Methods for reducing patient dose: rare-earth screens, filtration, spot-film technique and digital radiography

Different methods for dose reduction in diagnostic radiology are presented. The image quality achievable with these methods is compared with the patient dose required. There is no doubt that new film-screen systems with rare-earth screens permit a dose reduction by a factor of about 2 to 4 compared to conventional film-screen systems. The use of various filters, including edge filters, which influence the X-ray spectrum and so the dose is also described. A more expensive but promising method is the 100 mm spot-film technique. For instance, for radiography of the abdomen, roughly the same image quality is obtained with a fraction of the dose required for conventional radiography. Further possibilities of dose reduction are provided by electronic imaging and digital radiography. With regard to large area digital radiography there is no loss of resolution but an increase in dynamic range and a certain dose reduction. With these techniques dose reductions of a least 5-fold are possible. With appropriate use of these imaging techniques the image quality will be maintained. Quality assurance must be carried out carefully when a new technique is introduced, especially in digital radiography, due attention must be paid to the problem of trade-off between contrast resolution and spatial resolution. (author)