EFFECTS OF DOSE REDUCTION ON DIGITAL CHEST IMAGING USING A SELENIUM DETECTOR - A STUDY OF DETECTING SIMULATED DIFFUSE INTERSTITIAL PULMONARY-DISEASE

OBJECTIVE. The purpose of this study was to evaluate the effect of dos e reduction on the diagnostic performance of a new digital chest imagi ng system in which amorphous selenium is used as the X-ray detector, D iagnostic performance was assessed for the detection of simulated diff use interstitial pulmonary disease (DIPD). MATERIALS AND METHODS. DIPD was simulated by superimposing plastic sheets that contained small ra diopaque objects (birdseed) on an anthropomorphic chest phantom. We va ried the number of sheets from zero to four to simulate the degree of abnormality. We made 80 images with a standard X-ray dose, 80 images w ith 55% of the standard dose, and 80 images with 35% of the standard d ose. Six observers were asked to indicate the presence of DIPD using a five-level scale of confidence, Two hundred forty chest images were t hen analyzed using receiver operating characteristic (ROC) curves. RES ULTS. The area under the ROC curve was 87.2 for all readers with stand ard-dose imaging (95% confidence interval [CI], 83.7-90.7), 91.7 with 55% of the standard dose (95% CI, 88.8-94.6), and 90.0 with the 35% do se (95% CI, 87.1-92.9), The area under the ROC curve for subtle DIPD ( one superimposed sheet) was 75.3 for all readers with standard-dose im aging (95% CI, 67.1-83.5), 79.7 with 55% of the standard dose (95% CI, 71.9-87.5), and 70.3 with the 35% dose (95% CI, 61.7-78.9). For each dose, we observed a gradual improvement of the ROC curves with each ad ditional sheet superimposed on the chest phantom (p < .001). CONCLUSIO N. We found no significant difference in diagnostic performance among images made with a standard X-ray dose, those made with a 55% dose, an d those made with a 35% dose (95% CI).