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RTCA253 Exposures > Radiographic technique > Flashcards

Radiographic technique Flashcards

1
Q

The combination of the radiation quantity (mR/mAs) and radiation quality (HVL)

A

Exposure factors

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2
Q

What are the 4 main exposure factors?

A

KVP, mA, Exposure time, SID

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3
Q

controls how fast the electrons are sent across the tube

A

kVp

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4
Q

Controls Quality

A

KVP

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5
Q

Controls Quantity

A

mAs (directly proportional)

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6
Q

Beam penetrability of KVP

A

high energy, greater penetrating ability, more compton effect(scatter)

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7
Q

KVP

A
  • controls scale of contrast
    * increasing image noise production
    * reducing image contrast
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8
Q

affects number of x-rays produced (not energy)

A

mA

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9
Q

mA, quantity, and patient dose are ____ proportional

A

directly

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10
Q

determines the number of photons radiation quantity, OD and patient dose

A

mA

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11
Q

mA stations are usually

A

50, 100, 200, 300, 400 & 600

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12
Q

Three phase exposure time

A

1 ms

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13
Q

single phase exposure time

A

<8ms

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14
Q

Short exposure time ______ image blur.

A

reduces

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15
Q

Must ________ mA when using short exposure times to maintain x-ray intensity

A

mA

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16
Q

Formula for mAs

A

mAs= (mA) x (S)

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17
Q

key factor of optical density

A

mAs

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18
Q

mAs

A

changes the number of electrons

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19
Q

states the OD will be constant for any combination of mA and exposure time that results in constant mAs

A

Reciprocity Law

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20
Q

Distance affects x-ray ________ not _______

A

intensity; quality

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21
Q

Determine required change in mAs after a change in SID to maintain OD

A

square law

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22
Q

half-wave rectification

A

drops to zero

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23
Q

Full wave rectification

A

consistent but always drops to zero

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24
Q

3 phase power

A

6 or 12 pulse, energy higher, nearly constant output

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25
Q

high frequency

A

less 1% ripple, much better overall

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26
Q

Hypersthenic

A

5% population, massive type, chest and abdomen are very broad, lungs are short and wide, stomach is high and transverse

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27
Q

Sthenic

A

average body type, represents 50% of population, active or strong, stomach is more J-shape and lower, more slender version of hypersthenic

28
Q

Asthenic

A

opposite of hypersthenic, 10% of population, very frail and of poor muscle tone, narrow, long, shallow
diaphragm is low, heart is long and slender,
abdominal cavity rests mainly in the pelvic region

29
Q

Hyposthenic

A

35% of population, modification of the asthenic build, stomach is j-shaped and extends into the iliac crest region, high splenic flexure

30
Q

As thickness increases, ______ radiation is necessary for penetration.

A

more

31
Q

soft tissue technique

A

low kvp and high mAs

32
Q

Extremity technique (soft tissue and bones)

A

low kvp

33
Q

Chest technique (high contrast)

A

high kvp

34
Q

Abdomen (low contrast)

A

middle kvp

35
Q

Pathology

A

the destructive decrease or constructive increase in mass or composition has a direct effect on technical consideration

36
Q

image quality factors

A

Optical density, contrast, image detail, distortion

37
Q

The degree of blackening of the finished radiograph

A

Optical density

38
Q

when OD is high…

A

took dark, over exposed

39
Q

when OD is low…

A

too light, under exposed

40
Q

OD and mAs are _______ proportional.

A

directly

41
Q

when only mAs is changed it is either………

A

halfed or doubled

42
Q

___% increase required for visible change in OD for mAs.

A

30%

43
Q

____% increase is required for visible change in OD for kvp

A

4

44
Q

square law formula

A

mAs2/mAs1=(SID2)^2/(SID1)^2

45
Q

15% rule: To maintain OD a ___ increase in kvp would require a reduction of ____ the mAs

A

15%; half

46
Q

variation in OD between adjacent atomic structures

A

Contrast

47
Q

Contrast is controlled by

A

KVP (penetrability of the primary beam)

48
Q

The range of OD from the whitest portion to the blackest portion of the radiographic image

A

scale of contrast

49
Q

Short scale

A

low kvp, short scale, high contrast, “bone work”

50
Q

high contrast radiographs
used when an increase in contrast is desired
produces greater differences in black and white

A

short scale

51
Q

Long scale contrast

A

low contrast, many shades of grey, high kvp, “chest images”

52
Q

radiographs having optimal radiographic density and contrast to visualize area of interest

A

photographic properties

53
Q

5% rule

A

an increase in kvp by 5% may be accompanied by reduction in mAs by 30% to produce the same OD at a slightly reduced contrast scale.

54
Q

Sharpness of small structures or spatial resolution of the image

A

image detail

55
Q

image detail is evaluated by

A

sharpness and visibility

56
Q

the amount of clarity or blur in the visualization of the structural lines or borders of tissues in the image

A

sharpness

57
Q

Sharpness controlled by

A

FFS, SID, OID, intensifying screen

58
Q

The contrast resolution of ability to see the detail of the radiographic image

A

Visibility

59
Q

Loss of Visibility

A

refers to any factor that causes a deterioration or obscuring of the image detail (fog)

60
Q

The misrepresentation of object size and shape due to position of the tube, the anatomic part, and or image receptor

A

Distortion

61
Q

disadvantage of distortion

A

elongation, foreshortening

62
Q

advantage of distortion

A

allow better visualization of anatomy

63
Q

technique charts based on

A
  1. variable kvp
  2. fixed kvp
  3. high kvp
  4. AEC
64
Q

VARIABLE KVP CHART

A
  • varies according to thickness of anatomic part
  • provides radiographic with shorter scales of contrast
  • Ma and time stays the same, but you measure for kvp
65
Q

Fixed kVp chart

A
  • developed by arthur fuchs
  • kVp stays constant, mAs varies
  • provide radiographs with longer scale of contrast
  • seen group small, average, large
66
Q

high kvp chart

A
  • Used for barium exams, contrast exams, cxr,
  • ensures adequate penetration
  • requires a decrease in mAs
  • reduces patient dose
67
Q

AEC

A
  • the use of computer assisted automatic/electric timers and photocells
  • needs selection of kvp and od settings
  • patient positioning must be accurate
  • terminated when the image receptor has received the appropriate radiation exposure to correspond with OD settings
  • most AECs have 2s override

RTCA253 Exposures (6 decks)

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