SPI Practice Exam 1 Flashcards
1
Q
A longitudinal wave is characterized by __________.
A
particle motion in same direction as the direction of wave propagation
2
Q
Pulsed-wave operation is necessary for B-mode imaging because:
A
the depth to the reflector can be determined
3
Q
The output power of an ultrasound pulser determines the _________ of the acoustic pulse.
A
Intensity
4
Q
What can be said of the Doppler shift when the sound beam is parallel to the direction of travel of the red blood cells
A
It is at a maximum
5
Q
*The half-value-layer (or the half-intensity-depth) of a 3 MHz transducer
A
2 cm
6
Q
Two ultrasound transducers are used to perform Doppler exams on the same patient. The settings are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will produce the highest frequency shifts?
A
5.0 MHz
7
Q
Assuming soft-tissue, what is the amount of attenuation of sound from a 5 MHz transducer after traveling through 1 cm?
A
2.5 dB
*attenuation coefficient = 1/2f
8
Q
Which of the following transducers provides the maximum penetration?
A
2.25 MHz
9
Q
What is the primary disadvantage of multiple focal zones along each scan line of a two-dimensional image?
A
Decreased temporal resolution
10
Q
What happens to a digital image when the pixel density is increased?
A
There is more spatial detail in the display
11
Q
Which of the following produces a rectangular format?
A
Linear sequenced array
12
Q
Increasing the gain generally produces the same effect on the image as
A
Increasing the output power
13
Q
The speed of ultrasound in soft tissue is closest to
A
1540 m/s
14
Q
A video display that is limited to only black and white, with no other shades of gray, is called _______
A
Bistable
15
Q
Which Doppler function controls how many waveforms are displayed on the image at one time?
A
sweep speed
16
Q
*Sound power is measured in units of….
A
Watts
*note: talking about power
17
Q
Which of the following will reduce/eliminate aliasing?
A
Increase the Nyquist limit above the Doppler shift
18
Q
*Review
What receiver function converts the negative portion of the RF signal to positive?
A
Rectification
19
Q
You are using a transducer that produces a beam with a very wide elevational plane. Which of the following problems are you most likely to encounter as a result?
A
Slice thickness artifact
20
Q
Damping in a transducer
A
reduces the number of cycles in a pulse
21
Q
Looking at this image, what type of image mode was used?
- M mode
- A mode
- B mode
- Amplitude mod
A
M mode
22
Q
What principle states that sound is generated from the transducer as wavelets?
A
Huygen’s
23
Q
*If the amplitude is decreased by 50%, what is the corresponding change in power?
A
-6 dB
*note: review amplitude!
24
Q
Pulse duration is the ______ it takes for one ______ to occur
A
time; pulse
25
Which of the following describes Snell’s Law?
Law that describes the angle of a transmitted beam
26
A small (relative to the wavelength) reflector is said to __________ an incident sound beam
scatter
27
The axial resolution is primarily determined by:
spatial pulse length
28
Focusing...
Improves lateral resolution
29
With phased array transducers, the transmitted sound beam is swept by
varying the timing of pulses to the individual piezoelectric elements
30
What is the component of an ultrasound system that is made out of lead zirconate titanate?
Transducer***’***s active element
31
Assuming a fixed frequency, what happens if the diameter of an unfocused transducer is increased?
the length of the near zone increases
32
Avoiding a local temperature increase exceeding _____ should ensure that are no thermally induced biological effects
***2° C***
33
Manufacturing a transducer with more damping...
reduces the duty factor
34
Which of the following will improve a system’s temporal resolution?
Increased PRF
35
\*Review
Which of the following tasks is incorporated in the process of demodulation?
Rectification
36
Which of the following frequencies is in the “ultrasound” range?
1.5 MHz
37
Which of the following is a characteristic of the medium through which a sound is propagating?
impedance
38
**\*****Which one of the following statements is true about a single pulse of ultrasound emitted by a transducer?**
It contains a range of frequencies
39
Images magnified using ________ will have better quality due to preservation of the pixel density.
write zoom
40
Diagnostic ultrasound frequency range is:
2 to 20 MHz
41
Parenchyma appears on ultrasound as a pattern of gray dots. This interference pattern is a result of
acoustic speckle
42
**\*****The frequency of a CW transducer is determined by**
the frequency of the oscillator
43
What testing device is used to measure acoustic output (intensity) level?
Hydrophone
44
If the imaging depth is increased and the sector angle and line density remain the same:
the frame rate decreases
45
Spatial pulse length equals the number of cycles in a pulse multiplied by:
wavelength
46
Which of the following is NOT a method in which venous flow returns to the heart?
left ventricle contraction
47
What is the smallest element in a digital picture called?
The pixel
48
If the power of a wave is halved, the intensity ___________ its original value.
Is reduced to one-half its original value
49
The image is brighter at the level of the focal zone. Which of the following controls is best to correct this?
TGC
50
What is the difference between audible sound and ultrasound?
Ultrasound has a higher frequency
51
The propagation speed is highest in
bone
52
\*Review
Two ultrasound systems produce pulses. One pulse is 0.4 µs in duration and the other is 0.2 µs. Which pulse is most likely to produce the best radial resolution?
***0.2 μsec system***
53
Which of the following will not demonstrate aliasing of the Doppler signal?
Power Doppler
54
Which of the following is representative of the duty factor for continuous-wave (CW) ultrasound?
100%
55
With oblique or normal incidence, the angle of reflection always equals
the angle of incidence
56
The redirection of sound energy in many directions as a result of a rough boundary between two media is
scattering
57
\*Review dB
If the operator increases the acoustic output of the machine by 20 dB, the beam intensity is increased by
100 times
58
The piezoelectric effect describes how _______ is converted into ________ by a \_\_\_\_\_\_\_\_.
ultrasound; electricity; transducer
59
Which Doppler control rejects noise along the baseline?
Wall filter
60
The fundamental operating principle of medical ultrasound transducers is:
piezoelectric effect
61
\*Review TDR
**A 1.5D transducer has what ability?**
Electronically focus in the elevational plane
62
\*Review
A decrease in power or intensity by a factor of 2 represents a change of
-3 dB
63
If the line density changes but the imaging depth remains the same, what else must change?
frame rate
64
**\*Review**
**The density is the same in materials A and B, but the speed of sound in material B is 10% greater than the speed of sound in material A.**
The acoustic impedance in B is 10% greater than the acoustic impedance in A
65
A decrease in the thickness of a piezoelectric element will result in
an increase in the frequency of the transducer
66
\*Read question carefully!
**\*If red blood cells are traveling toward a transducer, the frequency emitted by the transducer is _____ the frequency reflected from the red blood cells**
Less than
67
**\*Which of the following do the source and the medium determine?**
axial resolution
68
Ultrasound energy is traveling through the soft-tissue. If the frequency is doubled, the propagation speed is
Unchanged
69
For perpendicular incidence, if the impedances of the media are the same, there will be no...
Reflection
70
The area between the face of an unfocused single-element transducer and the point where the beam starts to diverge is the
Fresnel zone
71
Axial resolution is affected by all of the following EXCEPT
focusing
72
Which of the following has time represented on the X-axis?
M mode
73
What is the term for adjusting the displayed brightness of the dots as they relate to attenuation?
Compensation
74
Which of the following will produce a transducer with a high Q-factor?
Continuous-wave transducer
75
Longitudinal resolution is also called
Axial
76
During a PW Doppler exam, aliasing is noted by the sonographer. Which of the following will decrease the likelihood of aliasing?
Selection of another imaging view that provides a decrease in the pulse repetition period
77
In real-time imaging the transmitted ultrasound beam is not continuously generated, but is pulsed. Approximately what fraction of time is the transducer actively generating sound waves?
1%
78
Lateral resolution is determined mainly by
beam diameter
79
As frequency is increased:
a three-cycle ultrasound pulse decreases in length
80
If the frequency is doubled…
the spatial pulse length will be one-half
81
**\*Why is the digital to analog (D to A) converter needed?**
The scan converter signal is digital and needs to be converted to analog
82
\*Review
The acoustic impedance of a matching layer in a transducer should have a value
between the acoustic impedance of the piezoelectric element and the acoustic impedance of tissue
83
\*Review
**\*Which of the following will create the fastest speed of sound?**
Low density, high stiffness
84
\*Review
Higher frequency transducers provide
improved lateral resolution
85
Far zone beam divergence can be reduced on a single-element transducer by using
a higher frequency transducer
86
What must be known in order to calculate distance to a reflector?
Travel time, propagation speed
87
Increasing the operating frequency:
improves spatial resolution
88
Which of the following is a true statement?
Most ultrasound machines have better axial resolution than lateral resolution
89
\*Watch out for spelling
**Ultrasound waves that are traveling through a medium consist of**
compressions and rarefactions
90
The particles in a medium vibrate in a ______________ motion under the influence of a sound wave
Longitudinal
91
Which of the following is proportional to the square of the amplitude?
Power
92
\*Review
**The average attenuation of ultrasound energy in the patient is approximately**
0.7 dB per cm per MHz
93
If the real time frame rate is increased and the lines per frame are unchanged, what else must happen?
imaging depth decreases
94
Relative sound intensity based on a logarithmic scale is expressed typically in units of:
decibel
95
An unfocused, single-element disc transducer that is 13mm in diameter has a diameter at the focal zone of:
6.5 mm
96
The “useful” artifact that one might see behind a weakly attenuating structure:
Enhancement
97
If the number of cycles in a pulse is reduced....
The pulse duration is reduced
98
\*Review TDR
Which of the following transducers fire the elements, in groups, in sequence?
linear sequenced array
99
If you wish to practice the ALARA principle, which of the following techniques should you employ?
Use the lowest transmit power that allows adequate tissue visualization
100
The minimum reflector separation required to produce separate echoes parallel to the beam is...
the radial resolution of the transducer
101
With 6 bits, what is the largest number of different shades of gray that can be stored?
64
102
\*Review
Which type of display has two polarized filters in front of a light source with crystals that twist and untwist?
Liquid Crystal Display
103
\*Review
A decrease in power or intensity by a factor of 2 represents a change of
-3 dB
104
Which transducer has the best axial resolution?
2 cycles/pulse, 4MHz
105
**\*Which of the following terms does not belong with the others?**
Decreased spatial pulse length
.
106
Review
**\*The typical range of pulse repetition frequencies in a pulse-echo ultrasound system is**
4,000 Hz to 15,000 Hz
.
107
Review
**\*Which of the following artifacts adds additional reflectors to the image?**
Reverberation
.
108
What is the name of the ultrasound technology used to measure the hardness of a mass lesion?
Elastography
.
109
\*Review
Which of the following is true regarding shades of gray in a B-mode image?
The more bits assigned to each pixel, the more shades of gray available
.
110
\*Review
**The attenuation of 5 MHz ultrasound in 4cm of soft tissue is:**
10 dB
111
If the number of lines per frame is kept constant, but the pulse repetition frequency is doubled, what is the effect on the maximum frame rate?
doubled
112
Which of the following provides for a wider field of view and a larger/longer image?
Extended field of view imaging
113
\*Review
An array transducer with electronic focusing will have what characteristic in the firing pattern of the elements?
There will be a curvature in the firing pattern
114
As the frequency of sound increases…
the amount of scatter is increased
115
\*Review
Side lobe artifact results from which of the following?
Acoustic energy radiating in a different direction other than the beam***’***s main axis
116
**\*Which of the following is a characteristic(s) of non-specular reflectors?**
they provide the internal texture of organs in B-mode imaging
117
Review
**\*The resonant frequency of a pulsed-wave ultrasound transducer is dependent on**
he thickness of the piezoelectric element and the speed of sound through the piezoelectric element
118
Which of the following does NOT affect lateral resolution?
bandwidth
119
If no refraction occurs as an oblique sound beam passes through the boundary between two materials, what must be identical between the two materials?
Propagation speed
120
Which of the following has the highest relative attenuation?
air
