Image quality evaluation of a direct digital radiography detector operating in a UK radiology department

This paper presents results of an image quality evaluation performed on a prototype DirectRay system (Sterling Diagnostic Imaging, Direct Radiography Corp.) operating in a UK radiology department. Physical imaging characteristics measured included characteristic (sensitometric) response, square-wave response function, Wiener spectrum and detective quantum efficiency (DQE). In addition, subjective image quality was assessed using a calibrated threshold contrast detail detectability (TCDD) test object. Results produced by the DirectRay system were compared with those achieved by a modern photo-stimulable computed radiography (CR) system. DirectRay and CR systems exhibit similarly wide exposure dynamic ranges, but in practice exploit this property in differing ways. Measured values of DQE(0) for the DirectRay system were found to be higher compared to those obtained for CR, for the majority of the exposure range examined. These results were confirmed subjectively by TCDD test-object analysis. No evidence of a 'memory artifact' phenomenon was found.