Temporal Resolution and Real-Time Imaging

Question 1

Which of the following will improve a system’s temporal resolution?

a. increased sector angle
b. increased line density
c. increased PRF
d. increased frequency

Answer 1

c. increased PRF

Question 2

True or False?

An ultrasound system with a longer pulse duration will generally have better temporal resolution.

Answer 2

False

Question 3

True or False?

The length of a pulse does not directly influence the temporal resolution.

Answer 3

True

Question 4

Two imaging systems produce acoustic pulses; one pulse is 0.4 usec long and the other is 0.2 usec long. Which is most likely to provide the best temporal resolution?

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

Answer 4

d. cannot be determined

Question 5

Which two factors determine temporal resolution?

a. speed of sound and depth of view
b. pixel size and sector size
c. focal zones and sector depth
d. propagation speed and frame rate

Answer 5

a. speed of sound and depth of view

Question 6

Which two controls determine a system’s temporal resolution?

a. frame rate and sector depth
b. focal zones and sector depth
c. propagation speed and frame rate
d. depth of view and pulses per image

Answer 6

d. depth of view and pulses per image

Question 7

True or False?

An ultrasound system with a shorter pulse repetition period (PRP) will have better temporal resolution than a system with a longer PRP.

Answer 7

True

Question 8

What is the primary disadvantage of multiple focal zones along each scan line of a two-dimensional image?

a. improved temporal resolution
b. decreased temporal resolution
c. improved lateral resolution
d. improved longitudinal resolution

Answer 8

b. decreased temporal resolution

Question 9

What is the primary advantage of multiple focal zones along each scan line of two-dimensional image?

a. improved temporal resolution
b. decreased temporal resolution
c. improved lateral resolution
d. improved longitudinal resolution

Answer 9

c. improved lateral resolution

Question 10

Which choice will result in increased frame rate and temporal resolution?

a. decreased propagation speed
b. decreased sector size
c. decreased lateral resolution
d. decreased pulse repetition frequency

Answer 10

b. decreased sector size

Question 11

True or False?

With sector scanning, images with greater detail (spatial resolution) are created when the number of acoustic pulses per degree of sector is increased.

Answer 11

True

Question 12

An ultrasound system with a 4.0 MHz transducer is used to image structures as deep as 15 cm. Twenty images are produced each second, each requiring 100 acoustic pulses. What is the PRF of the system?

a. 1,500 Hz
b. 300 Hz
c. 2,000 Hz
d. 4 MHz

Answer 12

c. 2,000 Hz

Question 13

Which of the following sector imaging systems will have the best image detail if all other parameters are identical?

a. a 90 degree sector with 100 pulses/image
b. an 80 degree sector with 40 pulses/image
c. a 70 degree sector with 84 pulses/image
d. a 60 degree sector with 60 pulses/image

Answer 13

c. a 70 degree sector with 84 pulses/image

Question 14

Of the following, which imaging modality has the poorest temporal resolution?

a. two-dimensional, real time
b. A-mode
c. color flow imaging
d. M-mode

Answer 14

c. color flow imaging

Question 15

Which ultrasound imaging modality has the best temporal resolution?

a. B-scanning
b. duplex imaging
c. color flow imaging
d. M-mode

Answer 15

d. M-mode

Question 16

All of the following reduce temporal resolution by increasing the number of pulses per image except:

a. increasing the number of foci
b. increasing line density
c. increasing field of view
d. increasing depth of view

Answer 16

d. increasing depth of view

Question 17

A sonographer reduced the sector size from 90 degrees to 30 degrees. Frame rate, however, did not change. What else happened?

a. imaging depth decreased
b. pulse duration increased
c. multi-focus was turned on
d. PRF was increased

Answer 17

c. multi-focus turned on