INFLUENCE OF PHOTON ENERGY ON THE GRAININESS OF INTRAORAL X-RAY FILM (NONSCREEN FILM)

Abstract

The purpose of this study was to clarify the influence of photon energy on the graininess of intraoral X-ray film. The photon energy was set at 10kV intervals from 40kV to 90kV. Total filtration used was 2mm or 12mm as the aluminium equivalent. Ag-particle size was determined microscopically by measuring the length on the X-axis of the particle image incorporated in the memory one-dimensionally. In order to compare with the graininess of screen film combination system, the particle size when X-ray film was exposed to visible ray from a fluorescent lamp was also determined. ULTRA speed film manufactured by Kodak Co. was used in this experiment.
Results: Among 10⁴ particle sizes thus determined, there were about 9 particles of 10μm in size from visible ray. On the other hand, approximately 10 particles were confirmed with 40kV, filter 2mm, 15 particles with 40kV, 12mm, 20 particles with 60kV, 12mm and 30 particles with 90kV, 12mm. When these particles were observed microscopically, it was revealed that the size of each Ag-particle was identical irrespective of the photon energy. However, a large mass of Ag-particle was found to be formed when the photon energy was high. Based on this evidence, the following conclusion could be drown:
Conclusion: In the case of screen film combination system, the film was sensitized with visible ray from the screen. In the case of intraoral X-ray film, on the other hand, the film was directly sensitized with X-rays. These findings may indicate that the latent image formation of Silver bromide grain is quite dissimilar between the two film types. It was also estimated that the mass formation of Ag-particles may be attributable to the scattered rays of secondary origin. The following schema represents a possible cause of radiographic mottle of nonscreen film.