Axial And Lateral Resolution Flashcards
What is the definition of resolution in imaging?
Accuracy in imaging
Resolution refers to the ability to distinguish between two structures in an image.
What is axial resolution?
The minimum distance that 2 structures positioned front-to-back can be apart and still produce 2 distinct echoes
Axial resolution is not adjustable and ranges from 0.1-1.0 mm; lower values indicate better resolution.
What is the formula for calculating axial resolution?
(mm) = SPL/2
SPL stands for spatial pulse length.
What is another name for axial resolution?
Longitudinal, Range, Radial, or Depth resolution (LARRD)
These terms emphasize the directionality of axial resolution.
What improves axial resolution?
- Higher frequency transducer
- Shorter spatial pulse length
- Shorter pulse duration
- Fewer cycles per pulse
- Lower numerical values
Higher frequency results in shorter pulses, enhancing resolution.
What is lateral resolution?
The minimum distance that 2 structures positioned side-by-side can be apart and still produce 2 distinct echoes
Lateral resolution is perpendicular to the sound beam’s main axis.
What is the formula for calculating lateral resolution?
(mm) = beam width
This indicates that lateral resolution is dependent on the width of the ultrasound beam.
What is another name for lateral resolution?
Angular, Transverse, Azimuthal resolution (LATA)
These terms highlight the aspect of lateral resolution in imaging.
What improves lateral resolution in the far field?
Higher frequency transducer
Higher frequency reduces beam divergence, enhancing lateral resolution.
What are the focusing techniques for improving resolution?
- Fixed focusing
- Conventional or mechanical focusing
- Electronic focusing
These techniques can involve both external and internal methods.
Does axial resolution change with depth?
No, it remains the same at all depths
Axial resolution is constant, regardless of depth.
What is the best condition for axial resolution in the near field?
Highest frequency and fewest cycles
This results in the shortest spatial pulse length.
What is the best condition for lateral resolution?
Narrowest beam width
Lateral resolution improves with smaller beam widths.
What is the relationship between crystal diameter and lateral resolution?
- Smallest diameter crystal = best lateral resolution
- Largest diameter & highest frequency = least divergence
Larger crystals can provide better lateral resolution due to their ability to focus the beam more effectively.
What happens to beam diameter in the near field as focal length is reduced?
Beam diameter decreases
This is part of the effects of focusing in ultrasound imaging.
What is the effect of focusing on the focal depth?
Focal depth is shallower
A shallower focal depth can affect image quality and resolution.
How does focusing affect beam diameter in the far zone?
Beam diameter in the far zone increases
This increase leads to more divergence of the beam.
What is the effect of focusing on the focal zone?
Focal zone is smaller
A smaller focal zone can improve image clarity.
Focusing only improves which type of resolution?
Lateral Resolution
Lateral resolution refers to the ability to distinguish two structures that are side by side.
What are the characteristics of continuous wave frequency?
Continuous Wave
This type of frequency is used in specific ultrasound applications.
What are the characteristics of pulsed wave frequency?
Pulsed Wave
Pulsed wave frequency is commonly used for imaging and diagnostics.
What defines the focal length in ultrasound?
Focal Length
Focal length is a critical parameter affecting image quality.
What is beam divergence?
Beam Divergence
Beam divergence describes how much a beam spreads out as it travels.
What are the two types of resolution in ultrasound?
- Lateral Resolution
- Axial Resolution
Lateral resolution refers to the ability to distinguish side-by-side structures, while axial resolution pertains to the ability to distinguish structures along the axis of the beam.
What determines sound beams?
Determinants of Sound Beams
These include various physical properties and parameters of the ultrasound system.
What factors determine beam width?
- Frequency of electrical signal from ultrasound system
- Thickness and speed of sound of ceramic (PZT)
- Diameter and frequency of sound of ceramic
These factors play a crucial role in shaping the ultrasound beam.
What does SPL stand for in ultrasound?
SPL
SPL stands for Spatial Pulse Length, an important factor in determining resolution.
What does PD stand for in ultrasound?
PD
PD stands for Pulse Duration, which affects the quality of the ultrasound image.
