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Flashcards in Test 2 Deck (70):
1

Pulse duration

PD=#cycles * time
PD=#cycles/f

2

Duty factor

DF= PD/PRP

3

Pulse repetition period

PRP=1/PRF

4

Pulse repetition frequecy

PRF=1/PRP

5

Time, distance, speed

Time=Distance/speed

6

Period

1/f

7

Frequency

1/p aka 1/T

8

Round trip time for 1cm depth in soft tissue

13usec
(1cm * 2)/1540m/s

9

Round trip time for non soft tissue

(depth * 2) / (speed)

10

What is round trip time for an unusual tissue with speed of 2000m/s to depth of 10cm?

(10cm * 2)/ (2000m/s)
(20cm)/200000cm/s)
.0001s
100usec

11

What does PD represent on a wave

the cylces, or actual wave portion
(/\/\/\)_____/\/\

12

What does the PRP represent on a wave

The section from begging of waves to next wave
(/\/\/\_____)/\/\/\

13

Duty Factor (DF)

Unitless
Represents the amount "on duty"

14

Continuous wave probe AKA

Pencil probe
Doppler only
Single element

15

Continuous wave PROS

sensitive

16

Continuous wave CONS

No image
Fixed focus=fixed depth

17

Mechanically steered transducer PROS

2D image
Wide field
"Static scanner"

18

Mechanically steered transducer CONS

Fixed focus
parts wear out

19

Mechanical annular array PROS

Rings give variable focus/depth
2D image
Wide field

20

Mehanical annular array CONS

Motion artifact
parts wear out

21

Linear switched array PROS

2D image
Electrical switches
Wide field
"one crystal after another"

22

Linear phased array PROS

2D image
Phased sequence
Variable focus
Steering
"Huygen's Principle"

23

Linear phased array CONS

Expensive
Fixed focus

24

Sector phased array PROS

2D image
Variable lateral focus
Small footprint=intercostal imaging
"curved linear"

25

Sector phased array CONS

Expensive
Fixed elevation focus

26

Other transducer types

1.5D
2D
3D
Trans-esophageal
Trans rectal
Intra-vascular
Waterpath=standoff

27

Damage to transducers

Heat
Dropping
Delamination
Cable damage

28

Heat damage

Adhesive wear and tear
Depolarization

29

Dropping damage

Crack case=exposed wires
Decreased probe sensitivity

30

Delaminiation

By caustic solvents (incorrect cleaning liquids)
Decreased probe sensitivity

31

Cable damage

System degradation
Decreased probe sensitivity

32

Frame rate sequence

Shoot one line
Shoot next line
...
All lines shot
Image forms
"Frame time"

33

Frame rate equation

Frame rate=Frame frequency
Frame rate=1/frame time

34

Line time

(13 usec * depth cm)

35

Frame time

Line time * # lines
(13 usec * depth) * (# lines)

36

Packet added

Color adds a packet to the frame time

37

Packet equations

Line time= (13usec * depth)
Packet time=(line time * #lines repeated)/packet
Frame time= (packet time * #lines)

38

Relations between frame time and frame freq

Increased frame time=decreased frame freq
Frame time=1/frame freq

39

Ways to improve frame rate

Decrease depth
decrease color box width
Turn off color

40

PZT

Electropotential energy>PZT>pressure
Ecectropotential energy

41

Sensitivity

Weakest signal detected

42

Improve sensitivity

Increase power
Increase intensity

43

What does power do to patients

Higher power increases exposure to patients

44

Power is proportional to

Power~Intensity~Amplitude^2

45

Gain=

20log(Amax/Amin)

46

Signal to noise ratio

High (signal >> noise), high quality image
Low (signal~noise), low quality image

47

Beam former

Creates phase delays to transmit signal
Applies phase delays to receive signal
Stable
Programmable
Accepts large Bandwidth

48

Types of beam formers

Synchronized beam
Focused beam
Beam steering
Steering and focusing

49

Synchronized beams

Signals come at the same time
/\/\___
/\/\___
/\/\___

50

Focused beam

Signals top and bottom come at same time, middle come at same time
__/\/\__
/\/\____
/\/\____
__/\/\__

51

Beam steering

Signals come at different times, patterned
____/\/\
__/\/\__
_/\/\___
/\/\____

52

Steering and focusing

Beams come at different times, but very closely timed
____/\/\
___/\/\_
__/\/\___
__/\/\___

53

What is important about receiver functions

They DO NOT affect exposure to patients

54

5 receiver functions

Amplification
Compensation
Compression
Demodulation
Reject

55

Amplification

Raises strength of reflections equally
-All waves will double
"turning up volume"

56

Compensation

Way to make up for attenuation
TGC, DGC, TDC
Tool that lets you brighten deeper part of screen to match top of screen
Equal Compensation
| |
| |
| |

57

Compression

Maintains relative difference in reflection
Considers limitations "shades of gray"
Keeps high peaks same, but will raise shorter peaks

58

Dynamic Range

20Log(Amax/Amin)
Unit=dB

59

Example of dynamic range

64 shades of gray
20log(64/1)
20(1.8)
36dB

60

Demodulation

Changes signal to more suitable
Rectification and Smoothing

61

Rectification

Takes any negative signals and flips them over the baseline to become positive
__/\ /\___ into: __/\/\/\__
\/

62

Smoothing

Takes the signals after rectification and turns them into one smooth signal
__/\/\__ into : __( )__

63

Reject

Removes low level reflections
Noise reduction
"rejection level"

64

A-mode

Amplitude
Plots magnitude of echoes
Higher peaks=bright

65

B-mode

Brightness
Bright=strong echoes
Dark=weak echoes/no echo

66

M-mode

Motion
plots echoes based on depth to transducer

67

What is the round trip for ultrasound to travel 4cm depth in soft tissue?

(13usec/cm)(4cm)
=52 usec

68

What is the roundtrip time for ultrasound to travel 8cm depth in soft issue?

(13usec/cm)(8cm)
104usec

69

What is the round trip time for ultrasound to travel through unusual tissue with speed 2000 m/s to depth of 10cm?

(depth * 2)/speed
(10cm*2)/2000m/s
(20cm)/200000cm/s
.0001s
100usec

70

What is the PRP insonating in soft tissue with a pulse at depth of 5cm?

(13usec/cm)(5cm)
65usec