MEDS12001 Lecture Notes - Lecture 5: Frame Rate
1 | P a g e
WHAT IS RESOLUTION?
Resolution is the act or process of distinguishing
something into its constituent parts or elements
Imaging has different types of resolution:
1. Detail/spatial
• There are 3 subtypes of spatial resolution:
o Axial resolution
o Lateral resolution
o Elevational resolution
2. Contrast
3. Temporal
4. (colour)
DETAIL/SPATIAL RESOLUTION
• The ability to distinguish between separate
reflectors and or structures in space
• Physical separation among 3 dimensions of
the sound beam:
o Axial dimension
o Lateral (width) dimension
o Slice thickness or Elevational dimension
AXIAL RESOLUTION
• Affected by SPL (Spatial Pulse Length)
find more resources at oneclass.com
find more resources at oneclass.com
2 | P a g e
SPL
• SPL = no of cycles in a pulse x wavelength
• Distance measure
• Shorter SPL are better
• SPL = n x λ
INFLUENCES OF AXIAL RESOLUTION
1. Transducer damping
o Which imaging modalities have the best
and worst axial resolution?
2. Frequency
o Frequency affects wavelength – so affects
SPL
o f = λ = SPL = axial resolution
(improves it)
o Smaller no of pulses = better axial
resolution)
o Best axial resolution = SPL/2
EXAMPLE
REAL NUMBERS
• Compare the axial resolution between 3MHz
and 12MHz frequencies in soft tissue with B-
mode imaging
• What is the SPL for 3MHz transducer?
• What is the SPL for 12 MHz transducer?
find more resources at oneclass.com
find more resources at oneclass.com
3 | P a g e
SOLVE FOR SPL
LATERAL RESOLUTION
• Azimuthal resolution
• Minimum reflector separation in the direction
perpendicular to the beam direction that can
produce two separate echoes
• Lateral resolution = beam width
LATERAL RESOLUTION
VARIES ALONG THE
BEAM
• Sound beams are not
uniform in beam width
• Lateral resolution varies
along the beam width
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Resolution is the act or process of distinguishing something into its constituent parts or elements. Imaging has different types of resolution: detail/spatial, there are 3 subtypes of spatial resolution, axial resolution, lateral resolution, elevational resolution, contrast, temporal (colour) Detail/spatial resolution: the ability to distinguish between separate reflectors and or structures in space, physical separation among 3 dimensions of the sound beam, axial dimension, lateral (width) dimension, slice thickness or elevational dimension. Axial resolution: affected by spl (spatial pulse length) Spl: spl = no of cycles in a pulse x wavelength, distance measure, shorter spl are better, spl = n x . Influences of axial resolution: transducer damping, which imaging modalities have the best and worst axial resolution, frequency, frequency affects wavelength so affects. Spl: f = = spl = axial resolution (improves it, smaller no of pulses = better axial resolution, best axial resolution = spl/2.
