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ch 12. Contrast, Spatial & Temporal resolution
Terms in this set (46)
the ability to differentiate one shade of gray from another
few gray shades =
poor contrast resolution
many gray shades=
good contrast resolution
visualizing detail in an image
spatial resolution is affected by
axial res, lateral res, line density,
poor spatial res
good spatial res
real-time imaging -
A series of frames displayed in rapid sequence to give the impression of constant motion. (movie)
the ability to accurately locate moving structures at any particular instant in time
Resolution pertaining to
"how high is the frame rate?" or
"how fast can each frame be made" or
"How good is my Movie" *****
Temporal Resolution depends only upon ____ _____.
more images per second improves
units of Frame Rate:
HZ or per second
frame rate is determined by 2 factors:
1. imaging depth
2. # of pulses per image
Frame rate is limited by 2 factors:
****1. The speed of sound in medium
2. Imaging depth
The speed of sound in the medium is a characteristic of the medium and ____________
cannot be changed.
four settings under sonographer control that affect temporal resolution:
1.max imaging depth
2.#of pulses per scan line (multi-focus)
3. sector size
4.line density(lines per degree of sector)
Setting determining Temporal Res:
Temp Res improves -
-imaging is shallower or made of fewer pulses
-less time to create an image
-more frames created each sec
Setting determining Temporal Res:
Temp Res degrades -
-imaging is deeper or made of more pulses
-more time to create an image
-frame rate decreases
With regard to maximum imaging depth, what will create a frame in less time?
Shallower depth of view makes a frame faster and improves temporal res.
If Imaging depth view is doubled the frame will be -------.
With regard to pulses per scan line, what will create a frame with fewer pulses?
single focus systems use fewer pulses, resulting in improved temp res
multi-focus _________ temporal res
with regard to sector size, what will create a frame with fewer pulses?
smaller sector angle creates images with fewer pulses, improving temporal res.
With regard to line density, what will create a frame with fewer pulses?
low line density images use fewer pulses, and have better temporal res.
lower line density degrades -
when line density is low ____ _______ is high
as temporal resolution improves (higher frame rate) _____________
image quality may degrade
as temporal res degrades ( Lower frame rate) ___________
image quality may improve
increasing the line density degrades temporal res, but improves
using multi-focus degrades ____________but improves lateral resolution
to increase frame rate without degrating image quality can be achieved by
making the color doppler box smaller
High Temporal Resolution =
-high frame rate
-fewer pulses per image
-low line density
-associated with better movie!, but lower quality image!!!
Low temporal resolution =
-Low frame rate
-more pulses per image
-multi-focus(improves lateral res)
-high line density( improves spatial res)
,associated with poor quality move, but higher quality images
Definition of Tf -
is the time required to make a frame
Tf and Frame rate (Fr) are
when a frame is made _______ , many frames are created each second.
when a frame is made _______, few frames are created each second.
Tf x FR =
When one frame is created in 1/50th of a second, then the frame rate will be
50/second or 50 HZ.
1/50th x 50=1
what is the fraction 1/50th in decimal form?
0.02 x 50= 1
when one frame is created in 1/10th of a second, then the frame rate will bw
10/sec or 10 hz
1/10th x 10= 1
frame rate typical values
Tf= 0.01-0.05 seconds (1/100th- 1/20th of a sec)
Short duration physiologic events can be missed when frame rats are
*** a sonographer changes an images sector size from 90 to 45 degrees. the frame rate remained unchanged. what else must have happened
the line density was doubled
*** a sonographer changes an images sector size from 90 to 45 degrees. Nothing else changes. The Frame rate is_________
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