Introduction

Abstract

Almost 90 years have passed since Roentgen took the first X-ray photograph in 1896. The dominant events in technological progress since that time include the development of the screen/film radiography system using a fluorescent screen and the fluorography system using an image intensifier (II) tube (Fig. 1.1). In addition, a number of imaging systems for visualizing the internal parts of the human body have been developed. Since the 1970s, computed imaging systems, which produce cross-sectional images of internal parts of the body by means of various kinds of signal, have appeared with the rapid progress in technology; these systems include X-ray CT, ultrasonic (US), nuclear magnetic resonance (MRI), and positron CT. X-ray CT and US, in particular, are extensively distributed and in common use today.