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RTCA253 Exposures > Radiographic Quality > Flashcards

Radiographic Quality Flashcards

1
Q

The exactness of representation of the anatomic part of interest in the finished radiograph

A

Radiographic quality

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2
Q

Factors of film (characteristic curve)

A

density, contrast, speed, latitude, processing, time, temperature

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3
Q

Geometric factors

A

distortion, magnification, blur

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4
Q

subject factors (contrast)

A

thickness, density, atomic #, motion

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5
Q

Evaluation criteria for quality

A

spatial resolution, contrast resolution, noise, artifacts

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6
Q

ability to image objects that have high subject contrast

A

spatial resolution

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7
Q

ability to detect or distinguish objects that have similar subject contrast

A

contrast resolution

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8
Q

The undesirable fluctuation of the OD of the image

A

Noise

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9
Q

Kinds of noise

A
  1. film graininess
  2. structure mottle
  3. quantum mottle
  4. scatter radiation
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10
Q

a result of insufficient mAs in which an uneven distribution of x-ray within the beam leave a blotchy or freckled appearance on the finished radiograph

A

Quantum mottle

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11
Q

high mAs, low KVP and slower screen result in a __________ of quantum mottle and a smoother more even image appearance.

A

reduction

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12
Q

Radiographic Quality Rules

A
  1. Fast image receptors have high noise and low spatial & contrast resolution
  2. High spatial & contrast resolution require low noise and slow image receptor
  3. Low noise accompanies slow image receptors with high spatial & contrast resolution
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13
Q

The measurement of light incident on a processed film (Io)and the level of light transmitted through the film (It)

A

Optical density

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14
Q

Base + fog =___

A

OD

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15
Q

Base + fog

A

unexposed and processed radiographic films have an OD of 0.1 - 0.3

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16
Q

Base Density number-

A

0.1

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17
Q

Fog density number-

A

does not exceed 0.2

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18
Q

Useful range of OD

A

0.25-2.5 LRE

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19
Q

Useful range of OD are dependent Upon:

A

Viewbox illumination, viewing conditions, shape of characteristic curve

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20
Q

Inherent in the film and influenced by processing

A

Image receptor contrast

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21
Q

determined by size, shape, and x-ray attenuating characteristics of the subject and the energy of the beam (kvp)

A

Subject contrast

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22
Q

Contrast is defined by the slope of the ______ _________.

A

straight line portion (average gradient )

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23
Q

For the same film type a change in ________ will affect contrast only when above of below the straight line portion

A

density

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24
Q

The slope of the straight line drawn between two points on the characteristic curve at 0.25 and 2.0 above B+F

A

Average Gradient

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25
Q

Average gradient formula

A

AG= OD₂ -OD₁/ LRE₂-LRE₁

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26
Q

Speed

A

the speed point on a film is defined as OD 1.0+ B+F

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27
Q

Film speed is affected by:

A

Immersion time, Temperature, chemical activity

28
Q

The longer the film is exposed to the chemicals the ________ the characteristic curve becomes indicating that contrast has been effected by an increase in density

A

straighter

29
Q

Image receptor speed formula

A

Speed= 1/ exposure in R to produce OD 1.0+B+F1)

30
Q

Receptor and speed formula

A

New image receptor speed/ old image receptor speed= Old mAs/ new mAs

31
Q

Latitude and contrast are _______ proportional

A

inversely

32
Q

The range of exposures that will produce densities within the diagnostic range

A

Latitude

33
Q

Latitude

A

The Range of exposures that will produce diagnostically acceptable OD ranges.

34
Q

Latitude formula

A 
Latitude= Eh -Eᵢ
Eh= high exposure point OD 2.5
Ei= low exposure point OD 2.25
35
Q

A narrow latitude film requires

A

greater exposure accuracy and produce short gray scales

36
Q

A film that has a wider latitude permits considerable variation in the exposure while still exhibiting densities within the diagnostic range produce ___ ____ ______ .

A

long grey scales

37
Q

All images appear larger radiographically than their actual size

A

Magnification

38
Q

__________ amount of magnification should be maintained

A

Smallest

39
Q

Magnification is dependent on _________ conditions of the exam

A

geometric

40
Q

magnification factor formulas

A

MF= image size/object size=SID/SOD

41
Q

Two factors affect image magnification

A

SID, OID

42
Q

The presentation of unequal magnification of different portions of the same object

A

Distortion

43
Q

Distortion is dependent upon

A
  • thickness of object/part
  • position
  • shape of the object
44
Q

Object thickness

A

the thicker the object the more distortion present on the final radiograph

45
Q

Object unsharpness

A
  • main problem is trying to image a 3-D object on a 2-D film

- human body is not straight edges and sharp angles

46
Q

____ X-ray beam width will produce a sharper image

A

smaller

47
Q

Fine detail = __________

A

small focal spot

48
Q

General Radiography uses ____________ focal spot

A

large

49
Q

Penumbra

A

fuzzy border, obscures true border

50
Q

The greater the distance between the source of the x-ray (tube) and the image receptor (cassette), the greater the image ____________.

A

sharpness

51
Q

Most exam are done at ______iinches

A

40

52
Q

the closer the object to the film, the _____ the detail.

A

sharper

53
Q

OID goes down, penumbra goes down, sharpness goes ___

A

up

54
Q

OID goes up, penumbra goes up, sharpness goes _____

A

down

55
Q

Objects not on the central axis appear ______.

A

distortion

56
Q

If the object plane and the image plane are not _____, image distortion will occur

A

parallel

57
Q

Misrepresentation on the radiograph of the actual relationships present among objects or parts

A

spatial distortion

58
Q

the misrepresentation by unequal magnification of the actual shape of the structure being examined

A

shape distortion

59
Q

Two kinds of shape distortion

A

Foreshortening and elongation

60
Q

Foreshortening

A

the image size is reduced as the angle of inclination along the central axis increases
-occurs only when the part is improperly aligned

61
Q

Elongation

A

the image size is lengthened as the inclination is increased
- occurs when the tube or the image receptor are improperly aligned. tube angle results in elongation never foreshortening

62
Q

the farther the part of interest is from the central ray of the image receptor with _______ the distortion

A

greater

63
Q

Focal spot blur is _________ on the cathode side of the tube

A

greater

64
Q

Focal spot blur occurs because

A

the focal spot is not a point, but rather a rectangular source (0.1-1.5mm)

65
Q

most important factor in determining spatial resolution

A

focal spot blur

66
Q

To minimize focal spot blur:

A

use small focal spots, decrease OID (position part and receptor as close as possible), increase SID to maximum allowed for exam

67
Q

Subject contrast is dependent upon

A

patient thickness, density, atomic # of the tissue, shape

- kvp must be controlled based on the evaluation of these factors

RTCA253 Exposures (6 decks)

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