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Flashcards in Real Time Imaging Deck (48):
0

What is duplex imaging?

machines that show real time and doppler at the same time

1

what is static scanning?

one frame at a time

could not image moving structures

ultrasound "photograph"

wide field of view

2

What is real time scanning?

multiple frames per second that are made up of multiple scan lines per frame

unit must wait until all echoes have been received and then send out the pulse

the time it takes for each scan line is a LIMITATION IN SPEED

3

What is the opposite of real time scanning?

static imaging - one picture

4

How are frames achieved?

with either mechanical or electronic beam steering

5

what is frame rate?

numerous frames per second - how fast or slow the frames are produced

6

Time is based on what kind of resolution?

temporal resolution

(spatial resolution is the one we are most concerned with comprised of axial, lateral and elevational)

7

Temporal resolution depends on....

frame rate

units or hertz - frames per second

8

What has the ability of a display to distinguish closely spaced events in time?

temporal resolution

ability to precisely position moving structures

expressed in milliseconds

9

Temporal resolution __________ as the frame rate increases

improves

10

**What determines the frames produced each second (frame rate), number of images stored per second?**

**sound speed in the medium**

**depth of imaging**

11

What is the limitation of frame rate?

the time it takes to propagate through the medium (tissue)

maximum imaging depth determined frame rate

Units - hertz or images per second

12

What is the speed of sound in soft tissue?

1.54 mm/us

13

if the imaging depth is shallow, how is the frame rate, higher or lower?

higher

improved temporal resolution

14

Temporal resolution has the ability to locate reflectors in _____

time

15

Do we adjust the frame rate or does the machine?

machine

16

frame rate and time have what kind of relationship?

inversely related and are reciprocals (image created in 1/10sec, frame rate is 10 frames/sec or 10Hz)

shallow imaging increases frame rate

deep imaging decreases frame rate

17

What is pulse repetition frequency and its equation?

pulses per second

PRF (Hz)=n X LPF X FR (Hz)

PRF = number of foci X lines per frame X Frame rate

18

to increase the number of foci the PRF must _________

increase

19

To increase the number of line per frame, the PRF must....

increase

20

Frame rate is directly related to

PRF

to increase the frame rate the PRF must increase

PRF = n X LPF X FR

21

If penetration increases, the PRF

decreases

penetration X n (foci) X LPF X FR < 77,000 cm/s

22

If penetration increases the frame rate

decreases

23

if the number of foci increases, the frame rate

decreases

diminishes temporal resolution

each scan line has superior lateral resolution

balance btw temporal and lateral resolution

24

if the lines per frame increase frame rate

decreases

25

if the sector size increases the frame rate

decreases

because it increases the number of pulses needed and decreases temporal resolution

26

What gives you the best temporal resolution?

higher frame rate

shallow imaging

single focus

finish slide 46

27

how do you diminish temporal resolution?

lower frame rate

deeper imaging

multiple focal points

wide sector

high line density

(all of this improves SPATIAL resolution)

28

What is another word for spatial resolution?

detail

29

What are the three different kinds of resolution?

spatial

temporal

contrast

30

how is real time imaging achieved?

with either mechanical or electronic beam steering

31

how does real time imaging give the impression of constant motion?

frames are displayed in a rapid fashion

32

If the number of pulses per frame has fewer pulses what happens to frame rate and temporal resolution?

Higher frame rate

improved temporal resolution

(fewer pulses - less information you acquire the faster you can make the frame rate)

33

Why is a narrow sector (field of view) better for temporal resolution?

fewer pulses per frame

higher frame rate

superior temporal resolution

34

How can the system change line density?

systems can alter the spacing btw the sound beams

35

What is line density based on?

the number of elements, channels, and footprint

36

how are line density and frame rate related?

inversely related

37

how is real time imaging affected with a low line density?

widely spaced lines

fewer pulses per frame

higher frame rate

superior temporal resolution

inferior spatial or detail resolution

38

How is real time imaging affected with high line density?

closely spaced lines

more pulses per frame

lower frame rate

inferior temporal resolution

superior spatial (detail-lateral) resolution

39

If you have a sector transducer what determines the frame rate?

a given depth

sector width

line density

40

What happens to frame rate if you reduce the sector width but maintain the number of lines?

unchanged frame rate

but increased line density i.e. lateral resolution

41

what happens to frame rate when you reduce sector width with a lower number of lines?

higher frame rate

42

What is the frame rate per second that the human eye can see flickering?

less than 15-20 fps

imaging uses 30-60 fps

43

What do you need to improve temporal resolution?

higher frame rate

shallow imaging

single focus

narrow sector

low line density

44

How is temporal resolution diminished?

lower frame rate

deeper imaging

multiple focal points

wide sector

high line density

45

If you are imaging a liver which is more important, temporal or spatial resolution?

spatial because livers don't move

46

What determines axial resolution? Lateral resolution? elevational Resolution? Temporal resolution? Contrast resolution?

Axial: Spatial Pulse length

Lateral: beam width

Elevational: plane thickness

Temporal/time: frame rate

Contrast: bits per pixel

47

If you are imaging the heart, which is more important temporal or spatial resolution?

Temporal resolution when you are evaluating movement

spatial resolution when you are evaluating detail