Images created one frame at a time
Static scanning
What does frame rate describe in ultrasound?
The amount of frames displayed per second
What is temporal resolution?
The “accuracy” in time of how precisely a system displays moving structures; determined by frame rate
What is the relationship between frame rate and temporal resolution?
Directly related. High frame rate = better temporal resolution. Low frame rate = poorer temporal resolution
What is the relationship of Frame rate and time for one frame (Tframe)?
inversely related and reciprocals
Ex: when an ultrasound system creates an image in 1/10 seconds, the frame rate is 10 frames/seconds or 10 Hz
What are the two sonographer controlled settings that determine frame rate?
Imaging depth
Number of pulses in each picture
If depth increases what happens to frame rate and temporal resolution?
Both decrease, deeper imaging slows down the system’s ability to update frames
If you increase the number of focus zones what happens to frame rate?
It decreases, because each focus requires an extra pulse per line
What is the relationship between imaging depth and frame rate?
inversely related
What is the relationship between number of pulses in each image and frame rate?
Pulses per frame and frame rate are inversely related
What three factors affect 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)
How does multi-focus affect frame rate and temporal resolution?
It decreases frame rate and diminishes temporal resolution, (because multiple pulses are being sent down each scan line)
What is the affect of increases sector size on temporal resolution?
Decreases temporal resolution, it requires more scan lines and more time per frame
What is the relationship between line density and temporal resolution?
inversely related, high line density = low temporal resolution
Why does multi-focus creates better lateral resolution?
because each scan line is focused at multiple depths, so it is narrow over a wide range of depths
What is line density?
The number of scan lines per degree of sector (how closely packed the lines are)
What is the trade off when using multi-focus?
Better lateral resolution but lower temporal resolution and frame rate
What happens to temporal resolution when line density increases?
it decreases because more pulses are needed for each frame
What happens to spatial resolution when line density increases?
Spatial (image quality) resolution increases, smaller gaps make for more detailed images
What does spatial resolution describe?
Image quality or detail accuracy
What improves lateral resolution?
multi-focusing
What improves spatial resolution?
higher line density
What are the two major functions of the ultrasound system?
- Preparation and transmission of electrical signals to the transducer, which creates a sound beam
- Reception of electrical signals from the transducer
What happens during the reception portion of the system?
