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Rad Science 1 > Ch11: Primary Factors > Flashcards

Ch11: Primary Factors Flashcards

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
What does mAs affect?
exposure to IR Patient dose quantity/intensity of the beam, x-ray photons
26
What does mAs NOT affect?
penetration ability (beam quality) spatial resolution/recorded detail brightness of an image
27
How do you calculate mAs?
ma x time
28
T/F Different combos of ma and time will create the same resulted mAs.
True
29
Why would you change the combination of mA and time?
if you want to manipulate the time of exposure Shorter time: peds, decrease motion Longer time: blur anatomy (ribs during breathing)
30
T/F Changing the combination of ma and time will result in a change in patient dose.
False As long as the resulting mAs is constant, the patient dose will also be the same
31
To maintain exposure/pt dose - as time decreases, ma must....
increase
32
To maintain exposure/pt dose - as ma increases, time must....
decrease
33
Why is it important to check EI after each exposure?
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
T/F increasing mAs will increase the brightness of an image
False mAs has no direct affect on image brightness
35
What determines brightness?
computer processing
36
T/F Digital imaging will alert you if the EI is out of range. The image will appear noisy.
False digital images will appear consistent despite improper exposure Automatic rescaling "edits" the image Can fix overexposure, not always underexposure
37
T/F In days of film, an image that is too bright means there was a high EI.
False brightness on film indicates a low EI
38
T/F On film, an image that is dark and has a short grayscale means there was a high EI
True Over exposure means that more will reach the IR, so the image will appear dark
39
T/F kilovoltage peak affects just quality
False kvp affects both quantity and quality
40
Define kVp
kilovoltage peak energy of electrons and # of photons created beam penetrability
41
define kilo
1,000 or 1.0 x 10^3
42
What is the purpose of kvp within the tube?
accelerates the electrons w/o it, the electrons would be created but wouldn't move into the anode
43
How does kvp affect quality?
affects the beam's energy and how much penetrability it has
44
How does kvp affect quantity?
affects the conversion of electron energy into xrays (photons)
45
Increasing kvp will ______ voltage potential
increase
46
Increasing kvp will _____ electron energy
increase
47
decreasing kvp will ______ xray beam energy
decrease
48
decreasing kvp will ______ penetrability of the beam
decrease
49
increasing kvp will ______ pt dose
increase
50
Decreasing kvp will ______ receptor exposure
decrease
51
Which has the lowest EI? 70 kvp @ 2 mas 50 kvp @ 2 mas 93 kvp @ 2 mas
50 kvp @ 2 mas
52
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
93 kvp @ 60 mA, 0.03 sec
53
T/F Before you adjust mAs, you need an adequate kvp or the technique adjustment won't improve your image.
True Adequate kvp is needed in order for the beam to penetrate the patient and reach the IR
54
T/F It is better to adjust your kvp in your technique.
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
What is the 15% rule?
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
What does "more k's, more grays" mean?
higher kvp means that there is a lower contrast, longer gray-scale/more shades of gray
57
T/F A higher kvp will equal less transmission, lower subject contrast, and more scatter
False High Kvp = more transmission lower contras (long grayscale) increases scatter while decreasing photoelectric interactions
58
T/F A lower kvp will equal less transmission, higher subject contrast, shorter grayscale, and more absorption
True
59
T/F Level of subject contrast depends on the body part being examined
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
What is kvp range for extremities?
in the 60s hands may be 50s
61
T/F For a particularly large or small patient, you can adjust the kvp so you have proper penetration.
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
What is kvp range for abdomens?
75-80 85 for large patient
63
What is kvp range for chests?
90-110
64
T/F the computer can fix images as long as the kvp is at an acceptable range for penetration
True to an extent, computer processing can fix the radiographic contrast (cannot fix contrast issues due to scatter)
65
T/F Exposure techniques using higher kvp and lower mAs are recommended.
True
66
If a patient has a cast on their leg, how would you change your technique?
increase
67
What special conditions would require you to adjust your technique?
Casts implants or replacements Both require an increase

Rad Science 1 (11 decks)

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