x ray film processing

1. FILM PROCESSING
DR PRAJWITH RAI

2. TYPES OF FILM FOR MEDICAL IMAGING
• Direct exposure
1. (Non screen type) film:
• Intraoral dental film, kidney surgery film,
• Radiation monitoring film
2. Screen Type film

3. TYPES OF FILM FOR MEDICAL IMAGING
• Single Emulsion film –
1. Screen type film
2. Photofluorographic film (Cine film)
3. Cathode ray tube(CRT) film: Polaroid film,
4. Duplication film
5. Subtraction film
6. Laser imaging film for use with Laser Imagers

4. STRUCTURE OF A DOUBLE EMULSION FILM
• Film base
• substratum layer
• Emulsion layer
• Super coat BASE
SUPERCOAT
ADHESIVE
EMULSION

5. PROPERTIES OF FILM BASE:
• Polyester (Polyethylene terephthalate resin)
• 0.18mm thick
• Provide support for the emulsion.
• The base is chemically inactive,
• Impermeable to water & processing solutions.

6. PROPERTIES OF FILM BASE:
• The basic requirements of a base are that it should
• transmit light
• have good dimensional stability and
• be non-inflammable.

7. SUBSTRATUM LAYER:
• Prevents separation of emulsion while processing.
BASE
ADHESIVE

8. EMULSION LAYER:
• . It is the part of the film that actually records the image. It is composed of two main
ingredients:
1. Silver halide crystals:
• light sensitive material in the emulsion.
• The “halide” is 90 – 99% AgBr & 1 – 10% AgI siver iodide (provide for higher sensitivity)
2. Gelatin:
• keeps the silver halide grains evenly dispersed
• prevents clumping of the grains.

9. GELATIN AgBr
EMULSION LAYER:

10. SUPER COAT / ANTI-STRESS LAYER
• Hardened gelatin
• The most superficical layer
• Protect the film emulsion from pressure Abrasion.
• Provides suitable surface characteristics
BASE
ADHESIVE

11. SINGLE EMULSION FILM
• emulsion on one side of the base only
• Non curl backing which is unique to single emulsion film
• made up of gelatin and an Antihalation layer.

12. ANTI-HALATION BACKING
• layer found in modern photographic film
• It is placed
• between the light-sensitive emulsion and the tough film base, or
• sometimes on the back of the film base.
• Rendered transparent or washed from the film during processing of the film

13. reducing contrast
re-exposing the emulsion,
reflecting off the pressure plate
or anything else behind the film
The light that passes through
the emulsion and the base
BASE
NO ANTI-HALATION
BACKING

14. GOOD contrast
NO re-exposing the emulsion,
absorbed by the opaque anti-
halation layer
The light that passes through
the emulsion and the base
BASE
WITH ANTI-HALATION
BACKING

15. SINGLE EMULSION VERSUS DOUBLE
EMULSION
Single Emulsion Film
↓ speed
↓ contrast
↑ Photographic sharpness
Double Emulsion Film
↑ speed
↑ contrast
↓ photographic sharpness

16. CHARACTERISTIC (H & D) CURVE
(HURTER & DRIFFIELD)
• H & D curve describes the response of a film or film screen system to different levels
of exposure
• It is a graph of optical density as a function of exposure plotted on a logarithmic
scale.
• It actually depicts the range of exposures over which the film has sufficient contrast
sensitivity.

17. PARTS OF A H&D CURVE:
• Toe – low exposure region
• Shoulder – high exposure region
• Slope – region of correct exposure

18. 0.01 0.1 1 10
1
2
3
Base – fog level
shoulder
Toe
slope

19. 0.01 0.1 1 10
1
2
3

20. 0.01 0.1 1 10
1
2
3

21. 0.01 0.1 1 10
1
2
3

22. 0.01 0.1 1 10
1
2
3