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52 Cards in this Set
- Front
- Back
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In the early days of diagnostic ultrasound, creating a single, two-dimensional image was time consuming. Images were displayed one frame at a time in a process called |
static scanning; it was impossible to image moving structures |
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Frame rate |
the system's ability to create numerous frames each second |
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Frame rate is determined by |
sound's speed in the medium the depth of imaging |
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Frame rate units |
Hz or "images per second" |
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Temporal Resolution |
"accuracy in time" ability to precisely position moving structures from instant to instant. excellent when a system produces many frames per second |
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Temporal resolution determined by |
high frame rate |
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Temporal resolution is reduced when |
few images are displayed per second (low frame rate) |
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What is the relationship between frame rate and the time required to make a single image? |
Frame rate and time for one frame are inversely related. |
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System settings that determine frame rate |
imaging depth number of pulses in each picture |
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Shallow Imaging |
short go-return time higher frame rate superior temporal resolution |
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Deep Imaging |
long go-return time lower frame rate inferior temporal resolution |
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T frame measured in Hz (time needed to make a single frame) = (formula) |
# pulses x PRP |
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Factors determining number of pulses per frame |
number of focal points sector size line density |
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Single Focus |
one pulse per scan line shorter Tframe higher frame rate better temporal resolution/poorer temporal resolution |
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Multi-focus |
many pulses per scan line longer Tframe lower frame rate diminished temporal resolution/improved lateral resolution |
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What is the main advantage of multiple focal zones? |
Although multi-focusing has a negative effect on temporal resolution, it improves the accuracy of the individuals images. W/ multi-focus, each scan line has better lateral resolution b/c it is narrow over a wide range of depths. |
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When the sonographer expands the sector size (also called ____), more ____ are required to create an image. |
field of view pulses temporal resolution decreases |
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Narrow Sector |
fewer pulses per frame shorter Tframe higher frame rate superior temporal resolution |
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Wide Sector |
more pulses per frame longer Tframe lower frame rate inferior temporal resolution |
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Although it is not always apparent, ultrasound systems can alter the spacing between sound beams. This is called |
line density |
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Low line density |
widely spaced lines,
fewer pulses per frame, shorter T frame, higher frame rate, high temporal resolution, poor spatial resolution |
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High line density |
tightly packed lines, more pulses per frame, longer Tframe, lower frame rate, low temporal resolution, excellent spatial resolution |
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What is the relationship between temporal and spatial resolution? |
indirect |
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Lateral resolution improves with |
multi-focusing |
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Spatial resolution improves with |
higher line density |
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Better- higher frame rate |
shallower imaging single focus narrow sector low line density |
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Worse- lower frame rate |
deeper imaging multiple focal points (improves lateral resolution) wide sector high line density (improves spatial resolution) |
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Which of the following forms of resolution improve when frame rate increases? lateral longitudinal temporal spatial resolution |
temporal resolution |
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Which of the following is consistent with improved temporal resolution? color doppler more gray shades more detail higher frame rate |
frame rate determines temporal resolution |
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All of the following decrease temporal resolution except: lower frame rate deeper imaging multi focus narrower sector |
narrower sector |
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A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. What happens to the frame rate? |
the frame rate will be halved b/c frame rate and imaging depth are inversely related. |
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A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. If the frame rate remains the same, which one of the following also occurs? increased line density wide sector multi focus imaging turned on narrower sector |
narrower sector |
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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? |
it is doubled |
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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 |
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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 |
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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 |
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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? |
increases |
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A sonographer reduced 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. |
remains unchanged |
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Which of the following is most important in determining frame rate of a system? speed of sound in the medium dynamic range of the receiver transducer frequency transmitter output |
speed of sound in the medium |
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Which of the following is most important in determining the frame rate of a system? depth of view dynamic range of the receiver transducer frequency transmitter output |
depth of view |
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What is the frame rate if each image of the ultrasound system is created in 0.02 (1/50) seconds? |
50 Hz |
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What is the time needed to make a single image if the frame rate of an ultrasound system is 20 Hz? |
1/20 seconds or 0.05 s |
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T or F. The critical factor in determining frame rate, line density, and imaging depth is the transducer style. |
False |
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T or F. The number of lines per frame and the frame rate determine the frequency. |
False |
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T or F. the number of lines per frame and the crate rate determine the PRF. |
True |
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T or F. If the imaging depth of a scan is 15 cm and there are 100 lines in the image, then the number of pulses making up the scan is 1500. |
False. |
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T or F. If the imaging depth of a scan is 15 cm and there are 100 lines in the image, then the number of pulses making up the scan is 100. |
True |
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T or F. If 100 scan lines make up an image and the frame rate is 30 per second, then the transducer's frequency is 3,000 Hz. |
False |
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T or F. If 100 scan lines make up an image and the frame rate is 30 per second, then the system's pulse repetition frequency is 3,000 Hz. |
True |
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When the frame rate is 30 Hz, how long does it take to create a frame? |
1/30 seconds |
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Under certain conditions, an ultrasound system creates each image in 0.01 seconds. What is the crate rate? |
100 Hz |
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What is the fundamental limitation of temporal resolution? imaging depth speed of sound in the medium line density sector size |
speed of sound in the medium |
