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trisemester 3 TCC > test 2 xray physics > Flashcards

test 2 xray physics Flashcards

1
Q

What happens to contrast when lower kVp is used?

A

Higher contrast image is created with a shorter scale of contrast (less steps between darkest and lightest)

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2
Q

What type of x-ray will create an image with less contrast?

High kVp and Low mAs

or

Low kVp and High mAs

A

High kVp and Low mAs

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3
Q

How does higher kVp/lower mA affect scatter?

A

More scatter

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4
Q

Where is the grid placed?

A

Behind the patient and in front of the image receptor (basically between patient and image receptor)

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5
Q

When using a grid, how does it affect the exposure to the patient?

A

It will increase the exposure to the patient anywhere between 4-5 times compared to no grid

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6
Q

How does a grid affect image quality?

A

Improved diagnostic image quality

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7
Q

What happens to non-scattered photons as they pass through a grid?

A

They pass through the radiolucent part of the grid, but some do still get absorbed by the lead strips

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8
Q

What is grid ratio?

A

Height of the lead strips divided by the distance between the lead strips (h/D)

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9
Q

What is the grid frequency?

A

Number of lines per inch or other unit of measurement

lines/inch

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10
Q

Pertaining to grids, what is the height of the lead strips divided by the distance between the lead strips?

A

Grid ratio

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11
Q

What is grid selectivity or “Sigma”?

A

Amount of primary radiation transmitted divided by the scatter radiation transmitted

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12
Q

If the grid ratio is very high, how much scatter goes through?

A

Very little scatter

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13
Q

If the grid ratio is very low, how much scatter goes through?

A

Lots of scatter goes through

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14
Q

What is a typical grid ratio for musculoskeletal imaging?

A

5:1 - 12:1 ratio

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15
Q

What type of grid ratio has better clean up and better contrast?

A

Higher ratio grids

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16
Q

What happens to patient dose as you increase the grid ratio?

A

It increases

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17
Q

Pertaining to grid frequency, what frequency is generally less efficient? (high or low)

A

High frequency

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18
Q

Pertaining to grid frequency, what frequency is generally more efficient? (high or low)

A

Low frequency

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19
Q

Do higher frequency grids require more or less dose?

A

More pt. dose

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20
Q

Most grids range from _____-_____ lines per centimeter

A

25-45 lines per centimeter

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21
Q

How can you increase grid ratio?

A

Increase the height of lead strips or decrease the distance between the lead strips

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22
Q

Where does grid cut-off occur?

A

The lateral margins of the grid, especially with closer source-image distances

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23
Q

What is the grid that involved grid strips that are angled to accommodate the increasingly divergent angle of photons further away from the central ray?

A

Focused grids - these are used for general radiography

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24
Q

Do higher ratio grids have more or less focal range than low ratio grids?

A

Less focal range

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25
What happens to focal range with a lower grid ratio?
It increases
26
What are crossed grids?
Grids with lead strips that run both lengthwise and side-to-side to reduce more scatter photons. (These are not usually used in general radiography)
27
What are some drawbacks to the air-gap technique?
There can be image magnification and distortion of the image Higher exposure is also necessary (about 10% increase per cm of air gap)
28
What projection includes a natural air gap?
Lateral cervical spine x-ray
29
What is the term for screen film radiography?
Analog radiography
30
What is the exiting beam also known as?
Remnant beam, it is the x-ray beam that forms the image
31
What is the purpose of the film?
To create a permanent record of the x-ray exiting beam
32
What are the major components of film?
Base - piece of plastic for physical support Emulsion - picture layers of the film Adhesive lay Supercoating - protection
33
Originally, glass was used as what part of the x-ray film?
Base
34
What type of material replaced the glass base very long ago, but was very flammable?
Cellulose nitrate
35
What type of material is currently used as the base of x-ray film?
Polyester
36
What makes up the emulsion layer of x-ray film?
A homogenous mixture of gelatin and silver halide crystals Gelatin provides = support Silver halide crystal = sensitive to light and X-ray
37
What type of formation is silver halide?
Crystal lattice formation
38
What are the components of the silver halide crystal that helps make up the emulsion layer of x-ray film?
Silver bromide 95% Silver iodide 5% Silver sulfide
39
What component of the silver halide crystal is extremely important in photosensitivity of film?
Silver sulfide
40
X-ray film is mostly exposed by light from what
Intensifying screens
41
Exposure of the film to light or x-ray photons causes a movement of electrons and/or atoms within the silver halide crystal is know as what? It is the invisible change in electron configuration of silver halide crystal.
Latent image formation
42
What is latent image?
It is the invisible change in electron configuration of silver halide crystal
43
What happens at the molecular level of the silver halide crystals when exposed to light/x-rays?
electrons accumulate at the silver sulfide "sensitivity specks" and reduce a very small number of the silver ions to metallic silver
44
Electrons accumulate at the silver sulfide "sensitivity specks" and reduce a very small number of the silver ions to _______________.
Metallic silver
45
What is the most common type of film used in general purpose radiography?
Screen film
46
What type of film is used in conjunction with intensifying screens?
screen film
47
What is the purpose of the intensifying screen?
To convert x-ray photon energy into visible light photons
48
What causes the "most" film exposure?
Visible light generated by the intensifying screen
49
Screen film that has emulsion on the front and back of it to increase speed is known as what?
duplex film
50
What effect does duplex film do when taking x-rays?
Increases speed of the system/decrease amount of radiation
51
What are important film characteristic that can be influenced by the kind of film that is being used?
Speed and Contrast
52
What color systems are used in x-ray?
Blue or Green
53
In what color wavelengths are x-ray films most sensitive to light?
Blue and Green spectra
54
If using blue sensitive film, what color light should be used?
blue
55
If using green sensitive film, what color light should be used?
greeeeeeeen
56
Which color is better for x-rays? Green or Blue?
DO NOT MATTER
57
What is the term for a light source that emits light in a spectra that the film has a low sensitivity to?
safe lights
58
are safe lights completely safe?
no, that are only safe at a limited time and intensity
59
Red safe light filters are safe for what color film?
blue and green
60
What is the maximum wattage for safe lights?
15 watts
61
What is the minimum distance that the safe light can be from the working surface?
5 ft.
62
What type of film is designed to be used without intensifying screens?
direct exposure film
63
What is direct exposure film used for?
Dental applications
64
What is the film that only has emulsion on one side?
single emulsion
65
How does duplicating film (film used to make a copy of x-rays) act compared to regular x-ray film?
Reacts in opposite fashion to regular x-ray film
66
What color do exposed areas of duplicating film become?
white | which is the opposite of x-ray film which turns black
67
What temperature should unexposed x-ray film should be stored?
below 68 deg.
68
How long will x-ray film last at room temperature?
45 days
69
What humidity should x-ray film be stored at?
Less than 60%
70
What should you avoid when handing unexposed film?
Avoid excess heat = <68 degrees Avoid excess humidity = <60% Avoid static electricity (occurs with <40% humidity) Avoid light or x-ray exposure Avoid mechanical force
71
If we have static electricity on an unexposed film, what can occur?
latent image can occur
72
Film that has been exposed to diagnostic x-ray is more sensitive to ______ or __________ than unexposed film
light; radiation fog
73
How do you remove lines/marks on exposed and processed x-ray films?
Denatured Alcohol, do not use water because it will make gelatin softer and can cause the image to be scratched
74
What do you do if your processed x-ray film is wet?
Let it dry but | Do not place next to anything because acts like glue
75
What is the term for converting latent image formation into visual (manifest) image?
film processing
76
What does film processing do at the atomic level?
It will potentiate the reaction of the ionic silver into metallic silver of the exposed crystals. (it turns black)
77
What are the 4 steps of film processing?
Developing Fixing Washing Drying
78
What stage of film processing involves the latent image becoming the manifest image?
Developing stage
79
What makes up the developer solution?
Water and Reducing agent (reduces ionized silver into metallic silver)
80
What color do exposed silver halide crystals become?
Black
81
What is the purpose of the fixing solution?
Stop the reduction reaction of the developer solution Removes unexposed emulsion Preserves the image
82
What chemical in the fixing solution stops the action of the developer?
Acetic acid
83
What solution stops the reduction reaction of the developer solution, removes the unexposed emulsion, and preserves the image?
Fixing solution
84
What are important variables in processing images?
Time, Temperature, Chemical concentration
85
What happens if film is left in developer solution for too long?
It will over-develop causing the reducing agent to begin to act on unexposed silver halide crystals. It will look like an over exposed film (black)
86
Is time more important in the developing or fixer stage?
developing
87
What stage is the most temperature dependent part of processing film?
developing
88
Developing temperature should not vary by more than how much degrees?
+/- 1 degree Fahrenheit
89
Excess temperature in developer solution will make film appear like what?
Over-exposed
90
What temperature do most automatic processes operate at for processing film?
95 degrees Fahrenheit
91
Proper chemical concentration is important in what stage(s) when processing film?
Developing and fixing stages
92
What happens to chemical strength/potency when a film is processed?
It diminishes
93
What happens to chemical strength/potency when developer/fixing solution is stored over time?
it will diminish
94
What removes residual chemicals from the emulsion when processing film?
Washing - "Water bath"
95
What color will the film look like over time if fixer solution is left on the film?
Rusty-brown/orange color
96
You notice an old x-ray that appears to have a rusty-brown/orange tint. What caused this?
Fixer solution was left on the image and not washed off properly
97
A small amount of _______ solution will ruin a large amount of _______ solution.
A small amount of fixer solution will ruin a large amount of developer solution.
98
What is the final stage of processing film?
Drying stage - using forced hot air
99
What is worse? Having some developer solution contaminate fixer solution or having some fixer solution contaminate developer solution?
Having some fixer solution contaminate developer solution is much worse.
100
why is having some fixer solution contaminate developer solution much worse?
has to do with the flow of processing. The fixer solution come after the developer solution and will have a worse affect with only a bit getting in

trisemester 3 TCC (25 decks)

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