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Phys 254 > Module 2: Memory And Display > Flashcards

Module 2: Memory And Display Flashcards

1
Q

What does memory allow us to do?

A
  1. Store image
  2. Grey scale
  3. Freeze frame
  4. Cine loop
  5. Ability to post process the image
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2
Q

Another name for memory is what?

A

Scan Converter

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3
Q

Modules or circuits are designed to do what?

A

Store ultrasound information and enables the machine to build the image

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4
Q

From the memory the image goes where?

A

A display or a recording device

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5
Q

What are some difference between analog and digital?

A

Analog - Digital
Continuous values - Discrete values
Prone to drift - stable
Less reproducible - reproducible

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6
Q

The analog scan converter is similar to what?

A

CRT except that the phosphor face is replaced with a wafer of silicon called dielectric matrix

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7
Q

How does a analog scan converter work?

A

Electrons are emitted by filament, pass through the deflection plates and strike the silicon wafer leaving a positive charge

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8
Q

For a analog scan converter, the charge is proportional to what?

A

Amplitude of signal strengths

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9
Q

What is the main advantage to the scan converter?

A

It allows for gray scale

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10
Q

Besides grey scale what is a benefit of analog scan converter?

A

It acts as a buffer between images and display with good short term memory

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11
Q

What is the disadvantage for analog scan converter?

A

The analog scan converter is prone to drift and there was no long term memory

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12
Q

What do we use today in terms of memory?

A

Digital scan converter or computer

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13
Q

Why is the digital scan converter reliable and versatile?

A

They can be connected to many other systems or cameras and have superior resolution

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14
Q

What is the matrix of the Digital scan converters?

A

Typically 1024 x 768 which is divided into small rectangular square picture elements called pixels

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15
Q

For digital scan converters each pixel contains what?

A

A digital number to represent the amplitude of the received echo

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16
Q

For a digital scan converter a 1024 x 768 matrix has how many pixels?

A

786,432

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17
Q

What is a matrix essentially?

A

A checkerboard arrangement of pixel locations on a grid

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18
Q

For a digital scan converter each square of the matrix stores what?

A

Data that represents the grayscale information of returning echoes

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19
Q

Computers operate in what?

A

Binary code

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20
Q

Because binary code is consisted of 1 and 0’s. How do we get several shades of grey?

A

The 1 and 0s get stacked. This combination of the binary digits can represent many shades of grey.

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21
Q

For digital scan converters a pixel is what?

A

Picture element and is the smallest form of display so this means the more pixels we have the better for resolution.

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22
Q

In terms of bit what is 1 bit?

A

1 or 0

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23
Q

What is 8 bits of data?

A

10010101 (bits in groups of 8)

24
Q

What are word?

A

Combination of bits expressed as a unit

25
Q

What is word length?

A

Number of bits in a word

26
Q

What is bit depth?

A

The word length at each address location

27
Q

What is RAM?

A

Random access memory - fast, rewritable, cheap and erased when the machine is turned off.

28
Q

What is ROM?

A

Read only memory - permanent and used for system function

29
Q

What is the formula for bit depth?

A

2^n (N is the bit depth or the number of bits used at each address location to store the echo data received)

30
Q

As we increase the bit depth, what happens?

A

We increase the shades of grey that the system can produce.

31
Q

What is the typical u/s machines bit?

A

8 bits

32
Q

The binary system relies on 2 digits - 1 or 0 represents what?

A

A system that is either on or off

33
Q

How to find the decimal number that represents the following binary numbers?

A

Place the binary number in the table and add all the 1’s

34
Q

Ultrasound systems operate to provide the best resolution images but is limited by what?

A

The type of display used

35
Q

The two considerations for binary made what are the two considerations made?

A

The number of pixels and the size of the pixels

36
Q

In terms of monitor resolution, the more pixel we have what would happen?

A

The resolution will be better

37
Q

Why would more pixels in a finite space increase the resolution?

A

The size of the pixels must decrease to fit the monitor

38
Q

In terms of display, modern day ultrasound units use what?

A

LCD monitor for display

39
Q

Earlier units uses what type of display?

A

CRT (cathode ray tube)
A mode and B mode used an Oscilloscope

40
Q

The Oscilloscope was the first to use what?

A

CRT

41
Q

For a oscilloscope it could only display using what?

A

X, Y axis and is not compatible with video signal.

42
Q

The CRT display accepts what?

A

Video signal and is capable of display a wide range of greys

43
Q

If equipped, the CRT is also capable of what?

A

Displaying colour which of course is useful for doppler applications

44
Q

What is a CRT?

A

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

45
Q

How does a CRT work?

A
  1. The electron beam is aimed at phosphor plate (positive)
  2. Electrical or magnetic deflection plates are used to steer the beam and the phosphor brightness will depend on the number of electors that strike it.
46
Q

For a CRT The number of electrons is dependent on what?

A

The amplitude of the video signal

47
Q

For CRT displays how do we obtain colour?

A

There are three electron guns that cause the phosphor to light up either red, green, or blue

48
Q

What is raster format?

A

The ability to move the electron beam

49
Q

So what happens with the raster format?

A

The beam is moved from left to right and in addition interlacing is used to first write the odd lines and then the even lines.

50
Q

A complete frame consists of what?

A

525 horizontal lines produced at 30 hz (frame rate)

51
Q

Each frame has how many fields?

A

Two fields, the odd and the even, produced at 60 Hz.

52
Q

Why does each frame has two fields?

A

It is done to help reduce the appearance of flicker to the observer

53
Q

Computer monitors are superior to CRTs how?

A

They have more scan lines and pixels and the pixels are smaller

54
Q

Where CRTs use 525 lines, Monitors use how many?

A

1024 x 768 higher

55
Q

The lines in displays are written with what?

A

Progressive manner with frame rate typically higher than 60 Hz

Phys 254 (19 decks)

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