An Xray image detection system consisting of a fluorescent screen optically coupled to a CCD camera can produce a large uniform image. In this system, it is difficult to produce a noise4ess image because of loss in the optical system. In order to improve the efficiency of light collection, we have developed a new screen with an interference filter. The angular distribution of the light from the new screen was improved, and the amount of light collected by the CCD was increased. The spatial resolution of the new screen was a little lower than that of the conventional screen. In this paper, we report a new application of an interference filter to a fluorescent screen, and report the performance.

In order to acquire 3D data of high contrast objects such as bone, lung and vessels enhanced by contrast media for use of 3D image processing, we have developed a 3D CT-scanner using cone beam X-ray. A 3D CT-scanner consisted of a gantry and a patient couch. The gantry consisted of an X-ray tube designed for cone beam CT and a large area two-dimensional detector mounted on a single frame and rotated around an object in 12 seconds. The large area detector consisted of a fluorescent plate and a charge coupled device video camera. The size of detection area was 600mm x 450mm capable of covering total chest. While an X-ray tube was rotated around an object, pulsed X-ray was exposed 30 times a second and 360 projected images were collected in a 12 second scan. 256 x 256 x 256 matrix image (1.25 mm x 1.25 mm x 1.25mm voxel) was reconstructed by a high-speed reconstruction engine. Reconstruction time was approximately 6 minutes. Cylindrical water phantoms, anesthetized rabbits with or without contrast media, a Japanese macaque were scanned with the 3D CT-scanner. The results seemed promising because they showed high spatial resolution in three directions, though there existed several points to be improved. Possible improvements were discussed.

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