Comparison of Film Sensitivity for ^99m Tcγ-Rays

—In order to record shadow holograms—

Abstract

Recently the new method of γ-ray imaging by holography has been studied at several nuclear medical laboratories. This holography is very simple type; On axis Fresnel zone plate made by lead (2 mm thickness) is placed between γ-ray source and a detector, and its shadow is recorded as a hologram.
The hologram obtained is illuminated by parallel beam of He-Ne laser (6328 Å), and image of radioisotope distribution in the object is reconstructed by diffraction. The better the resolution of the shadow hologram, the better reconstructed images are obtained. So that the detector recording γ-ray hologram must be selected seriously.
In this paper, three kinds of medical X-ray film were used as the detector of hologram to compare film sensitivity. Generally these medical X-ray films have poor sensitivity for γ-rays of ^99mTc. In order to intensify the, film sensitivityy for γ-rays of ^99mTc, combinations with six kinds of intensifying screens were studied. In result, good film sensitivity was obtained by RP (Kodak Co.) film combinating with KZ-S fluorescent intensifying screen.
The fluorescent screen was better than fluorometallic screens with similar properties. Using this film-screen combination, shadow holograms could be recorded for 2-3 minutes and images could be optically reconstructed.