SPI Review
You are performing a 3D ultrasound and notice the volume rate is 8 Hz. What does this represent?
# of volumes scanned per second
range of periods commonly produced by US systems
. 06-.5 microsec (think- a wave with a frequency of 2 MHz would have a period of .5 microsec, and a 15 MHz would have a period of .06 microsec)
How many lines of site are sampled/displayed in A-mode?
1
Aliasing occurs with pulsed-wave Doppler when the frequency shift is greater than _____ the Doppler PRF
1/2
frame rate range of B-mode ultrasound
10-50 Hz
What is the maximum number of shades of gray in an 8-bit digital scan converter?
256 (2^8 or 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2)
Which of the following contributes to improve the axial resolution in a B-mode image? A. increased aperture B. increased bandwidth C. focusing with an acoustic lens D. increased dynamic range E. beam steering
B. increased bandwidth
which action would decrease frame rate? a. increasing PRF b. increasing acoustic scan line density c. decreasing sector width d. decreasing the number of focal zones e. decreasing image depth
B. increasing acoustic scan line density (explanation: temporal resolution is determined by the frame rate. As the density of the acoustic scan lines increases, lateral resolution increases but frame rate decreases because it takes additional time to perform the pulse-listen sequences for each new line of site. All of the other choices would result in increased temporal resolution, and frame rate.)
Which of the following human tissues has the highest rate of attenuation of an ultrasound wave? Liver, fat, fluid, lung, or blood vessels?
Lung
T/F: lateral resolution is improved by focusing
True
all array transducers allow you to control focal depth: T/F
True
phased array always means adjustable and multi-focus: T/F
True
A sonographer can adjust the PRF/PRP: T/F
True (by changing imaging depth)
You are imaging a structure containing two media having the same acoustic impedance. What will occur at the boundary of the two structures?
all of the sound will be transmitted
What is the term used to describe the reduction in the intensity of sound as it propagates through tissue?
attenuation
What term is used to describe the reduction in the intensity of sound as it propagates through tissue?
attenuation
When you select harmonic imaging, which artifact is less likely to be observed? a. refraction b. shadowing c. ring-down d. grating lobes e. speed of sound
d. grating lobes
increasing the frequency on a multifrequency transducer from 3.5 MHz to 5.0 MHz will:
decrease wavelength
acoustic impedance is ???
density x propagation speed
what is the F number?
focal length ÷ aperture
another term for digital scan converter:
image memory
When you have one focal zone, how many pulse/listen cycles are required for each acoustic scan line in one image frame?
one
spatial resolution is determined by the number of ______ in the scan converter matrix.
pixels
axial resolution=
spatial pulse resolution / 2
vector array shape
trapezoidal
intensity is affected by attenuation: T/F
true
Does PRP depend only on the source of the sound wave?
yes (although, it does INCREASE with depth/DECREASE with shallower imaging... regardless, it is only determined by the sound source)
(increased) acoustic exposure is directly related to
(increased) transmit power
duty factor range in sonographic imaging:
0.1-1%
How many lines of sight are sampled and displayed on the monitor in A-mode?
1
How many pulses per scan line are typically used with color Doppler?
1-2
What type of transducer improves volume averaging?
1.5D or multi-row array
thickness of the active element = ____ of the wavelength
1/2
thickness of matching layer = _____ of the wavelength
1/4
Which tranducer frequency would have the thinnest crystal? 15, 10, 7, or 5 MHz?
15 MHz, the higher the frequency, the thinner the crystal
If the amplitude of a wave decreases from 27 pascals to 9 pascals, and the power of the wave is 27 watts, what is the wave's final power?
3 watts (one-ninth of its original value)
What technology is most helpful to obtain accurate anatomic volume measurements?
3D imaging
What is 4D imaging?
3D imaging with the addition of time
velocity of ultrasound wave through bone:
4080 m/s
The frequency of a continuous wave pulse is 5 MHz. The wave is then pulsed with a duty factor of .1. What is the new frequency?
5 MHz.... the fact that the wave is pulsed does not alter the frequency of the signal.
depth of focus (mm) = diameter (mm) ^2 x Frequency (MHz) divided by _________
6
Doppler pulses used for diagnostic purposes are typically ___ cycles long
6-20
You measured an area reduction of 90% in an artery. This is equal to a diameter reduction of:
75% (Explanation: Area percent stenosis and diameter are not equal. A 50% diameter stenosis is approximately equal to a 75% area stenosis and a 75% diameter stenosis is approximately equal to a 90% area stenosis.)
five transducers are imaging a vessel at different incident angles. The arrow indicates the direction of blood flow. Which transducer will detect the largest Doppler frequency shift?
A
Preprocessing functions may be defined as:
A function that is performed before the echo data are stored in memory
a linear array will produce which of the following image shapes? (flip notecard for image)
A, C, and E
Which transducer will exhibit the LEAST amount of volume averaging? A. Mechanical single element B. 1.5D of multi-row array C. Linear array D. Phased array E. Convex array
B. 1.5 D or multi-row array
According to the doppler equation, which of the following is NOT true? a. increasing doppler frequency will increase the frequency shift b. increasing doppler interrogation angle will increase the frequency shit c. decreasing the reflector speed will decrease the frequency shift d. no frequency shift is detected when the doppler beam strikes the reflector with perpendicular incidence e. velocity inormation can be obtained from the frequency shift if the angle of incidence is known
B. increasing doppler interrogation angle will increase the frequency shift
The terms "ensemble length" and "dwell time" are synonymous with: A. persistence B. packet size C. pulse repetition frequency D. color threshold E. autocorrelation
B. packet size
While imaging a cyst, you notice shadowing posterior to each lateral border of the cyst. What is the source of the shadows?
Bending of the sound beam due to different media propagation speeds
Decreased pressure occurs in areas of high flow speeds. This is known as the:
Bernoulli effect
What is a disadvantage of a water-path scanner?
Bubbles in the fluid can inhibit sound transmission into the body
What control should you adjust to modify the image if the attenuation coefficient of the tissue is very high?
Compensation (aka TGC/depth gain compensation)
Which control would you adjust to alter the dynamic range of the displayed echoes?
Compression
Describe analog signal.
Continuous variation of the signal is possible, and does NOT have discrete steps (discrete values belong to digital devices)
focused linear phased array firing pattern
D shaped- when not being electronically steered
Standard for handling/transferring images and medical information between computers
DICOM
Axial resolution is improved with: A. Increased bandwidth B. Shorter pulse length C. Shorter wavelength D. B and C E. All of the above
E. All of the above
While performing an ultrasound examination, you decide to adjust the system settings to improve the image. Which of the following is not user-adjustable? A. frequency B. power C. gain D. compensation (TGC) E. echo arrival time
E. echo arrival time
Which is an assumption of sonographic imaging that determines how detected echoes are mapped in the image?
Echoes originate from the most recently transmitted pulse
T/F: lateral resolution remains constant throughout scanning depth
False
Increase focusing helps improve axial resolution: T/F
False (pulse length increases as focusing increases, degrading axial resolution but improving lateral resolution)
What advantage is obtained by steering a linear array transducer to create a trapezoidal shape in an ultrasound image?
Improved field of view
A waveform from the internal carotid artery obtained at a Doppler angle of 45 degrees shows aliasing. What would help you unwrap this waveform?
Increase the PRF
What is the advantage of using multiple transmit focal zones?
Increased lateral resolution
Describe the occurrence of diastolic flow reversal in the arterial system.
It is seen in and proximal to high-resistance vessels.
mode that produces a display more similar to a tracing than actual anatomic image:
M-mode
what does this describe? Depth of reflectors along a single line of site vs. time
M-mode
When you change the transmit frequency, what is also altered?
Number of cycles per second
PRP is the inverse of:
PRF
What is automatically decreased by the system to avoid range ambiguity when you increase the scanning depth?
PRF
what system function is limited by the speed of sound in tissue?
PRF
You are using a transducer that produces a beam with a very wide slice thickness. What problem are you most likely to encounter as a result?
Partial volume artifact (explanation: Partial volume artifact is also known as *slice thickness artifact*. It occurs when the slice thickness is wider than the structure being imaged. In other words, if you are imaging a small vessel in a sagittal plan, it may appear to contain echoes. Yet when you turn transverse to the vessel, you see that it is completely free of echoes. The source of the echoes in the sagittal plane is the slice thickness artifact. The beam is wider than the vessel. Tissue on both sides of the vessel reflects signals from that depth to the transducer. These echoes are placed at that depth on the image, artfatually filling in the vessel.)
What is the unit of impedance?
Rayl
what physics concept best explains the difference in signal strength between the 5 and 6.3 MHz doppler frequencies in the following image?
Rayleigh scattering
Which intensity is not applicable to continuous wave ultrasound?
SPPA & SAPA
Rayleigh scattering intensity is proportional to frequency raised to the 4th power: T/F
T
What occurs when you image a structure with oblique incidence?
The angle of reflection will be oriented away from the transducer resulting in decreased visualization of the structure.
What occurs when you image a structure with oblique incidence?
The angle of reflection will be oriented away from the transducer, resulting in decreased visualization of the structure.
The transducer you are using transmits wide-bandwidth pulses whose frequency content is 2-5 MHz, how would you describe the reflected echo signals after they have traversed the tissue?
The echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies (explanation: because higher frequencies are absorbed more quickly than lower frequencies, the reflected signals will be dominated by lower frequency components compared to the transmitted pulse.)
The transducer you are using transmits wide-bandwidth pulses whose frequency content is 2-5MHz. Describe how the echo signals will be shifted and why.
The echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies. (Because higher frequencies are absorbed more quickly than lower frequencies, the reflected signals will be dominated by lower frequency components compared to the transmitted pulse.)
Diagnostic ultrasound is limited in its diagnostic application to the adult brain because-
The great acoustic impedance mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface.
With A-mode, the strength of the echo signal is represented how?
The height of the spike
What does the mechanical index on an ultrasound indicate?
The likelihood of cavitation during an ultrasound exam
describe sound propagation through a medium
The molecules oscillate back and forth to propagate sound waves but do not move from one end of the medium to the other
When you change the transmit frequency, what is altered?
The number of cycles per second
When you adjust the PRF, you are changing:
The number of pulses per second
If the number of cycles in a pulse is increased but the wavelength remains the same, what has changed?
The pulse duration is increased
How would you describe diffuse reflection?
The reflected beam is scattered in various directions.
Using the following image: You are using a conventional linear array transducer to image this phantom which contains two fluid-filled tubes. Why does the tube labeled "B" contain echoes, whereas the tube labeled "A" does not?
The slice thickness at the level of B was greater than at the tube A
What is the purpose of preamplification of the incoming signal that occurs in the transducer assembly?
To increase echo voltages before noise is induced through the cable
As a wave travels through a medium with a faster propagation speed, the wavelength increases. T/F
True
Higher frequencies have a deeper focus than lower frequencies : T/F
True
Larger crystals have better lateral resolution in the far field than smaller crystals: T/F
True
T/F: lateral resolution is also known as azimuthal resolution
True
T/F: lateral resolution is defined as the minimum separation required to resolve two structures perpendicular to the beam axis
True
T/F: lateral resolution is equal to beam width
True
Frequency does NOT affect impedance: T/F
True (impedance is associated only with the medium)
You are imaging a 3D dataset that has anisotropic resolution. What does this mean?
Unequal resolution is present between imaging planes.
Can amplitude be changed by a sonographer?
Yes- by increasing output power voltages
Loss of fluid energy through inertia is greatest in what kind of vessel?
a tortuous vessel with multiple obstructions
An example of a specular reflector is: a. pericardium b. liver parenchyma c. red blood cells d. ascites e. hematoma
a. pericardium
With a 1D linear array, where is the dimension of the sound beam in the out-of-plane dimension the narrowest? a. point of mechanical focusing b. point of electronic focusing c. the beam is the same width throughout the image d. in the far field e. at a depth equal to 1/2 of the transducer aperture
a. point of mechanical focusing
What is sensitivity?
ability of the system to detect weak echoes
the transfer of acoustic energy into heat is termed:
absorption
attenuation of the sound beam is affected by:
absorption, scattering and reflection
What term describes the effects that a medium has on a sound wave?
acoustic propagation properties
interference patterns of scattered echoes are seen with what artifact?
acoustic speckle
What information is present on A-mode?
amplitude and reflector distance
With A-mode, the internal contents of a simple cyst will appear as:
an area with no spikes
intensity is equal to the power in a beam divided by the ____ of the beam
area (units are watts/cm^2)
crystal damping (by the backing material/*damping element*) enhances ______ resolution
axial
what represents the best measure of resolution for modern day ultrasound scanners?
axial
You are scanning a large mass that is composed primarily of fat. What are you most likely to encounter?
axial misregistration of objects distal to the mass on the screen, caused by the slower propagation speed through fat.
if the number of cycles in the transmitted pulsed wave is increased: a. axial resolution is degraded b. lateral resolution is degraded c. spatial pulse length becomes shorter d. rate of attenuation is increased e. penetration is decreased
axial resolution is degraded (keep in mind, axial resolution is proportional to pulse length. Axial resolution is degraded as pulse length increases, and pulse length is increased by increasing the number of cycles in the pulse.)?
An image that shows the color significantly overwriting the vessel wall is best explained by what?
axial resolution is lower with color Doppler compared to B-mode
Which transducer will exhibit the LEAST amount of volume averaging? a. mechanical single element b. 1.5 D or multi-row array c. linear array d. phased array e. convex array
b. 1.5 D or multi-row array
If the velocity scale on a color map is 17 cm/s and the flow direction is at zero degrees to the sound beam axis, the colors on either end of the bar would represent: a. a peak velocity of 17 cm/sec b. an average velocity of 17 cm/sec17 cm/sec c. a peak velocity of 34 cm/sec d. a peak velocity above 17 cm/sec e. a peak velocity below 17 cm/sec
b. an average velocity of 17 cm/sec
If you increase the Doppler transmit frequency, which of the following will result? a. velocity will increase b. Doppler frequency shift will increase c. the penetration will increase d. the frame rate will increase e. the Nyquist limit will increase
b. doppler shift will increase
Which of the following minimizes the degree to which beam width varies with depth? a. apodization b. dynamic aperture c. coprocessing d. rectification e. frame averaging
b. dynamic aperture
If the sound wave hits a rough surface, and the propagation speed is unchanged at the interface, which most correctly describes the sound-tissue interaction that will take place when the ultrasound wave strikes the jagged interface? a. specular reflectioin b. scattering c. diffraction d. refraction e. none of these
b. scattering
the rate of sound attenuation is LOWEST in: a. air b. water c. liver d. bone e. lung
b. water
_______ is responsible for transmit focusing
beam former
what part of the transducer is responsible for apodization, beam steering, focusing, and aperture control?
beam former
what system component is responsible for transmit focusing?
beam former
What imaging technique can produce grating lobes?
beam steering
Which factor LEAST influences axial resolution? damping, beam width, frequency, pulse duration, or pulse frequency?
beam width
PRP is the time from the start of one pulse to the _______ of the next pulse
beginning
Digital to analog conversion of the ultrasound signal must occur at what part of the imaging process?
between the scan converter and the display
What receiver function is not adjustable? a. amplification b. compensation c. demodulation d. rejection e. a and d
c. demodulation
color flash artifact is obscuring the anatomy of interest in an exam of the abdominal aorta. What can you do to reduce the impact of the flash? a. increase color gain b. decrease PRF c. increase wall filter d. increase packet size e. increase doppler transmit frequency
c. increase the wall filter
Which of these adjustments increase the duty factor? a. increased gain b. increased output power c. increased PRF d. increased scanning time e. increased TGC
c. increased PRF
Which of the following statements about turbulent flow is NOT true? a. it can be predicted by the Reynolds number b. It is responsible for murmurs, bruits, and thrills c. it causes increase in pressure downstream d. it occurs where there are abrupt variations in vessel diameter e. it is affected by velocity
c. it causes increase in pressure downstream (pressure is reduced distal to a stenosis in turbulent flow)
Which of the following is NOT a limitation of M-mode scanning: a. information is obtained along only one line of site b. motion lateral to the transducer is not displayed c. motion axial to the transducer is not displayed d. the two-dimensional shape of a structure is not shown e. all of the above
c. motion axial to the transducer is not displayed
When you change the transmit frequency, which of the following is altered? a. displacement amplitude of the particles in the medium b. speed at which the sound wave propagates through the medium c. number of cycles per second d. pulses transmitted per second e. number of electrical impulses applied to the transducer per second
c. number of cycles per second
While performing a sonogram, you encounter the following interfaces. Which will produce the weakest reflected signal? a. organ parenchyma/fluid b. organ parenchyma/air c. organ parenchyma/organ parenchyma d. organ parenchyma/bone e. organ parenchyma/ligament
c. organ parenchyma/organ parenchymma (reflected signal strength depends on the acoustic impedance MISMATCH)
M-mode display is most commonly used for what type of ultrasound imaging?
cardiac
spectral mirroring (image on other side of card) How would you fix it?
change the doppler angle
What control should you adjust to modify the image if the attenuation coefficient of the tissue is very high?
compensation (TGC/depth gain compensation)
What control is used to alter dynamic range?
compression
What receiver function is responsible for decreasing the difference between the smallest and largest received signal amplitudes?
compression
Harmonic imaging improves what?
contrast resolution, side lobe artifact and reverberation (this is because the second harmonic that is used has twice the transmitted frequency)
To get the largest possible field of view in both the near field and at depth, what type o array transducer would be most preferable?
curved array
During the performance of a sonogram, you would most likely to encounter refraction in what view?
curved interface
You are most likely to encounter refraction in what view during an ultrasound?
curved interface
convex is another term for ??
curved/curvilinear
Which of the following would be most helpful to enhance the contrast difference between tissues having subtle variations in echogenicity? a. decreasing acoustic power output b. decreasing scan line density c. performing a read-zoom over the area of interest d. changing the gray-scale map assignment e. increasing the overall receiver gain
d. changing the gray-scale map assignment
which of the following is NOT a function of the receiver? a. amplification b. RF to video conversion c. demodulation d. dynamic aperture e. compression
d. dynamic aperture
if you are using a transducer with poor elevational resolution, which of the following problems are you most likely to encounter? A. inability to resolve two structures that lie close together and parallel to the path of the beam b. inability to resolve two structures that lie close together, perpendicular to the path of the beam, and parallel to the long axis of the transducer c. inability to penetrate through dense tissue d. inability to clearly demonstrate small cystic structures e. inability to demonstrate rapidly moving structures accurately
d. inability to clearly demonstrate small cystic structures
which scanning mode does NOT rely echo ranging to determine interface location? a. m-mode b. pulsed wave doppler c. static b-mode d. transmission e. a-mode
d. transmission
which scanning mode does NOT rely on the principle of echo ranging to determine interface location? a. m-mode b. pulse-wave doppler c. static b-mode d. transmission e. a-mode
d. transmission
increasing the frequency on a multifrequency transducer from 3 to 5 MHz will:
decrease the wavelength
what effect will you see if you increase the reject level?
decreased amount of low-level echoes
The hyperechoic region (acoustic enhancement, seen on image following this question) results from:
decreased attenuation through a fluid-filled structure
what main advantage will you have by choosing a transducer with a thinner slice over the imaging plane?
decreased volume averaging
Increasing the dynamic range setting affects the ultrasound image by:
decreasing image contrast
Pulse Repetition Period (PRP) is longer with _____ imaging
deep
The ________ function of the receiver converts electrical signals from radiofrequency to video form.
demodulation
For soft tissue, one of the factors responsible for determining acoustic impedance is:
density (*z=pc* z is the rayl- unit for acoustic impedance, p is density, and c is speed of sound)
factors in acoustic impedance:
density and compressibility
What determines acoustic impedance?
density and propagation speed of the medium
acoustic impedance is determined by what?
density and propagation speed of the medium
acoustic impedance=
density x propagation speed
While scanning a curved structure, you notice shadowing at the lateral edges of the structure. What is required for this artifact to occur?
different media propagation speeds
Which phenomenon is associated with a pattern produced by a sound beam after passing through a small aperture?
diffraction
What system control converts the numbers stored in memory to proportional voltages that control the brightness on a CRT (cathode ray tube) monitor?
digital to analog converter
Phase quadrature detection is commonly used for determining ________ in a Doppler instrument.
direction
pulse duration is the length of time a pulse takes to transmit, and spatial pulse length is the _________ of that same pulse length.
distance
To calculate the amplitude of a wave, you would subtract the minimum value from the maximum value, and ________ for the answer.
divide that number by 2 (ex. maximum value- 60 lb./inches squared, minimum value 20 lb./inches squared.... answer is 20 lb./inches squared)
spectral mirroring occurs if:
dopper angle of interrogation is near 90 degrees
What information is colorized in an image using power Doppler?
doppler signal amplitude
if frequency is doubled, absorption is _________
doubled
The ratio of the largest to the smallest signal that a system can handle is termed what?
dynamic range
the ratio of the largest to smallest signal that a system can handle
dynamic range
What type of focusing is performed by delay circuitry upon reception?
dynamic receive focusing
What limitation is present when you use a high PRF Doppler? a. frame rate b. spatial resolution c. sensitivity to slow flow d. range resolution e. C and D
e. C and D
You want to use 3D imaging to display an anatomic structure because 3D has the following advantage over 2D imaging: a. higher frame rates b. better spatial resolution c. ability to display image planes impossible to obtain with 2D imaging d. ability to display orthogonal plans simultaneously e. C and D
e. C and D
what reynold's number would result in turbulent flow? a. 200 b. 300 c. 2000 d. 3000 e. C and D
e. C and D
you want to use 3D imaging to display an anatomic strucutre because it has the following advantage over 2D: a. higher frame rates b. better spatial resolution c. ability to display image planes impossible to obtain with 2D d. ability to display orthogonal planes simultaneously e. C and D
e. C and D
Which display mode may be used to calculate distance measurements? a. a-mode b. b-mode c. m-mode d. b and c only e. a, b, and c
e. a, b, and c
The Reynolds number increases with increasing: A. flow speed B. vessel diameter C. blood density D. blood flow viscosity E. all of the above
e. all of the above
Which of the following can mirror image artifact occur? a. b-mode b. spectral doppler c. color doppler d. power doppler e. all of the above
e. all of the above
Which of the following increases as frequency increases? a. absorption b. scattering c. attenuation d. A and C only e. all of the above
e. all of the above
Which of the following interactions of sound and tissue decreases the intensity of the transmitted beam? a. absorption b. reflection c. scattering d. conversion of sound to heat e. all of the above
e. all of the above
You are imaging a rounded mass with irregular borders. The mass has a much slower propagation speed than surrounding tissue. What sound-tissue interaction will be encountered as the ultrasound propagates through this interface? a. refraction b. reflection c. absorption d. scattering e. all of the above
e. all of the above
which of the following transducers produces side lobes? a. mechanical b. linear sequential array c. phased array d. convex array e. all of the above
e. all of the above
You may observe sound attenuation by all of the following EXCEPT: a. reflection b. scattering c. conversion of sound to heat d. absorption e. compression
e. compression
You are imaging with a 5MHz linear array transducer. What sound parameter stays constant as the beam propagates through the tissue? a. frequency b. intensity c. amplitude d. wavelength e none of the above
e. none of the above
what component would you NOT find in A-mode? a. clock b. transmitter c. transducer d. scan converter e. receiver
e. receiver
how is reflector depth determined with pulse-echo ultrasound?
echo arrival time
What physical concept allows us to determine the location of an interface by measuring the elapsed time between the transmitted pulsed ultrasound wave and the detected echo from that interface?
echo ranging
linear sequential array steering
electronic
linear phased array steering
electronic (called "phasing")
how is the trapezoidal field of view obtained with a linear array transducer?
electronic beam steering
Rejection reduces _______ in the ultrasound system
electronic noise
You are scanning a phantom containing multiple rows of identical 5 mm spherical fluid structures embedded in a tissue-mimicking material. What type of resolution is best evaluated with this phantom?
elevational
What type of resolution is most affected by the mechanical focus on a linear array transducer?
elevational resolution
Which artifact is related to beam attenuation?
enhancement
When sound strikes a specular reflector at an oblique angle, the angle of reflection is:
equal to but opposite the angle of incidence
what should you limit if the thermal index exceeds 1?
exposure time
Smaller crystals have less beam divergence than a larger crystal: T/F
false
attenuation is affected by propagation speed: T/F
false
imaging frame rate decreases when you increase dynamic range: T/F
false
imaging frame rate decreases when you increase frame averaging: T/F
false
A sonographer can change the duration of a pulse: T/F
false. The duration of a pulse is determined solely by the transducer.
annular phased array shape
fan/sector
linear phased array shape
fan/sector
advantage of tightly curved array:
field of view is improved
in the scan converter, interpolation is performed to:
fill in the empty pixels that occur between acoustic scan lines
according to Poiseuille's equation, what will happen to flow if pressure difference increases?
flow rate will increase
What describes the f number?
focal length divided by the aperture
Elevational resolution can be improved by:
focusing with an acoustic lens
What contributes to improve the elevation resolution in a B-mode image?
focusing with an acoustic lens
What control could you adjust to improve the signal-to-noise ratio on the image?
frame averaging
pulse duration = # of cycles divided by ???
frequency
the number of cycles that an acoustic variable completes in a second
frequency
the speed of sound in the PZT is directly related to the _____ of the transmitted sound
frequency (faster sound in PZT = higher frequency)
what two controls affect the spatial resolution of the color image?
frequency and line density
Wavelength depends on what two factors?
frequency and propagation speed
What aspect of the doppler spectrum is color-encoded with color doppler?
frequency shift (NOT: amplitude, power, velocity, bandwidth)
amplification in the receiver
gain
order of speed, starting with slowest: liquid, gas, solid
gas, solid, liquid
What Doppler control removes frequencies below a given threshold, resulting in a clean zero baseline?
high pass filter
PRP and PRF are related to _______
imaging depth (PRP is "bigger" for deep imaging, PRF is "bigger" for shallow imaging: higher PRF= shorter PRP and vice versa)
propagation speed error occurs in which sonographic appearance?
improper axial position of an echo
What would be the most likely result from increasing the transmit frequency of the color doppler?
improved sensitivity to slow flow
you have increase the packet size while using color doppler to evaluate flow. What positive result will occur from this action?
improved signal-noise ratio
banding can occur from
incorrect TGC
How would you optimize an image to better show posterior shadowing of a calcification?
increase the frequency
if you encounter lateral splaying, you should do what?
increase the number of focal zones
What would be the most likely result from lowering the color threshold?
increased color writing on the vessel/cardiac wall
What is the advantage of using multiple transmit focal zones?
increased lateral resolution
(Imagine) 2 images are displayed, the one on the left is blurry, the one on the right is more crisp. There are no focal points or frequency settings in site. How were the system controls adjusted to optimize the image on the right?
increased line density
Which of the following properties would result in increased prop. speed of sound through a medium?
increased stiffness
acoustic impedance increases with what?
increased tissue density, and increased propagation speed
increasing packet size _______ the number of pulses per scan line of a color image, resulting in poorer frame rate
increases
Loss of fluid through intertia:
is greatest in a tortuous vessel with multiple obstructions
What benefit would you obtain by choosing a transducer having a large diameter compared to one having a small diameter?
it can focus at greater depths
What happens when pressure is applied to a pzt crystal?
it emits an electrical signal
if amplitude is cut in half, what happens to power?
it is 1/4 of its original value
if amplitude triples, what happens to the intensity?
it is increased nine-fold (ex. if the area of the beam stays the same but the amplitude of the wave triples, intensity increases nine-fold, 3^2=9)
what is the purpose of the radiofrequency shield that is placed around the crystal and backing material o the ultrasound probe?
it reduces the electromagnetic interference
flow condition in which parallel streamlines of flow are present within a tube:
laminar flow
Increased aperture helps to improve _______ resolution
lateral
increasing the number of scan lines in one frame improves what type of resolution?
lateral
refraction of the sound beam would be manifested as artifact with ________ displacement of the reflector
lateral
what type of resolution is most affected by electronic focusing and dynamic aperture?
lateral
With a standard one-dimensional linear array transducer, what type of resolution is affected most by electronic focusing and dynamic aperture?
lateral resolution
measuring the lateral width of a target on a phantom is most closely related to
lateral resolution
The term for a transducer that has an array of rectangular elements arranged in a straight line is:
linear array
What transducer type is best suited to vascular imaging?
linear array
what control optimization should you make to improve color doppler sensitivity to slow flow?
lower the wall filter setting
Which of the following human tissues has the highest rate of attenuation? Liver, fat, fluid, lung, or blood vessels?
lung
What is an advantage of using a 3D/4D transducer with automated sweep compared to a traditional transducer with a freehand sweep?
measurement accuracy
annular steering
mechanical
For a linear array transducer consisting of a single row of elements, what method is most used to focus the beam in the elevational direction?
mechanical focusing
how would you characterize an ultrasound wave in human tissue?
mechanical, longitudinal wave
frame rate decreases when color Doppler is activated because:
more pulses are fired on each line of sight
It is assumed in sonographic imaging that echoes originate from the __________ pulse
most recently transmitted
What artifact may result in both an axial and displacement of a reflector on the ultrasound image?
multipath reflections
What is the purpose of applying multiple matching layers to the transducer face?
multiple layers results in an increase in transducer bandwidth
What is the purpose of applying multiple matching layers to the transducer face?
multiple matching layers result in increased transducer bandwidth
What is an advantage of a water-path scanner?
near field reverberations are reduced
does output power affect the propagation speed?
no
does the spatial pulse length change with depth?
no
does the speed of sound change when duty factor changes?
no
does frequency affect sound propagation?
no (only the medium determines speed)
You are imagine with a 5 MHz linear array transducer. What sound parameter stays constant as the beam propagates through the tissue? Frequency, intensity, amplitude, wavelength, or none of these?
none of these
pulse duration= period x _____
number of cycles in a pulse
A-mode display is most commonly used for what type of ultrasound imaging?
opthalmologic
The terms "ensemble length" and "dwell time" are synonymous with:
packet size
What system control on Doppler adjusts the PRF?
packet size?
A method used to improve frame rates with multizone electronic focusing is termed:
parallel processing
what artifact commonly results in echoes filling in the lumen of small vessels?
partial volume
you are using a transducer that produces a beam with a very wide slice thickness. What problem are you most likely to encounter as a result?
partial volume artifact
A commonly used process for determining direction in a Doppler instrument is:
phase quadrature detection
What array transducer fires all of the elements or each acoustic scan line, using small time delays to steer the beam?
phased array
You are reviewing an ultrasound image that has a sector display formate that narrows to a point at the transducer surface. What kind of transducer was most likely used to acquire this image?
phased array
the optimal transducer for cardiac scanning:
phased array
the conversion of an incident pressure wave to an electrical signal is the ??
piezoelectric effect
acoustic variables
pressure, density, particle motion
units for amplitude
pressure- pascals *(typically 1-3 million pascals)* density- g/cm^3 particle motion- inches, cm, or any distance measurement decibels
The control that sets the gray scale brightness at hich color will be displayed, instead of gray scale at a pixel location, is termed:
priority
The control that sets the gray-scale brightness at which color will be displayed instead of gray-scale at a pixel location is termed:
priority
axial resolution is determined chiefly by:
pulse duration
A type of sonography imaging that transmits two pulses of opposite phase in rapid succession so they can be cancelled out upon reception is termed:
pulse inversion harmonics
the packet size in color Doppler refers to the number of:
pulse-listen cycles per acoustic scan line
PRF is a part of what system component?
pulser
If you increase the PRF to eliminate aliasing, what artifact could be introduced?
range ambiguity
bandwidth refers to:
range of frequencies in a pulse
TGC is a part of what system component?
receiver
linear sequential array shape
rectangular
_____ converts the negative portion of the radiofrequency signal to positive?
rectification
Increasing the wall filter during Doppler sampling will:
reduce display of low-frequency shifts
purpose of subdicing:
reduce grating lobes
What can be done to reduce the presence of grating lobes in an image obtained with a linear array transducer that employs phasing to steer the beam?
reduce or eliminate beam steering
The technique of frame averaging during real-time acquisition is designed to:
reduce random noise
Increasing the threshold ________ the display of weak echoes.
reduces
The shadow depicted from a stone is primarily the result of what sound-to-tissue interaction?
reflection
what sound-tissue interaction is necessary to form an ultrasound image?
reflection
Oblique incidence and different media propagation speeds are two conditions present to cause what artifact?
refraction
When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?
remains the same
The arrow in the following image depicts flow below the zero baseline. These echoes represent:
retrograde flow due to poststenotic turbulence
Comet tail artifact is the result of _________
reverberation
artifact that has equidistant horizontal bands that decrease in brightness with depth
reverberation
What artifact is associated with resonance of a gas bubble?
ring-down
the range equation describes the relationship between:
round-trip pulse travel time and distance to the reflector
When you "freeze" an image, where is the echo information stored?
scan converter
where are images stored in the ultrasound system?
scan converter
What can you do to enhance the visibility of a specular reflector?
scan with perpendicular incidence
What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?
scattering
PRF is the number of pulses it takes to transmit into the body each ________
second (note: typical value of PRF is 1,000-10,000 pulses per second)
PRP is shorter with ______ imaging
shallow
The relative amplitude of the signal compared to the amplitude of the noise describes:
signal-to-noise ratio
If the beam is wider than the vessel, tissue on either side of that vessel will send back reflections, resulting in fill-in of the fluid structure. This problem is represented by what type of resolution?
slice thickness
An ultrasound image is brighter in the near field and less bright in the far field. This is due to:
sound attenuation
Shadowing occurs primarily because of what?
sound attenuation
what is a side lobe?
sound beam emitted from the transducer that travels in a different direction from the main beam
if you wish to improve border definition, what imaging enhancement should you use?
spatial compounding
what is the best axial resolution that can be obtained with a given transducer?
spatial pulse ÷ 2
What system control on Doppler adjusts the PRF?
spectral velocity scale
What factors affect impedance?
stiffness, density, propagation speed
Pulsing of the transmitted sound wave is necessary for real-time imaging because:
the depth of the interface rom which the echo originated can be determined
The incoming raw echo signals must be compressed into smaller dynamic range because:
the display cannot accommodate the wide dynamic range of the incoming signals
When you perform a Doppler exam, the frequency of the transmitted frequency is determined by what?
the frequency of the electrical signal applied to the transducer
Diagnostic ultrasound is limited in its diagnostic application to the adult brain because:
the great acoustic impedance mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface?
With A-mode, the strength of the echo signal is represented by:
the height of the spike
What does the mechanical index indicate on an ultrasound exam?
the likelihood of cavitation during and ultrasound exam
Blood vessels usually appear anechoic on B-mode imaging because:
the reflection from the RBC's is too week to be displayed
You will NOT see refraction in the sonographic image if:
the sound beam is perpendicular to the interface (refraction= bending of the sound beam and occurs whenever the beam strikes an interface where the prop. speed is different between the two media and the angle of incidence is NOT perpendicular)
wavelength is determined by ______
the sound source and the medium
What determines the *initial* amplitude of an ultrasound wave?
the transducer (crystal)
what error will occur if the angle correct cursor is NOT adjusted parallel to the vessel wall?
the velocity estimation will be inaccurate
spatial pulse length is determined by:
the wavelength of each cycle in a pulse (which is determined by source and medium), as well as the length of the pulse (which is dependent on both the medium and source as well)
spatial pulse length=
the wavelength times the number of cycles in the pulse
What is the maximum number of imaging planes that can be obtained from manipulating a volume data set?
there is no limit
What is the maximum velocity limit for a 3MHz CW Doppler unit operating at 4cm of depth?
there is no limit with CW
An image shows a pseudoaneurysm sac. In the image, gray-scale echoes within the flow are visible and the color does not fill the aneurysm sac completely. What control is used to optimize the image to allow the color to write over the gray-scale echoes?
threshold
Dynamic receive focusing uses....?
time delays before echo signals from array elements are combined
What information is present on M-mode?
time, motion pattern, and amplitude
Spatial compounding helps demonstrate _________ that are not perpendicular to the sound beam
tissue boundaries
Which imaging technique may increase visualization of the reflections from blood flow on the real-time ultrasound image?
tissue harmonic imaging
what is the purpose of the gel coupling between the transducer and the skin?
to provide a medium for sound transmission since ultrasound does not propagate through air
What is the purpose of curving the transducer elements or applying a lens over the elements?
to provide focusing in the out-of-plane (elevational) direction
what is the purpose of curving the transducer elements or applying a lens over the elements?
to provide focusing in the out-of-plane (elevational) direction
What is the purpose of subdicing?
to reduce grating lobes
What determines the period of a US wave?
transducer
intensity is initially determined by the _______
transducer
what component of the ultrasound system converts electrical energy from the pulse into acoustic pulses?
transducer
Order in which the US signal travels:
transducer, receiver, scan converter, display
according to the doppler equation, for any given velocity, the frequency shift will increase by increasing the:
transmit frequency
Higher frequencies have less beam divergence than lower frequencies : T/F
true
Reynolds number increases with increasing flow speed and larger tube diameter: T/F
true
if you are using a particular machine/transducer to image soft tissue, the SPL will always be the same: T/F
true
sound travels at approximately one mile per second through tissue. T/F
true
tissue harmonic imaging improves visualization of posterior shadowing to a calcification: T/F
true
Scattering intensity is proportional to frequency raised to the fourth power: T/F
true (if frequency is 2, Rayleigh scattering would be 16)
How many levels of information can a single bit represent?
two
The rate of sound attenuation is lowest in: (air, water, liver, bone, lung)
water
The rate of sound attenuation is lowest in: air, water, liver, bone, or lung?
water
units for power
watts
spatial pulse length = # of cycles x ???
wavelength
what is an advantage of single-crystal or pure-wave crystal transducers? a. wide bandwidth b. lower frequencies at higher resolutions c. absence of aliasing with pulsed doppler d. higher frame rates e. greater steering angles
wide bandwidth
