XRay Physics Flashcards
1
Q
When fast moving electrons collide with matter in any form, what is produced?
A
X-Rays
2
Q
In an x-ray tube, this is done by directing a stream of electrons at a high speed against a ….
A
metal target
3
Q
As they interact with the atoms of the target, the electrons give up most of their energy in the form of…
A
Heat
4
Q
However, about 1% of their energy is emitted as….
A
X-Radiation
5
Q
The x-ray tube is inside a heavily lead-lined protective housing & is located…
A
Within a glass envelope (Pyrex) inside the tube housing
6
Q
The tube consists of 2 electrode called the…
A
Cathode & Anode
7
Q
Which electrode consists of a large filament, a small filament, and a focusing cup.
A
Cathode
8
Q
The filaments serve as the source of _____ in the production of x-rays, and are made of _____.
A
Electrons
Tungsten
9
Q
What occurs when a current is applied to the filament?
A
Thermionic Emission
The coil of the wire becomes very hot, boiling off electrons
10
Q
What controls the quantity of electrons (mA) emitted from it?
A
Temperature of the filament
11
Q
What determines the number of x-rays created?
A
Number of electrons
12
Q
This is part of the cathode and encases the two filaments. Place where thermionic emission occurs.
A
Focusing Cup / Filament Cup
13
Q
The Positive Electrode in the x-ray tube
A
Anode
14
Q
Most x-ray tubes consist of a _____ anode.
A
Rotating
Rotating target receives electrons as they move from cathode to anode.
15
Q
What is the reason for the rotating target?
A
Dissipate the heat generated
16
Q
Rotating Anode exposes an area of the tungsten target of the anode, which is called the _____.
A
Focal Spot
17
Q
The focal spot will be determined by the …
A
Size of Filament chosen
18
Q
Smaller filament = ?
A
Better detail
19
Q
The Line Focus Priniciple has the effect of making the actual focal spot size appear _____ when viewed from the position on the film.
A
Smaller
20
Q
The smaller the target angle = ?
A
The smaller the effective spot
21
Q
Stream of electrons narrows down to an….
A
effective beam
22
Q
What heats the filament causing a boiling off of electrons?
A
Milliamperage (mA)
23
Q
Milliamperage Per Second (mAs)
More Current = ?
A
More Current = More electrons produced = more x-rays produced = greater radiograph density (darker)
24
Q
The overall blackening on a film?
A
Density
25
Density term used to describe structures that produce more blackening on the film
Radiolucent
26
Density term used to describe structures that produce less blackening on the film (whiter on x-ray)
Radio-opaque
27
T/F: The relationship between mAs and density are directly proportional
True
28
What is the primary method to control the blackening on the film?
Changing the mAs
29
mAs increases = ?
More film exposure
30
What is the minimum change of mAs that it takes to see a minimum change in density on the film?
30%
31
If the mAs is doubled, the density is ....
Doubled
32
If the mAs is halved, the density is...
Halved
33
The force applied to accelerate the electrons from the cathode to the anode at the time of exposure is...
Kilovoltage (kVp)
34
T/F: The greater the force of the kVp, the greater the numbers of high energy x-ray photons will be produced.
True
35
T/F: Wavelength and frequency are inversely related
True
36
T/F:
Low kVp = low energy = weak penetration
High kVp = high energy = strong penetration
True
37
Higher kVp produces (longer or shorter) wavelengths with a greater ability to penetrate the body tissue
Shorter
38
The difference in density between two structures.
Contrast
39
Contrast makes detail....
visible
40
T/F: kVp controls contrast but they are inversely related
True
41
Low kVp = ____ Contrast = Short Scale
High
42
Low kVp film will have _____ differences in dark and light areas. (ex: Black & White film; bone = Underexposed)
Sharp
43
Low kVp produces ____ scatter, however, the amount of radiation absorbed by the patient is ____
Less Scatter
| Increased Radiation
44
High kVp = ____ Contrast = Long Scale
Low
45
T/F: High kVp film shows very little differences between densities. (ex: more shades of grey; soft tissue)
True
46
High kVp produces ____ scatter, however, the amount of radiation absorbed by the patient is ____
More Scatter
| Less Radiation
47
To lower your contrast - longer scale of contrast - more shades of grey - you must:
Increase kVp by 15% & Decrease mAs by 50%
| Double Density
48
To raise your contrast - shorter scale of contrast - fewer shades of grey - more black & white - you must:
Decrease kVp by 15% & Increase mAs by 100%
| Half Density
49
What is the prime method to control density?
mAs
50
T/F: The relationship between kVp and density is NOT proportional.
True
51
Explain the 15% rule?
An increase in kVp by 15% will double overall density of the film, whereas, a decrease by 15% will cut the density in half.
52
Denser tissue absorbs x-rays whereas less dense tissue transmits more x-rays. What are the radiographic densities as seen on an x-ray:
- Gas
- Fat
- Muscle, Water, Soft Tissue
- Bone, Metal
Gas - BLACK
Fat - BLACK
Muscle, Water, Soft Tissue - GRAY
Bone, Metal - WHITE
53
T/F: The rotating target is angled thus producing a varied intensity
True
54
The intensity of the x-ray is greater at the ____ side.
Cathode
55
Since intensity and density decrease on the anode side of the film, place the thinner portion of what is being x-rayed towards the anode end.
Anode-Heel Effect
56
Cathode or Anode?
- Less X-Ray
- Smaller effective focal spot
- More detail
- Thinner body part
Anode side
57
Cathode or Anode?
- More XRay
- Larger effective focal spot
- Less detail
- Thicker body part
Cathode side
58
This represents the length of space from the focal spot (or tube) to the recording medium (or film)
Focal Film Distance (FFD) / Source Image Distance (SID)
59
What happens when you increase the FFD?
Image gets smaller & clearer, which decreases magnification and distortion.
60
What happens when you decrease FFD?
Image gets bigger & blurrier
61
Intensity of radiation varies inversely with the square of the distance from the source.
Inverse Square Law
62
If a 40" FFD is doubled to an 80" FFD, the intensity of the radiation is ____, so the mAs must be increased _____ to maintain same amount of film blackening.
Intensity is 1/4
| mAs must increase by 4x
63
If an 80" FFD is halved to a 40" FFD, the intensity of the radiation is _____ the intensity from the 80" if no factors are changed.
4x
64
Intensifying screens consist of _____ crystals.
Fluorescent
65
Large crystals (more light) work quickly, but yield...
Less detail
66
Faster screens = Higher Contrast = Short Scale = ?
Less pt exposure
67
Small crystals (less light) work slowly, but offer....
More detail
68
Slow screens = Lower Contrast = Long Scale = ?
More pt exposure
69
Intensifying screens increase density on the film by...
Intensifying the action of the x-rays
70
_____ is the picture made by the useful beam
Umbra
71
_____ is the blurry halo parts of the image (unsharpness)
Penumbra
72
What is caused by having the tube too close to the film (short FFD), having the pt too far from the film (long OFD), or having too big of a filament on the cathode making the focal spot too big.
Penumbra
73
Distance between the patient and the film
Object Film Distance (OFD)
74
As you increase the OFD, the image becomes....
bigger & blurrier (more penumbra)
75
As you decrease the OFD, the image becomes...
smaller & more clear (more detail)
76
T/F: Object should be as close to film as possible for better detail.
True
77
The pressure exerted by the film holder as it encloses the x-ray film. Pressure should be evenly distributed across the surface of the film.
Screen-film contact
78
What is the best test for screen film contact?
Wire-Mesh test
79
T/F: Poor screen film contact reduces the image sharpness of the image.
True
80
What are the two types of distortion?
Size & Magnification
81
Distortion can be affected by...
OFD & FFD
82
When x-rays strike an object one of three things can occur...
Scattered, Absorbed, or Penetrated
83
How can you reduce scatter radiation?
1. Grids
2. Air Gap Technique
3. Collimators
4. Filters
84
A device of alternating strips of lead and spacer material. This is placed between the patient and the film. The sole purpose is to improve quality of the radiograph by absorbing scatter radiation. The use of this will require an increase in exposure factors to maintain density. This increases patient dose of radiation.
Grids
85
What is the Grid Ratio?
Height of the lead strips to the distance b/t the strips
86
What is the Grid Ratio in a chiropractic office?
12:1
87
What is the Air Gap Technique?
6-10" between the patient and the film
This distance b/t the body part and the film causes scatter radiation to diverge away from the film, which reduces pt dose but can distort or magnify the image.
88
Limits the size of the beam to the size of the body part you need to capture on film.
Collimation
89
What is the best way to reduce scatter radiation to the patient as well as to the film?
Collimation
90
Preferential removal of low energy photons (those not capable to get all the way to the screen). This stops the weak photons from entering the patient's body thus protecting them from scatter radiation.
Filtration
91
What are filtrations usually made from?
Aluminum
92
Used to identify irradiation of patients; measures the radiation energy absorbed.
Radiation Absorbed Dose (RAD)
93
1 RAD = ___ REM
1
94
This unit is typically applied to occupationally exposed persons. It identifies the biological effectiveness of the radiation absorbed. It's measured on radiation workers by a photosensitive badge worn on the collar.
Radiation Equivalent Man (REM)
95
What is the safe limit of REM per year?
5 REMs (or RADs) per year
96
The number of REMs a person can get in a lifetime without getting radiation poisoning.
Maximum Permissible Dose (MPD)
97
What is the MPD in a lifetime?
MPD = 5 (age 18)
98
Type of radiation: majority of useful beam; interacts with the target nucleus; a high intensity electron hits an inner shell electron, which is knocked out of its position in orbit, and an outer shell electron then fills its spot.
Bremsstrahlung aka Braking Radiation
99
Primary form of scatter
| A moderate energy x-ray knocks out an outer-shell electron, which causes a loss of energy.
Compton scatter
100
A low energy x-ray that changes direction with no energy loss. Contributes to film fog.
Classical Scatter aka Thompson Scatter aka Coherent Scatter
101
A low energy photon is absorbed by the subject creating a latent image on the film.
Photoelectric Effect
102
This is caused by the fluctuation of the number of photons absorbed by the intensifying screens to form the image on the film. Faster screens produce more of this. The use of high mAs, low kVp will decrease this.
Quantum Mottle aka Radiographic Noise
103
Solution temperatures that are too hot will _____ density.
Increase
104
Solution temperatures that are too low will produce radiographs with _____ density
Insufficient
105
Processing factor that brings out the latent image by developing the exposed silver halide crystals.
Developer
106
The component of the Developer that produces shades of gray and black & uses Phenidone/Hydroquinone.
Reducer/Developer
107
The component of the Developer that produces swelling of emulsion using Na+ Carbonate.
Accelerator/Activator
108
The component of the Developer that controls oxidation using Na+ Sulfite or K Sulfite
Preservative
109
The component of the Developer that protects unexposed crystals & uses Potassium Bromide/Iodine
Restrainer
110
The component of the Developer that controls swelling of emulsion & uses Glutaraldehyde.
Hardener.
111
Processing factor that removes the exposed silver halide crystals
Rinse
112
Processing factor that hardens the image, making it permanent on the film
Fixer
113
The component of the Fixer that neutralizes the developer aka "Stop Bath" & uses Acetic Acid.
Acidifier/Activator
114
The component of the Fixer that removes undeveloped Ag Halide aka "Hypo Solution" & uses Ammonium/Na+ Thiosulfate
Clearing Agent
115
The component of the Fixer that stiffens/shrinks the emulsion & uses Potassium Aluminum
Hardener
116
The component of the Fixer that maintains the pH of the fixer & uses Sodium Sulfite
Preservative
117
Processing factor that removes the developer & the fixer
Washing
118
If light leak, developer temperature too hot, overexposure
Dark Films
119
If developer temperature too low, chemicals need replacing
Light films
120
Inadequate developer
Brown films
121
Inadequate fixer
Milky films
122
Insufficient washing
Greasy films
123
Old film, hot developer, contaminated chemicals
Increased fog
124
Insufficient fixing
Soft Emulsion
125
How should you store the film to avoid pressure damage
Vertically
126
Steps up or steps down the power
Transformer
127
One form of energy to another
Transducer
128
Beam of radiation loses energy as it passes thru matter
Attenuation
129
What is added to the base of xray rilm to reduce glare
Green or blue tint
