Principles of Radiographic Imaging: An Art and A Science: Chapter 11,12 & 13 Radiographic Imaging Flashcards


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1

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

2. Direct Square Law

Exposure maintenance formula

3

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

4. milliamperage- second mAS

The unit used to describe the product of tube current and exposure time.

5

5. Penetrability

The ability of the x-ray to pass through structures and tissues.

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6. Prime factor

Factors related to x-ray emission that are under the direct control of the radiographer; milliamperage, kilovoltage, and distance.

7

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.

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8. x-ray quality

The penetrating ability of the x-ray beam. Kilovoltage and filtration are the main factors.

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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.

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10. The principle controlling factors for quantity is

mAs

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11. The principle controlling factor for quality is

kVp

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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

13. mAs is calculated by

mA X time

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14. What does mAs stand for

milliamperage per second

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15. what is the formula for mAs

mA X time

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16. What is mAs the measure of

tube current

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17. What happens as mAs is increased

density increases

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18. as mAs doubles the exposure does what

doubles

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19. what happens to the filament of the circuit as mA is increased

thermionic emission

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20. Density is the

the amount of blackening on the image that is determined by exposure. mAs is the primary controller.

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21. What is D-max

The maximum density a film can achieve (Film only)

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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.

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23.When does the reciprocity law fail

The law fails at very short times (below 10 milliseconds) and very long times (6-7 seconds)

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24. Low kVp gives an image what type of contrast

high contrast

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25. An increase in kVp by 15% will do what to the exposure

double the exposure

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26. A decrease in kVp by 15% will do what to the exposure

cut the exposure by 1/2

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27. x-ray intensity does what as distance from the tube decreases

increases

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28. x-ray intensity will do what as the distance from the tube increases

decrease

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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.

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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

31. Density maintenance formula

mAs1/mAs2 = D1 2/D2 2

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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.

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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

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34. What are three prime factors that affect x-ray emission

mAs, kVp, Distance

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35. What is the unit of measurement for x-ray quantity?

roentgen (R)

36

36. Define ampere?

The unit of current

37

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

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

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

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

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.

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42. Backscatter radiation

Photons that deflect back towards the source, traveling in the opposite direction of the incident photon.

43

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.

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44. Characteristic photon

An x-ray photon created by the electron transfer from one shell to another.

45

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.

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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

47. Compton (or recoil) electron

The dislodged electron resulting from compton scattering

48

48. Compton scattered photon

The photon the exits the atom in a different direction as a result of compton scattering.

49

49. Negatron

A negatively charged electron resulting from pair production

50

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

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

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

53. photoelectron

An ionized atom with a missing inner-shell electron resulting from ejection of the electron due to photoelectric absorption.

54

54. Positron

A positively charged electron resulting from pair production.

55

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

56. Scattering

The interactions of x-ray photons and matter that cause a change in direction of the photons

57

57. Secondary radiation

A characteristic photon created by occurring outside the x-ray target.

58

58. Five Basic interactions between x-rays and matter

1. photoelectric absorption

2. Coherent Scattering

3. Compton Scattering

4. Pair production

5. Photodisintegration

59

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

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

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

62. What happens to the atom after photoelectric absorption

the atom becomes ionized

63
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63. What type of interaction is this?

Compton scatter interaction

64
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64. What type of interaction in this?

Coherent scatter interaction

65
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65. What type of interaction in this?

Photoelectric interaction

66
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66. What type of interaction in this?

Pair Production

67
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67. What type of interaction in this?

Photodisintegration interaction

68

68. Subject Density

Will be altered by changes in the amount or type of tissue being irradiated

69

69. Subject Contrast

Degree of differential absorption resulting from the differing absorption characteristics of the tissues in the body

70

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

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.