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trisemester 3 TCC > chapter 10 xray physics > Flashcards

chapter 10 xray physics Flashcards

1
Q

Image quality defined as?

A

is the fidelity of anatomical structures by the image

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2
Q

the most important factors affecting quality of the image?

A

resolution

noise and artifacts

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3
Q

what are the 2 different forms of resolution

A

spatial and contrast

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4
Q

noise is defined as in an image?

A

random variation in optic denstiy of image

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5
Q

what is optic density?

A

how much light can be transmitted through

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6
Q

which of the 5 basic interaction of matter are considered important when it comes to noise?

A

compton because it deals with scatter e-

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7
Q

what is film grain and how does it contribute the image?

A

it is finite small silver crystals that make up the image itself

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8
Q

how does film grain affect the noise?

A

larger the film grain the more noise there is

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9
Q

what are structure mottles?

A

they are large phosphor crystals of the intensifying screen

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10
Q

how does structure mottles contribute the noise?

A

the larger the mottle structre the more noise there is

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11
Q

how does speed affect the noise and resolution?

A

as speed increases the higher the noise is and the lower the resolution is

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12
Q

how does higher speed affect the pt. dose and heat production?

A

as the speed increases the pt. dose decreases and the heat damage to the anode decreases

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13
Q

slower speed has what affect on the image?

A

the resolution will increase but the pt. dose will increase and the heat damage to the anode

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14
Q

the characteristic curve is used for _____ systems?

A

analog

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15
Q

characteristic curve is for analog systems and it shows a response curve for xray films that demonstrated what characteristics?

A

density, contrast, speed, latitude

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16
Q

When a xray machine uses film what characteristics of processing must you take into consideration?

A

time and temperature

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17
Q

characteristic curve shows a relationship between what?

A

optical density and the radiation exposure.

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18
Q

how would optical desntiy appear on the film?

A

as different shade of grey

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19
Q

what happens to the optical density as the radiation exposure increases?

A

it becomes more black so it will increase

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20
Q

what is another name for the characteristic curve?

A

hurter and driffield or H & D curve

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21
Q

contrast of the radiographic image refers to the?

A

difference between the gray shades that comprise the image?

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22
Q

the straighter the line is of the H & D curve shows what?

A

represents that any change in the exposure will make a greater change in film

23
Q

the straighter the line represent the film has what?

greater contrast OR Less contrast?

A

greater contrast in response to the exposure

24
Q

when looking at a characteristic curve you can notice which one is faster by noticing what about the exposure?

A

how much radiation exposure it takes

25
Q

the human eye can perceive optical densities in between what range?

A

0.25 (clear) and 2.5 (black)

26
Q

the xray film base is of what material?

A

polyester

27
Q

what is the OD of the xray film base?

A

0.1

28
Q

what is added to the xray film base to reduce glare in the view box?

A

blue dye

29
Q

how would you describe fog when it comes too OD?

A

any additional OD to the on a processed xray film that does not have a purpose will result in fog

30
Q

why is base and fog measured?

A

for quality control

31
Q

what is a desnitometer?

A

measure the OD of materials such as the film

32
Q

Base + fog should not exceed?

and should not be lower than?

A
  1. 3

0. 25

33
Q

the latitude of the H & D curve demonstrates what?

A

the amount of exposure

34
Q

what does the magnification factor show a relationship between?

A

image size and object size

35
Q

focal film distance is also known as?

A

source image distance

36
Q

SOD is known as

A

source object distance

37
Q

OID is known as

A

object image distance

38
Q

what do measure by dividing SID by SOD

A

the magnification

39
Q

how does a smaller object distance affect the shadow?

A

it will get smaller

40
Q

is you increase the OID what happens to the magnification?

A

it gets bigger

41
Q

if you decrease the SOD or the OID what happens to the shadow?

A

it will get bigger

42
Q

how would a longer SOD affect the magnification?

A

reduces magnification

43
Q

distortion is defined as?

A

uneven magnification

44
Q

what may contribute to distortion

A

size
shape
position/orientation

45
Q

how does the shape of the object affect the shadow?

A

directly

46
Q

how does the shape of an object affect the grey shade?

A

does not change

47
Q

when considering object position what is important?

A

object symmetry with the image source

48
Q

as the object thickness what happens to the edge sharpness?

A

there will be 1/2 shadow area

49
Q

why is an objects orientation in space important?

A

a distorted image that apears foreshortened will be produced the more lateral to the central axis it lies

50
Q

due to distortion in the apparent length due to the orientation of space is the apparent length a good indicator to actual size?

A

no

51
Q

how does kVp effect the contrast changes?

A

higher kVp produces lower contrast with longer scale of grey shades and lower kVp produces higher contrast image with shorter scale pf grey shades

52
Q

kVP is the controlling factor of what?

A

contrast

53
Q

the mAs is the primary controlling factor of what?

A

film exposure

54
Q

why does short exposure times yield better image quality?

A

reduced pt. motion,

trisemester 3 TCC (25 decks)

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