Replacement of Film Radiography by Digital Techniques and Enhancement of Image Quality

New digital detectors were developed for medical applications, which have the potential to substitute the X-ray film. Digital Detector Arrays (DDA: Flat Panel Detectors, Line Detectors) and Imaging Plates (Computed Radiography, CR) allow a fast acquisition of radiographic images with higher dynamic than film. Especially DDA’s allow a radiographic inspection with considerable higher image quality than classical film radiography. Both benefits will be considered. Companies report about a reduction of exposure time down to 5 25% for CR and DDA radiography in comparison to NDT film exposures. This provides together with the reduction of consumables and chemical waste economical and ecological benefits and short amortisation periods. But this does not always provide the same image quality as film radiography. The interrelationship between exposure time, photon flow and image quality will be discussed. The wall thickness contrast sensitivity of DDAand CR-systems is basically controlled by the exposure conditions. This can also imply the risk of misapplication. A special multi gain correction for DDA’s yields an extraordinary increase of the radiographic image quality. The contrast sensitivity can be improved by up to 10 times. Fine wall thickness changes of 2/1000 of the total wall thickness can be visualised. This requires the selection of longer exposure times, even longer than typical for radiographic film exposures. It opens new application areas for very sensitive technologies e.g. in the nuclear power industry. European and USA standards for film radiography are analysed to derive correct requirements for the digital image quality and procedures for prediction and measurement of image quality.