Radiography in Modern Industry - Kodak

PhotofluorographyIn photofluorography (See Figure 101) the image on the fluorescent screen is photographed witha camera on small or even miniature film rather than viewed directly. In medicine, the economy ofthis procedure has made it useful in the examination of large groups of people for disease of thechest. In rendition of detail, photofluorography is superior to fluoroscopy because the film can beviewed with ample illumination; the photon exposure can be integrated to a high exposure level:and the photographic process enhances the contrast of the fluorescent image on the screen.Figure 101: Schematic diagram of an industrial photofluorographic unit. Details ofcommercial units may differ from this illustration.Compared to full-sized radiography, the factors that diminish detail in the miniaturephotoradiograph are the graininess and diffusion in the fluorescent screen, the limitations of thelens in definition, and the relatively greater influence of film graininess in the small image. Sincerequirements of medical and industrial radiography are not the same, photofluorographic units foreach application may be expected to differ from one another in many details. In the industrialfield, photofluorography has been used for the inspection of parts for which the sensitivityrequirements are not severe, and where the value of the part is too low to permit the expense ofconventional radiography.A modification of photofluorography is cinefluorography--the production of x-ray motion pictures.In the simplest form of cinefluorography, the still camera shown in the figure above is replaced bya motion-picture camera. This form of the technique is limited to relatively thin specimens, to lowframe rates, or to both, because the available fluorescent-screen brightness is restricted by thepermissible x-ray tube loads. Cinefluorography can be extended to thicker specimens or higherframe rates by the use of an image intensifier in place of the simple fluoroscopic screen.Cinefluorography is essentially a research tool, and as a consequence the details of theapparatus depend very strongly on the requirements of the particular investigation.Radiography in Modern Industry 163