ASSESSING X-RAY FILM PHOTOGRAPHIC PERFORMANCE

Question 1

Factors to consider when assessing x-ray film photographic performance,

Answer 1

1. Density
2. X-ray exposure
3. Relative exposure
4. The characteristic curve

Question 2

Density

Answer 2

Degree of blackness on a processed radiograph.

Question 3

Ways of measuring density

Answer 3

• Transparency
• Opacity

Question 4

Transparency

Answer 4

Is the measure of the intensity of light transmitted (It) through the film
and expressed as a fraction or percentage of the intensity (Io) of light incident on
the film

Question 5

transmission ratio

Answer 5

the ratio of the intensity of light transmitted to the intensity of light incident on the film.

Question 6

Opacity

Answer 6

A quantity which increases as blackening increases and as exposure increases
* Opacity = Io/It
* A perfectly transparent area of an image has an opacity of 1

Question 7

Relationship between opacity and optical density.

Answer 7

opacity in logarithmic terms produces a
term called optical density .

Optical density = log10 Opacity.log10Io/It

Question 8

Relative exposure

Answer 8

refers to a specific value within a digital X-ray image that provides information about the detector response to radiation.

Question 9

How is relative exposure carried out.

Answer 9

Divide a sheet of film into ten small areas and expose each area using the same
tube kilovolts ((kV) and tube current (mA) but different exposure times

Question 10

Log relative exposure.

Answer 10

The relative exposure values can vary from unity to several thousands in a given
radiograph for that reason we use the log relative exposure because values from 0-1.5

Question 11

Importance of using the Log relative exposure

Answer 11

It can be used in comparing the speed and sensitivity of various types of films through the use of characteristic curves.

Question 12

Define a characteristic curve

Answer 12

is a graph that illustrates the way in which a film or film screen system responds to different levels of exposure.

Question 13

Characteristic curve

Answer 13

It is a plot of optical density (D) against log relative exposure

Question 14

Three steps are involved in the production of a characteristic curve.

Answer 14

• Exposing and processing the film
• Measuring the densities
• Plotting the curve

Question 15

How different is a step wedge from sensitometer.

Answer 15

A step wedge is exposed to x-rays or a sensitometer is exposed to light