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Rad Science 1 > Ch11: Primary Factors > Flashcards

Ch11: Primary Factors Flashcards

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1
Q

Define mA

A

of electrons flowing from cathode to anode

Milliamperage
of the current to the filaments
determines thermionic emission
Tube Current

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2
Q

What two components make up mAs?

A

milliamperage and time (in seconds)

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3
Q

What are primary exposure factors?

A

mA
seconds (time)
KvP (kilovoltage peak)

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4
Q

Which factor(s) affect quality of the xray beam?

A

kvp

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5
Q

Which factor(s) affect quantity of the xray beam?

A

ma
time
kvp

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6
Q

How does mA increasing affect tube current/quantity?

A

increases

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7
Q

How does mA increasing affect # electrons at the filament?

A

increases

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8
Q

How does mA increasing affect pt dose?

A

increases

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9
Q

How does mA decreasing affect tube current/quantity?

A

decreses

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10
Q

How does mA decreasing affect # of electrons at the filament?

A

decreases

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11
Q

How does mA decreasing affect pt dose?

A

decreases

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12
Q

What does time of exposure mean?

A

amount of time the electrons are flowing in the tube and xrays are being created

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13
Q

What measurement is time recorded?

A

seconds

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14
Q

What benefits are there to a shorter exposure time?

A

decreases motion or blur

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15
Q

What q’s are related to time?

A

quantity only

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16
Q

How does increased time affect # of electrons at filament?

A

increases

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17
Q

How does increased time affect # of xrays and patient dose?

A

increases

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18
Q

How does decreased time affect # of electrons at filament?

A

decreases

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19
Q

How does decreased time affect # of xrays and patient dose?

A

decreases

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20
Q

What does mAs control?

A

amount of thermionic emission at the filament and the number of photons created at the anode

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21
Q

Define thermionic emission

A

boiling off of electrons from a filament (within the cathode) by a flow of electrical current

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22
Q

What is quantity?

A

intensity/amount of radiation striking/reaching the IR

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23
Q

Is ma and time a inverse or direct relationship?

A

inverse
as mA increases, time needs to decrease in order to maintain exposure

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24
Q

is mAs indirect/directly proportional to quantity?

A

direct
need the right combo to penetrate at the correct EI

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25
Q

What does mAs affect?

A

exposure to IR
Patient dose
quantity/intensity of the beam, x-ray photons

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26
Q

What does mAs NOT affect?

A

penetration ability (beam quality)
spatial resolution/recorded detail
brightness of an image

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27
Q

How do you calculate mAs?

A

ma x time

28
Q

T/F Different combos of ma and time will create the same resulted mAs.

A

True

29
Q

Why would you change the combination of mA and time?

A

if you want to manipulate the time of exposure
Shorter time: peds, decrease motion
Longer time: blur anatomy (ribs during breathing)

30
Q

T/F Changing the combination of ma and time will result in a change in patient dose.

A

False
As long as the resulting mAs is constant, the patient dose will also be the same

31
Q

To maintain exposure/pt dose - as time decreases, ma must….

A

increase

32
Q

To maintain exposure/pt dose - as ma increases, time must….

A

decrease

33
Q

Why is it important to check EI after each exposure?

A

digital processing will adjust an image even if the exposure it too high or low
ensure the EI is in range and adjust technique if pt dose is too high or low

34
Q

T/F increasing mAs will increase the brightness of an image

A

False
mAs has no direct affect on image brightness

35
Q

What determines brightness?

A

computer processing

36
Q

T/F Digital imaging will alert you if the EI is out of range. The image will appear noisy.

A

False
digital images will appear consistent despite improper exposure
Automatic rescaling “edits” the image
Can fix overexposure, not always underexposure

37
Q

T/F In days of film, an image that is too bright means there was a high EI.

A

False
brightness on film indicates a low EI

38
Q

T/F On film, an image that is dark and has a short grayscale means there was a high EI

A

True
Over exposure means that more will reach the IR, so the image will appear dark

39
Q

T/F kilovoltage peak affects just quality

A

False
kvp affects both quantity and quality

40
Q

Define kVp

A

kilovoltage peak
energy of electrons and # of photons created
beam penetrability

41
Q

define kilo

A

1,000 or 1.0 x 10^3

42
Q

What is the purpose of kvp within the tube?

A

accelerates the electrons
w/o it, the electrons would be created but wouldn’t move into the anode

43
Q

How does kvp affect quality?

A

affects the beam’s energy and how much penetrability it has

44
Q

How does kvp affect quantity?

A

affects the conversion of electron energy into xrays (photons)

45
Q

Increasing kvp will ______ voltage potential

A

increase

46
Q

Increasing kvp will _____ electron energy

A

increase

47
Q

decreasing kvp will ______ xray beam energy

A

decrease

48
Q

decreasing kvp will ______ penetrability of the beam

A

decrease

49
Q

increasing kvp will ______ pt dose

A

increase

50
Q

Decreasing kvp will ______ receptor exposure

A

decrease

51
Q

Which has the lowest EI?
70 kvp @ 2 mas
50 kvp @ 2 mas
93 kvp @ 2 mas

A

50 kvp @ 2 mas

52
Q

Which has the highest EI?
70 kvp @ 200 mA, 0.01 sec
50 kvp @ 75 mA, 0.027 sec
93 kvp @ 60 mA, 0.03 sec

A

93 kvp @ 60 mA, 0.03 sec

53
Q

T/F Before you adjust mAs, you need an adequate kvp or the technique adjustment won’t improve your image.

A

True
Adequate kvp is needed in order for the beam to penetrate the patient and reach the IR

54
Q

T/F It is better to adjust your kvp in your technique.

A

False
kvp also affects contrast, so your image quality will decrease if kvp is decreased too much
kvp changes absorption and transmission properties b/c it changes the amount of penetration

55
Q

What is the 15% rule?

A

15% increase in kvp will double # of photons
15% decrease in kvp will half # of photons

In order to keep the exposure/quality, need to adjust the mas accordingly.
increase in kvp = double mas
decrease in kvp = half mas

56
Q

What does “more k’s, more grays” mean?

A

higher kvp means that there is a lower contrast, longer gray-scale/more shades of gray

57
Q

T/F A higher kvp will equal less transmission, lower subject contrast, and more scatter

A

False
High Kvp = more transmission
lower contras (long grayscale)
increases scatter while decreasing photoelectric interactions

58
Q

T/F A lower kvp will equal less transmission, higher subject contrast, shorter grayscale, and more absorption

A

True

59
Q

T/F Level of subject contrast depends on the body part being examined

A

True
some body parts may not show all anatomy/detail b/c of differential absorption, but there is enough contrast for the doctors to see what they need

60
Q

What is kvp range for extremities?

A

in the 60s
hands may be 50s

61
Q

T/F For a particularly large or small patient, you can adjust the kvp so you have proper penetration.

A

True
the desktop has an option for “large” or “small” or “peds” which will adjust the technique for you to avoid over or under exposure

62
Q

What is kvp range for abdomens?

A

75-80
85 for large patient

63
Q

What is kvp range for chests?

A

90-110

64
Q

T/F the computer can fix images as long as the kvp is at an acceptable range for penetration

A

True
to an extent, computer processing can fix the radiographic contrast (cannot fix contrast issues due to scatter)

65
Q

T/F Exposure techniques using higher kvp and lower mAs are recommended.

A

True

66
Q

If a patient has a cast on their leg, how would you change your technique?

A

increase

67
Q

What special conditions would require you to adjust your technique?

A

Casts
implants or replacements

Both require an increase

Rad Science 1 (11 decks)

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