Analysis of Various Technologies for Digital X-Ray Image Detector Design

Abstract

Clinical use of digital X ray apparatuses demonstrated advantages of digital X ray technology over film X ray tech nology. Comparison of digital X ray technology and film X ray technology revealed that these advantages were mainly due to diversity in devices for X ray image detection, pro cessing, imaging, and storage. In contrast to film X ray technology, this diversity in digital X ray apparatuses pro vides independent optimization of corresponding func tions. Isolation of detection function as a separate func tional unit gave rise to a variety of imaging detection tech nologies. These technologies are described in detail in [1 3]. However, the literature gives no comparative economi cal, engineering, and application analysis. X Ray image intensifiers (XRII) with detectors combining X ray screen -optical unit -transmitting video tube; X ray screen -objective -electronic optical converter (EOC) -objective -transmitting video tube; X ray vidicon failed to compete with X ray film systems on the medical market. XRII with X ray EOC (XREOC) are still being produced and used in clinics [4]. It is safe to suggest that digital tech nology of X ray detectors will be successfully used in med icine. The goal of this work was to compare technologies for digital X ray image detector design for general radiology.Exhaustion of silver resources worldwide and increase in the cost of X ray film (5 10 g of silver per m 2 ) encouraged the search for new alternative methods of X ray imaging in the 1970s. Nudelman and coworkers (USA) started to develop digital X ray apparatuses based on XREOC, video systems, and computers. Departments of digital X ray diagnosis (filmless and paperless) and were established, and economical and medical efficiency of digital X ray diagnosis was demonstrated [5].In addition to XREOC, many other digital detectors are used in commercially available X ray apparatuses pro duced by many manufacturers. The research in this direc tion is being continued and dozens of commercial compa nies are involved in development of digital X ray detectors. Detectors Based on X Ray Electronic Optical ConvertersDetectors with XREOC are presently used in clinics instead of X ray detectors of other types. This is due to higher quantum efficiency and sensitivity of digital X ray detectors based on XREOC. The quantum efficiency of the digital X ray detectors based on XREOC at low spa tial frequency is limited only by incomplete X ray absorp tion in the input XREOC screen, provided that optical system and video camera are optimal. The quantum effi ciency of the amplifiers available from Electron, Ltd., St. Petersburg, Russia with working fields 215 360 mm and CCD matrix (512 × 512, 1024 × 1024, and 2048 × 2048 pixels) is 0.5 0.7 depending on XRII and X ray imaging mode. XRII of XREOC implements multi stage X ray image transformation into video signal. X Ray quanta are transformed into optical photons in an X ray screen and then to electrons (in the photocathode). The electrons are conveyed to the output screen by electronic optics...