Digital storage phosphor chest radiography: An ROC study of the effect of 2K versus 4K matrix size on observer performance

PURPOSE: To compare observer performance in the detection of abnormalities on 1,760 x 2,140 matrix (2K) and 3,520 x 4,280 matrix (4K) digital storage phosphor chest radiographs. MATERIALS AND METHODS: One hundred sixty patients who underwent dedicated c omputed tomography (CT) of the thorax were prospectively recruited into the study. Posteroanterior and lateral computed radiographs of the chest were acquired in each patient and printed in 2K and 4K formats. Six radiologists independently analyzed the hard-copy images and scored the presence of par enchymal (opacities less than or equal to2 cm, opacities >2 cm, and subtle interstitial), mediastinal, and pleural abnormalities on a five-point confi dence scale. With CT as the reference standard, observer performance tests were carried out by using receiver operating characteristic (ROC) analysis. RESULTS: Analysis of averaged observer performance showed 2K and 4K images were equally effective in detection of all three groups of abnormalities. I n the detection of the three subtypes of parenchymal abnormalities, there w ere no significant differences in averaged performance between the 2K and 4 K formats (area below ROC curve [A(z)] values: opacities less than or equal to2 cm, 0.62 +/- 0.056 [standard error] and 0.59 +/- 0.045; opacities >2 c m, 0.86 +/- .025 and 0.85 +/- 0.030; subtle interstitial abnormalities, 0.7 3 +/- 0.041 and 0.72 +/- 0.041). Averaged performance in detection of media stinal and pleural abnormalities was equivalent (A(z) values: mediastinal, 0.70 +/- 0.046 and 0.73 +/- 0.033; pleural, 0.85 +/- 0.032 and 0.86 +/- 0.0 33). CONCLUSION: Observer performance in detection of parenchymal, mediastinal, and pleural abnormalities was not significantly different on 2K and 4K stor age phosphor chest radiographs.