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Radiology > Chapters 3 & 4 > Flashcards

Chapters 3 & 4 Flashcards

1
Q

2 reasons why rare earth element screens are preferred over the calcium tungstate

A
  • less radiation exposure

- faster

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2
Q

elements intensifying screens emit blue light

A

calcium tungstate screens

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3
Q

elements in the intensifying screens emit green light

A

rare earth screens

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4
Q

why is a short object film used in oral radiography

A

reduce penumbra and magnification

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5
Q

relationship between the central ray of the xray beam and the object and film must be attained in order to prevent distortion of the image

A

perpendicular

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6
Q

3 factors that effect film contrast in radiology

A
  • exposure
  • processing
  • film type
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7
Q

slight vibration of the tube head during film exposure will result in an increase in the size of what structure in the x-ray tube

A

focal spot

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8
Q

substance that has ability of “converting to light” has what property

A

florescent

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9
Q

the three basic elements of an x-ray tube needed to produce xrays are

A
  • available source of free electrons
  • high voltage to impact speed to the electrons
  • target that is capable of stopping/slowing the electrons
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10
Q

what distance factor directly influences magnification of images on the film

A

target-object distance

object-film distance

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11
Q

a radiograph that is light in density is most likely caused by which exposure problem

A

too low kVp

too low mA

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12
Q

if a change from the long scale contrast technique to a short scale contrast technique and maintain same densitity what should be done

A

decrease kVp and increase mA

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13
Q

oral structures of greater density may require increased penetration by xray photons this can be done how?

A

increase kVp

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14
Q

Intensifying screens used in extraoral radiography

A

Less radiation exposure to patient
But can also
Decrease sharpness of radiographic image

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15
Q

increasing kVp causes the resultant radiograph to have

A

longer scale of contrast

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16
Q

what will result in a radiographic image that has many gradiations of gray from totally white to completely black

A

long scale contrast (low contrast)

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17
Q

what does ALARA stand for

A

as low as reasonably achievable

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18
Q

increasing kVp results in

A

low contrast (long scale contrast)

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19
Q

when the mA is increased what must be adjusted to compensate for this increase in order to make a film with the same contrast

A

decrease exposure time

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20
Q

when voltage is increased

A

electrons move from cathode to anode with more speed

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21
Q

exposure time is measured in

A

impulses

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22
Q

term that describes how dark and light areas are differentiated on a film

A

contrast

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23
Q

overall blackness or darkness of a film is termed

A

density

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24
Q

if kilovoltage is decreased with no other variations in exposure factors, the result will

A

appear lighter

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25
Q

a radiograph that has few dark and light areas with many shades of gray is said to have

A

low contrast

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26
Q

shadow cast rules are often referred to as

A

geometric factors

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27
Q

contribute to the quality of the radiographic image. factors that related to relationship of angles, points, lines or surfaces

A

geometric factors

28
Q

highest voltage to which the current in the tube rises during an exposure is called

A

kilovoltage peak

29
Q

when contrasted with the use of 85 to 100 kV for dental x-rays, the use of 65 to 75 kV produces

A

less penetrating dental x-rays with the longer wavelength

30
Q

when kilovoltage peak settings are used (65 to 70kVp) a film with _________ will result

A

high contrast

31
Q

a film with high contrast

A

is useful for the detection and progression of dental carries

32
Q

according to the inverse square law, the intensity of radiation is______proportional to the ________from the source of radiation

A

inversely

square of distance

33
Q

according to the inverse square law if the length of the target film distance is cut in half the resultant beam is _______ intense

A

four times

34
Q

according to the inverse square law, what factor must be adjusted if the target film distance is doubled

A

object film distance

35
Q

the paralleling technique is recommended over the bisecting angle technique because

A

it gives a less distorted picture of root length

36
Q

the intensity of x-radiation at any given distance from the source of radiation varies

A

inversely with the square of the distance

37
Q

when an 8 inch target film distance is changed to a 16 inch target film distnace (keeping kVp and mA constant) the exposure time should be

A

quadrupled

38
Q

to increase penetrability of the xrays their wavelength should be

A

shortened by increasing kVp

39
Q

the size of the focal spot in the xray tube influences the radiographic

A

definition

40
Q

the optical or overall density of an intraoral film indicates the

A

degree of darkness

41
Q

optical density is a function of

A

kVp, mA, and exposure time

42
Q

subject contrast is primarily a function of

A

kVp

43
Q

how do you change from a low contrast to a high contrast image and still maintain density

A

decrease kVp and increase mA

44
Q

image magnification may be minimized by

A

long cone

45
Q

image sharpness on a radiograph is increased by

A

using a small focal spot size

46
Q

small focal spot size

A

increases sharpness

47
Q

short scale contrast (high contrast)

A

fewer shades of gray and more black against white

48
Q

gray tones indicate

A

differences in absorption of the xray photons by the various tissues of the oral cavity

49
Q

kVp of short scale contrast

A

low kVp (60-70)

50
Q

long scale contrast (low contrast)

A

low and gradual because there are many shades of gray

51
Q

kvp of long scale contrast

A

higher kVp (80-100)

52
Q

structures that permit the passage of xrays with little or no resistance

A

radiolucent

53
Q

structures that are dense and absorb or resist passage of xrays

A

radiopaque

54
Q

high kVp

A

lower contrast

55
Q

low kVp

A

higher contrast

56
Q

increased scatter radiation

A

lower contrast

57
Q

decreased scatter radiation

A

higher contrast

58
Q

large focal spot

A

decrease sharpness

59
Q

long target-image receptor distance

A

increase sharpness

60
Q

short target-image receptor distance

A

decrease sharpness

61
Q

short object-image receptor distance

A

increase sharpness

62
Q

long object image receptor distance

A

decrease sharpness

63
Q

focal spot

A

small area on the target where bombarding electrons are converted to xrays

64
Q

“dead-man” exposure switch

A

automatically terminates the exposure when operators finger stops pressing on the timer button

65
Q

what absorbs heat during xray production in tube head

A

air or gas

Radiology (6 decks)

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