1. 15 percent rule
The 15 percent rule states that an increase in kVp by 15 percent will cause a doubling in exposure, the same effect as doubling the mA or doubling exposure time.
2. Direct Square Law
Exposure maintenance formula
3. Exposure maintenance formula
A direct square law; mAs must increase when distance increases, and vice versa, in order to maintain image receptor exposure.
4. milliamperage- second mAS
The unit used to describe the product of tube current and exposure time.
5. Penetrability
The ability of the x-ray to pass through structures and tissues.
6. Prime factor
Factors related to x-ray emission that are under the direct control of the radiographer; milliamperage, kilovoltage, and distance.
7. Reciprocity Law
The dentistry on an x-ray film should remain unchanged as long as the intensity and duration of the x-ray exposure remains unchanged.
8. x-ray quality
The penetrating ability of the x-ray beam. Kilovoltage and filtration are the main factors.
9. x-ray quantity
The measure of the number of photons in the useful beam. Measured in R (roentgen). Milliamperage-second, kilovoltage, Distance and filtration are the main factors.
10. The principle controlling factors for quantity is
mAs
11. The principle controlling factor for quality is
kVp
12. mAs is
A measure of the tube current and is equal to the number of electrons crossing from cathode to anode. Exposure time is also directly proportional to the number of electrons crossing the tube.
13. mAs is calculated by
mA X time
14. What does mAs stand for
milliamperage per second
15. what is the formula for mAs
mA X time
16. What is mAs the measure of
tube current
17. What happens as mAs is increased
density increases
18. as mAs doubles the exposure does what
doubles
19. what happens to the filament of the circuit as mA is increased
thermionic emission
20. Density is the
the amount of blackening on the image that is determined by exposure. mAs is the primary controller.
21. What is D-max
The maximum density a film can achieve (Film only)
22. Reciprocity law
the density on an x-ray film should remain unchanged as long as the intensity and duration of the exposure remains unchanged.
23.When does the reciprocity law fail
The law fails at very short times (below 10 milliseconds) and very long times (6-7 seconds)
24. Low kVp gives an image what type of contrast
high contrast
25. An increase in kVp by 15% will do what to the exposure
double the exposure
26. A decrease in kVp by 15% will do what to the exposure
cut the exposure by 1/2
27. x-ray intensity does what as distance from the tube decreases
increases
28. x-ray intensity will do what as the distance from the tube increases
decrease
29. Inverse square law
the intensity of the radiation at a given distance from the point of the source is inversely proportional to the square of the distance.
30. A radiographer makes an exposure using the standard 40 inch SID . An ionization chamber measures the radiation at 40 inch SID to be 5 R. The same exposure is made at 45 inch SID what is the new intensity.
5R/I 2= 452/402
I2=3.9
the new intensity is 3.9R
31. Density maintenance formula
mAs1/mAs2 = D1 2/D2 2
32. The density maintenance formula demonstrates what?
a relationship where mAs needed for an exposure is directly proportional to the square of the SID and as SID increases the mAs must also increase to maintain adequate blackening on the film.
33. A radiographer exposes a patient's chest at the bedside using 3 mAs, 75 kVp at 72 SID. A second radiograph is needed but as a result of a change in the patient's condition, only 54 inch SID can be used what should the new mAs be for the 54 inch SID?
3mAs/x mAs = 722/ 542
2916(3)/x = 5184
x= 1.69 mAs
34. What are three prime factors that affect x-ray emission
mAs, kVp, Distance
35. What is the unit of measurement for x-ray quantity?
roentgen (R)
36. Define ampere?
The unit of current
37.What is the relationship between mAs and density/IR exposure?
The densities are a direct result of an x-ray exposure to the film and intensifying screens (IR)
38. What effects does increased kVp have on the speed and energy of the electrons in the x-ray tube?
Increase kVp will cause an increase in the speed and energy of the electrons applied across the x-ray tube.
39. What is the relationship between kVp and density/IR exposure
Increase kVp causes an increase in penetrability, which will result in an image with less contrast. the effect of kVp on density/IR exposure will be detailed.
40. Annihilation reaction
Matter being converted back into energy as a result of a position combing with a negative electron, which creates two photons moving in opposite directions
41. Attenuation
The reduction in the number of x-ray photons in the beam, and subsequent loss of energy, as the beam passes through matter.
42. Backscatter radiation
Photons that deflect back towards the source, traveling in the opposite direction of the incident photon.
43. Characteristic cascade
The reaction of electrons dropping into the holes created during a characteristic interaction until there is only a hole in the outer shell.
44. Characteristic photon
An x-ray photon created by the electron transfer from one shell to another.
45. Coherent scatter
An interaction between x-rays and matter characterized by interaction between a very-low-energy x-ray photon and matter causing the electron to vibrate at the same frequency as the incident photon, which then produces a secondary photon but travels in a different direction.
46. Compton effect also called Compton scattering
An interaction between x-rays and matter characterized by an incident x-ray photon interacting with a loosely bound outer-shell electron, resulting in removal of the electron from the shell, which then proceeds in a different direction as a scattered photon.
47. Compton (or recoil) electron
The dislodged electron resulting from compton scattering
48. Compton scattered photon
The photon the exits the atom in a different direction as a result of compton scattering.
49. Negatron
A negatively charged electron resulting from pair production
50. Pair production
An interaction between x-rays and matter characterized by the conversation of the energy of an x-ray photon into matter in the form of two electrons.
51. Photodisintegration
An interaction between x-rays and matter characterized by the interaction between a high-energy photon and the nucleus. The high energy photon strikes the nucleus; the nucleus absorbs all the photon's energy and then emits a nuclear fragment.
52. photoelectric absorption
An interaction between x-rays and matter characterized by an incident electron with slightly greater energy than the binding energy of the electrons in the inner shells, ejecting an electron from the inner shell while being absorbed in the reaction, resulting in an ionized atom.
53. photoelectron
An ionized atom with a missing inner-shell electron resulting from ejection of the electron due to photoelectric absorption.
54. Positron
A positively charged electron resulting from pair production.
55. Radiation fog
The result of scattered photons striking the radiographic film and placing a density on the film that is unrelated to the patient's anatomy.
56. Scattering
The interactions of x-ray photons and matter that cause a change in direction of the photons
57. Secondary radiation
A characteristic photon created by occurring outside the x-ray target.
58. Five Basic interactions between x-rays and matter
1. photoelectric absorption
2. Coherent Scattering
3. Compton Scattering
4. Pair production
5. Photodisintegration
59. Rule one that governs the possibility of a photoelectric interaction
The incident x-ray photon energy must be greater than the binding energy of the inner-shell electron.
60. Rule two that governs the possibility of a photoelectric interaction
A photoelectric interaction is more likely to occur when the x-ray photon energy and the electron binding energy are nearer to one another.
61. Rule three that governs the possibility of a photoelectric interaction.
A photoelectric interaction is more likely to occur with an electron that is more tightly bound in its orbit.
62. What happens to the atom after photoelectric absorption
the atom becomes ionized
63. What type of interaction is this?
Compton scatter interaction
64. What type of interaction in this?
Coherent scatter interaction
65. What type of interaction in this?
Photoelectric interaction
66. What type of interaction in this?
Pair Production
67. What type of interaction in this?
Photodisintegration interaction
68. Subject Density
Will be altered by changes in the amount or type of tissue being irradiated
69. Subject Contrast
Degree of differential absorption resulting from the differing absorption characteristics of the tissues in the body
70. Subject Detail
Dependent on the position of structures within the body and the body's placement in relationship to the film. One primary factor that affects this is distance.
71. Subject distortion
Characterized by the position of the patient. If the patient is not positioned specifically to demonstrate a particular structure this is misrepresentation of size or shape may occur.