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RAD 122 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

Exact quantities

A

Digital

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2
Q

To go from analog to digital: assign __________ after ________ the analog curve

A

A numerical value (quantization)

Sampling

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3
Q

Sample at least twice; at least twice the frequency = good representation

A

Nyquist theory

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4
Q

⬆️matrix ️size _____ ️resolution

A

⬆️

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5
Q

⬆️pixels _____ ️resolution

A

⬆️

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6
Q

The assignment of 1’s and 0’s
0=
1=

A 
0= open
1= closed
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7
Q

The smallest unit

Single unit of data

A

Bit

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8
Q

1 byte =_____ bits

A

8

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9
Q

CR is ______ in its latent form

A

Analog

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10
Q

Where is the latent image stored in a PSP

A

In the phosphor layer

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11
Q

What are the phosphors made of in a PSP

A

Barium fluoro halides doped with europium

Halides can be iodine or bromide

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12
Q

What does CR eliminate from film screen system

A

Chemical processing

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13
Q

What happens to PSP when hit with xray

A

50% return to ground state immediately resulting in light (luminescence)
The other 50% is stored in phosphor crystals (losing signal over time must be read promptly)

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14
Q

T/F CR PSP is extremely sensitive to scatter radiation

A

True

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15
Q

How many shades of gray are found in digital CR image

A

10000

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16
Q

In the reader slow scan = _______

A

Mechanical drive

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17
Q

Fast scan =_______

A

Lasar row by row rastar scan function

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18
Q

_________ layer of PSP prevents backscatter from reaching the image

A

Reflective layer

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19
Q

What collects light and converts to an electric signal in reader

A

Photomultiplier tube

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20
Q

What is ADC

A

Analog to digital converter

Sampling and quantifization

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21
Q

What I the last step in reader before PSP is returned to case

A

PSP is flashed with a bright white light to release left over energy

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22
Q

What is ghosting

A

Left over image on PSP

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23
Q

CR advantages

A

Computerized image
Initially less expensive
Easy for mobile imaging

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24
Q

CR has ⬆️or⬇️contrast resolution than film

A

⬆️

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25
Q

Disadvantage to CR

A

️decrease special ️resolution

Creep (ALARA)

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26
Q

Histogram errors may be caused by

A

Caddy cornering body part
Random placement of body parts
Selectin wrong body part on console

27
Q

Histogram errors can result in

A

Improper rescaling of image
Improper index #
Improper masking

28
Q

Continuously varying (clock with a second hand, latent image in CR and film)

A

Analog

29
Q

Imaging plate layers from top to bottom (6)

A 
Protective clear coat
Phosphor layer
Reflective/ protective
Base
Anti static
Lead
30
Q

Why are 3 main sub system components of CR reader

A

Mechanical components
Optical components
Computer modules

31
Q

How is xray turned to light with DR indirect TFT

A

Indirect using scintillator with cesium iodide or gadolinium oxysulfide

32
Q

What converts light into electrons in DR TFT flat panels

A

Photodiode amorphous silicon

33
Q

TFT flat panels are considered

A

Active matrix array (AMA)

34
Q

What turns xray into light with DR indirect CCD

A

Scintillator cesium iodide

35
Q

How does light travel in DR CCD

A

In fiber optic bundles

36
Q

What turns light into electrons in DR CCD

A

Multiple CCD photodiodes

37
Q

Layers of CCD

A

Scintillator - cesium iodide
Fiber optics
Multiple CCD photodiodes

38
Q

Layers of TFT

A

Scintillator - cesium iodide/ gadolinium oxysulfide
Amorphous silicon - photodiode
Pixel matrix with photodiode, storage capacitor and TFT switch

39
Q

Number of shades of gray a pixel can represent

A

But depth

40
Q

Using the laser to read the imaging plate, the laser is ________um in size and the narrower the beam _______ the ️resolution

A

100

Better

41
Q

Digital radiography was first introduced by

A

Fuji 1981

42
Q

Computed radiography cassettes and film/screen cassettes can be used interchangeably t/f

A

True

43
Q

Computed radiography screens respond to radiation with

A

Photostimuable luminescence

44
Q

A photo stimulator phosphor in a metas table state will emit light

A

Immediately
When stimulated
Over time

45
Q

Europium is the ______ if the photostimulable phosphur

A

Activator

46
Q

The computed radiography cassette is called a ________ plate

A

Imaging

47
Q

The photostimulable phosphur screen is handled in a _____

A

Reader

48
Q

The computed radiography reader is made up of ______,_______, and ______ modules

A

Mechanical
Optical
Computer

49
Q

The four steps of creating an image with computed radiography are

A

Metastable state, stimulate, read, and erase

50
Q

Following the laser stimulation o the photostimulable phosphur the excited electrons are

A

Mostly stabilized

51
Q

The digital imaging plate can sit for some time after the erase cycle

A

False

52
Q

The laser is one of the ______ features of the computed radiography reader

A

Optical

53
Q

Optical filters are used to filter out the _____ light an allow the_____ light to reach the photodetector

A

Stimulated, emitted

54
Q

The output signal from the photostimulable phosphor plate is converted from analog to digital by the

A

Photodetector

55
Q

Computed radiography and screen film imaging both have a

A

Latent image

56
Q

Spatial resolution ️contrast ️resolution noise and artifacts are identical in screen film imaging an CR

A

False

57
Q

The principal source o noise in CR is

A

Scatter

58
Q

The 400 ️️speed film screen systems are still faster than computed radiography image receptors

A

False

59
Q

With computed radiography the ️contrast is

A

Constant regardless of radiation exposure

60
Q

The computed radiography image has

A

Wide exposure latitude and improved ️contrast ️resolution

61
Q

When switching from screen film imaging to computed radiography which step is eliminated

A

Reloading the cassette and chemical processing

62
Q

_________ is prevented by flooding the erased imaging plate with bright light

A

Ghosting

63
Q

Computed radiography imaging produces ______ grey levels

A

10000

64
Q

Switching from screen film imaging to computed radiography can ____ pt dose

A

Reduce

RAD 122 (3 decks)

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