Radiographic Technique Flashcards
(101 cards)
1
Q
What controls quantity?
A
mAs
2
Q
What influences and determines the quantity and quality of x-rays ?
A
Exposure Factors
3
Q
Radiation quality refers to x-ray beam penetrability, best measured by what?
A
HVL (Half Value Life)
4
Q
What are the (4) prime exposure factors?
A
- kVp
- mA
- Exposure time
- SID
5
Q
High kVp _____ image contrast.
A
Reduces
6
Q
What controls how fast the electrons are sent across the tube?
A
Kilovolts
7
Q
What controls beam quality?
A
kVp
8
Q
What controls beam penetrability?
A
kVp
9
Q
What controls the radiographic scale of contrast?
A
kVp
10
Q
What determines the # of photons, radiation quantity, OD and patient dose?
A
mA
11
Q
What affects the number of x-rays produced?
A
mA
12
Q
What are the available mA stations?
A
50, 100, 200, 300, 400 & 600
13
Q
Does changing the mA change the kinetic energy of e-?
A
No
14
Q
What relationship does mA quantity and patient dose have?
A
They are directly proportional
15
Q
Short exposure time _____ image blur
A
Reduces
16
Q
What must you do when using short exposure times to maintain x-ray intensity?
A
Increase mA
17
Q
Single phase can not produce an image under…
A
8ms
18
Q
Three phase can produce an image under…
A
1ms
19
Q
mAs=
A
(mA)x (s)
20
Q
What does mAs control?
A
- Radiation quantity
- Changes the number of electrons
- Optical density
- Patient dose
21
Q
Does mAs change the energy of x-rays produced?
A
No, just the number
22
Q
mAs is a key factor in the control of ________ ________.
A
Optical Density
23
Q
What is the reciprocity law?
A
OD will be constant for any combination of mA and exposure time that results in constant mAs
24
Q
Does distance have much affect on quality?
A
No
25
Does distance have an affect on density?
Yes
26
Does distance affect x-ray intensity?
Yes
27
What does the square law do?
Determines the required change in mAs after a change in SID to maintain OD
28
What are some patient factors when determining technique?
- Body habitus
- Thickness of part
- Body composition
- Pathology
29
What are the (4) types of body habitus?
1. Hypersthenic
2. Sthenic
3. Hyposthenic
4. Asthenic
30
Define:
| Hypersthenic
- Short & wide
- Chest and abdomen are broad
- 5%
- Lungs are short and wide
- Stomach is high and transverse
31
Define:
| Sthenic
- Average body type
- 50% of population
- Active or strong
- Slender version of Hypersthenic
32
Define:
| Asthenic
- Opposite of Hypersthenic
- 10% of population
- Frail, poor muscle tone
- Narrow, long, shallow
- Diaphragm is low
- Abdominal cavity rests in pelvic region
33
Define:
| Hyposthenic
- 35%
- High splenic flexure
- Stomach is J shaped and extends into iliac crest region
34
In general, what kind of technique does a soft tissue neck require?
Low kVp & high mAs
35
In general, what kind of technique do extremities require?
Low kVp
36
In general, what kind of technique does a chest require?
High kVp
37
In general, what kind of technique does an abdomen require?
Middle kVp
38
What are the (4) image quality factors?
Key word DICO
1. Disorientation
2. Image Detail
3. Contrast
4. Optical Density
39
What is OD?
The degree of blackening of the finished radiograph
40
When OD is high=
- Too dark
| - Overexposed
41
When OD is low=
- Too light
| - Underexposed
42
OD can be controlled by mAs and SID? T/F
True
43
Quantity=
mAs
44
Quality=
HVL
45
What is more efficient, a single phase or a three phase?
3 phase
46
When SID is shortened, what happens to your mAs?
It goes down
47
When SID is increased, what happens to your mAs?
It goes up
48
What are the (4) types of generators?
1. Half wave rectification
2. Full wave rectification
3. 3 phase power
4. High frequency generator
49
Half Wave:
- Only produces x-rays half the time
- Drops to zero every time
- x-rays are not produced on negative side
- Rarely used
50
Full Wave:
-Consistant, but drops to zero
51
3 phase power:
- 6 & 12 pulse
- Nearly constant output & exposure
- energy is higher
- Higher quantity & quality
52
High frequency:
- Less than 1% ripple
- Constant output
- Great efficiency
53
What are the effects of a destructive disease?
- Destroying part of tissue, bone, ligaments
| - Taking away, making more lucent
54
What are the effects of a constructive disease?
- Growing
| - Dense
55
How much of in increase is required for a visible change in OD?
30%
56
When mAs is doubled, you get...
Double the density
57
When only mAs is changed it is either ____ or ____.
Halved or doubled
58
When mAs is doubled=
Your density is doubled
59
When kVp is changed it must be increased by __% to produce a visible change in OD.
4%
60
The 15% rule is the same as?
Doubling the mAs
61
To maintain OD a 15% increase in kVp would require a reduction of ____ the mAs.
Half
62
Does the 15% rule apply to kVp or mAs?
kVp
63
A strip that goes from black to white quickly would have a...
- Short scale
- High contrast
- Lower kVp
- Black and white
64
A strip that goes from black to white slowly would have a...
- Long scale
- Low contrast
- High kVp
- Many shades of gray
65
What is contrast?
Differences between things that are adjacent to one another
66
Contrast is controlled by...
kVp
67
A result of the differences in attenuation of the x-ray beam as it penetrates various structures.
Contrast
68
The variation in OD between adjacent anatomic structures.
Contrast
69
A chest would have what scale of contrast?
Long scale of contrast
70
Short scale contrast gives you ___ contrast radiographs.
High
71
High contrast radiographs would have...
- Short scale contrast
| - Fewer shades from white to dark
72
Bone work would have short scale ____ contrast
High
73
Long scale contrast produces _____ shades of gray.
Many
74
How much kVp is requited to see a difference in contrast?
4 kVp
75
At low kVp, how much change is needed to see a difference?
2 kVp
76
At high kVp, how much kVp is needed to see a difference?
10 kVp
77
High kVp will give you ___ contrast.
Low
78
A chest has ___ subject contrast.
High
79
High subject contrast has ____ variations in tissue composition
Greater
80
A hand has ____ subject contrast.
Low
81
An abdomen has ____ subject contrast.
Low
82
What is the 5% rule?
An increase in kVp by 5% requires a reduction in 30% mAs
83
What is image detail?
Sharpness of small structures or spatial resolution of the image
84
How is image detail evaluated?
Sharpness of image detail
| Visibility of image detail
85
What is sharpness?
Clarity or blur of the structural lines
86
What is visibility?
Seeing that there is anatomy
87
Sharpness is controlled by...
- Focal spot size (FSS)
- SID
- OID
- Intensifying screen
88
What can reduce visibility?
Fog
89
What is distortion?
Misrepresentation of an object and shape due to position of the tube or anatomic part
90
What are disadvantages of distortion?
- Elongation
| - Foreshortening
91
What is an advantage of distortion?
Allows for better visualization of anatomy
92
Variable kVp chart:
- kVp varies according to thickness of anatomic part
- Provides radiographs with shorter scales of contrast
- Other factors stay the same
93
Fixed kVp chart:
- kVp stays constant
- mAs varies
- Developed by Arthur Fuchs
- Provides longer scales of contrast
94
High kVp chart:
- Used for barium exams, contrast exams, CXR
- Ensures adequate penetration
- Decrease in mAs
- Reduces patient dose
95
AEC:
- Use of computer assisted automatic/ electric timers and photocells
- Patient positioning must be accurate
- Terminated when the image receptor has received the appropriate radiation exposure
- Most have 2s override
96
An increase of 15% in kVp is equivalent to...
Doubling the mAs in terms of density
97
Long scale contrast:
- Low contrast
- Many shades of gray
- Higher kVp
98
Short scale contrast:
- High contrast
- Black and white
- Lower kVp
99
What controls contrast?
kVp
100
What controls density?
mAs
101
A high grid ratio will produce a short scale contrast? T/F
True
