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arrt prep > essentials of DR & CR > Flashcards

essentials of DR & CR Flashcards

1
Q

what plate does CR use?

A

PSP plate

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2
Q

CR is also called

A

cassette based

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3
Q

the psp plate is made out of what

A

barium fluorohalide dope with europium*

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4
Q

scintillation means

A

light

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5
Q

DR image receptors

A
  1. flat panel
  2. CCD
  3. CMOS
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6
Q

what does CCD stand for

A

charged couple device

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7
Q

what does CMOS stand for

A

complementary metal oxide semi- conductor

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8
Q

if you want breast implants, and INDIRECT WAY to get implants is….

A

amorphous silicon

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9
Q

direct uses

A

amorphous selenium

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10
Q

both CR & DR are

A

digital

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11
Q

computed radiography is the generic term applied to an imaging system comprised of….

A
  1. photostimulable storage phosphor: to acquire the x-ray projection image
  2. CR reader: to extract the electronic latent image
  3. digital electronics: to convert the signals to digital form
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12
Q

Flat panel DR system may use either ________

A

indirect
direct

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13
Q

direct detectors

A

Convert exit radiation directly into electric charges, speeding image construction

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14
Q

indirect detectors

A

convert exit radiation first to visible light, then to electrical charges

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15
Q

electrical signals from either direct or indirect detectors are converted from

A

analog to digital

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16
Q

viewing of the digital image, normally takes place on a computer monitor also known as? 

A

-cathode ray tube ( CRT)
-Liquid crystal display (LCD)

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17
Q

exposure latitude

A

the range of exposures that produce quality images at appropriate patient doses

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18
Q

dynamic range

A

includes the good the bad and the ugly
-quantum mottle ( low exposure)
-saturation ( high exposure)
-the range of exposures that may be captured by a receptor

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19
Q

what is a histogram? 

A

it’s a graphic display
-is constructed to show the radiograph or the distribution of pixel values, indicating low, proper or high contrast
-sorts it into a bar graph
-sorting your candy after halloween

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20
Q

quantum mottle

A

grainy
noisy
ITS NOT BLURRY ***
-caused by too few photons hitting the image receptor

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21
Q

quantum mottle versus quantum noise

A

mottle: used be in film
noise: digital
it’s the same thing *

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22
Q

CR and DR artifacts

A
  • dust
    -improper use of grids
    -scatter radiation is easily imaged in digital imaging
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23
Q

DICOM stands for

A

Digital imaging and communication system 

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24
Q

PACS

A

Picture archiving and communication system 

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25
Q

RIS

A

radiology information system 

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26
Q

HIS

A

hospital information system 

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27
Q

ghost image 

A

when you see remnants of a prior exposure because the plate didn’t get erased enough 

28
Q

dose creep

A

when techs increase the mAs to eliminate noise which increases pt dose.

29
Q

what clears the CR plate

A

a really BRIGHT WHITE LIGHT

30
Q

what is a FOV?

A

how much of the patient you are seeing
-small FOV gives you smaller pixels

31
Q

CR barcode label is used to

A

allows the technologist to label the image with the patient information 

32
Q

label and order the imaging plate construction for CR ( hint there’s six steps) 

A
  1. Protective layer
  2. Phosphor or active layer
  3. Conductive layer
  4. Support layer
  5. light shield reflective layer
  6. Backing layer
33
Q

protective layer

A

Thin, tough, clear plastic that protects the active phosphor layer
-made of carbon or magnesium
-no image producing qualities. 

34
Q

phosphor or active layer 

A

this is a layer of photo stimulable phosphor from the barium fluorohalide family , ability to store and release energy 

35
Q

Conductive layer

A

layer of material that grounds the imaging plate from electrostatic charge - increases spatial resolution by absorbing light

36
Q

support layer

A

Semi rigid material that gives the imaging sheet some strength 

37
Q

light shield reflective Layer

A
  • sends light in a forward direction when released in the reader prevents unwanted light from affecting the unexposed latent image
38
Q

backing layer

A

Soft polymer that protects the back of the cassette
prevent unwanted background radiation from affecting on expose latent image 

39
Q

latent image

A

invisible image

40
Q

after exposure CR process is what? list in order

A
  1. The imaging plate must be processed to release the latent image from the radiation detector( image plate)
  2. The lane image or stored energy is released from the phosphor layer by placing the image play into a laser reader.
  3. The CR laser reader uses a red helium, neon laser light to scan the information from the imaging plate.
  4. When the red laser hits the imaging play, the plate releases a blue visible light.
  5. Dislyte is done captured by the photo multiplier tube to create the manifest image(visible image)
  6. Image plate is erased with a bright white light in return to cassette. 
41
Q

manifest image

A

the visible image

42
Q

when the plate is going through the reader, the mechanism that moves the imaging plate is called ____ scan. the direction of laser is called ____ scan.

A

slow scan
fast scan

43
Q

Reading the imaging plate for CR

A

-Red laser light skins in a raster pattern at two easy.
- Laser scans multiple times as imaging plate moves through reader
-light produced detected by photo multiplier.
-When the red laser hits, the imaging plate plate releases a blue visible light.
- laser = light amplification by stimulated emission of radiation
-The diameter of the Laser beam affects the spatial resolution of CR imaging system

44
Q

what does the photomultiplier tube do?

A

The photo multiplier tube is used to convert small amount of light into an amplified electrical signal.

45
Q

what doesto the Analog to digital converter do?

A

The resulting signal from the photo multiplier tube the analog to digital converter, determines the number of shades of gray in the image.
- concerts the electrical signal and turns it into a digital one!

46
Q

how long will the imaging plate hold the image before it disappears

A

up to 8 hrs

47
Q

primary erasure for CR plate

A

The CR plate was accidentally left in the x-ray room during another exposure in the area of the primary been the primary erasure option should be used

48
Q

secondary erasure for CR plate

A

used for background radiation CR plate that are outside of the x-ray room but have not been used for 24 to 48 hours should be secondary erased.
- background radiation 

49
Q

ghosting error

A

CR plate erasure error
One image is properly exposed, but then you see the other image outside the collimated field
the cause: incomplete erasure of imaging plate.
* think of a ghost it stills there*

50
Q

CR grid error

A

Morrie pattern
wavey

51
Q

what is used to erase the CR plate

A

a bright white light

52
Q

digital radiography are spilt into two categories… what are they?

A
  1. indirect
    - TFT set up
    -CCD set up
  2. Direct
53
Q

indirect has a 3 step process

A
  1. x-rays interact with image receptor.
  2. X-rays are converted to let using a scintillator
  3. Light is converted to electrons.
    Material used is amorphous silicon. ( indirect way to get fake boobs)
    XLE
54
Q

direct is a 2 step process

A
  1. x-rays interact with image receptor.
  2. X-rays are directly converted to electrons
    - skips like conversion step!
    material used is amorphous selenium*
    XE 
55
Q

TFT System layers: indirect!

A

-made up of three layers.
1.scintillator
2.photodiode
3. TFT

56
Q

scintillator layer 

A

it’s the first layer
- it is a light layer
- x-ray photons were converted to light photons
-disadvantage= is it produces light in all directions which reduces spatial resolution
material cesium iodide** or galolinium

57
Q

photo diode layer

A

Second layer comprised of amorphous silicon
- the silicon senses, visible light,
- each x-ray, photon, absorbed within the scintillating layer, generates a sparkle, a visible light that is detected by the silicon sensor.
-Converting incoming light photons from the scintillation layer into electric charge.

58
Q

TFT

A

third layer
- comprised by in array of matrix a very small detector element (DELS)
- Each DEL is comprised of capture, element or pixel detector( PIXEL)
- and there’s a storage capacitor
- acts like a switch and sends it to ADC
-collects the electrical signal
- they don’t convert anything!

59
Q

fill factor

A
  • is the percentage of the pixel an additional radiographic image that is sensitive to the incoming x-ray beam in allows conversion of incident x-ray beam into light.
    Higher fill factor = higher, spatial resolution!
    -higher fill factor preferred! 50-80%
60
Q

CCD model- for Indirect

A
  1. scintillator
  2. fiber optics ( coupling device, connects the two components)
  3. CCD
61
Q

scintillation layer for CCD indirect system

A

x-rays interact with scintillation layer and converts x-rays indivisible light 

62
Q

what does the fiber optics / lenses do?

A

The scintillation layer is optically couple to the CCD sensor chip
- basically connects the scintillation layer and the CCD

63
Q

CCD’s are able to do both jobs which are?

A

-convert light photons to electrical signals,
-as well as an electrical signals to the computer for processing
- does the job of the photodiode and the TFT*!!

64
Q

CCD vs CMOS

A

updated CCD they do the same thing!

65
Q

direct conversion layers

A
  1. semiconductor.
  2. thin Flat panel transistor
    * NO SCINTILLATOR!!!

arrt prep (24 decks)

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