1-6.
PHOTOFLUOROGRAPHIC FILM
Photography of the x-ray image on a fluorescent screen (photography) requires
the use of either of two types of single-coated photographic film. One type is more
sensitive to the blue fluorescence of one kind of fluorescent screen; the other is most
sensitive to the green fluorescence of another kind of screen. These films are usually
supplied in rolls or sheets.
1-7.
FILM CHARACTERISTICS
At the time of manufacturing, the manufacturer determines not only the speed of
sensitivity of the film, but also other characteristics such as density, contrast, detail, and
inherent film fog. The characteristic of film is important since it has a bearing on the
quality of the finished radiograph. Manufacturers express the characteristics of their
films through a "characteristic curve" which is commonly referred to as an "H and D
curve," so named after Hurter and Driffield who first used it to describe the response of
SECTION III. CHEMISTRY OF FILM PROCESSING
1-8.
MANUAL DEVELOPER SOLUTION
The chemistry of the solutions in automatic and manual processing is basically
the same. There are a few variations between the two and these occur in the
developer. Because of these variations, the developer solution will be addressed in
detail from both manual and automatic processing. The manual developer solution is
composed of four basic agents: an activator, reducers, a restrainer, and a preservative.
Each of the agents is mixed with water, which acts as a solvent. Because each of the
agents has its own specific function, each one will be dealt with in a separate
paragraph.
a. Activator. The activator (or alkali), sodium carbonate, softens the gelatin of
the emulsion and provides the necessary alkaline medium to the solution so that the
reducing agents can diffuse into the emulsion and attack the exposed silver bromide
crystals. In general, the more alkaline the developer, the more powerful and rapid is its
action. A disadvantage of sodium carbonate is that when a film is processed in an x-ray
developer containing it and then transferred to a warm acid-fixing bath, tiny bubbles of
carbon dioxide gas may form in the soft gelatin. As the bubbles escape, they form tiny
craters or pits in the emulsion, thereby breaking up the normal character of the silver
image. The finished film or radiograph is blistered. To overcome this effect, the
temperature of the developer, rinse, and fixer solutions should be approximately the
same.
MD0954
1-9