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Physics > Memory & Display > Flashcards

Memory & Display Flashcards

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1
Q

What is memory responsible for?

A

Greyscale - allows to differentiate tissues

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2
Q

What does memory enable?

A

Free frame
Cine-loop
Ability to post-process

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3
Q

What is another name for memory?

A

Scan converter

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4
Q

What is the function of modules or circuits?

A

Store US information and enables machine to build an image

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5
Q

How does the system write memory?

A

Vertical to horizontal since monitors write their information horizontally

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6
Q

Where does the image go after memory?

A

Display or recording device

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7
Q

What was the scan conversion process historically?

A

Analog process

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8
Q

What do the current systems use to convert memory?

A

Distal scan converter

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9
Q

What is the difference b/w analog and digital?

A

Analog- continuous values, prone to drift, less reproducible

Digital- discrete values, stable, reproducible

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10
Q

What is a analog scan converter similar to?

A

CRT

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11
Q

What was the phosphate face in the analog scan converter replaced with?

A

Wafer silicon

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12
Q

What is the wafer silicon called in the analog scan converter?

A

Dielectric matrix

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13
Q

What happens to the electrons when emitted from the filament?

A

Pass through deflection plates and strike silicon wafer

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14
Q

What kind of charge is produced when the electrons strike the silicon wafer?

A

Positive charge

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15
Q

What is the positive charge proportional to?

A

Amplitude of signals strengths

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16
Q

Why is the analog scan converter prone to drift?

A

The positive charges fade over time and are erased

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17
Q

What was the main advantage of the analog scan converter? (2)

A

Allows for a grey scale

Acts as a buffer b/w image and display with good short term memory

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18
Q

What was a disadvantage with analog scan converters?

A

Prone to drift with no long term memory

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19
Q

Why do we used digital scan converters today?

A

Reliable and versatile
Can connect to other systems or cameras
Superior resolution

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20
Q

What does a digital scan converter consist of?

A

A matrix typically 1024X768 - divided into a rectangular square of pixels (picture elements)

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21
Q

What does each pixel contain and represent?

A

Contains a digital number to represent amp of received echo

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22
Q

How do we know the amp from the matrix size?

A

Multiple the matrix = # of pixels = amp

Ex: 1024X768=786432

Therefore the amp is 786432

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23
Q

What does each pixel on the matrix represent?

A

Each pixel stores data corresponding to a specific tissue - it represents the greyscale for returning echos

Each pixels corresponds to a specific depth

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24
Q

In what code does the computer operate?

A

Binary code

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25
Q

What is the data in each square of the matrix equal to?

A

A 1 or 0 therefore a shade of grey…

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26
Q

How do we display more then 1 shade of grey per square?

A

Matrices can be stacked on top of one another which each square in every matrices having its own #

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27
Q

What happens when there are multiple matrices stacked on top of each other? Why?

A

More matrices = more shapes of grey due to the different combinations of binary digits

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28
Q

What is the smallest form of display?

A

Pixel

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29
Q

How does having more pixels affect resolution?

A

Better resolution

30
Q

What is a bit?

A

One binary digit - either 1 or 0

31
Q

What is a byte?

A

8 bits

32
Q

What is a word?

A

Combination of bits expressed as a unit

33
Q

What is word length?

A

of bits in a word

34
Q

What is bit depth?

A

The word address at each address location

35
Q

What is RAM?

A

Random access memory

Fast, re-writable, cheap and erased when machine is turned off

36
Q

What is ROM?

A

Read only memory

Permanent and used for system functions (pre-sets)

37
Q

What determines how good our contrast resolution will be?

A

Bit depth

38
Q

What is contrast resolution?

A

How well the tissue differentiation is (distinguish tissue from background)

39
Q

What increases contrast resolution?

A

Increase of BD

40
Q

What helps control the contrast resolution?

A

Dynamic range

41
Q

What does “n” represent in the formula for calculating shades of grey?

A

N is the bit depth or # of bits used at each address location to store the echo data received

42
Q

What would the bit depth be of 4?

A

n = 4 = 16 shades of grey (bit depth)

2. 2

43
Q

How many bits does a typical US machine have?

A

8

44
Q

The binary system replies on 2 digits (1 or 0) which represents what?

A

Represents a circuit that is either on or off

45
Q

What is the advantage of having a binary system for the computer?

A

Allows for a stable and fast process since the computer only has to process 2 numbers

46
Q

Binary is great for computers but sonographers prefer a more meaningful decimal #

We can calculate the decimal # from the binary # by placing the binary # in the table….

A

See page 9 of notes

47
Q

What part of the system is resolution limited by?

A

Type of display used

48
Q

What are 2 considerations made when assessing monitor resolution?

A

Number of pixels

Size of pixels

49
Q

Hoe does changing the amount of pixels affect monitor resolution?

A

Increase amount of pixels= better resolution

50
Q

How does changing the depth affect monitor resolution?

A

Decrease the depth= improved resolution

51
Q

What type of monitors are used for digital display today?

A

LCD

52
Q

What type of monitors were used in earlier units?

A

CRT

Other modes: A, B and M mode used oscilloscope

53
Q

How did an oscilloscope work?

A

Could only display using an X & Y axis at

Refer to picture on pg 12 of the notes

54
Q

Was the oscilloscope compatible with video signal?

A

No

55
Q

How does the CRT tube work?

A

Accepts a video signal and is capable of displaying a wide range of greys

56
Q

Is the CRT equipped for displaying color? What is the color useful for?

A

It is capable and useful in Doppler applications

57
Q

What are the colours used in the CRT? How?

A

CRT had 3 electron guns - cause phosphor to light up as either red, blue and green

58
Q

What is a CRT?

A

Large glass vacuum tube that contains a cathode or source of electrons (negative)

59
Q

Where is the electron aimed?

A

Phosphor plates (positive)

60
Q

What are electric or magnetic deflections plates used for?

A

Used to steer the beam

61
Q

What does the phosphor brightness depend on?

A

of electrons that strike it

62
Q

What is the # of electrons dependent on?

A

Amplitude of the video signal

Stronger the amp= stronger electrons

Stronger electrons= brighter shade of grey

63
Q

What is a raster format?

A

Specific method used to move the electron beam

64
Q

How is the beam moved in raster format?

A

From left to right in addition to interlacing (writes odd then even lines)

65
Q

Why is interlacing used?

A

Gives us the ability to see things in real time by writing all the odd lines and then even lines - reduced our ability to see flicker

66
Q

What does a complete frame consist of?

A

525 horizontal lines produced at 30Hz (FR) — might see flicker

67
Q

Each frame has 2 fields- odd and even- what are they produced at?

A

60Hz - eliminates flicker

Refer to page 14 for picture

68
Q

Why are computer monitor superior to CRTs?

A

Have more scan lines and pixels

Pixels are smaller

69
Q

How many scan lines does a CRT use? Monitor use?

A

CRT 525 lines

Monitor 1024X768 or higher

70
Q

What kind of manner are the lines written? What does this mean?

A

Lines are written in a progressive manner which allows FRs typically higher then 60Hz

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