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D1 Radiology > OMR LEcture 4 > Flashcards

OMR LEcture 4 Flashcards

1
Q

film has 2 principal components

A
  1. emulsion - coats both sides

2. base - supporting b=plastic materia

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2
Q

what the is the emulsion?

A

-(chemical coating) it is the photon sensitive silver halide grain and suspension vehicle

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3
Q

what type of film is used intra-orally?

A

direct exposure

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4
Q

what is sheet film used for?

A
  • intensifying screens

- used for Panographic, TMJ and Cephalometric x-rays

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5
Q

how should the film dot be oriented?

A
  • dot oriented toward the tube head (radiation source) and the dot goes toward the slot
  • the raised bump points to the source of radiation
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6
Q

what is intra-oral film size 0?

A

0 = pedo

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7
Q

what is intra-oral film size 1?

A

1= adult anterior

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8
Q

what is intra-oral film size 2?

A

2= adult posterior

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9
Q

what is intra-oral film size 3?

A

3 = long posterior

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10
Q

what is intra-oral film size 4?

A

4= occlusal

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11
Q

how does the size of the silver halide crystals affect the speed of the film?

A

-the larger the crystals of silver halide the faster the film speed

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12
Q

what film is the slowest?

A

c film = slowest
-has smaller grains
need more light and photons to expose this

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13
Q

what film is the fastest?

what does it look like?

A

F film is the fastest

-it it more grainy

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14
Q

D fil is ASA about?

A

100

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15
Q

benefit of cassettes?

A

Cassettes require less radiation to expose film

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16
Q

radiographic dentist is influenced by what 6 things?

A
  1. mA
  2. kVp
  3. exposure time
  4. focal spot to film distance
  5. subject density
  6. subject thickness
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17
Q

in the film packet where is the lead place?

A

in the back

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18
Q

how to know by the radiograph id the film was in backwards?

A

-if a pattern is evident- means the lead film backing was in front

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19
Q

what is the order or contents of the film packet from the back to the front?

A 
outer package
lead foil backing
inner paper wrap
dental film
inner paper 
outer package
-tube head
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20
Q

what is the function of a grid in a cassette?

A

grids reduce scatter and “fog” radiation

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21
Q

what are the 5 steps of processing film in the dark

A
  1. developer- converts exposed silver halide crystals (latent image) to metallic silver grains
  2. wash - removes developer
  3. fixer - removes undeveloped silver halide crystals and then hardens and shrinks the emulsion
  4. wash - removes the fixer
  5. drying - makes it safe to handle
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22
Q

what does the developer do?

A

the developer converts the exposed silver halide crystals to metallic silver grains

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23
Q

what does the fixer do?

A

fixer - removes undeveloped silver halide crystals and then hardens and shrinks the emulsion

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24
Q

the intraoral film is ___________?

the cassette film is ___________?

A

intraoral film = monochromatic

cassette film = polychromatic

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25
Q

what happens to very 10 degrees celsius increase in the processing temperature?

A

the rate of the reaction dubles

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26
Q

number 1 vs number 2 introral film sizes for the # of radiographs taken

A 
#1 - 21 radiographs taken
#2 - 18 radiographs taken
-less exposure
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27
Q

at 68 degrees how long does it take to process the film?

A

5 minutes

28
Q

at 80 degrees how long does it take to develop film?

A

2.5 minutes

29
Q

what is the most economical means of developing films?

A

manual processing

  • but its most time consuming
  • produces the best radiographs
30
Q

what is the most efficent way to process film?

A

automatic processors

31
Q

what type of film requires less exposure time and why?

A
  • fast film because it has larger silver halide crystals

- downside is it is grainy

32
Q

fast or slow film requires more radiation or photons to expose it?

A
  • slow speed film requires more radiation b/c the silver halide crystals are smaller
  • higher resolution image
33
Q

what type of speed films are more used in dentistry and why?

A

fast speed film b/c of decreased exposure

34
Q

what are the 3 advantages of digital x-rays?

A
  1. lower patient exposure
  2. faster radiographs
  3. more eco friendly
35
Q

digital films reduce the amount of exposure by how much?

A

50-80 percent

36
Q

what type of film is placed in a cassette?

A

panoramic or TMJ film

37
Q

cassettes have increased or decreased definition?

A

decreased definition - bc angle of light photons (cascading effect from photon interaction with rare earth intensifying screen)

38
Q

intensifying screens are used in cassettes

A

decrease the exposure or radiation

39
Q

what are 3 things that decrease the quality of radiographs from cassettes and degrade the cassette.

A
  • dirt
  • light leakage
  • static electricity
40
Q

direct vs indirect digital

A
  • direct = the sensor connects directly to a computer and provides immediate images
  • indirect = a reusable phosphor plate is used instead of film. After x-ray exposure a latent image is scanned in a special scanner. The digitized image is stored and read on a computer.
41
Q

under exposed looks what color?

A

white

42
Q

over exposed looks what color?

A

black

43
Q

what is the standard language for the electronic communication of digital images?

A

DICOM

44
Q

what does DICOM stand for?

A

digital image and communication in medicine

45
Q

how is most digital data stored?

A

in DICOM format

46
Q

what is contract resolution?

A

the ability to distinguish different densities in an image

47
Q

what are densities limited by?

A

noise of the film

48
Q

computer monitors are only able to display how many bits?

A
  • only 8 bits - they can not display the accuracy of the sensor
49
Q

what is spatial resolution?

A

the ability to distinguish fin detail

50
Q

what is the pixel size of CCD and CMOS ?

pixel size of film?

A 
digital = 20 um 
film = 8 um
51
Q

what is the sensor latitude?

A

the ability to capture a range of exposures

52
Q

sensor latitude of CCD and CMOS vs. film? also PSP?

A
  • CCD and CMOS sensors similar to film

- PPS has greater latitude than other sensors and film

53
Q

What are the 3 types of digital sensors?

A
  1. Photostimulable storage phosphor plate (PSP)
  2. Charge-coupled devices (CCD) - early sensors
  3. Complementary Metal Oxide Semiconductor (CMOS)
54
Q

disadvantage of automatic processor for film?

A

-have to use a lot more chemicals

55
Q

sensor sensitivity of PSP systems compared to F speed film?

A

-PSP systems allow dose reduction of abut 50% compared to F speed film (fastest film)

56
Q

CCD, CMOS and PSP require a dose equal to what film speed?

A

200

-F-speed film has a speed of 125

57
Q

how does a digital sensor work?

A

-x-ray photons are converted to visible light as they hit the CsI scintillator. This light is channeled via the fiberoptic taper to the CCD.

58
Q

x-rays hit the _______ and are converted to visible light?

A

CSI scintillator

59
Q

what happens to the light photons created by the CSI scintillator?

A

the light photons hit the silicone layer releasing electrons. The negative electrons are drawn to the positive well

60
Q

what leads to blooming in digital x-rays?

A

overexposure (distortion and burned out)

61
Q

spatial resolution is determined digitally by _______

A

the size of the pixels (20 um)

vs film of 8 um

62
Q

the average grayscale value of _____ adjacent pixels in a high resolution image is assigned to create on pixel in a high contrast image.

A

4

63
Q

6 bit vs 8 bit vs 16 bit for grayscale

A

6 bit = 64 shades-our eyes can only view 64 shades of gray
8 bit = 256 shades - the monitor
16 bit = 65.535 shades - the senor

64
Q

on a grayscale what is the color with the value of 0. What is the color for the value of 65,000

A 
0 = black 
65,000 = white
65
Q

how to optimize the grayscale?

A

use computer to take away some of the shades of gray to increase contrast
-loose detail to increase contrast

66
Q

what does smoothing do?

A

it averages the gray scale

D1 Radiology (1 decks)

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