Flat-Panel Digital Radiography

Abstract

The technical aspects of flat-panel digital radiography (FPDR) systems are described in detail in this chapter. The essential elements of these detectors include a definition of FPDR, system components, types of FPDR systems, design characteristics, operational principles, image processing, and imaging performance characteristics, as well as image artifacts and basic features of wireless digital detectors. The definition of these systems includes the use of amorphous silicon (a-Si) and amorphous selenium (a-Se) to produce digital images using a set of electrical components specifically designed to produce digital radiographic images in a manner different than computed radiography (CR) technology. Two common FPDR systems include the indirect and direct digital detector technologies. While the former produces images using an X-ray scintillator (X-ray conversion layer), followed by an amorphous silicon (a-Si) photodiode flat-panel layer, with a thin-film transistor (TFT) array for readout of the electrical charges by the photodiode array, the latter is based on the use of a photoconductor such as amorphous selenium (a-Se) to detect X-ray photons from the patient and convert them directly into electrical charges. A TFT array and associated electronics are also used to collect and store the changes for subsequent readout. The EI is also characteristic of FPDR systems and provide a visual cue as to the amount of exposure used for a particular examination and whether the exposure falls within guidelines suggested by the manufacturer. In addition pre-processing and post-processing present the raw data “for processing” and “for presentation,” respectively. Finally, the chapter concludes with a description of imaging performance characteristics (such as spatial resolution, modulation transfer function, dynamic range, detective quantum efficiency, image lag, and artifacts) and wireless digital radiography detectors.