# Unit 1 (Density)

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 Author: 2015RT ID: 233280 Filename: Unit 1 (Density) Updated: 2013-09-07 10:17:26 Tags: radiography Folders: Description: Imaging - Unit 1 Density Show Answers:

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1. In film, it is called density. On the computer, it is called __________.
Brightness
2. Two photographic factors that allow detail to be seen:
• Density
• Contrast
3. Typical OD range
.25 - 2.5

.25 is lower density; whiter

2.5 is higher density, darker
4. Instrument used to measure density.
Densotometer
5. What is density?
variations of darkness; the black and white
6. When changing density, do you use window level or window width?
window level
7. What is the main controlling factor of density?
mAs (mass)
8. 3 Lightening techniques:
Bright "hot" lights - higher intensity; higher amps (higher numbers) means more light penetrating

• Digital optical scanner - adjust the settings
• Duplication (copying) - an older machine reprints the film lighter/darker
9. main elements of the body that the x-ray interacts with:
hydrogen (water component, body tissue, low atomic #)

oxygen (water component, body tissue, low atomic #)

calcium (bone, high atomic #)
10. Does increasing mAs increase or decrease density?
Increasing mAs increases density.

Decreasing mAs decreases density.
11. What is the "rule of thumb" when increasing mAs to change density?
Double it to increase, Half it to decrease
12. How much of a change is needed, in mAs, before a change in density is discernible to the naked eye?
a 30% change.
13. If you need to increase the kVp by a certain percent, how do you go about it (mathematically)?
multiply the kVp by the percent needed with a 1. in front of it.

Example: to increase 15%, multiply by 1.15
14. If you need to decrease the kVp by a certain percent, how do you go about it (mathematically)?
multiply the kVp by the number you would add to the percent amount to make it equal 100, but with a decimal point in front.

• Example: decrease 15%, multiply by .85
• Example: decrease 60%, multiply by .4
15. What type of radiation are we using? What is special about it?
16. What is the main influencing factor of density?
kVp
17. To change the density by changing the kVp, what is the generalized rule for increments?
Change in 15% increments...the 15% rule
18. generators, listed from weakest energy to strongest energy:
• single phase
• 3-phase, 6-pulse
• 3-phase, 12-pulse
• high frequency
19. Changing the kVp changes the ______ of the beam.
energy
20. If you have good technique on a high frequency machine, what would you have to do if you changed to a single phase machine?
You would have to increase your technique since it's a weaker beam. It would need increased power to show the same image as well as a stronger machine.
21. Define Blooming.
causing pixel size to become larger than the nominal or state size; a distortion
22. Describe the expected influence of the focal spot on density when the unit has been properly calibrated.
There should be no difference between large and small focal spots.
23. What is the anode heel affect?
An effect that alters the intensity of radiation (and therefore the density) between the anode and cathode ends of the x-ray tube.

up to 45% difference depending on the angle of the anode
24. Which end always has greater image receptor exposure, the cathode end or the anode end?
the cathode end, by up to 45%. it gets "hotter"
25. The patient's head is located on the ______ side, and the feet are located on the _______ side.

feet: cathode
26. Towards the cathode side, the density is ________.
Greater (up to 45%)
27. SID is short for:
Source-to-image receptor distance
28. What is the SID conversion formula?
• mAs1 (SID1)2
• ____= ____
• mAs2 (SID2)2
29. Inverse Square Law
• I1 D22
• _ = ___
• I2 D12

• The law affects exposure in inverse proportions to the square of the distance.

30. As an example of the inverse square law, if you re exposed to 400mR of scatter radiation when 1 ft away from your patient, how much radiation are you exposed to if you move to 2 ft away from your patient? 4 ft away?
• 100mR at 2ft
• 25mR at 4 ft
31. In this class...what will we always do with distance when it comes to formulas?
Square anything to do with distance!!
32. When distance increases, density ____________.
decreases
33. When collimation increases, density __________.
decreases
34. When field size increases, density __________.
increases
35. When beam restriction increases, density __________.
decreases
36. As field size decreases, intensity ___________.
decreases (exposed to less photons)
37. Increased filtration will ____________ density.
decrease
38. Filtration ___________ overall average energy of the beam.
increases
39. As tissue thickness increases, film density __________.
decreases
40. What happens as the atomic number of tissue gets higher?
The tissue absorbs more of the x-ray, allowing less x-ray to pass through to the film. Therefore, the film density is less where there is tissue with high atomic number, making it look lighter. Bone is an example of tissue with a high atomic number.
41. Where is the highest atomic number in the body?
the teeth (because of the enamel)
42. Tissue type is affected by which 2 main factors?
• the average atomic number
• the density of the tissue
43. Does denser tissue increase or decrease density on the film?
decrease
44. You may have to __________the density when making large tube angles.
increase
45. In pathology, an additive __________ density and creates an effect called __________.
46. In pathology, a destructive _________ density and creates an effect called _________.
destructive: increases density and is radiolucent.
Fluid in the lungs (pneumonia)
48. Example of a Destructive:
Emphysema
49. When grid ratio increases, density ___________.
decreases
• advantage: absorbs scatter; less reaches film
• disadvantage: increases exposure to patient
51. Grid Conversion Formula
• GCF1 mAs1
• ____ = ____
• GCF2 mAs2
52. What is the GCF if there is no grid?
1
53. What is the GCF for the Grid ratio of 5:1?
2
54. What is the GCF for the grid ratio of 6:1?
3
55. What is the GCF for the grid ratio of 8:1?
4
56. What is the GCF for the grid ratio of 10:1?
5
57. What is the GCF for the grid ratio of 12:1?
5
58. What is the GCF for the grid ratio of 16:1?
6
59. Consider using a grid once the part being x-rayed reaches _______ in size.
10cm
60. Calcium is high in what type of absorption?
photo-electric absorption
61. When Relative Speed (RS) increases, density ________.
increases
62. RS conversion formula:
• RS1 mAs2
• ___= ___
• RS2 mAs1
63. With the same technique, which would show the greater density, a pediatric cassette or a regular cassette?
pediatric cassette
64. With the same technique, which would show the greater density, a regular cassette or a fine detail cassette?
regular cassette
65. When film processing time increases, density __________.
increases
66. When film processing temperature increases, density __________.
increases
67. When chemical activity increases, density __________.
increases
68. Describe the "formula reminder" for how to calculate density when working with mA and time.
69. If the density of matter is increased, then the density of the receptor is _________.
decreased
70. Density & Brightness are _________ porportional.
inversely
71. the more dense the an object the harder it will be for the xray to pass through and _____ will be absorbed.
more
72. When you measure with the Densitometer you want the numbers to fall within what range?
0.25 - 2.5
73. What is OD range?
how much light is transferred through
74. An increase in mAs causes an increase in chance of density and a ________ to exposure.
increase
• dark radiographs have too much information (too dark)
76. The "Rules" for changes in technical factors can sometimes only apply to a _________________.
range of circumstances.
77. What is density a controlling factor for?
mAs
78. if you double mAs, then density is _____.
doubled.
79. mAs is changed by a factor of __.
2
80. minimum ___ change to visualize change in density of radiographic image.
30%
81. Increase in kVp does what to scatter? Why?
increase due to more energy
82. Change in kVp results in a change in the kinetic energy of what?
electrons in the tube
83. the more energy of electrons, the ____ they hit the anode.
harder
84. if you decrease density by half what do you do to kVp?
kVp x .85
85. if you double density, what do you do to kVp?
kVp x 1.15
86. what affects average energy of the beam?
generator configuration (might be more accurate to change kVp to maintain density).
87. Single phase generator emits ____ density than high frequency.
less
88. High frequency generators emit ____ density than single phase.
more
89. Which type of generator exposes the patient more?
single phase
90. as you increase density, the energy of the generator _____.
increases
91. Because single phase generator puts out less energy than a high frequency generator, it exposes the patient to more or less?
more bc the less energy the harder it is for xrays to pass through the mass and more is absorbed by the patient.
92. what kind of effect does the focal spot have on density?
no effect
93. What is the focal spot?
part of the disk where electrons hit the anode and produce xray
94. although the focal spot size has no effect on density it can have an effect on what?
detail
95. Which side is positive the anode or cathode?
anode
96. the altering intensity of the beam across the cathode/anode axis is called?
the anode heel effect
97. how does the electron travel?
goes from the cathode and hits the anode
98. where are xrays expelled from?
the anode heel
99. Why do you put the patient head on the end of the tube that has the cathode?
Bc it has a greater central ray intensity than the anode side
100. if you double distance you exposure is ____ of what it was.
1/4
101. if you increase distance and do not increase mAs, what happens to density?
density decreases
102. if you increase your distance by half you get how many times the  exposure?
4 (density is increased)
103. if you double mAs, decrease kVp by __?
15%
104. If you half mAs, increase kVp by __?
15%
105. A filter is like a ___?
cloud
106. increase in filtration will ____ density.
decrease
107. what is the key purpose of a filter?
reduce exposure to the patient
108. An increase in filtration causes an _______ intensity of ____ beams.
increase ; high
109. What absorbs low energy of xray?
aluminum
110. Because higher energy rays are not filtered by the filter, they can go through the patient which ______ exposure to patient dose.
reduces
111. increase beam restriction ____ density.
decreases
112. The tissue thickness (density) increases as the anatomical number goes ____.
up
113. the thicker the part the ____ density on the IR.
less
harder
115. the more radiolucent an object is the easier the beam can pass through so the ____ the density.
higher
116. When scatter is absorbed to the grid, the xray absorbed to the IR is decreased causing density to ______.
decrease
117. a bigger part, causes _____ scatter.
increase
118. An ______ in grid ratio will absorb more scatter.
increase
119. If you increase the Relative Speed (RS), density _____.
increases
120. What does relative speed mean?
how well the screen can emit light in a reaction to light
121. _______ resolution in lower speeds of relative speed.
greater
122. High speed screens are used to ___ exposure.
decrease
123. The higher speeds cause increases in density, so you can ______  technique.
decrease
124. what is the AG readers magic number?
1.69
125. An increase in time, temp, and chemical activity during film processing causes density to _______.
increase

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