Detection of small pulmonary nodules on chest radiographs: efficacy of dual-energy subtraction technique using flat-panel detector chest radiography

AIM:We investigated the effect of a double-exposure dual-energy subtraction (DES) technique on the performance of radiologists detecting small pulmonary nodules on flat-panel detector (FPD) chest radiographs. MATERIALS AND METHODS:Using FPD radiography we obtained 41 sets of chest radiographs from 26 patients with pulmonary nodules measuring ≤ 20 mm and from 15 normal subjects. Each data set included standard- and corresponding DES images. There were 6 non-solid-, 10 part-solid-, and 10 solid nodules. The mean size of the 26 nodules was 15.0 ± 4.8 mm. We performed receiver operating characteristic (ROC) analysis to compare the performance of 8 board-certified radiologists. RESULTS:For the 8 radiologists, the mean value of the area under the ROC curve (AUC) without and with DES images was 0.62 ± 0.05 and 0.68 ± 0.05, respectively; the difference was statistically significant (p = 0.02). For part-solid nodules, the difference of the mean AUC value was statistically significant (AUC = 0.61 ± 0.07 vs. 0.69 ± 0.05; p < 0.01); for non-solid nodules it was not (AUC = 0.62 ± 0.10 vs. 0.61 ± 0.09; p = 0.73), and for solid nodules it was not (AUC = 0.75 ± 0.10 vs. 0.78 ± 0.08; p = 0.23). For nodules with overlapping bone shadows, the difference of the mean AUC value was statistically significant (p = 0.03), for nodules without overlapping, it was not (p = 0.26). CONCLUSION:Use of a double-exposure DES technique at FPD chest radiography significantly improved the diagnostic performance of radiologists detecting small pulmonary nodules