Resolution Flashcards
3 aspects of resolution
detail (spatial)
contrast
temporal
detailed resolution can be further divided into
axial
lateral
elevational
axial resolution is the ability to
separate reflectors along the path of the beam
axial resolution dependent on
SPL
axial resolution calculated by
1/2 SPL
increase f = ____ SPL = ____ axial res
decrease
increase
5 things relating to better axial resolution
higher f probes
decreased wavelength
wide bandwidths
low Q factor
increased damping
wide bandwidths = ____ pulse
shorter
axial resolution AKA and what to remember it as
LARD
longitudinal
range
depth
lateral resolution is the ability to
separate reflectors perpendicular to the path of the beam
lateral resolution is dependent on the ______, therefore it ___is/is not___ constant with depth
width of the beam
is not
near zone = _____ (con/divergent) = ____ lat resolution
convergent
increased
what area has the best lat resolution
focal zone
far zone = _____ (con/divergent) = ______ lat resolution
divergent
decreased
increase focus = ______ divergence in far field = ____ lat res
increase
decrease
lateral resolution is directly related to the ____ of the beam
width
beam width decreased = ______ lateral resolution
increases
5 things relating to better lateral resolution
distance from probe
amount of focusing
size of aperture
higher the f
NZL
increase focus by increasing delay = ____ NZL
decrease
NZL affected by (3)
aperture
f
amount of focusing
lateral resolution AKA and how to remember it by
LATA
angular
transverse
azimuthal
decrease NZL = ____ lat resolution for NZ/focal point, ____ lat resolution in far field
increase
decrease
increase aperture = _____ NZL = _____ lat resolution in far field
increase
increase
elevational resolution is what
the ability to separate reflectors perpendicular to the image plane of the beam
elevational resolution is dependent on the ___ of the ____ but in the ___ axis
width
beam
Z-axis
beam width in. the z-axis ____ = increased elevational resolution
decreases
4 things relating to better elevational resolution
distance from probe
higher the f
NZL
amount of focusing in Z plane
elevational res AKA (2)
slice thickness
section thickness
contrast resolution is the ability
to distinguish subtle differences in tissue gray scale
contrast resolution is related to the systems ____
bit depth
higher bit depth = ____ shades of grey
more
more shades of grey gives the operator more control over the ____
dynamic range
reducing dynamic range = ____ the ability to distinguish subtle differences in grayscale
increase
temporal resolution is the ability to
appreciate moving structures in real time (or moving probe)
temporal res is related to the systems ____
frame rate
frame rate increases = ____ temporal resolution
increases
temp resolution is defined by FR and FR is related to the _____
PRF
PRF formula for temp resolution
PRF (Hz) = n x LPF x FR (Hz)
n= number of foci
LPF = lines per frame
FR = framte rate or frames/s
____ of the sound plays an important role in the PRF as well
penetration
penetration (cm) x n x LPF x F ≤ _____
77 000 cm/s
why is 77 000 cm/s used
it represents half of the average speed of sound in soft tissue (154000cm/s)
temp res related to 5 things
depth of penetration
number of foci
sector width
number of lines per frame
frame rate
deeper = _____ pulses per second = ____ temp res
less
decreased
more foci = ____ temp res
decrease
2 foci = _____ time = ____ temp res
double
1/2
less scan lines = _____ interpolation
increases
decrease sector width = _____ temp res
increase
