Chapter 10 Lateral Resolution

Question 1

What are synonyms for lateral resolution

LATA

Answer 1

Lateral
Angular
Transverse
Azimuthal

Question 2

Lateral Resolution is

Answer 2

the ability to distinguish 2 structures (value of LA= minimum distance) when they are side by side or perpendicular

Question 3

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

Answer 3

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

Question 4

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

Answer 4

the lateral res is approx = to the width of the us pulse

Question 5

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?

Answer 5

the duration of the pulse is unrelated to lateral res

Pulse duration affects axial res.. therefore the question cannot be determined

Question 6

t/f the pulse duration does not profoundly influence the lateral res

Answer 6

true

primary determinant of lateral res is the sound beams diameter.

Question 7

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

Answer 7

system G bc it has narrower beam width at the end of the nearfield

Question 8

t/f When using standard ultrasonic imaging instrumentation , the lateral res has a higher numerical value than the axial res

Answer 8

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

Question 9

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.

Answer 9

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

Question 10

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?

Answer 10

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

Question 11

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

Answer 11

True
if all other variables are equal– higher frequency is narrower than lower frequency pulses
Narrower beams improve lateral resolution

Question 12

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

Answer 12

true
higher freq = shorter SPL
Short SPL = better range res

Question 13

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

Answer 13

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

Question 14

which of the following focusing tech is different from the others
lens
curved crystal
fixed 
phased

Answer 14

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

Question 15

which of the following techniques is external focusing
lens
curved crystal
electronic focusing

Answer 15

lens

Question 16

which of these terms means adjustable focusing or multi-focusing?
dynamic aperature
harmonics 
frequency agility 
phased array

Answer 16

phased array transducers all

1. multi-focus capabilities
2. focal depth can be changed by the sonographer

Question 17

which of these tech. is consistent with variable or multi focusing?
lens
curved crystal
electronic

Answer 17

electronic
it is achieved with phasing of electronic signals
it is controlled by the sonographer and is multi focused

Question 18

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

Answer 18

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

Question 19

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

Answer 19

end of the near zone - beginning of the far zone =

focal zone

Question 20

t/f in comparison to other locations along the length of an ultrasound beam focusing is generally ineffective int eh far zone

Answer 20

true
focus narrows beam @ focus = better image
the beam still diverges below the focus

Question 21

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

Answer 21

this cannot be determined bc the info is for lateral res and the question askes for the axial

Question 22

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

Answer 22

5mm
unfocused sound beams w disk shaped crystal have hour glass shape
at the focus the beam diameter is 1/2 the PZT crystal

Question 23

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

Answer 23

1.2 cm
bc unfocused disk shape PZT = hourglass shape
2 near zone lengths = same diameter as PZT