Ch 13 Flashcards
Static Imaging
images displayed one frame at a time
“picture”
Real Time Imaging
each frame is created and displayed very quickly, providing the impression of constant motion
“movie”
Duplex Imaging
real time imaging and Doppler at same time
Frame rate
system’s ability to create numerous frames each second
Two things that determine frame rate
speed of sound in medium
depth
Units of frame rate
Hz
Temporal Resolution
ability to precisely position moving structures from instant to instant
Speed is a fundamental limition of what?
temporal resolution
4 factors that affect temporal resolution
- depth
- focus
- Sector Size
- Line Density
If shallower or fewer pulses
go return time
t frame
frame rate
temporal resolution
short go-return time
shorter t frame
higher frame rate
superior temporal resolution
If deeper or more pulses
go return time
t frame
frame rate
temporal resolution
long go-return time
longer t frame
lower frame rate
inferior temporal resolution
t frame
time for one frame to be created
t frame and frame rate relationship
inversely related
pulses x PRP =
t frame
Example:
100 x 1/1000 second = 1/10 second or 10 Hz
Factors Determining number of pulses per frame
number of focal points
sector size
line density
Imaging depth and frame rate are what related?
Inversely
Pulse per frame and frame rate are what related?
inversely
Single Focus
pulses per frame t frame frame rate temporal resolution lateral resolution
one pulse per scan line shorter t frame higher frame rate better temporal resolution poorer lateral resolution
Multi-focus
pulses per frame t frame frame rate temporal resolution lateral resolution
many pulses per scan line longer t frame lower frame rate dimished temporal resolution improved lateral resolution
Frame rate and time are what related?
inversely related
t frame x frame rate =
1
Example:
1/10 of a second, frame rate = 10 frames/second or 10 Hz
Narrow Sector
pulses per frame
t frame
frame rate
temporal resolution
fewer pulses per frame
shorter t frame
higher frame rate
superior temporal resolution
Wide Sector
pulses per frame
t frame
frame rate
temporal resolution
more pulses per frame
longer t frame
lower frame rate
inferior temporal resolution
how to change sector size?
field of view
Triplex Imaging
Pulse Waves, Color Doppler and real time imaging
Low Line Density
spaced line pulses per frame t frame frame rate temporal resolution spatial resolution
widely spaced line fewer pulses per frame shorter t frame (faster) higher frame rate high temporal resolution poor spatial resolution
High Line Density
spaced line pulses per frame t frame frame rate temporal resolution spatial resolution
tightly packed line more pulses per frame longer t frame lower rate rate lower temporal resolution excellent spatial resolution
What is line density?
alter the spacing between sound beams
Better Temporal
Resolution depth focus sector density frame rate
shallow imaging single focus narrow sector low line density higher frame rate
Worse Temporal
Resolution depth focus sector density frame rate
deep imaging
multiple focal points (improves lateral resolution)
wide sector
high line density (improves spatial resolution)
lower frame rate
Image vs movie quality
Some system settings produces an excellent photograph are inconsistent with producing an excellent movie. A low frame rate and poor temporal resolution create a great image but a poor movie
