Effect of dose levels on the diagnostic performance of a selenium-based digital chest system

RATIONALE AND OBJECTIVES. To evaluate the effect of dose reduction on diagn ostic performance by using a digital chest imaging system in which amorphou s selenium serves as the x-ray detector. METHODS. Two hundred forty-seven patients were examined with the selenium s ystem. Three sets of images were made in each patient: one set with a stand ard x-ray dose, one set with 55% of the standard dose, and one set with 35% of the standard dose. All 741 images were read by two radiologists. The di agnostic value of each set of images for detection of pulmonary, mediastina l, and pleural pathology was analyzed with receiver operating characteristi c (ROC) methodology by using computed tomography as the reference standard. The authors also assessed the effect of sex, height, and weight of the pat ients on the diagnostic performance of the readers. RESULTS. The areas under the ROC curves for the detection of various abnorm alities at 100%, 55%, and 35% of the standard dose for observer 1, respecti vely, were pulmonary opacities 0.82, 0.83, 0.84; interstitial disease 0.71, 0.70, 0.72; mediastinal disease 0.81, 0.80, 0.77; and pleural abnormalitie s 0.71, 0.72, 0.72. There were no statistically significant differences bet ween the two observers. CONCLUSIONS. No statistically significant difference was found between the radiologists' performance in detecting abnormalities with standard x-ray do se images and the performance with images made with 55% and 35% of the stan dard dose. Sex, height, and weight had no influence on diagnostic performan ce.