Digital chest radiography is a rapidly evolving method for imaging the chest. In its current form, it has been shown to be diagnostically equivalent to conventional chest radiography. Since analog screen-film chest radiography is technologically mature and digital chest radiography is still in a process of moderate innovation, it is likely that the diagnostic quality of digital chest radiography will, in the future, be superior to that of conventional chest radiography, replacing it for many uses. Digital chest radiographs can be produced by three competing methods: film digitization, systems that store the energy of the encoded X-ray photons for later extraction, and near-real-time systems for extracting the encoded X-ray information. For each of these methods, there are trade-offs in labor versus machine costs. To date, there is no evidence that any one method is diagnostically superior to the other, although digitized film requires that the original film be of high quality to achieve a high-quality digitized image. The two other types of digital acquisition are more robust to exposure differences. Once in digital form, image processing provides important advantages in correcting and improving disease conspicu-ity. Digital images are the input data for computer-aided detection systems. They allow digital storage, transmission, retrieval, and soft-copy display. There are likely to be continued improvements in image quality based on improved image-processing methods, energy subtraction, and temporal subtraction.

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