Visualization of blurring process due to analog components in a digital radiography system using a simple method

To obtain useful medical X-ray images for diagnosis, it is necessary to accurately evaluate the characteristics and fully understand the features of the system to determine the imaging target and conditions. This study describes the performance of a digital radiography (DR) system in detail and proposes a method for characterizing the blurring process due to the presence of analog components in an imaging system. Our method does not involve any specialized technique, such as a simulation that requires long computing time on a high-performance computer. The method is based on the concept of the modulation transfer function (MTF). The functions that corresponded to the MTF of the analog components of the system when the Fourier transform was performed were examined. Indirect conversion type flat-panel detectors (FPD) in the general radiography energy range and direct conversion type FPD in the mammography were used for verification. A Gaussian function and Lorentz function were synthesized for modelling the blurring process of the indirect type FPDs. The spreads and shapes of the modeled functions depended on the systems. For the direct conversion type FPD, a combination of a Lorentz function with a narrow width and an impulse function characterized the results. Furthermore, based on the structure of each detector and the signal transfer process, the visualized results were considered reliable. The results of these experiments will aid in the detailed understanding of the image quality characteristics of the DR system by the feasible approach.