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Radiologic Exposures > Final Review: Prime Factors > Flashcards

Final Review: Prime Factors Flashcards

1
Q

Prime exposure factors

A

kvp
mAs
mA
exposure time
Distance(d)
SID

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2
Q

Beam penetrability
how many photons will penetrate anatomy
numerically represented by HVL

A

Quality

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3
Q

intensity of beam
how many photons are within the beam (determined by mAs , kvp, distance filtration)
measured in Roentgens

A

Quantity

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4
Q

Factors affecting xray emission
Quantitative and qualitative

A

Quantitative:
mAs
kilovoltage
distance
filtration

Qualitative:
Kilovoltage
Filtrations

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5
Q

determines beam quantity or intensity

A

mA

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6
Q

The unit for current:

A

Ampere

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7
Q

when you change the current to the filament it changes:

A

it changes number of electrons released throw thermionic emission

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8
Q

when you change mA station on equipment it changes:

A

changes current to filament

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9
Q

-controls duration of exposure
-directly proportional to intensity of beam
short exposure times useful in reducing motion artifacts

A

Exposure time

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10
Q

which factor is seen as a whole in which is demonstrated as individual

A

kvp - as a whole
kev- is individual

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11
Q

smallest OID as possible and long SOD does what

A

decreases magnification

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12
Q

change from 200mA to 300mA is a change in what

A

50% increase in number of electrons emitted from filament
50% increase in number of photons
**if not change made to exposure time, patient dose also increases

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13
Q

mA * seconds =

A

mAs

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14
Q

Controls:
quantity
Image receptor exposure
patient dose

A

mAs

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15
Q

Same image receptor exposure will result from different mA and time selections (intensity and duration), provided that mAs totals are equal

A

mAs Reciprocity

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16
Q

when you increase our distance what do you do to your technique

A

increase technique to reach IR

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17
Q

what is the relationship of mA and time when total mAs maintained:

A

inverse

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18
Q

with mAs and digital imaging, mAs still controls the intensity and the number of photons reaching the patient and the IR. However what happens when mAs is too high or too low.

A

-if mAs is too high, computer automatically rescales the image to appear with adequate density
-if mAs too low, quantum mottle will still occur

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19
Q

-Quantified as a numerical value to indicate radiation intensity to a digital image
-Two common terms: exposure index(EI#) and S#

A

Image Receptor Exposure

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20
Q

-Traditional term for infrared (IR) exposure to film
-Amount of silver deposited on hard copy film image

A

Density

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21
Q

More density=

A

darker film image

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22
Q

less density=

A

lighter film image

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23
Q

overall blackness

A

Density in film

24
Q

-how dark or light digital image appears on monitor
-does not correspond to IR exposure

A

Brightness

25
-primarily controls beam quality -energy and penetrability -influences: scatter/secondary radiation production -dramatic effect on radiographic contrast if using film technology
kVp
26
Increases beam penetrability and quantity
increasing kvp
27
decreases beam penetrability and quantity
decreasing kvp
28
Because kvp affects both quality and quantity, change of only 15% will cause doubling of exposure
15%
29
what should not be used to control IR exposure
kvp should not be used to control IR exposure
30
15% if maintenance of exposure desired:
-decrease kvp by 15% and double mAs -increase kvp by 15% and reduce mAs by 50%
31
-xrays produced from a "point source" in the xray tube -inverse square law applies as it increases, beam intensity decreases
Distance (SID)
32
Intensity of radiation at given distance from point source is inversely related to the square of distance between object and source
Inverse Square Law
33
Doubling the distance, reduces the beam intensity by a factor of 4
Inverse Square Law
34
-provides technique correction for change in SID -maintains same image density/IR exposure
Exposure Maintenance formula
35
Be sure to look at the separate handouts that have been given to us throughout the semester (math, relationship charts, packets)
36
what does longer SID do
-reduced entrance skin exposure -improves image quality
37
tabletop radiography 40 inches =
100 cm
38
chest radiography and other selected exams 72 inches=
180cm
39
Exposure indicator values used to assess image quality and ALARA compliance
-kvp selected to maximize receptor exposure -distance selected based on desired beam geometry -mAs adjusted to meet exposure needs
40
ALARA
As low as reasonably achievable
41
for Digital image receptor systems what is contrast controlled through:
controlled through computer post processing
42
-image noise values impacted -digital data drop with excessive exposures
extremely high or low exposures do not produce acceptable image quality
43
what is the primary controlling factor for image receptor exposure
mAs
44
what does window width associate with:
contrast window width left and right associates with contrast and kvp
45
Low contrast
-Long Scale (many grays) -increased kvp (ex.chest xray) -wide window width -wide latitude -elephant herd
46
High Contrast
-short (fewer grays) -decreased kvp (ex.hand xray) -narrow window width -narrow latitude -zebra
47
increased kvp increases transmission, increases energy, increases Compton which increases what dose?
occupational
48
when you increase your kvp what happens to contrast
decreases
49
when you decrease your kvp what happens to your contrast
increases
50
when you increase your time what happens to your time
decreases and vise versa
51
Practice: -indirect square long -reciprocity -direct square law -15% rule
52
The radiograph must exhibit differences in the brightness levels or densities in order to differentiate among the anatomic tissues
image contrast
53
a result of the absorption characteristics of the anatomic tissue radiographed and the quality of the xray beam
subject contrast
54
the ability to distinguish among types of tissues is determined by the differences in brightness levels or densities in the image or contrast
subject contrast
55
number of different shades of gray that can be stored and displayed in a digital image
Gray scale
56
the range of densities visible on film
Scale of contrast

Radiologic Exposures (11 decks)

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