Studies on imaging properties of a novel medical digital radiography system and its clinical applications [In Japanese

Abstract

This dissertation describes the imaging properties of a novel digital radiography (DR) system. This 2048×2048‐matrix image intensifier‐TV‐DR system was introduced in January 1990. The basic imaging properties of the system were investigated in terms of system linearity, resolution, noise, and detectability of low contrast objects. It was found that the image quality is sufficient for close fluoroscopic GI‐tract examinations. The imaging properties of this system depend on the incident exposure rate, the level of signal current from the TV image pickup tube and also the size of the iris (diaphragm) in the TV lens. To obtain high‐resolution images, the incident exposure should be adjusted to obtain a small iris diaphragm and a low level of signal current. If, on the other hand, high resolution is not required the incident exposure can be reduced by increasing the iris diaphragm. Therefore, using the knowledge of these relationships, the DR system parameters and exposure levels should be determined when acquiring clinical images and evaluating the imaging properties. We have ascertained the performance of this DR system through our extensive investigation. This novel medical digital radiography system has been used for mass screening the upper GI‐tract of more than 12 500 patients.