Martin Uffmann, MD Cornelia Schaefer-Prokop, MD Ulrich Neitzel, PhD Michael Weber, BSc Christian J. Herold, MD Mathias Prokop, MD Index terms: Experimental study, 40.1215 Radiations, exposure to patients and personnel Radiography, comparative studies, 40.1215 Radiography, flat panel, 40.1215 Radiography, storage phosphor, 40.1215 Published online 10.1148/radiol.2312021662 Radiology 2004; 231:506 –514 Abbreviations: CR = computed radiography DR = digital radiography 1 From the Department of Radiology, University of Vienna Medical School, Allgemeines Krankenhaus Wien, Waeh- ringer Guertel 18 –20, A-1090 Vienna, Austria (M.U., C.S.P., M.W., C.J.H.); Department of Radiology, University Medical Center Utrecht, the Nether- lands (M.P.); and Philips Medical Sys- tems, Hamburg, Germany (U.N.). Re- ceived December 9, 2002; revision requested February 7, 2003; final revi- sion received September 13; accepted September 29. Address correspon- dence to M.U. (e-mail: martin.uffmann @univie.ac.at). Author contributions: Guarantors of integrity of entire study, M.U., M.P.; study concepts, M.U., M.P., U.N.; study design, M.P., M.U.; literature research, M.U., U.N.; exper- imental studies, C.S.P., M.U.; data ac- quisition, M.U., C.S.P.; data analysis/ interpretation, M.P., M.U., M.W.; statistical analysis, M.W.; manuscript preparation and editing, M.U., C.S.P.; manuscript definition of intellectual content, M.U., C.S.P., U.N., M.P.; manuscript revision/review, C.J.H., M.U.; manuscript final version ap- proval, M.U., M.P. © RSNA, 2004 Skeletal Applications for Flat-Panel versus Storage-Phosphor Radiography: Effect of Exposure on Detection of Low-Contrast Details 1 PURPOSE: To compare exposure requirements for similar detection performance with flat-panel detectors and the most recent generation of storage-phosphor plates in the simulated scatter of typical skeletal radiographic examinations. MATERIALS AND METHODS: A contrast-detail test object was covered with varying thicknesses of acrylic to simulate skeletal exposure conditions in the wrist, knee, and pelvis. Three series were obtained with increasing thicknesses of a simu- lated soft-tissue layer (5, 10, and 20 cm) and increasing tube voltage (50, 70, and 90 kVp). A fourth series was obtained with exposure conditions adapted to the phantom instructions (75 kVp). Images were acquired with a flat-panel detector (cesium iodide scintillator) and storage-phosphor plates at five exposure levels (speed class range, 100 –1,600). Five readers evaluated 84 images to determine the threshold contrast of 12 lesion diameters (range, 0.25–11.1 mm). Statistical signif- icance of differences between the two digital systems was assessed with two-way analysis of variance. RESULTS: A linear relationship was found between the number of detected lesions and the logarithm of exposure (R 2  0.98 for all series). On average, the flat-panel system required 45% less exposure than did the phosphor plates when 20-cm-thick acrylic was superimposed on the test object. Differences in exposure requirements were smaller with decreasing thicknesses of simulated soft-tissue layers and lower tube voltages (39% at 10 cm and 70 kVp, and 17% at 5 cm and 50 kVp). All differences were statistically significant. CONCLUSION: Flat-panel radiography provides improved contrast detectability and a potential for exposure reduction compared with those with storage-phosphor radiography. The best performance was achieved with conditions comparable to those for radiography of the trunk and lowest for conditions that simulate radiog- raphy of the extremities. © RSNA, 2004 Storage-phosphor radiography (hereafter, computed radiography [CR]) is a widely ac- cepted and applied technique for skeletal imaging. On the basis of its wide dynamic range, soft tissues and bones can be adequately visualized when appropriate image processing is applied (1). As a function of anatomic area or diagnostic indications, skeletal radiography is subject to varying scatter conditions and spatial resolution requirements. These variable conditions are reflected in different acquisition parameters with respect to voltage and exposure. Flat-panel radiography (hereafter, digital radiography [DR]) with a cesium iodide (CsI) amorphous silicon matrix detector has been recently introduced. Compared with CR, it is characterized by increased quantum efficiency and lower system noise, which may be used 506 R adiology