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Ultrasound Physics Ch. 13

Terms in this set (45)

a process in which images are displayed one frame at a time
static scanning
What is the most important operational parameter associated with an ultrasound "movie"?
frame rate
the system's ability to create numbers frames each second
frame rate
What 2 things determine frame rate?
-speed of sound in the medium
-imaging depth
describes the ability to precisely position moving structures from instant to instant; pertains to "accuracy in time"
temporal resolution
What determines temporal resolution?
frame rate
Displaying a high number of images per second (high frame rate) __________ temporal resolution.
improves
Temporal resolution is _________ when few images are displayed per second (low frame rate).
reduced
What is the relationship between frame rate and the time required to make a single image?
Frame rate and time for one frame (Tframe) are inversely related, and are reciprocals.
Tframe x frame rate= ?
1
What 2 sonographer-controlled settings of an ultrasound system determine frame rate?
-imaging depth
-number of pulses in each picture
How does imaging depth affect temporal resolution?
Imaging depth and frame rate are inversely related.
__________ imaging increases frame rate and improves temporal resolution.
shallow
_______ imaging decreases frame rate and degrades temporal resolution.
deeper
With shallow imaging depth and temporal resolution there is....
-short go-return time
-shorter Tframe
-higher frame rate
-superior temporal resolution
With deeper imaging depth and temporal resolution there is...
-long go-return time
-longer Tframe
-lower frame rate
-inferior temporal resolution
Imaging depth and Tframe are __________ related.
directly
How does the number of pulses in each image affect temporal resolution?
Pulses per frame and frame rate are inversely related.
_______ frame rates are possible when each individual image is made with fewer pulses.
higher
______ frame rates occur when each image is made with more pulses.
lower
What factors determine the number of pulses needed to create an image?
-number of pulses per scan line (multi-focus vs. single focus
-sector size
-lines per angle of sector (line density)
With single focus and temporal resolution there is....
-one pulse per scan line
-shorter Tframe
-higher frame rate
-better temporal resolution
-poorer lateral resolution
With multi-focus and temporal resolution there is...
-many pulses per scan line
-longer Tframe
-lower frame rate
-diminished temporal resolution
-improved lateral resolution
With multi-focus, each scan line has better _______ resolution because it is narrow over a wide range of depths.
lateral
What is another name for sector size?
field of view
When the sonographer expands the sector size, _____ pulses are required to create an image. _______ resolution decreases.
more; temporal
With narrow sector and temporal resolution there is...
-fewer pulses per frame
-shorter Tframe
-higher frame rate
-superior temporal resolution
With wide sector and temporal resolution there is...
-more pulses per frame
-longer Tframe
-lower frame rate
-inferior temporal resolution
Field of view and frame rate are _________ related.
inversely
an ultrasound's system ability to alter the spacing between sound beams
line density
When line density is low, ____ pulses create each image and the frame rate is high. Temporal resolution is high.
few
When line density is high, the number of pulses per image ________ and the frame rate drops. Temporal resolution decreases.
increases
Line density and frame rate are ________ related.
inversely
What is the main advantage of high density?
Although high line density has a negative effect on temporal resolution, the gaps between the lines are smaller. These smaller gaps improve the accuracy of each individual images.
With high line density, each image contains more detail, known as ________________ resolution.
improved spatial (detail)
With low line density and temporal resolution there is...
-widely spaced lines
-fewer pulses per frame
-shorter Tframe
-higher frame rate
-high temporal resolution
-poor spatial resolution
With high line density and temporal resolution there is...
-tightly packed lines
-more pulses per frame
-longer Tframe
-lower frame rate
-low temporal resolution
-excellent spatial resolution
What improves lateral resolution?
multi-focusing
What improves spatial resolution?
higher line density
What are the operational settings for better, higher frame rate?
-shallower imaging
-single focus
-narrow sector
-low line density
What are the operational settings for worse, lower frame rate?
-deeper imaging
-multiple focal points (improves lateral resolution)
-wide sector
-high line density (improves spatial resolution)
each frame is created and displayed very quickly, providing the impression of constant motion
real-time imaging
ultrasound "photograph"
static imaging
ultrasound "movie"
real-time imaging
Tframe = ?
# pulses x PRP
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