Chapter 10 Lateral Resolution Flashcards
What are synonyms for lateral resolution
LATA
Lateral
Angular
Transverse
Azimuthal
Lateral Resolution is
the ability to distinguish 2 structures (value of LA= minimum distance) when they are side by side or perpendicular
The focus of an ultrasound beam is the location where the beam is the broadest optimum transverse resolution is frequency is the highest finest depth resolution is obtained
the focus of an ultrasound beam is the location where the beam is the most narrow
The narrowest portion of the beam provides the optimal transverse or lateral resolution
the lateral res of an ultrasound system is primary determined by the width of the pulse length of the us pulse duration of the sound pulse none of the above
the lateral res is approx = to the width of the us pulse
two ultrasound systems produce acoustic pulses. one pulse is .4 usec in duration and the other is .2usec. which pulse will most likely provide best lateral res?
the duration of the pulse is unrelated to lateral res
Pulse duration affects axial res.. therefore the question cannot be determined
t/f the pulse duration does not profoundly influence the lateral res
true
primary determinant of lateral res is the sound beams diameter.
Two ultrasound systems havae near zone lengths of 8cm. @the focus system G’s lateral res is 3mm
system P’s lateral res is 5mm
which system will produce the higher quality pics
system G bc it has narrower beam width at the end of the nearfield
t/f When using standard ultrasonic imaging instrumentation , the lateral res has a higher numerical value than the axial res
True
most imaging systems have better axial res. the lateral res will have a higher value
this is bc sound pulse is typically wider than half its length
two ultrasound systems have a near zone lengths of 8cm. @there foci system Q’s lateral res is 3mm and system H is 5mm. Which system will correctly display two small structures at a depth of 8cm
the obj are side by side and .4cm apart.
Lateral res is approx by beam diameter @specific depth:
System q produces more accurate images if structures are .4cm apart bc beam is 3mm @focus
5mm is too wide for 4mm structural difference to display them separately
The lateral res of an ultrasound system is 4mm
two structures are 3mm apart side by side in relation to sound beam’s main axis
what will appear on the system’s display?
ONe echo
bc when the value of distance between the structures is less than the value of a system’s lat res then they are not resolved
t/f when using an instrument typical of today;s imaging devices, a higher frequency transducer is likely to mildly improve the system;s lateral res
True
if all other variables are equal– higher frequency is narrower than lower frequency pulses
Narrower beams improve lateral resolution
t/f when using an instrument typical of today’s imaging devices–higher frequency tx is likely to midly improve the system’s axial res
true
higher freq = shorter SPL
Short SPL = better range res
What will lower the the value of an ultrasound system's lateral resolution ? decrease the #of cycles in the pulse increase the effectiveBM increase the PRP use an acoustic lens
use and acoustic lens
diameter of the beam must be reduced to lower the value of the lateral res
beam diameter of the beam is decreased by using an acoustic lens
which of the following focusing tech is different from the others lens curved crystal fixed phased
Phased focusing is achieved with the electronics of an ultrasound system— +it is adjustable via beam former
focusing with lens or curved crystal is fixed
which of the following techniques is external focusing
lens
curved crystal
electronic focusing
lens
which of these terms means adjustable focusing or multi-focusing? dynamic aperature harmonics frequency agility phased array
phased array transducers all
- multi-focus capabilities
- focal depth can be changed by the sonographer
which of these tech. is consistent with variable or multi focusing?
lens
curved crystal
electronic
electronic
it is achieved with phasing of electronic signals
it is controlled by the sonographer and is multi focused
All of the following occur w/ focusing except:
lower intensity at the focus
shorter near zone length
more compact focal zone
smaller diameter beam diameter at the end of the near zone
focusing does not lower the beams intensity at the focus
with focus the near zone is shallower
focal zone smaller
beam is narrower at the focus
in which region of the sound beam is focus most effective shallow near zone end of the near zone deep in the far zone throughout entire length
end of the near zone - beginning of the far zone =
focal zone
t/f in comparison to other locations along the length of an ultrasound beam focusing is generally ineffective int eh far zone
true
focus narrows beam @ focus = better image
the beam still diverges below the focus
two us systems have near zone length= 8cm
@focus, system S lateral res = 3mm
system C lateral res = 5mm
which system system will best display two structures that are one in front of the other
this cannot be determined bc the info is for lateral res and the question askes for the axial
the diameter of a disc shaped unfocused piezoelectric crystal is 1cm. What is the best estimate for the minimum lateral res of the ultrasound system ? 1mm 5mm 1cm 5cm
5mm
unfocused sound beams w disk shaped crystal have hour glass shape
at the focus the beam diameter is 1/2 the PZT crystal
The diameter of a disc shaped unfocused piezoelectric crystal is 1.2cm. The near zone length is 8cm. What is the best estimate for the lateral resolution at a depth of 16cm? .06cm 1.2cm 8cm 16cm
1.2 cm
bc unfocused disk shape PZT = hourglass shape
2 near zone lengths = same diameter as PZT
