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 diagnostic performance by using a digital chest imaging system in which amorphous selenium serves as the x-ray detector.

Methods: Two hundred forty-seven patients were examined with the selenium system. Three sets of images were made in each patient: one set with a standard 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 diagnostic value of each set of images for detection of pulmonary, mediastinal, and pleural pathology was analyzed with receiver operating characteristic (ROC) methodology by using computed tomography as the reference standard. The authors also assessed the effect of sex, height, and weight of the patients on the diagnostic performance of the readers.

Results: The areas under the ROC curves for the detection of various abnormalities at 100%, 55%, and 35% of the standard dose for observer 1, respectively, 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 abnormalities 0.71, 0.72, 0.72. There were no statistically significant differences between the two observers.

Conclusions: No statistically significant difference was found between the radiologists' performance in detecting abnormalities with standard x-ray dose images and the performance with images made with 55% and 35% of the standard dose. Sex, height, and weight had no influence on diagnostic performance.