• X-ray film is a gelatin-covered polyester base. An emulsion coating both sides of the film contains ting silver halide crystals that are sensitive to such things as visible light X-rays, gamma rays, heat, moisture and pressure. X-ray film should not be used if outdated as it may fog and markedly compromise its diagnostic usefulness.

• The composition of x-ray film is similar to that of a photographic film. Radiation sensitive emulsion is coated on both sides of a transparent base (double emulsion film).

• A thin layer of adhesive is used to achieve firm attachment between the emulsion and base.

• The emulsion is protected from scratches, pressure or contamination during use by a thin layer of gelatin called supercoating. Thickness of a radiographic film is about 0.25mm.

THE STRUCTURE OF THE X – RAY  FILM

• If an undeveloped X-ray film is examined in daylight it will be found to consists of a flexible base of either cellulose acetate or polyester plastic coated on both sides with thin layers of apple-green photographic emulsion.

Film base

• Firm film base provides supported to fragile.

Film emulsion

• Emulsion is composed of a homogenous mixture of gelatin and silver halide crystals.

Film speed

• Speed of an x-ray film refers to the relative sensitivity to a given amount of radiation. Unlike photographic camera films, no numbers are given to indicate speed of x-ray film.

• Basically films are designated as standard, fast or ultra fast.

Types of Screen Film:

• Standard                                    

• Fast                              

• Ultra fast

UNEXPOSED FILM STORAGE

• If films are kept for a long period in an unsuitable place, storage fog will develop. Sensitive materials should be stored in a cool, dry room away, the wall or cupboard should be lined with lead of 105 mm thickness ( or material of the lead equivalent ) for voltage up to 100 k V.

• In tropical or hot, humid climates, the films are best kept in cold storage until shortly before a box is required . after opening , a box of films should not be put back into cold storage .

• Film emulsion is sensitive to pressure, so film boxes should be stacked on end in the store. Where there is a good delivery services , do not keep a large stock of films. Write the date of arrival on the boxes so that they are used in that order.