Coconote
AI notes
AI voice & video notes
Try for free
🔍
Understanding Axial and Lateral Resolution
May 4, 2025
Unit 10: Axial and Lateral Resolution
Key Concepts
Resolution
: Describes how detail is displayed; higher resolution equates to more accurate displays.
Types of Resolution in Ultrasound
:
Spatial Resolution: Dependent on monitor pixels and scan lines.
Contrast Resolution: Ability to differentiate shades of gray.
Temporal Resolution: Accuracy of moving objects.
Elevational Resolution: Accuracy in thin slices of anatomy.
Lateral Resolution
: Accuracy of side-by-side structures.
Axial Resolution
: Accuracy of parallel reflectors to sound beam.
Axial Resolution (Section 10.1)
Definition
: The ability to accurately image reflectors parallel to the sound beam.
Dependent on
: Spatial Pulse Length (SPL).
Calculation
: Axial Resolution = SPL / 2.
SPL Formula
: SPL = Number of Cycles in Pulse × Wavelength.
Importance of Numerical Value
: Lower values indicate better resolution.
Improving Axial Resolution
:
Use high-frequency transducers for shorter wavelengths and SPLs.
Include backing material in transducer to reduce cycles per pulse.
Synonyms
: Longitudinal, Range, Radial, Depth Resolution.
Lateral Resolution (Section 10.2)
Definition
: Ability to image reflectors perpendicular to the sound beam.
Dependent on
: Beam Width.
Calculation
: Lateral Resolution = Beam Width.
Beam Anatomy
:
Beam narrows at the focus and diverges in far field.
Best lateral resolution occurs at the focus.
Improving Lateral Resolution
:
Smaller transducer diameter for near-field.
Larger transducer diameter for reduced far-field divergence.
High-frequency transducers for minimized divergence.
Synonyms
: Angular, Transverse, Azimuthal Resolution.
Clinical Application (Section 10.3)
Choosing Equipment
: Balance high frequency for detailed imaging with lower frequency for depth.
Optimizing Image
: Use high frequency and adjust focus.
Focusing Techniques (Section 10.4)
Types of Focusing
:
Lenses: External fixed focus, uses refraction.
Curved Elements: Internal fixed focus, uses curved PZT crystals.
Electronic Focusing: Adjustable, used in multi-element transducers (arrays).
Electronic Focusing
: Allows adjustment of the focus, improving image resolution by placing focus at or just below the area of interest.
Effects of Focusing (Section 10.5)
Focused vs Unfocused Beams
:
Focused beams have smaller diameters in near field.
Focused beams shorten near zone length, increase divergence after focal zone.
Reduced focal zone length and diameter in focused beams, improving lateral resolution.
Conclusion
Axial resolution is generally better than lateral due to smaller SPL values.
Focus on using high-frequency, few-cycle transducers to improve both axial and lateral resolution.
Practice problems and review material to reinforce understanding.
📄
Full transcript