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Radiology > Imaging > Flashcards

Imaging Flashcards

1
Q

Different types of dental film & their qualities?

A

D speed = slower, more radiation, better image quality
F speed = faster, less radiation, loss of image quality (still diagnostic)

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2
Q

What are the contents of the film packet?

A
  • packet with opening tab
  • lead foil
  • black light proof paper
  • film
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3
Q

Purpose of lead foil in film?

A
  • protect from back scatter radiation that can cause a re-exposure
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4
Q

In a cross-section of film what is it composed of from outside in?

A
  • supercoat: thin layer hard plastic
  • emulsion: gel & silver-halide crystal
  • adhesive
  • base: plastic
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5
Q

The chemical changes in film processing are dependent on what factors?

A
  • time, temperature, & concentration
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6
Q

What is a pixel?

A

“picture element”
- smallest portion of sensor/image capable of being recorded & then printed/displayed

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7
Q

What are the 4 general steps in digital image formation?

A
  • x-ray shadow
  • shadow image detected by digital sensor
  • numerical pixel values sent to computer
  • digital image on computer screen
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8
Q

How are numerical values assigned to each pixel?

A
  • pixels are electrified by x-ray
  • each pixel has pre-exposure charge
  • x-ray photons make it to sensor change the charge
  • the thicker/denser object, the less photons can affect the charge of the pixel
  • net effect is that there is a shadow of electric charges on the sensor reflective of the thickness/density of the body part
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9
Q

What is meant by digitization?

A

electrical voltage is converted into numerical value by computer

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10
Q

How is the digital image displayed on the computer screen?

A
  • computer assigns gray value for each number to the location on the XY grid axis of the sensor
  • gray values are displayed in visual format on monitor
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11
Q

Example of semi/indirect dental digital radiography?

A

PSP: phosphor storage plate

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12
Q

Examples of direct dental digital radiography?

A

CCD: charge coupled device
CMOS: complementary metal oxide semiconductor

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13
Q

What is the PSP plate coated with?

A
  • crystalline halide emulsion: BaFBrEu2+
    –> Europium doped barium fluorobromide
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14
Q

What is the purpose of doping the PSP plate in europium?

A

holds the charge

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15
Q

Describe the steps of the PSP detector?

A
  • x-rays hit PSP plate coated in BaFBrEu2+ producing a latent image of ionized phosphors
  • PSP scanned with red laser beam
  • emit fluorescent light from excitation of valence electrons in ionized fluorophosphors
  • intensified by photomultiplier tube
  • light intensity converted to digital data
  • expose to strong light to erase residual images by neutralizing charges
  • reuse
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16
Q

T/F PSP plates are sensitive to light?

A

true, but not as sensitive as film (up to 10s)

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17
Q

What type of solid state sensor requires analog to digital converter?

A

CCD: charge coupled device

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18
Q

What is the function of the analog to digital converter?

A

electrical signal from sensor must be read out here before sent to computer

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19
Q

What is the size comparison of film, PSP, and digital sensors?

A

all similar in size because based off film

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20
Q

What is the minimum thickness a digital sensor can have?

A

4 mm (rigid & not as comfy in mouth)

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21
Q

What is the scintillator function in solid state sensors?

A

optimized for resolution & low noise
- cesium iodide

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22
Q

What are the components of digital sensors?

A
  • electronic substrate (ceramic)
  • imaging chip
  • fiber optic face plate (xray filter)
  • CSI scintillator
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23
Q

What are the drawbacks of direct sensors?

A
  • rigid & uncomfortable
  • actual image capturing area is less than external size (78%)
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24
Q

What is the pixel size in solid state sensors?

A

15 uM2

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25
Q

T/F solid state/direct sensors have greater resolution than film?

A

false: but still diagnositc

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26
Q

What is the main difference between CCD & CMOS?

A

CCD requires an additional/adjunct power box to convert photon energy into electrical digital signal

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27
Q

What is the sequence of the CCD detector?

A
  • x-ray
  • scintillating material
  • light photons
  • silicon
  • e- in wells of pixel
  • pixel signals transferred in sequential manner (charge-coupling) to be digitized
  • read-out amplifier
  • images on monitor
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28
Q

What is the sequence of the CMOS detector?

A
  • x-ray
  • scintillating material
  • light photons
  • silicon
  • e- in wells of pixels & converted to voltage
  • smoother signal digitization
  • software processing
  • images on monitor
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29
Q

Which is faster & efficient at transferring electrical signal into digital image?

A

CMOS

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30
Q

Which has greater power consumption? CCD or CMOS

A

CCD

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31
Q

Which is more sensitive to x-rays? CCD or CMOS

A

CCD (positive)

32
Q

Which has higher noise? CCD or CMOS

A

CMOS

33
Q

Which has a simple readout? CCD or CMOS

A

CMOS

34
Q

What are the pixel signals in CCD & CMOS?

A

CCD: e-
CMOS: voltage

35
Q

What is the chip output for CCD & CMOS?

A

CCD: voltage (analog)
CMOS: bit (digital)

36
Q

What is the system complexity & sensor complexity of CCD?

A

high / low

37
Q

What is the system complexity & sensor complexity of CMOS?

A

low / high

38
Q

Is CMOS or CCD a new technology?

A

CMOS

39
Q

What is a bit?

A

depth of colors / gray shades that a pixel can show
aka: number of shades of gray

40
Q

How do you calculate the number of shades of gray?

A

2^bit

41
Q

What is the ideal bit range & why?

A

8-16 (any higher and we just cannot see those extra shades)

42
Q

Why is digital imaging appealing?

A
  • significantly less radiation
  • better image?
  • rapid acquisition & storage
  • image PORTABILITY
  • lower cost (less chair time, no additional costs for equipment, no darkroom)
  • environmentally friendly
43
Q

What type of digital image modification describes the use of mathematical operations called matrix transformations?

A

qualitative

44
Q

What type of digital image modification describes measuring lengths / # of pixels for length, area, value, etc.?

A

quantitative/analytical

45
Q

What are examples of qualitative modifications?

A
  • magnify
  • adjust contrast
  • brightness
  • grayscale
  • colors
  • swap b&w
46
Q

What are post-display mathematical algorithms used to modify the digital signal?

A

image manipulations/enhancements

47
Q

T/F imaging manipulations can increase the images diagnostic accuracy?

A

false

48
Q

Is noise reduction used in dental radiographs?

A

NO, may degrade or remove important diagnostic information

49
Q

What describes making dark shades darker and light shades lighter?

A

sharpening

50
Q

Is the sharpening/edge enhancement feature used in dentistry?

A

NO, can simulate disease / change density pattern completely

51
Q

What does penumbra mean?

A

unsharp

52
Q

How does the size of the radiation source (focal spot) affect the sharpness?

A

the smaller the focal spot, the sharper the image // less penumbra
–> due to less xray photons

53
Q

How does source to object distance affect image sharpness?

A

The farther the object away from the xray source the sharper the image
–> less divergent photons // more parallel

54
Q

What factors can we manipulate to increase sharpness?

A
  • source-to-object (length of cone)
  • object-to-receptor (place receptor close to tooth)
55
Q

How does object-to-receptor distance affect image sharpness?

A

the closer the object to the receptor, the sharper the image
–> less divergent photons due to less time to diverge away from tooth

56
Q

What are the 2 rules to minimize magnification?

A
  • source to object distance
  • object to receptor distance
57
Q

How does the source to object distance affect magnification?

A

the farther the object from the source the less magnification

58
Q

How does the object to receptor distance affect the magnification?

A

The closer the receptor to the object the less magnification

59
Q

What term describes unequal magnification or variance from true shape?

A

distortion

60
Q

What factors affect distortion of the image?

A
  • alignment of receptor, object & beam
61
Q

What are the 2 rules to minimize distortion?

A
  • beam perpendicular to object & receptor
  • object & receptor should be parallel
62
Q

How does foreshortening occur?

A
  • tooth is not parallel to receptor & the beam is perpendicular to the receptor
63
Q

How does elongation occur?

A
  • tooth is not parallel to receptor & beam is perpendicular to tooth
64
Q

What technique do we use at UMKC for periapical radiography?

A

paralleling

65
Q

What length cone should you use with the paralleling technique?

A

long

66
Q

What is the alternative method for taking PA radiographs?

A

bisecting angle

67
Q

What length cone should you use for the bisecting angle technique?

A

short

68
Q

What is the limitation of the paralleling technique?

A

maxilla is curved & cannot always get receptor close to tooth (object to receptor distance increased)

69
Q

How do we compensate for the curvature in the maxilla with the parallelling technique?

A

we use a long cone (source to object distance increased)

70
Q

What can occur if the beam and receptor are not aligned properly?

A

cone cut

71
Q

How does the bisecting angle technique work?

A
  • tooth & receptor are not parallel
  • beam is directed perpendicular to the bisecting line
72
Q

How many radiographs compose a full mouth series (FMS)?

A

18 or 20

73
Q

What are the 2 methods for radiographic localization?

A
  • right angle
  • tube shift / SLOB
74
Q

How to do the right angle method for localization?

A
  • straight on PA
  • cross-sectional occlusion
75
Q

How to do tube shift technique?

A
  • straight on PA
  • shift tube M or D
  • if object moves same direction as shift then it is lingual
  • if object moves opposite direction as shift then it is buccal

Radiology (5 decks)

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