Image Quality and Visibility (6)

Question 1

Define Radiographic Sensitivity

Answer 1

The size of the smallest detail that can be seen on a radiograph.

Question 2

Radiographic sensitivity depends on these two independant factors:

Answer 2

1. contrast

2. definition

Question 3

Subject factors

Answer 3

• absorption difference in specimen
• wavelength/energy level of primary radiation
• effects of secondary radiation from scatter

Question 4

Film factors (Contrast)

Answer 4

• type of film (grain size)
• film processing chemistry
• development time
• amount of agitation
• film density

Question 5

Two factors affecting Contrast:

Answer 5

1. subject factors

2. film factors

Question 6

Two factors affecting definition:

Answer 6

1. geometric factors

2. film factors

Question 7

Geometric factors

Answer 7

• focal size/source size
• source-to-film distance (focal film distance)
• specimen-to-film distance
• degree of thickness change in specimen
• specimen movement during exposure

Question 8

Film factors (Definition)

Answer 8

• type of film (grain size)
• mottling
• wavelength/energy level of primary radiation
• development time
• other film processing factors

Question 9

Radiographs may exhibit any one of these four characteristics:

Answer 9

1. low contrast, poor definition
2. low contrast, good definition
3. high contrast, poor definition
4. high contrast, good definition

Question 10

Define radiographic definition

Answer 10

the ability to see a sudden change in density based on the dimensions of the exposed object.
- sharpness of image outline

Question 11

Define radiographic contrast

Answer 11

The comparative level of brightness of two adjacent areas in a radiograph.
- difference between densities/light or dark areas on film from the amount of penetrating radiation

Question 12

Define subject contrast

Answer 12

Ration of radiation intensities transmitted in two portions of varying thicknesses/material densities on a part.
- nature of specimen and radiation used

Question 13

Define Latitude

Answer 13

Films ability to cover a range of thicknesses of a particular specimen within a useful range of densities.
- high contrast film = narrow latitude

Question 14

Define film contrast

Answer 14

Steepness of the characteristic curve of the film.

• grain size
• processing
• resultant density
• type of screens
• wavelengths

Question 15

Define geometric unsharpness

Answer 15

the degree of sharpness or definition of a radiographic image

Question 16

Types of IQI’s

Answer 16

• Plaque (hole)

- wire (DIN and ASTM)

Question 17

What is a calibrated film density strip?

Answer 17

step wedge of 5 steps, densities 1-4.
used to compare readings from the densitometer with the known readings.
- calibrated every 90 days
- replaced every year