Masahiro Endo

High-luminance fluorescent screen with interference filter

An x-ray 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 noiseless 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.

Image restoration of cone-beam CT images using wavelet transform

We have been developing a computerized scheme to restore cone-beam CT images that are degraded by scatter radiation. In reconstructing 3D image, the cone-beam CT scanner has some advantages over helical CT scanner in shorter reconstruction time and in higher spatial resolution. However, because large amount of scatter radiation is included in 2D projection data, the quality of reconstructed image is worse and cupping artifacts appear in CT images. We have tried to improve the quality of reconstructed images using the multiresolution analysis. To achieve this, the projection data was decomposed into several signals with different spatial resolution and then reconstructed from these decomposed signals by multiplying weighting factors. Moreover, using these weighting factors, we have designed the optimal filter to reconstruct the CT images without any extra computing time. Our results showed that the CT images were enhanced the contrast and improved the quality.