Chapter 7 Kremkau Final review Flashcards
improper Doppler-shift information from a pulsed spectral-Doppler or color- Doppler instrument when the true Doppler exceeds one-half the pulse repetition frequency
aliasing
echo-free
anechoic
a series of closely spaced reverberation echos
comet tail
leakage of strong signals in one direction channel of a Doppler receiver into the other channel; can produce the spectral_doppler mirror image artifact
cross-talk
increase in echo amplitude from reflectors that lie behind a weakly attenuating structure
enhancement
having relatively weak echoes.
hypoechoic
an artifactual gray-scale, color flow, or Doppler signal appearing on the opposite side of a strong reflector
mirror image
the Doppler-shift frequency above which aliasing occurs; one-half of the pulse-repetition frequency
nyquist limit
an artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received from the first pulse
range ambiguity
multiple reflections
reverberation
reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure
shadowing
thickness of the scanned tissue volume perpendicular to the scan place
slice thickness
the granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue
speckle
propagation speed that is different from the assumed value (1.54 mm/us)
speed error
The pulser of an instrument automatically reduces the PRF for deeper imaging to avoid the _____ artifact.
range ambiguity
If an echo arrives 143 us after the pulse that produced it was emitted, it should be located at a depth of ____ cm. If a second pulse was emitted 13 us before the arrival of this echo, it will be placed incorrectly at a depth of ____ cm.
11, 1
If the propagation speed in a soft tissue path is 1.60 mm/us, a diagnostic instrument assumes a propagation speed too _____ and will show reflectors too _____ the transducer.
low, close to
True or false:
Mirror image can occur with only one reflector.
false
The most common artifact encountered in Doppler ultrasound is _____.
aliasing
Which of the following can reduce or eliminate aliasing?
a. increased PRF
b. increased Doppler angle
c. increased operating frequency
d. use of continuous wave mode
e. more than one of the above
e (a b d)
True or false
Shadowing results in decreased echo amplitudes
true
Propagation speed error results in improper ____ position of a reflector on the display
axial
To avoid aliasing, a signal voltage must be sampled at least ____ time(s) per cycle.
2
If the highest Doppler-shift frequency present in a signal exceeds _____ the PRF, aliasing will occur.
one-half
When Doppler gain is set too high, which artifact is likely to occur?
spectrum mirror image
Which artifact should be suspected if one observes twin gestational sacs when scanning through the rectus abdominis muscle?
refraction
Range ambiguity can occur in which of the following?
a. imaging instruments
b. duplex instruments
c. pulsed-wave Doppler instruments
d. color flow instruments
e. all of the above
e
If red represents a positive Doppler shift and blue represents a negative one, what color is seen for normal flow toward the transducer? What color is seen for aliasing flow toward the transducer? What colors are seen for normal flow away and for aliasing flow away from the transducer?
red, blue, blue, red
When a pulse is emitted before all the echoes from the previous pulse have been received, which artifact occurs?
range ambiguity
When a strong reflector is located on the scan plane, which of the following artifacts is likely to occur?
location mirror image
if the PRF is 4 kHz, which of the following Doppler shifts will cause aliasing?
a. 1 kHz
b. 2 kHz
c. 3 kHz
d. 4 kHz
e (c d)
If the PRF is 10 kHz, which of the following Doppler shifts will cause aliasing?
a. 1 kHz
b. 2 kHz
c. 3 kHz
d. 4 kHz
e. none of the above
e
There is no problem with aliasing as long as the Doppler shifts are ______ half the PRF.
less than
True or false
If Doppler shift is 2.6 kHz, no aliasing would result with a PRF of 10 kHz.
true
When a pulse is emitted before all the echoes from the previous pulse have been received, which artifact occurs?
range ambiguity
When a strong reflector is located in the scan plane, which of the following artifacts is likely to occur?
a. aliasing
b. range ambiguity
c. spectrum mirror image
d. location mirror image
e. speckle
d
Increasing PRF to avoid aliasing can cause the following:
a. baseline shift
b. range ambiguity
c. spectrum mirror image
d. location mirror image
e. speckle
b
Which of the following decreases the likelihood of range-ambiguity artifact?
a. decreasing operating frequency
b. decreasing PRF
c. decreasing Doppler angle
d. baseline shift
e. increasing pulser output
b
Range ambiguity produces which error in a spectal-Doppler studies?
incorrect gate location
Range ambiguity producces which error in anatomic imaging?
range too short
If a pulse is emitted 65 us after the previous one, echoes returning for beyond, ______ cm will produce range ambiguity.
5
If the maximum imaging depth is 5 cm, the frequency is 2 MHz, and the Doppler angle is zero, what is the maximum flow speed that will avoid aliasing and range ambiguity?
300 cm/s
True or False
Solving aliasing be decreasing operating frequency increases the possibility of range-ambiguity artifact.
true
True or False
If operating frequency is increased to decrease the possibility of range ambiguity ( by increasing attenuation), the possibility of alising increases.
true
if a pulsed-wave Doppler sample volume is located at a depth of 8 cm, the sampled echoes arrive at what time following the emission of the pulse?
104 us
Which of the following instruments can produce aliasing?
a. continuous-wave Doppler
b. pulsed-wave Doppler
c. duplex
d. color Doppler
e. more than one of the above
e (b c d)
The pulser of an instrument automatically reduces the PRF for deeper imaging to avoid the ______ artifact.
range ambiguity
If an echo arrives 143 us after the pulse that produced it was emitted, it should be located at a depth of ____ cm. If a second pulse was emitted 13 us before the arrival of this echo, it will be placed incorrectly at a depth of ____cm.
11, 1
If the propagation speed in soft tissue path is 1.60 mm/us, a diagnostic instrument assumes a propagation speed too _____ and will show reflectors too ______ the transducer.
low, close to
Mirror image can occur with only one reflector.
false
The most common artifact encountered in Doppler ultrasound is ____
aliasing
Which of the following can reduce or eliminate aliasing?
a. increased PRF
b. increased Doppler angle
c. increased operating frequency
d. use of continuous wave mode
e. more than one of the above
e
The fine texture in soft tissue indicated the excellent resolution that actually exists there.
false
The fact that a beam, as it scans through tissue, has some nonzero width perpendicular to the scan plane results in the ______ artifact.
slice thickness
Which of the following can cause improper location of objects on a display?
a. shadowing
b. enhancement
c. speed error
d. mirror image
e. refraction
f. grating love
c
Refraction can cause shadowing
true
Reverberation results in added reflectors being imaged with equal ______.
separation
In reverberation, subsequent reflections are _____ than previous ones.
weaker
Enhancement is caused by a _____.
weakly attenuating structure
Which of the following can correct or eliminate aliasing?
a. decreased PRF
b. decreased Doppler angle
c. increased operating frequency
d. baseline shifting
e. more than one of the above
d
shadowing results in decreased echo amplitudes
true
Propagation speed error results in improper _____ position of a reflector on the display.
axial
To avoid aliasing, a signal voltage must be sampled at least ___ times per cycle(s).
2
If the highest Doppler-shift frequency present in a signal exceeds ______ the PRF, aliasing will occur
one-half
There is no problem with aliasing as long as the Doppler shifts are _____ half the PRF.
less than
If Doppler shift is 2.6 kHz, no aliasing would result with a PRF of 10 kHz
true
If red represents a positive Doppler shift and blue represents a negative one, what color is seen for normal flow toward the transducer? What color is seen for aliasing flow toward the transducer? What colors are seen for normal flow away and for aliasing flow away from the transducer?
red blue blue red
When a pulse is emitted before all the echoes from the previous pulse have been received, which artifact occurs?
range ambiguity
When a strong reflector is located in the scan plane, which of the following artifacts is likely to occur?
a. aliasing
b. range ambiguity
c. spectrum mirror image
d. location mirror image
e. speckle
d
Increasing PRF to avoid aliasing can cause:
range ambiguity
Which of the following decreases the likelihood of range ambiguity artifact?
a. decreasing operating frequency
b. decreasing PRF
c. decreasing Doppler angle
d. baseline shift
e. increasing pulser output
b
Range ambiguity produces which error in spectral-Doppler studies?
incorrect gate location
Range ambiguity produces which error in anatomic imaging?
range too short
If a pulse is emitted 65 us after the previous one, echoes returning from beyond _____ cm will produce range ambiguity.
5
If the maximum imaging depth is 5 cm, the frequency is 2 MHz, and the Doppler angle is zero, what is the maximum flow speed that will avoid aliasing and range ambiguity?
300 cm/s
Solving aliasing by decreasing operating frequency increases the possibility of range-ambiguity artifact
true
If operating frequency is increased to decrease the possibility of aliasing increases.
true
If a pulsed-wave Doppler sample volume is located at a depth of 8 cm, the sampled echoes arrive at what time following the emission of the pulse?
104 us
Which of the following instruments can produce aliasing?
a. continuous-wave Doppler
b. pulsed-wave Doppler
c. duplex
d. color Doppler
e. more than one of the above
e
