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Rad tech subjects > ch 26-27-28-29physics > Flashcards

ch 26-27-28-29physics Flashcards

1
Q

which of the 2 image properties determines if the IR was sufficiently exposed?

A

density

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2
Q

structural details are made up of ________ and _______.

A

density and contrast

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3
Q

density is considered an ______ _______ _______.

A

image quality factor

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4
Q

are brightness and density interchangeable?

A

no

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5
Q

a monitor control function that can change light and dark on an image on the display monitor

A

brightness

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6
Q

with film and digital radiography the key to a visible image is….

A

having the correct IR exposure

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7
Q

window level controls

A

brightness

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8
Q

when the IR receives too many photons and records to much information it is called

A

overexposure

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9
Q

when the IR did not receive enough information it is considered

A

underexposed

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10
Q

what is the controlling factor of density for film and digital radiography?

A

mAs

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11
Q

with film we need to adjust mAs _____% to see a visible change in density

A

30

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12
Q

why must we monitor density with the Ei number?

A

because regardless of the exposure the computer system will attempt to rescale the histogram so the images acceptable to the eyes

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13
Q

what is the general rule of thumb for density

A

make changes in increments of doubles or halves

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14
Q

what is the primary influencing factor of density?

A

mAs

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15
Q

in what two ways does kv alter the intensity of the beam that reaches the IR?

A

controls the energy of the e- that strike the anode

controls the average energy of the X Ray photons produced at the anode target

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16
Q

a change in kv alters the intensity of the beam when mAs and other factors _____ ______ ______.

A

stay the same

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17
Q

what is the minimum change in kv to see a noticeable change in density ? the recommended?

A

5%. 15%

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18
Q

when is the 15% rule used?

A

when you want to change the contrast of an image but keep the same density

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19
Q

what factor do you adjust if you only want to change density only?

A

mAs

20
Q

what are the OTHER influencing factors for density?

A 
focal spot size only from blooming
anode heel effect
distance 
filtration 
beam restriction
anatomical part 
grid
IR 
film speed
21
Q

what makes up the detail of an image?

A

contrast

22
Q

the difference between adjacent densities/IR exposure?

A

contrast

23
Q

define dynamic range:

A

contrast as it is displayed on a monitor in digital imaging

“range of brightness”

24
Q

what digital process controls brightness on a digital image?

A

window width

25
Q

what affects grayscale bit depth?

A

contrast/dynamic range/ ww on the z axis

26
Q

why is contrast hard to adjust?

A

because any change in density will effect contrast

27
Q

why is low contrast often desired?

A

it has more differences in density

28
Q

what are the two properties that make detail visible ?

A

density and contrast

29
Q

how do we manipulate contrast in film?

digital?

A

kvp

ww

30
Q

what are the 2 types of contrast?

A

IR contrast ( film/ digital)

subject contrast

these make up IMAGE CONTRAST

31
Q

what are the 4 factors that can affect IR contrast in film?

A

intensifying screen
film density
d log e curve
processing

32
Q

digital IR contrast:

as digital images go through post processing both the _______ and the ______ affect the final image contrast displayed

A

histogram and LUT

note: the correct mAs and kvp must be chosen by the tech to ensure the correct exposure to the IR and desired differential attenuation

33
Q

define subject contrast:

A

the range of differences in the intensity of the X Ray beam AFTER attenuation

34
Q

subject contrast depends on:

A

kv, amount and type of tissue radiated

35
Q

higher kvp produces _____ contrast

A

decreased

36
Q

what type of interaction creates decreased contrast

A

Compton

37
Q

digital scatter causes ______ contrast

A

decreased

38
Q

how does AMOUNT of irradiated material affect contrast?

A

affects the number of X rays that reach the IR

39
Q

the anatomical structures of interest are visible only when ________ ________ exists between the densities

A

sufficient contrast

40
Q

what type of interaction causes high contrast

A

photoelectric interactions

41
Q

discerning contrast is difficult if an image has poor ___ _________

A

IR exposure/ density

42
Q

in digital, KVP can no longer be assessed by viewing the difference between densities or brightness……why?

A

the response curve is LINEAR

43
Q

what is the controlling factor of contrast?

main influencing factor ?

A

kvp

mAs

44
Q

OTHER influencing factors of contrast:

A

focal spot size (not likely )

anode heel effect. (very little effect)

distance
filtration 
beam restriction
anatomical part
grid
f/s combo
processing
45
Q

what 3 things determine the actual recorded detail

A

matrix size

pixel size

grayscale bit depth

Rad tech subjects (16 decks)

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