URR part 2 Flashcards
Non specular reflector increases with increasing ______
frequency
______ relies on Rayleigh scattering from red blood cells to demonstrate the flow on the image
Doppler imaging
System sensitivity should be ______ for all types of Doppler imaging.
increased
Although higher frequency transducers result in greater amounts of ______, penetration of the beam must still be adequate to properly demonstrate flow in deeper structures
Rayleigh scattering
Time of flight or go-return time refers to the time sound travels to and from the transducer
range equation
total time for the pulse to reach a reflector and return to the transducer
range equation
used to calculate distance to the transducer
range equation
US system uses this reflector information to locate pixel placement on the screen
range equation
d = c x 1/2
range equation
in soft tissue, every 13 us of time of flight, the reflector is 1 cm deeper
13 us rule
Cosine of 0 degrees=
1
cosine of 60 degrees =
0.5
cosine of 90 degrees =
0
A CW probe is not limited by the ____ and _____ because the beam is not pulsed
PRF
Nyquist limit
What is the primary factor that determines the resistance characteristics of the arterial signal displayed by PW Doppler?
part it is supplying
Which of the following is a limitation of Analog Doppler?
a. cannot detect flow velocities over 300 cm/s
b. cannot detect flow velocities less than 60 cm/s
c. overestimates high velocities and underestimates low velocities
d. unable to detect post stenotic turbulence and spectral broadening
d
Which of the following will improve a color Doppler image by averaging previous frames to create a new image?
a. sensitivity
b. gain
c. priority
d. persistence
d
If the peak systolic velocity is 3 m/s, what is the peak pressure gradient?
36 mm/Hg
Bernoulli equation
pressure gradient = 4(velocity) squared
When evaluating a focal stenosis of an artery, where should you place the cursor to obtain the highest velocity related to the stenosis?
at the narrowest point in the vessel or immediately distal to the focal point of the stenosis
occurs with slow moving bloow flow and the reflections from the congregated red blood cells
Rouleaux formation
Blood flow at a focal stenosis will demonstrate:
increased resistance
How is the PRP reduced in Doppler imaging?
decreasing imaging depth
Decreased imaging depth = _______ PRP
decreased
number of pulses emitted per second
pulse repetition frequency
PRF is determined by:
the source of the sound
Pulser PRF =
5 kHz
US PRF =
5 kHz
Technologist adjusts the PRF in 2D imaging by using the ______
depth control
Technologist adjusts the PRF in Doppler imaging by using the ______
velocity scale control
PRF is ______ related to imaging depth
inversely
PRF is the reciprocal of ____
PRP
As PRF increases, PRP ______
decreases
Average diagnostic PRF US
1-10 kHz
An increase in imaging depth leads to ______ PRF with a _____ in duty factor
decrease
decrease
The number of pulses per second decreases so that they acn:
travel deeper into the body
time from start of transmission of one pulse to the start of transmission of the next pulse
PRP
In Doppler imaging, this is described as the time from pulse transmission to the time of the Doppler sample displaying the first shift
PRP
Technologist can adjust PRP with the _____
depth control
PRP is the reciprocal of ____
PRF
As PRP increases, PRF _____
decreases
Deeper imaging requires a long time between pulses = ______ PRF
increase
average PRP diagnostic US
100 us - 1ms
Transmission time + receive time =
PRP
also known as field of view
sector angle
The greater the number of scan line per sector degree, the better the _____
spatial resolution
Increasing the sector angle _____ frame rate because fewer pulses are required to produce the small field of view
increases
Decreasing the sector angle improves _______
temporal resolution
in a sector image, the number of scan line per degree of the sector
line density
In a rectangular image, the number of scan lines per cm
line density
Increasing line density _____ the number of pulses per frame
increases
Increasing the line density imroves ______ resolution
spatial
Increasing the line density _____ frame rate
decreases
Increasing the line density, ____ temporal resolution
degrades
If the sector angle contains 100 scan lines and you decrease the sector to 1/2 the size, the new sector angle will contain ___ scan lines
50
If the sector angle contains 100 scan lines and you increase the sector to 2x the size, the new sector angle will contain ____ scan lines
200
Smaller sectors have ____ line density, _____ frame rate, and _____ temporal resolution
lower
increase
better
Increasing line density will improve _____ resolution with most lateral sides of the sector image
detail
refers to decreasing line density within the us system fill in the “gaps” between the fewer lines with averaged information
fill-in interpolation
Fill-in interpolation improves _____ resolution
spatial
range of highest to lowest frequencies in each pulse
bandwidth
Presence of backing/damping layer reduces the number of cycles in a pulse and _____ the bandwidth
broadens
Longer pulses result in ____ bandwidth
narrower
Narrow bandwidth leads to an increase in the Q factor and spatial pulse length =
poor image quality
_____ bandwidth decreases Q factor and improves image quality
Broad
also known as damping factor
Q factor
unitless number that represents the amount of damping applied
Q factor
Ratio of the transducer frequency and the frequencies in the bandwidth
Q factor
Q factor is _____ related to transducer frequency
directly
Higher frequencies have ____ QF
higher
Resolution improves with ____ QF
lower
Imaging transducer have ____ QF
low
Doppler transducers have ____ QF
high
Therapeutic transducers have ___ QF
high
Amount (%) of time pulse transmission is occurring related to time of transmission and receiving pulses
duty factor
The technologist can adjust duty factor with the _____
depth control
Increased imaging depth equals ___ DF
decreased
Decreased PRF and PD lead to _____ DF
decreased
Increased PRP will _____ the duty factor
decrease
(PD x PRP) x 100%
Duty factor
Pulse US DF average
0.1 %
Continuous DF average
q100%
The higher the Df, the greater the risk of ______
bioeffects
increases efficiency of sound transmission in and out of the body
matching layer
usually made of plastic and protects the elemtents
matching layer
Thickness of the matching layer measures ____ wavelength of the sound in the matching layer materal
1/4
Which of the following correctly describes how the elements of a sequential linear transducer are excited?
a. in a specific order that does not change
b. varies with transmitted frequency of the transducer
c. varies with exam preset selection on the system
d. elements are excited left to right with a 0.01 ms between each voltage spike
a
Which of the following can be used to improve beam penetration on cases of high body mass index?
a. higher frequency transducer
b. activate harmonic imaging
c. increase transmit power
d. deactivate coded excitation
c
When switching to a higher frequency transducer during an ultrasound exam, what other setting will need to be adjusted to maintain quality images?
far field gain
Increasing ____ will increase the ability of the system to display fine details on the image.
pixel density
______ refers to the process of programming the receiving elements to use the higher frequency reflections for more superficial structures and lower frequency reflections for deeper structures
dynamic frequency tuning
B-mode display is termed:
brightness mode
Which of the following will be negatively affected by spatial compounding?
a. signal to noise ratio
b. spatial resolution
c. temporal resolution
d. speckle reduction
c
Changing the sweep speed on m-mode will change what characteristic of the display?
x-axis
As the pulse repetition period decreases, _____
a. the imaging depth decreases
b. the imaging depth increases
c. amplitude increases
d. the pulse repetition frequency decreases
a
Which of the following will allow for the display of the most shades of gray on the image?
a. small pixel size with 16 bits/pixel
b. large pixel size with 24 bits/pixel
c. large pixel size with 8 bits/pixel
d. small pixel size with 8 bits/pixel
b
Which of the following is a primary factor in determining the frame rate of an ultrasound system?
a. propagation speed in tissue
b. transducer frequency
c. output power
d. axial resolution
a
Which of the following is related to an increase in the spatial pulse length of an US beam produced by the transducer?
a. decrease in probe frequency
b. remove a focal zone
c. decreased imaging depth
d. increased beam width
a
Activation of B-color is used to improve:
contrast resolution
Harmonic frequencies are generated:
as the sound wave travels through the medium
Increasing the image size, while increasing the number of pixels in the real-time image indicates:
write magnification
If the output power setting is at 100% and this indicates 0dB, decreasing the power by:
6 dB will decrease the power output to 25% of the original power
While scanning the thyroid, you select three focal zones for the image, 1cm, 2cm, and 3cm depth. Which focal zone will demonstrate the highest beam intensity?
1cm
If you increase the sector angle from 45 to 90 degrees and reduce the line density by 50%, what happens to the frame rate?
unchanged
Which of the following will not affect the signal to noise ratio on a 2D image?
a. temporal compounding
b. frequency compounding
c. harmonic imaging
d. spatial compounding
a
You are scanning at a depth of 5cm using a 3MHz transducer and switch to a 5 MHz transducer without changing the depth setting. Which transducer has the greatest pulse repetition frequency?
the have the same PRF
What part of the ultrasound system is responsible for changing the PRF with changes in imaging depth>
pulser
Which of the following is true regarding signal-to-noise ratio?
a. a low signal-to-noise ratio image is preferred for 2D imaging
b. the signal to noise ratio is increased by increasing the overall gain
c. noise is helpful in producing an accurate image
d. a high signal to noise ratio image is preferred over a low signal to noise ratio image
d
Which statement correctly describes the Q factor?
a. a lower Q factor is associated with a longer spatial pulse length
b. a short spatial pulse length is associated with a high numerical value for axial resolution
c. the higher the Q factor, the better the axial resolution
d. better axial resolution is seen with shorter spatial pulse lengths and low Q factor
d
Increasing the edge enhancement setting will:
a. produce a smoother image
b. increase image contrast
c. amplify reflections on the edges of the image
d. improve contrast resolution
b
What system control should be turned off when attempting to demonstrate posterior shadowing from a suspected renal or biliary stone?
spatial compounding
The gray scale map is adjusted to a new map just prior to freezing the image. This is an example of:
applying preprocessing
If the entire image is too bright, what console adjustment should you make first?
decrease the output power
Which of the following describes the preferred placement of the focal zone on standard imaging?
a. just below the area of interest on the image
b. approximately 3 cm from the face of the transducer
c. just above the area of interest on the image
d. approximately 1cm from the bottom of the image sector
a
_____ improves penetration and axial resolution/.
coded excitation
Which of the following will improve lateral resolution at all depths on the image?
a. decrease probe frequency
b. dynamic receive focusing
c. use >3 focal zones
d. dynamic transmit focusing
b
The cine function on the ultrasound system:
a. is performed by the pulser
b. is used to improve temporal resolution
c. is a type of postprocessing
d. is only available on a phased array
c
Which of the following will require the highest levels of time gain compensation?
a. 10 MHz near field
b. 10 MHz far field
c. 5 MHz near field
d. 5 MHz far field
b
Which of the following relies on the non-linear behavior of sound waves?
a. harmonic imaging
b. CW Doppler
c. dynamic frequency tuning
d. compound imaging
a
What is the best way to reduce slice thickness artifact that is causing false echoes in a superficial structure?
use a standoff pad