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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
Q

-primarily controls beam quality
-energy and penetrability
-influences: scatter/secondary radiation production
-dramatic effect on radiographic contrast if using film technology

A

kVp

26
Q

Increases beam penetrability and quantity

A

increasing kvp

27
Q

decreases beam penetrability and quantity

A

decreasing kvp

28
Q

Because kvp affects both quality and quantity, change of only 15% will cause doubling of exposure

A

15%

29
Q

what should not be used to control IR exposure

A

kvp should not be used to control IR exposure

30
Q

15%
if maintenance of exposure desired:

A

-decrease kvp by 15% and double mAs
-increase kvp by 15% and reduce mAs by 50%

31
Q

-xrays produced from a “point source” in the xray tube
-inverse square law applies
as it increases, beam intensity decreases

A

Distance (SID)

32
Q

Intensity of radiation at given distance from point source is inversely related to the square of distance between object and source

A

Inverse Square Law

33
Q

Doubling the distance, reduces the beam intensity by a factor of 4

A

Inverse Square Law

34
Q

-provides technique correction for change in SID
-maintains same image density/IR exposure

A

Exposure Maintenance formula

35
Q

Be sure to look at the separate handouts that have been given to us throughout the semester (math, relationship charts, packets)

A
36
Q

what does longer SID do

A

-reduced entrance skin exposure
-improves image quality

37
Q

tabletop radiography
40 inches =

A

100 cm

38
Q

chest radiography and other selected exams
72 inches=

A

180cm

39
Q

Exposure indicator values used to assess image quality and ALARA compliance

A

-kvp selected to maximize receptor exposure
-distance selected based on desired beam geometry
-mAs adjusted to meet exposure needs

40
Q

ALARA

A

As low as reasonably achievable

41
Q

for Digital image receptor systems what is contrast controlled through:

A

controlled through computer post processing

42
Q

-image noise values impacted
-digital data drop with excessive exposures

A

extremely high or low exposures do not produce acceptable image quality

43
Q

what is the primary controlling factor for image receptor exposure

A

mAs

44
Q

what does window width associate with:

A

contrast window width left and right
associates with contrast and kvp

45
Q

Low contrast

A

-Long Scale (many grays)
-increased kvp (ex.chest xray)
-wide window width
-wide latitude
-elephant herd

46
Q

High Contrast

A

-short (fewer grays)
-decreased kvp (ex.hand xray)
-narrow window width
-narrow latitude
-zebra

47
Q

increased kvp increases transmission, increases energy, increases Compton which increases what dose?

A

occupational

48
Q

when you increase your kvp what happens to contrast

A

decreases

49
Q

when you decrease your kvp what happens to your contrast

A

increases

50
Q

when you increase your time what happens to your time

A

decreases and vise versa

51
Q

Practice:
-indirect square long
-reciprocity
-direct square law
-15% rule

A
52
Q

The radiograph must exhibit differences in the brightness levels or densities in order to differentiate among the anatomic tissues

A

image contrast

53
Q

a result of the absorption characteristics of the anatomic tissue radiographed and the quality of the xray beam

A

subject contrast

54
Q

the ability to distinguish among types of tissues is determined by the differences in brightness levels or densities in the image or contrast

A

subject contrast

55
Q

number of different shades of gray that can be stored and displayed in a digital image

A

Gray scale

56
Q

the range of densities visible on film

A

Scale of contrast

Radiologic Exposures (11 decks)

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