Chapter 12/13 Q&A: test 1 Flashcards Preview

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Flashcards in Chapter 12/13 Q&A: test 1 Deck (40):
1

Mechanical scanning produces pictures that are similar in shape to linear phased array images

True

2

Many active elements fire at almost the same time in a mechanical scanner

False

There is only one active element in a mechanical scanner

3

Many active elements fire at almost the same time in a phased array scanner

True

4

Which transducer is best described as mechanically steered and fixed, single focus?

mechanical

5

Which transducer is best described as mechanically steered and multi-focus?

Annular phased array

6

Which transducer creates a rectangular shaped image?

linear sequential array

7

A linear phased array transducer has 128 crystals. How many of these crystals are fired to create a single sound beam?

128

With linear phased array transducers, all the active elements are fired

8

A linear sequential array transducer has 128 crystals. How many of these crystals are fired to create a single sound beam?

a small group

With linear sequential array transducers, a small group of active elements are fired

9

In a linear phased array, what is the firing pattern that steers a beam to the left or right?

The firing pattern that steers a beam to the left or right is electronic slope

10

In linear phased arrays, what is the firing pattern that focuses a sound beam?

The firing pattern that focuses a sound beam is electronic curvature

11

There are large time delays in the firing pattern of a linear phased array transducer

False

there are tiny time delays

12

A machine that displays A-mode and two-dimensional images is called a duplex scanner

False

a machine that displays Doppler and 2D images is a duplex scanner

13

Which transducer improves elevational resolution?

1 1/2 dimensional array

14

Side lobes degrade axial resolution

False

15

Side lobes degrade lateral resolution

True

16

Which form of resolution improves when frame rate increases?

temporal resolution

temporal resolution is directly related to frame rate

higher frame rates improve temporal resolution

17

What is consistent with improved temporal resolution?

higher frame rate

Frame rate determines temporal resolution

Higher frame rates(lower Tframe) result in improved temporal resolution

18

What decreases temporal resolution?

lower frame rate

deeper imaging

multi-focus

19

A sonographer adjusts an ultrasound scan to double the depth of view from 5cm to 10cm.

What happens to the frame rate?

the frame rate is halved

frame rate and imaging depth are inversely related

20

A sonographer adjusts an ultrasound scan to double the depth of view from 5cm to 10cm.

If the frame rate remains the same, what will also occur?

narrower sector

21

A sonographer adjusts an ultrasound machine to change the sector size from 90 to 45 degrees. Nothing else changes. What happens to the frame rate?

the frame rate is doubled

22

A sonographer adjusts an ultrasound system to change the sector size from 90 to 45 degrees. The frame rate was unchanged. What else must have happened?

line density was doubled

23

A sonographer, using a phased array ultrasound system, turns off the multi-focus feature. What is the most likely consequence of this action?

temporal resolution improves

24

A sonographer increases the line density from 1 line per degree of sector to 3 lines per degree of sector. What is the most likely consequence of this action?

temporal resolution decreases

25

A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 2 lines per degree. No other changes are made. What will happen to the frame rate?

frame rate increases

26

A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 3 lines per degree. No other changes are made. What will happen to temporal resolution?

temporal resolution is unchanged

27

What is most important in determining the frame rate of a system?

speed of sound in a medium

28

What is most important in determining the frame rate of a system?

depth of view

29

What is the frame rate if each image of the ultrasound system is created in 0.02sec (1/50sec)?

50Hz

frame rate and Tframe are reciprocals

30

What is the time needed to make a single image if the frame rate of an ultrasound system is 20Hz?

0.05s (1/20)

frame rate and Tframe are reciprocals

 

31

The critical factor in determining frame rate, line density, and imaging depth is the transducer style

false

its time

32

The number of lines per frame and the frame rate determine the frequency.

false

it determines PRF

33

The number of lines per frame and the frame rate determine the PRF.

true

34

If the imaging depth of a scan is 15cm and there are 100 lines in the image, then the number of pulses making up the scan is 1500.

false

number of pulses would be 100

35

If the imaging depth of a scan is 15cm and there are 100 lines in the image, then the number of pulses making up the scan is 100.

true

36

If 100 scan lines make up an image and the frame rate is 30 per second, then the transducer's frequency is 3,000Hz.

false

a transducer's frequency is independent of the characteristics of the image that it creates.

37

If 100 scan lines make up an image and the frame rate is 30 per second, then the system's pulse repetition frequency is 3,000Hz.

true

PRF is the number of pulses created per second. It is lines per image multiplied by frame rate.

38

When the frame rate is 30Hz, how long does it take to create a frame?

1/30 sec

frame rate and Tframe are reciprocals

39

Under certain conditions, an ultrasound system creates each image in 0.01 seconds. What is the frame rate?

100Hz

frame rate and Tframe are reciprocals

40

What is the fundamental limitation of temporal resolution?

speed of sound in the medium