Radiographic Quality

Question 1

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

Answer 1

Radiographic quality

Question 2

Factors of film (characteristic curve)

Answer 2

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

Question 3

Geometric factors

Answer 3

distortion, magnification, blur

Question 4

subject factors (contrast)

Answer 4

thickness, density, atomic #, motion

Question 5

Evaluation criteria for quality

Answer 5

spatial resolution, contrast resolution, noise, artifacts

Question 6

ability to image objects that have high subject contrast

Answer 6

spatial resolution

Question 7

ability to detect or distinguish objects that have similar subject contrast

Answer 7

contrast resolution

Question 8

The undesirable fluctuation of the OD of the image

Answer 8

Noise

Question 9

Kinds of noise

Answer 9

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

Question 10

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

Answer 10

Quantum mottle

Question 11

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

Answer 11

reduction

Question 12

Radiographic Quality Rules

Answer 12

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

Question 13

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

Answer 13

Optical density

Question 14

Base + fog =___

Answer 14

OD

Question 15

Base + fog

Answer 15

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

Question 16

Base Density number-

Answer 16

0.1

Question 17

Fog density number-

Answer 17

does not exceed 0.2

Question 18

Useful range of OD

Answer 18

0.25-2.5 LRE

Question 19

Useful range of OD are dependent Upon:

Answer 19

Viewbox illumination, viewing conditions, shape of characteristic curve

Question 20

Inherent in the film and influenced by processing

Answer 20

Image receptor contrast

Question 21

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

Answer 21

Subject contrast

Question 22

Contrast is defined by the slope of the ______ _________.

Answer 22

straight line portion (average gradient )

Question 23

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

Answer 23

density

Question 24

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

Answer 24

Average Gradient

Question 25

Average gradient formula

Answer 25

AG= OD₂ -OD₁/ LRE₂-LRE₁

Question 26

Speed

Answer 26

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

Question 27

Film speed is affected by:

Answer 27

Immersion time, Temperature, chemical activity

Question 28

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

Answer 28

straighter

Question 29

Image receptor speed formula

Answer 29

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

Question 30

Receptor and speed formula

Answer 30

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

Question 31

Latitude and contrast are _______ proportional

Answer 31

inversely

Question 32

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

Answer 32

Latitude

Question 33

Latitude

Answer 33

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

Question 34

Latitude formula

Answer 34

``` Latitude= Eh -Eᵢ Eh= high exposure point OD 2.5 Ei= low exposure point OD 2.25 ```

Question 35

A narrow latitude film requires

Answer 35

greater exposure accuracy and produce short gray scales

Question 36

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

Answer 36

long grey scales

Question 37

All images appear larger radiographically than their actual size

Answer 37

Magnification

Question 38

__________ amount of magnification should be maintained

Answer 38

Smallest

Question 39

Magnification is dependent on _________ conditions of the exam

Answer 39

geometric

Question 40

magnification factor formulas

Answer 40

MF= image size/object size=SID/SOD

Question 41

Two factors affect image magnification

Answer 41

SID, OID

Question 42

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

Answer 42

Distortion

Question 43

Distortion is dependent upon

Answer 43

- thickness of object/part - position - shape of the object

Question 44

Object thickness

Answer 44

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

Question 45

Object unsharpness

Answer 45

- main problem is trying to image a 3-D object on a 2-D film | - human body is not straight edges and sharp angles

Question 46

____ X-ray beam width will produce a sharper image

Answer 46

smaller

Question 47

Fine detail = __________

Answer 47

small focal spot

Question 48

General Radiography uses ____________ focal spot

Answer 48

large

Question 49

Penumbra

Answer 49

fuzzy border, obscures true border

Question 50

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

Answer 50

sharpness

Question 51

Most exam are done at ______iinches

Answer 51

40

Question 52

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

Answer 52

sharper

Question 53

OID goes down, penumbra goes down, sharpness goes ___

Answer 53

up

Question 54

OID goes up, penumbra goes up, sharpness goes _____

Answer 54

down

Question 55

Objects not on the central axis appear ______.

Answer 55

distortion

Question 56

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

Answer 56

parallel

Question 57

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

Answer 57

spatial distortion

Question 58

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

Answer 58

shape distortion

Question 59

Two kinds of shape distortion

Answer 59

Foreshortening and elongation

Question 60

Foreshortening

Answer 60

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

Question 61

Elongation

Answer 61

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

Question 62

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

Answer 62

greater

Question 63

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

Answer 63

greater

Question 64

Focal spot blur occurs because

Answer 64

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

Question 65

most important factor in determining spatial resolution

Answer 65

focal spot blur

Question 66

To minimize focal spot blur:

Answer 66

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

Question 67

Subject contrast is dependent upon

Answer 67

patient thickness, density, atomic # of the tissue, shape | - kvp must be controlled based on the evaluation of these factors