9 Axial + Lateral Resolution Flashcards
What is resolution?
Ability to image accurately
What is axial resolution?
Ability to distinguish 2 structures that are close to each other front-to-back, parallel-to, or along the beam’s main axis
What is LARRD resolution?
Longitudinal
Axial
Range, radial
Depth
What type of pulses provide LARRD resolution?
Shorter pulses
What is the equation of LARRD resolution?
LARRD resolution (mm) = spatial pulse length (mm)/2
What improves LARRD resolution?
Less ringing, fewer cycles in pulse
Higher frequency sound, shorter wavelength
What transducer produces the best axial resolution?
Transducers with the highest frequency and the fewest numbers of cycles per pulse
What is the definition of lateral resolution?
The minimum distance that 2 structures are separated by side-to-side or perpendicular to the sound beam that produces 2 distinct echoes.
What is LATA resolution?
Lateral
Angular
Transverse
Azimuthal
What does lateral resolution equal?
Beam diameter
Where is lateral resolution best?
At the focus or one near zone length from the transducer
What is point-spread artifact?
When 2 side-by-side structures are closer together than the beam width, only 1 wide is seen on the image
Which resolution is better LATA or LAARD?
LAARD resolution
How can lateral resolution be assessed at a variety of depths?
Using a test phantom and measuring the width of a reflection created by a pin in the phantom
Wider reflection at depths further away from the focus exhibit poor lateral resolution
What are the beam shape & divergency of high frequency pulsed US?
In far field, higher freq pulsed sound has narrower beams compared to lower frequencies in far field
