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Physics > Ultrasound Instrumentation > Flashcards

Ultrasound Instrumentation Flashcards

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1
Q

What does analog refer to?

A

Variable which can contain a number of variables

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2
Q

What does the CRT consist of?

A

Glass vessel that contains an electron gun that is heated and produces free electrons from the cathode filament

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3
Q

How are electrons accelerated across the glass container?

A

High voltage

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4
Q

How is the electron beam focused?

A

By vertical and horizontal deflection plates

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5
Q

What is the electron beam focused to hit?

A

Phosphor screen

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6
Q

What is emitted by the phosphor screen when the electron beam hits it?

A

Light- proportional to intensity/amp of electrons

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7
Q

What was the oscilloscope initially used for?

A

A-mode

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8
Q

What type of CRT allows the image to be viewed directly during and after image build up?

A

Special purpose storage CRT

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9
Q

What type of scanning used special purpose storage CRT?

A

B-mode scanning

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10
Q

What is the most basic way of displaying US information?

A

CRT

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11
Q

What replaced the use of special purpose storing CRT?

A

TV screen

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12
Q

What is the positive end within the glass envelope?

A

Phosphor end

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13
Q

What contains the 10000volts with in the glass envelope that applied across the tube?

A

Vacuum

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14
Q

What happens when there is an increase in the amount of electrons liberated at the filament?

A

Brighter picture

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15
Q

What does the control grid do?

A

Method of controlling the amount of electrons which proceed to the phosphor end of the tube

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16
Q

Why is a large size of dot not the best for creating an image?

A

A large dot size will eradicate the benefits of even the best axial resolution

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17
Q

What is the purpose of the focusing lens?

A

Focuses a wide stream of electrons into a narrow tightly coiled beam

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18
Q

What is the purpose of the x and y focusing plates?

A

Also you to steer the electrons toward the imaging plate

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19
Q

What is the storage mesh?

A

Electrons pass through the collector mesh and hit the storage mesh knocking the electrons off leaving a positively charged latent image

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20
Q

What is the collector mesh?

A

Grounding device- attracts those little old dislodged electrons and safely grounds them out

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21
Q

What are the flood gun(s)?

A

Spray a gentle flood of electrons towards the phosphor

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22
Q

How does the latent image leave the storage mesh?

A

Electrons from the gun are attracted to the areas of positive charge on the storage mesh, and it is at these places that these electrons get through the storage mesh and to the phosphor

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23
Q

What were the 2 main disadvantages of CRTs?

A
  1. Image deterioration was rapid

2. Few shades of grey - bistable

24
Q

What is a analog scan converter?

A

Stores an image in one form and displays it in another form

25
Q

How does the ASC work?

A

Stores the image as a series of electrical charges on a dielectric matrix and then reads out this information for display as dots of light on a conventional television monitor

26
Q

What was the major advantage of the analog scan concerted?

A

Grey scale

27
Q

Are their flood guns in the analog scan converter?

A

No

28
Q

What is the purpose of the field mesh/anode?

A

Cause electrons to strike the target at right angles, and also to collect the stray electrons which are deposed from the dielectric matrix

29
Q

What is another name for dielectric matrix?

A

Storage target

30
Q

What is the dielectric matrix made of?

A

Silicon wafer

31
Q

What occurs to the electrons when they reach the target?

A

Dislodge electrons from the matrix leaving a positive charge forming the latent image

32
Q

How is the latent image read in the ASC?

A

Signal plate placed behind matrix- medium energy level electrons are accelerated through the positively charged areas on the matrix in a raster scan fashion

33
Q

What occurs after passing through the positively charged areas of the matrix?

A

The electron beam carries with it information regarding the relative signal amplitudes

34
Q

What controls the level of brightness or spot brightness of the US signal in the TV monitor?

A

Video signal

35
Q

How many scan lines are there in each conventional frame on a TV?

A

525

36
Q

What is the FR of a conventional TV?

A

30

37
Q

How long is each field (odd and even) formed in?

A

1/60th of a second

38
Q

What is the FR when our eyes can detect flicker?

A

20

39
Q

In A mode what does the height of deflection measure?

A

Strength of returned echo

40
Q

When is A Mode useful?

A
  1. Determine whether an echo –free structure is fluid-filled or contains solid homogenous material
  2. If a structure is pulsatile
  3. Aid in cyst puncture
  4. Use in echoencephalography
41
Q

How are echo signals represented in B-mode?

A

Brightened dots corresponding to echo intensity/amp

42
Q

What is B-mode used to display?

A

Static and real time scanners

M-mode

43
Q

What is the advantage of static B scanning?

A

Large FOV

44
Q

What are the disadvantages of static b scanning?

A

Long imaging distance
Scan arm was difficult to maneuver
Very operator dependent
Image was static

45
Q

What is m-mode?

A

A series of B mode dots being displayed on a moving time basis

46
Q

What is a limiting factor of m-mode?

A

Represents only one anatomical plane

47
Q

What is c-mode (constant depth scanning)?

A

Incorporation of static b scanning using additional electronics

48
Q

What is PRF?

A

Number of voltage pulses sent to the transducer each second

49
Q

What are the PRF ranges?

A

4-15kHz (5-30 in Doppler)

50
Q

How should you PRF be sent to receive information for display at a rapid rate?

A

High PRF

51
Q

What can improve the reduction of acoustic output (reduced echo amplitude)?

A

An increase of amplifier gain!

52
Q

What are the operations occurring in pulse delay?

A

Steering, scanning, transmission focusing, aperture and apodization

53
Q

What is a channel?

A

Independent signal path consisting of a transducer element, delay and possibly other electronic components

54
Q

Define gain as a ratio

A

Ratio of the amplifier output to the electric power input

55
Q

What functions accomplish reception apodization and dynamic aperture function?

A

Part of the summer (adder) process

Physics (3 decks)

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