Improvement of X-ray CT image quality by digital filter method, 1

With the advent of computed tomography (CT), it has become increasingly familiar in the fields of jaw and oral cavity. Because both hard and soft tissues in the jaw and oral cavity were anatomically complicated, CT techniques focusing on the soft tissues are required. The present study was thus designed to examine various digital filter methods for the improvement of image quality. Three kinds of each low-pass and high-pass filters were examined from both visual and physical viewpoints. All of the three kinds of low-pass filters and two kinds of high-pass filters allowed low contrast resolution to be enhanced. In addition, low-pass filters and high-pass filters provided high definition in the range of low frequency and in the range of high frequency, respectively. If either low-pass or high-pass filter method is selected, the low contrast resolution in the area corresponding to soft tissues would be enhanced, and definition obtained would also be superior to that on CT images used in the medical field. (N.K.)