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Exposures II > Ch.21 > Flashcards

Ch.21 Flashcards

1
Q

-evolved in 1980s
-uses the technology of storage phosphors
pioneered by Eastman Kodak

A

Computed Radiography (CR)

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2
Q

CR two step process

A

-acquisition
-image processing and display

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3
Q

associated with photostimulable imaging plates

A

CR

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4
Q

is considered an activator as it maintains the presence of electron holes in the PSP

A

Europium

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5
Q

Common PSP phosphors

A

-Barium fluorohalide bromides
-Barium fluorohalide iodides

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6
Q

-reusable plates
-rigid sheet of several layers
-records and transmits image from xray beam
-inserted into cassette
-transferred to reader assembly for processing

A

photostimulable imaging plates

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7
Q

-best between 35 and 50 kev
-absorb more low energy radiation than radiographic film
- more exposure needed if applied kvp is outside of this range

A

K-edge attenuation

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8
Q

-more sensitive to scatter both before and after exposure, than radiographic film
-sensitive to low levels of radiation energy

A

PSP’s

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9
Q

is a digital radiographic imaging modality that uses a photostimulable storage phosphor
imaging plate (PSP or IP), typically inside
a cassette.

A

CR

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10
Q

is the method by which the data are collected from the imaging plate

A

Raster pattern

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11
Q

what type of sampling frequency gives you better detail

A

Higher sampling frequency

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12
Q

how the laser reads the CR (zig zag pattern)

A

Raster

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13
Q

what laser is erasing image, making a stable state again

A

white laser

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14
Q

what laser reads the electrons

A

red laser

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15
Q

which laser involves helium neons helps release phosphor

A

blue/violet laser

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16
Q

-xrays expose cassettes and latent image is stored in IP
-rules of positioning remain the same
-wider exposure latitude than film/screen

A

Image Acquisition

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17
Q

-Electron pattern stored in active layer of exposed IP
-Fluorohalides absorb beam through photoelectric interactions

A

latent Image production

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18
Q

if you wait to process the image for CR how much energy is lost within 8 hours

A

latent image will lose approximately 25% of its energy in 8 hours
**important to process cassette shortly after exposures

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19
Q

Two types of scanning:

A

Fast scan and slow scan

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20
Q

which scan is reading the image

A

Fast scan

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21
Q

Which scan is the plate moving through the reader

A

Slow Scan

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22
Q

-trapped eletcrons freed
-electrons move to lower energy state
-light captured by PM tubes
-PM tubes convert light to analog electronic signal
-Analog electronic signal sent to analog to digital converter
-ADC sends digital data to computer for additional processing
-IP erased via exposure to intense light

A

Reading CR data

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23
Q

Determines number of density values
-affects density and contrast of system

A

Pixel Bit depth

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24
Q

dependent upon sampling frequency and plate size

A

Matrix size

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25
Q

-raw data located and prepared
-what anatomical part is selected
-orientation of part on IP
-number of projections on IP

A

Preprocessing

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26
Q

image file size affected by

A

-pixel size
-matrix
-bit depth

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27
Q

CR Image processing
Tow step process:

A

-pre-processing
-post processing

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28
Q

-exposure field recognition
-histogram analysis
-grayscale analysis

A

pre processing

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29
Q

-frequency processing
-spacial location processing

A

post processing

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30
Q

with this processing, you can not change it or manipulate it

A

pre processing

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31
Q

With this processing, you can manipulate the image

A

post processing

32
Q

-computer looks at distribution of exposure on plate
-improper placement yields histogram analysis errors

A

Exposure field recognition

33
Q

-algorithm that detects edges of exposure versus nonexposure
-can sometimes be triggered by prosthetics or implants

A

Collimator edge identification

34
Q

-obtained image data does not match reference histogram
-computer cannot find collimated edges
-prosthetic devices
-abnormal areas of increased or decreased attenuation

A

histogram analysis errors

35
Q

clinically irrelevant data not included in image display

A

Histogram analysis: data clipping

36
Q

examples of histogram equalization

A

-normal chest xray
-bone enhanced histogram image
-soft tissue histogram image

37
Q

Cr’s responce to radiation

A

linear and nonlimiting

38
Q

for CR what cassette size is the best spacial resolution

A

Smallest cassette

39
Q

grid error that occurs with digital image receptor systems when the grid lines are cap-tured and scanned parallel to the scan lines in the imaging plate readers. This error occurs with grids used in a stationary fashion for examinations such as mobile radiography or translateral hip images.
grid lines must be running in the same direction as the movement of the laser beam that is scanning the
imaging plate

A

Moire effect

40
Q

This is your phosphor layer

A

europium flurohalide

41
Q

math algorithm of how it is read

A

Nyquist Frequency

42
Q

how often the lead occurs

A

grid frequency

43
Q

what technique is there not enough of if there is quantum noise

A

mas

44
Q

grid artifact your :

A

moire

45
Q

pixel pitch and size is inversely related to:

A

spacial resolution

46
Q

-spacial location processing
-frequency processing
-egde enhancement
-image smoothing
-image stitching

A

post processing

47
Q

Th minimum separation between two objects at which each can be distinguished as two seperate objects in the image;most similar to sharpness of detail

A

spacial resolution

48
Q

distance between center of one pixel to center of adjacent pixel

A

pixel pitch
-decreased pixel pitch=increased spacial

49
Q

The ability of the imaging system to distinguish between small objects that attenuate the x-ray beam in a similar manner; improves the visibility of the minimum density differences or shades of gray; most similar to gray scale

A

Contrast resolution

50
Q

wider window width =

A

increased contrast resolution

51
Q
  • Increased bit depth =
A

increased contrast resolution

52
Q

Increased dynamic ranges =

A

increased contrast resolution

53
Q

Manipulation of image appearance after exposure

A

post processing

54
Q

brightness alteration

A

window level

55
Q

contrast alteration

A

window width

56
Q

ount of luminance or light emission of the display monitor; opposite of density, the term used to describe blackness in film/screen

A

brightness

57
Q

what does this do to the pixel value
High brightness = high x-ray photon attenuation =

A

low pixel value

58
Q

A term used to describe the shades of gray seen in an image. In digital imaging, it is called gray scale and represents the number of different shades that can be stored and displayed on the monitor.

A

Contrast

59
Q

The minimum separation between two objects at which each can be distinguished as two separate objects in the image; most similar to film/screen’s sharpness of detail

A

 Resolution (Spatial)

60
Q

CANNOT be manipulated after exposure; dependent on image acquisition and display factors which include:

A

o Pixel size
o Number of pixels
o Pixel density
o Pixel pitch
o Sampling frequency

61
Q

Converts analog signal from the image receptor/detector to a digital signal for computer to manipulate for processing, display, and storage

A

Analog-to-Digital Converter (ADC)

62
Q

A continuously varying quantity

A

analog signal
* EX: film/screen systems, x-ray photons, light, electricity are produced in varying quantities, resulting in a continuous wave of varying energies

63
Q

A series of discrete values (used to determine pixel brightness)

A

Digital signal
Computers use discrete values (0,1)

64
Q

Automatic image software function that adjusts pixel brightness values or ranges to their expected levels for the anatomy being imaged

A

Image rescaling

65
Q

Process that takes place in the computer where the raw digital image data are corrected for flaws that are inherent in the x-ray beam, the elements and electrical circuitry of the particular imaging system, or the physical elements and electrical circuitry of the computer

A

pre processing

66
Q

Preset or reference histogram characteristics stored by the computer for each anatomical area and view; used to rescale the image if exposure conditions do not match the “ideal”

A

Look up Tables

67
Q

Generated by dividing a scanned area into pixels and determining the signal intensity for each pixel; can be calculated for specific anatomy and procedures.

A

Histogram

68
Q

What does the phosphor layer hold

A

The phosphor layer holds the pho-tostimulable phosphor, which is the active component in the plate.

69
Q

has a built in picture perfect image that is compared to
very important to select the correct body part

A

histogram

70
Q

what are examples that would show up white

A

shielding, bone, soft tissue, air

71
Q

element of phosphor

A

Europium doped barium fluorohalide

72
Q

Histogram
Look up table
Bit depth

A

Pre processing

73
Q

Window leveling
Window width
Annotation
Any manipulation to an image

A

Post processing

74
Q

lower atomic number
means what about the transmission to ir

A

more transmission to IR

75
Q

bone absorbs more so what does that mean about what is being transmitted to IR

A

less transmission to IR

76
Q
A

Exposures II (7 decks)

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