What is the structure of an X-ray film?
In this article:
- X-ray Film Comprises Seven Distinct Layers: A standard industrial X-ray film is approximately 0.5 mm thick and includes seven layers, with a transparent polyester or cellulose triacetate base at its core
- Dual Emulsion Layers Enhance Sensitivity: Both sides of the base are coated with radiation-sensitive emulsion layers suspended in gelatine, effectively doubling the film’s speed and improving image capture
- Protective Gelatine Layers Prevent Damage: Hardened gelatine layers are applied over the emulsion to protect against scratches and handling damage during processing and inspection
- Substratum Layer Ensures Adhesion: A thin substratum layer bonds the emulsion to the base, ensuring structural integrity and consistent image quality across the film
- Silver Halide Crystals Enable Radiation Detection: The emulsion contains microscopic silver halide crystals that react to ionizing radiation, forming the latent image that is later developed into a visible radiograph
An X-ray film, total thickness approx. 0.5 mm, is made up of seven layers, see figure 1-7:
• a transparent cellulose triacetate or polyester base (d).
On both sides of this base are applied:
• a layer of hardened gelatine (a) to protect the emulsion
• emulsion layer (b) which is suspended in gelatine, sensitive to radiation
• a very thin layer called the substratum (c) which bonds the emulsion layer to the base
The normal X-ray film, therefore, has two coatings of emulsion doubling the speed compared to a film with a single emulsion layer. Photographic emulsion is a substance sensitive to ionising radiation and light, and consists of microscopic particles of silver halide crystals suspended in gelatine.
Note: In the past radiography on paper was not unusual. In this ‘ instant cycle’ process results became available within 60 seconds. The quality of the images, however, was extremely poor and the life of the film limited to a few months. The availability of better and faster “instant cycle” techniques such as digital radiography (see in a later section), has made radiography on paper obsolete