Chapter 12/13 Q&A: test 1 Flashcards
Mechanical scanning produces pictures that are similar in shape to linear phased array images
True
Many active elements fire at almost the same time in a mechanical scanner
False
There is only one active element in a mechanical scanner
Many active elements fire at almost the same time in a phased array scanner
True
Which transducer is best described as mechanically steered and fixed, single focus?
mechanical
Which transducer is best described as mechanically steered and multi-focus?
Annular phased array
Which transducer creates a rectangular shaped image?
linear sequential array
A linear phased array transducer has 128 crystals. How many of these crystals are fired to create a single sound beam?
128
With linear phased array transducers, all the active elements are fired
A linear sequential array transducer has 128 crystals. How many of these crystals are fired to create a single sound beam?
a small group
With linear sequential array transducers, a small group of active elements are fired
In a linear phased array, what is the firing pattern that steers a beam to the left or right?
The firing pattern that steers a beam to the left or right is electronic slope
In linear phased arrays, what is the firing pattern that focuses a sound beam?
The firing pattern that focuses a sound beam is electronic curvature
There are large time delays in the firing pattern of a linear phased array transducer
False
there are tiny time delays
A machine that displays A-mode and two-dimensional images is called a duplex scanner
False
a machine that displays Doppler and 2D images is a duplex scanner
Which transducer improves elevational resolution?
1 1/2 dimensional array
Side lobes degrade axial resolution
False
Side lobes degrade lateral resolution
True
Which form of resolution improves when frame rate increases?
temporal resolution
temporal resolution is directly related to frame rate
higher frame rates improve temporal resolution
What is consistent with improved temporal resolution?
higher frame rate
Frame rate determines temporal resolution
Higher frame rates(lower Tframe) result in improved temporal resolution
What decreases temporal resolution?
lower frame rate
deeper imaging
multi-focus
A sonographer adjusts an ultrasound scan to double the depth of view from 5cm to 10cm.
What happens to the frame rate?
the frame rate is halved
frame rate and imaging depth are inversely related
A sonographer adjusts an ultrasound scan to double the depth of view from 5cm to 10cm.
If the frame rate remains the same, what will also occur?
narrower sector
A sonographer adjusts an ultrasound machine to change the sector size from 90 to 45 degrees. Nothing else changes. What happens to the frame rate?
the frame rate is doubled
A sonographer adjusts an ultrasound system to change the sector size from 90 to 45 degrees. The frame rate was unchanged. What else must have happened?
line density was doubled
A sonographer, using a phased array ultrasound system, turns off the multi-focus feature. What is the most likely consequence of this action?
temporal resolution improves
A sonographer increases the line density from 1 line per degree of sector to 3 lines per degree of sector. What is the most likely consequence of this action?
temporal resolution decreases
A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 2 lines per degree. No other changes are made. What will happen to the frame rate?
frame rate increases
A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 3 lines per degree. No other changes are made. What will happen to temporal resolution?
temporal resolution is unchanged
What is most important in determining the frame rate of a system?
speed of sound in a medium
What is most important in determining the frame rate of a system?
depth of view
What is the frame rate if each image of the ultrasound system is created in 0.02sec (1/50sec)?
50Hz
frame rate and Tframe are reciprocals
What is the time needed to make a single image if the frame rate of an ultrasound system is 20Hz?
0.05s (1/20)
frame rate and Tframe are reciprocals
The critical factor in determining frame rate, line density, and imaging depth is the transducer style
false
its time
The number of lines per frame and the frame rate determine the frequency.
false
it determines PRF
The number of lines per frame and the frame rate determine the PRF.
true
If the imaging depth of a scan is 15cm and there are 100 lines in the image, then the number of pulses making up the scan is 1500.
false
number of pulses would be 100
If the imaging depth of a scan is 15cm and there are 100 lines in the image, then the number of pulses making up the scan is 100.
true
If 100 scan lines make up an image and the frame rate is 30 per second, then the transducer’s frequency is 3,000Hz.
false
a transducer’s frequency is independent of the characteristics of the image that it creates.
If 100 scan lines make up an image and the frame rate is 30 per second, then the system’s pulse repetition frequency is 3,000Hz.
true
PRF is the number of pulses created per second. It is lines per image multiplied by frame rate.
When the frame rate is 30Hz, how long does it take to create a frame?
1/30 sec
frame rate and Tframe are reciprocals
Under certain conditions, an ultrasound system creates each image in 0.01 seconds. What is the frame rate?
100Hz
frame rate and Tframe are reciprocals
What is the fundamental limitation of temporal resolution?
speed of sound in the medium
