Chapters 3 & 4 Flashcards Preview

Radiology > Chapters 3 & 4 > Flashcards

Flashcards in Chapters 3 & 4 Deck (65)
Loading flashcards...
1

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

-less radiation exposure
-faster

2

elements intensifying screens emit blue light

calcium tungstate screens

3

elements in the intensifying screens emit green light

rare earth screens

4

why is a short object film used in oral radiography

reduce penumbra and magnification

5

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

perpendicular

6

3 factors that effect film contrast in radiology

-exposure
-processing
-film type

7

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

focal spot

8

substance that has ability of "converting to light" has what property

florescent

9

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

-available source of free electrons
-high voltage to impact speed to the electrons
-target that is capable of stopping/slowing the electrons

10

what distance factor directly influences magnification of images on the film

target-object distance
object-film distance

11

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

too low kVp
too low mA

12

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

decrease kVp and increase mA

13

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

increase kVp

14

Intensifying screens used in extraoral radiography

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

15

increasing kVp causes the resultant radiograph to have

longer scale of contrast

16

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

long scale contrast (low contrast)

17

what does ALARA stand for

as low as reasonably achievable

18

increasing kVp results in

low contrast (long scale contrast)

19

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

decrease exposure time

20

when voltage is increased

electrons move from cathode to anode with more speed

21

exposure time is measured in

impulses

22

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

contrast

23

overall blackness or darkness of a film is termed

density

24

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

appear lighter

25

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

low contrast

26

shadow cast rules are often referred to as

geometric factors

27

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

geometric factors

28

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

kilovoltage peak

29

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

less penetrating dental x-rays with the longer wavelength

30

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

high contrast

31

a film with high contrast

is useful for the detection and progression of dental carries

32

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

inversely
square of distance

33

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

four times

34

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

object film distance

35

the paralleling technique is recommended over the bisecting angle technique because

it gives a less distorted picture of root length

36

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

inversely with the square of the distance

37

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

quadrupled

38

to increase penetrability of the xrays their wavelength should be

shortened by increasing kVp

39

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

definition

40

the optical or overall density of an intraoral film indicates the

degree of darkness

41

optical density is a function of

kVp, mA, and exposure time

42

subject contrast is primarily a function of

kVp

43

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

decrease kVp and increase mA

44

image magnification may be minimized by

long cone

45

image sharpness on a radiograph is increased by

using a small focal spot size

46

small focal spot size

increases sharpness

47

short scale contrast (high contrast)

fewer shades of gray and more black against white

48

gray tones indicate

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

49

kVp of short scale contrast

low kVp (60-70)

50

long scale contrast (low contrast)

low and gradual because there are many shades of gray

51

kvp of long scale contrast

higher kVp (80-100)

52

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

radiolucent

53

structures that are dense and absorb or resist passage of xrays

radiopaque

54

high kVp

lower contrast

55

low kVp

higher contrast

56

increased scatter radiation

lower contrast

57

decreased scatter radiation

higher contrast

58

large focal spot

decrease sharpness

59

long target-image receptor distance

increase sharpness

60

short target-image receptor distance

decrease sharpness

61

short object-image receptor distance

increase sharpness

62

long object image receptor distance

decrease sharpness

63

focal spot

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

64

"dead-man" exposure switch

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

65

what absorbs heat during xray production in tube head

air or gas