Ch. 13 Physics: Real- Time imaging Flashcards
True or false:
two-dimensional images were created through a time-consuming process called static scanning and is still used today.
False
Today all modern ultrasound instruments are capable of real-time imaging.
describes a systems ability to create numerous frames (images) each second.
Frame rate
Frame rate is determined by …..
Sound speed within the medium – most important
Imaging depth
Frame Rate is ___________ to Temporal Resolution
Proportional
What is the typical frame rate per second?
30 - 60 frames per second
Maximum imaging depth determines frame rate with speed of sound in soft tissue considered at a constant ________.
1.54km/s
What is frame rate measured in?
Hz
Accuracy in time – the ability to precisely position moving structures from instant to instant
Temporal resolution
Temporal resolution is determined by what?
Frame rate
_______ frame rate improves temporal resolution
High
_______ frame rate reduces temporal resolution
Low
If it takes 1/30 of a second to make a frame, then the frame rate is ……
30 frames per sec, or 30 Hz
T frame x frame rate = 1
Is the temporal resolution controlled or not controlled by the sonographer?
Controlled
How is temporal resolution controlled?
Imaging depth
Number of pulses per frame
Imaging depth and frame rate are _________ related
inversely
What is the formula for image depth?
Tframe = # pulses x PRP
Shallow depths allow for a _______ frame rate
higher
Deeper imaging requires more time to create and results in ______ frame rate
slower
To maintain better temporal resolution, we would want the most ________ image.
Shallow
_________________ also affects the frame rate since the more pulses needed to create an image would take more time….then the temporal resolution would decrease.
Pulses per image
What are the three factors that determine the number of pulses needed to create the image?
Number of pulses per scan line (multi-focus vs. single focus)
Sector size
Line density
What increases lateral resolution, but only at a trade off reducing temporal resolution?
Multi-focus
Also known as field of view
Sector size
By expanding the ___________, more pulses are required to create an image so temporal resolution decreases
sector size
The number of scan lines in the sound beam.
Line density
So what do you think happens to the temporal resolution with
increased line density?
It would decrease
what would happen to our spatial resolution with increased line density?
It would increase
More lines = increased detail (spatial resolution), but _____ frame rate (decreased temporal resolution)
slower
Few lines = decreased detail (spatial resolution), but _____ frame rate (increased temporal resolution)
faster
