Lateral Resolution and Focusing

Question 1

The focus of an ultrasound beam is the location where the _____.

a. beam is the broadest
b. optimum transverse resolution is
c. frequency is the highest
d. finest depth resolution is obtained

Answer 1

b. optimum transverse resolution is

Question 2

The lateral resolution of an ultrasound system is primarily determined by the ____.

a. width of the sound pulse
b. length of the ultrasound pulse
c. duration of the sound pulse
d. none of the above

Answer 2

a. width of the sound pulse

Question 3

Two ultrasound systems produce acoustic pulses. One pulse is 0.4 usec in duration and the other is 0.2 usec. Which pulse will most likely provide the best lateral resolution.

a. 0.4 usec
b. 0.2 usec
c. they are the same
d. cannot be determined

Answer 3

d. cannot be determined

Question 4

True or False?

The pulse duration does not profoundly influence the lateral resolution.

Answer 4

True

Question 5

Two ultrasound systems have near zone lengths of 8 cm. At the focus, System G’s lateral resolution is 3.0 mm, whereas System P’s is 5.0 mm. Which system will produce higher quality images pictures at their foci?

a. System P
b. System G
c. both will be of similar quality

Answer 5

b. System G

Question 6

True or False?

When using standard ultrasonic imaging instrumentation, the lateral resolution has a higher numerical value than the axial resolution.

Answer 6

True

Question 7

Two ultrasound systems have near zone lengths of 8 cm. At their foci, System Q’s lateral resolution is 3.0 mm and System H’s is 5.0 mm. Which system will correctly display two small structures at a depth of 8 cm? The objects are side by side and are 0.4 cm apart.

a. System H
b. System Q
c. both produce similar quality pictures

Answer 7

b. System Q

Question 8

The lateral resolution of an ultrasound system is 4 mm. Two structures are separated by 3 mm and lie side by side in relation to the sound beam’s main axis. What will most likely appear on the system’s display?

a. two weak echoes, 4 mm apart
b. two bright echoes, 3 mm apart
c. one echo
d. two bright echoes, 7 mm apart

Answer 8

c. one echo

Question 9

True or False?

When using an instrument typical of today’s imaging devices, a higher frequency transducer is likely to mildly improve the system’s lateral resolution.

Answer 9

True

Question 10

True or False?

When using an instrument typical of today’s diagnostic imaging devices, a higher frequency transducer is likely to improve the axial resolution.

Answer 10

True

Question 11

What will lower the value of an ultrasound system’s lateral resolution?

a. decrease the # of cycles in the pulse
b. increase the effective damping material
c. increase the pulse repetition period
d. use an acoustic lens

Answer 11

d. use an acoustic lens

Question 12

Which of the following focusing techniques is different from the others?

a. lens
b. curved crystal
c. fixed
d. phased

Answer 12

d. phased

Question 13

Which of the following techniques is internal focusing?

a. lens
b. curved crystal
c. electronic

Answer 13

b. curved crystal

Question 14

Which of the following techniques is external focusing?

a. lens
b. curved crystal
c. electronic

Answer 14

a. lens

Question 15

Which of these terms means adjustable focusing or multi-focusing?

a. dynamic aperture
b. harmonics
c. frequency agility
d. phased array

Answer 15

d. phased array

Question 16

Which of these techniques is consistent with variable or multi-focusing?

a. lens
b. curved crystal
c. electronic

Answer 16

c. electronic

Question 17

All of the following occur with focusing except:

a. lower intensity at the focus
b. shorter near zone length
c. more compact focal zone
d. smaller diameter beam diameter at the end of the near zone

Answer 17

a. lower intensity at the focus

Question 18

In which region of a sound beam is focusing most effective?

a. the very shallow near zone
b. the end of the near zone
c. very deep in the far zone
d. throughout its entire length

Answer 18

b. the end of the near zone

Question 19

True or False?

In comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone.

Answer 19

True

Question 20

Two ultrasound systems have near zone lengths of 8 cm. At the focus, System S’s lateral resolution is 3.0 mm, whereas System C’s is 5.0 mm. Which system is most likely to appropriately display two small body structures that lie, one in front of the other, at depths of 8.6 and 9.0 mm?

a. System C
b. System S
c. both have comparable quality
d. cannot be determined

Answer 20

d. cannot be determined

Question 21

The diameter of a disc-shaped, unfocused piezoelectric crystal is 1 cm. What is the best estimate for the minimum lateral resolution of the ultrasound system?

a. 1 mm
b. 5 mm
c. 1 cm
d. 5 cm

Answer 21

b. 5 mm

Question 22

The diameter of a disc-shaped, unfocused piezoelectric crystal is 1.2 cm. The near zone length is 8 cm. What is the best estimate for the lateral resolution at a depth of 16 cm?

a. 0.6 cm
b. 1.2 cm
c. 8 cm
d. 16 cm

Answer 22

b. 1.2 cm