element thickness
c. speed of sound in tissue
d. element impedance
e. all of the above
b
The fundamental operating principle of medical ultrasound transducers is ____.
piezoelectric effect
The axial resolution of a transducer is primarily determined by ______.
spatial pulse length
The lateral resolution of a transducer is primarily determined by:
the aperture
Increasing frequency _____
improves resolution
ultrasound bioeffects ______
are not confirmed below a spatial peak-temporal average intensity of 100 mW/cm^2
Diagnostic ultrasound frequency range is _____
2 to 20 MHz
What determines the upper and lower limits of frequency range useful in diagnostic ultrasound?
resolution and penetration
Reverberation causes us to think there are reflectors that are too great in ______.
number
A flat-panel display is composed of a backlighted rectangular matrix of thousands of ______ display elements.
LED or liquid-crystal
In an ultrasound imaging instrument, a flat-panel display may be used as a _____.
display
The compensation (time gain compensation) control ______.
compensates for attenuation
An image professor changes signals from ____ to _____ format.
scan line, image
enhancement is caused by
weajly attenuating structure
echo intensity is represented in image memory by
a number
which of the following is (are) performed in a signal processor?
a. filtering
b. detection
c. compression
d. all of the above
e. none of the above
d
Increasing the PRF ______
decreases maximum unambiguos depth
Attenuation is corrected by ______
compensation
What must be known to calculate distance to a reflector?
travel time, speed
Which of the following improve(s) sound transmission from the transducer element into the tissue?
a. matching layer
b. Doppler effect
c. damping material
d. coupling medium
e. a and d
e
Lateral resolution is improved by _____.
focusing
Axial resolution is improved by ______.
damping
An image memory divides the cross-sectional image into _____.
pixels
In general, as a reflector approaches a transducer at constant speed, the positive Doppler-shift frequency _____.
decreases or remains constant
A reduction in vessel diameter produces a(n) ______
increase in flow resistance
decrease in area
increase in flow speed
decrease in flow speed
Which of the following increases vascular flow resistance?
a. decreasing vessel length
b. decreasing viscosity
c. decreasing vessel diameter
d. decreasing pressure
e. decreasing flow speed
c
The Doppler effect occurs as _____
blood moves relative to the vessel wall
When a reflector is moving toward the transducer, ______
the Doppler shift is positive (higher frequency)
Doppler sample volume is determined by _______.
beam width
pulse length
frequency
amplifier gate length
Doppler shift frequencies _______.
are generally in the audible range and can be applied to a loudspeaker
The quantative presentation of frequencies contained in echoes is called ______.
spectral analysis
The Doppler frequency shift is caused by ______.
relative motion between the transducer and the reflector
The Doppler effect is a change in _____.
wavelength and frequency
The Doppler shift is zero when the angle between the sound direction and the movement (flow) direction is ____ degrees.
90
Duplex Doppler presents ______
anatomic (structural) data and physiological (flow) data
True or False:
The Doppler shift frequencies are usually in a relatively narrow range above 20 kHz.
false
Continuous wave sound is used in ______.
some Doppler instruments
As advantage of continuous wave Doppler over pulsed Doppler is _______
no aliasing
In color-Doppler instruments, hue can represent _____.
sign (+ or -) of Doppler shift
flow direction
magnitude of the Doppler shift
amplitude of the Doppler shift
The Doppler effect for a scatterer moving toward the sound source causes the scattered sound (compared with incident sound) received by the transducer to have ______.
increased frequency
Duplex Doppler operation includes _____.
pulsed-wave Doppler and B-scan imaging
If the Doppler shifts from normal and stenotic arteries are 4 kHz and 10 kHz, respectively, for which will there be aliasing with a PRF or 7 kHz?
normal artery and stenotic artery
The signal processor in a Doppler system compares the _____ of the output with the returning echo voltage from the transducer.
frequency
In the Doppler equation that follows, which can normally be ignored?
fD = 2fv / (c-v)
v in the denominator
For which of the following is the reflected frequency less than the incident frequency?
a. advancing flow
b. receding flow
c. perpendicular flow
d. laminar flow
e. all of the above
b
Doppler ultrasound can measure flow speed in the _____.
heart and veins
Which of the following are fluids?
a. gas
b. liquid
c. solid
d. a and b
d
The mass per unit volume of a fluid is called its
density
The resistance to flow offered by a fluid is called
viscosity
Viscosity divided by density is called
kinematic viscosity
if the following is increased, flow increases.
pressure difference and pressure gradient
Flow resistance depends most strongly on _____.
vessel radius
Proximal to, at, and distal to a stenosis, ______ must be constant.
volume rate
Added forward flow and flow reversal in diastole are results of _____ flow.
pulsatile
A broad spectrum indicates _____ flow.
turbulent
While diameter at a stenosis decreases, the following pass(es) through a maximum.
a. flow speed at the stenosis
b. flow speed proximal to the stenosis
c. volume flow rate
d. Doppler shift at the stenosis
e. a and d
e
The Doppler shift (kHz) for 4 MHz, 50 cm/s, and 60 degrees is ____.
1.3
Physiologic flow speeds can be as much as ____% of the propagation speed in soft tissues.
0.3
Which Doppler angle yields the greatest Doppler shift?
a. -90
b. -45
c. 0
d. 45
e. 90
c
Doppler-shift frequency does not depend on _____
amplitude
The Fourier transform technique is not used in color-Doppler operation because it is not _____ enough.
a. slow
b. fast
c. bright
d. cheap
e. none of the above
e
Which of the following on a color-Doppler display is (are) presented in real time?
a. gray-scale anatomy
b. flow direction
c. Doppler spectrum
d. a and b
e. all of the above
d
For a 5-MHz instrument and a 0-degree Doppler angle, 100-Hz filter eliminates flow speeds below____.
3 cm/s
For a 7.5 Mhz instrument and a 0-degree Doppler angle, a 100 h Hz filter eliminates flow speeds below _____.
1 cm/s
The functions of a Doppler detector include:
amplificatin
phase quadrature detector
demodulation
A later amplifier gate time means a(n) ______ sample volume depth
deeper
The Doppler shift is typically ______ the source frequency.
one-thousandth
Approimately _____ pulses are required to obtain one line of color Doppler information
10
There are approximately _____ samples per line on a color Doppler or display.
200
Which of the following Dopper operations can produce aliasing?
a. continuous wave
b. pulsed
c. duplex
d. color
e. more than one
e
For normal flow in a large vessel, a _____ range of Doppler shift frequencies is received.
narrow
Doppler signal power is proportional to:
cell density
Stenosis affects:
peak systolic flow speed
end diastolic flow speed
spectral broadening
wndow
Spectral broadening is a ____ of the spectral trace.
vertical thickening
While stenosis is increased, ______ increase(s)
systolic Doppler shift
diastolic Doppler shift
spectral broadening
Flow reversal in diastole (normal flow) indicates _____.
high distal flow resistance
Approximately ______ fast Fourier transforms are performed per second on a spectral dislay.
100 to 1000
Each fast Fourier transform appears on a spectral display as ______.
vertical line
Hue is ____.
a. color seen
b. light frequency
c. brightness
d. mix with white
e. more than one above
e
A component not included in continuous-wave Doppler operation is a(n):
gate
On a spectral display, amplitiude is indicated by _____.
brightness
Doppler shift can change because of changes in _____.
velocity
speed
direction
frequency
A gate-open time of 10 us corresponds to a sample volume length (millimeters) of:
7.7
Sample volume width is determined by
gate-open time
pulse duration
What problem(s) is (are) encountered if pulse repetition frequency is 10 kHz, sample volume is located at 10 cm depth, and the Doppler shift is 4 kHz?
range ambiguity
What problem(s) is (are) encountered if pulse repetition frequency is 10 kHz, sample volume is located at a 10 cm depth and the Doppler shift is 6 kHz?
aliasing
What problem(s) is (are) encountered if pulse repetition frequency is 10 kHz, sample volume is located at a 10 cm depth, and the Doppler shift is 6 kHz?
aliasing
range ambiguity
The functions of a color-Doppler signal processor include
amplification
phase quadrature detection
demodulation
autocorrelation
If all cells in a vessel were moving at the same constant speed, the spectral trace would be a _____ line.
thin horizontal
Doppler power displays:
are independent of Doppler angle
are more sensitive than Doppler-shift displays
are independent of aliasing
show uniform flow presentations
For a physiologic flow speed, a 5 - MHz beam could produce a Doppler shift of about:
5 kHz
Spectral analysis is performed in a Doppler instrument:
electronically
mathematically
The Doppler shift is proportional to
flow speed
Which of the following can be used to evaluate the performance of a Doppler instrument?
a. contrast detail phantom
b. string test object
c. flow phantom
d. b and c
e. all of the above
d
Place the following instruments in general order of increasing acoustic output:
spectral Doppler
sonographic
color Doppler
sonographic, color, spectral
If operating frequency is 5 MHz, Doppler angle is 60 degrees, pulse repetition frequency is 9 kHz, and the Doppler shift is 2 kHz, what problem is ecountered if the angle is changed to zero?
a. aliasing
b. range ambiguity
c. mirror image
d. refraction
e. non
e
When angle correction is applied on a color-Doppler display, the Nyquist limits (in centimeters per second) on the color map
increase
When angle correction is applied on a color Doppler display, the Nyquist limits (in kilohertz) on the color map
do not change
Flow is _____ if it appears red on a color-Doppler display
undetermined
Two different colors in the same vessel indicate
flow reversal
sector scan
vessel curvature
aliasing
The following increase(s) the amount of color appearing in a vessel
a. increased color gain
b. increased wall filter
c. increased priority
d. increased pulse repetition frequency
e. more than one of the above
e
Which of the following on a color-Doppler display is (are) presented as a two-dimensional, cross-sectional display?
a. increased wall filter
b. increased pulse repetition frequency
c. increased ensemble length
d. baseline shift
e. more than one of the above
e
Which of the following on a color-Doppler display is (are) presented as a two-dimensional, cross-sectional display?
a. gray-scale anatomy
b. flow direction
c. Doppler spectrum
d. a and b
e. all of the above
d
Comparing gray with white is an example of
luminance
comparing red and green is an example of
hue
There are about _____ frames per second produced by a color-Doppler instrument
a. 10
b. 20
c. 40
d. 80
e. more than one above
e
The autocorrelation technique yields
the mean Doppler shift
a sign of the Doppler shift
a spread around the mean (variance)
Increasing ensemble length _____ color sensitivity and accuracy and _____ frame rate.
improves, decreases
Which control can be used to help with clutter?
wall filter
Doubling the width of a color window produces a(n) _____ frame rate
halved
Steering the color window to right or left changes the ______
the Doppler angle and Doppler shift
Lack of color in a vessel may be attributed to:
low color gain
Which control(s) can help with aliasing?
a. wall filter
b. gain
c. smoothing
d. pulse repetition frequency
e. more than one of the above
d
Pulse duration is the _____ for a pulse to occur.
time
Spatial pulse length equals the number of cycles in the pulse multiplied by ______
wavelengths
If pulse duration is 1 us and the pulse repetition period is 100 us, duty factor is _____.
1%
The attenuation of 5-MHz ultrasound in 4 cm of tissue us
10 Db
If the maximum value of an acoustic variable in a sound wave is 10 units and the normal (no sound) value is 7 units, the amplitude is _____ units.
3
Impedance equals propagation speed multiplied by
density
Which of the following cannot be determined from the others?
a. frequency
b. amplitude
c. intensity
d. power
e. beam area
a
For perpendicular incidence, in medium 1, density equals 1 and propagation speed equals 3; in medium 2, density equals 1.5 and propagation speed equals 2. What is the intensity reflection coefficient?
0
For perpendicular incidence, if the intensity transmission coefficient is 96%, what is the intensity reflection coefficient?
4%
The colors presented on a Doppler-power display present the _____ of the spectrum.
area
For oblique incidence and a medium 2 speed that is equal to twice the speed of medium 1, the transmission angle will be about _____ times the incidence angle.
2
The range equation describes the relationship of
reflector distance, propagation time, and sound speed
Axial resolution in a system equals _____
the minimum reflector separation expected to be displayed
In soft tissue, two boundaries that generate reflections are separated in axial distance (depth) by 1 mm. With a two cycle pulse of ultrasound, the minimum frequency that will axially resolve these boundaries is _____
2 MHz
