Development of a High-performance Dual-energy Chest Imaging System. Initial Investigation of Diagnostic Performance

Rationale and Objectives: The aim of this study was to assess the performance of a newly developed dual-energy (DE) chest radiographic system in comparison to digital radiographic (DR) imaging in the detection and characterization of lung nodules. Materials and Methods: An experimental prototype was developed for high-performance DE chest imaging, with total dose equivalent to a single posterior-anterior DR image. Projections at low and high peak kilovoltage were used to decompose DE soft tissue and bone images. A cohort of 55 patients (31 men, 24 women; mean age, 65.6 years) was drawn from an ongoing trial involving patients referred for percutaneous computed tomography-guided biopsy of suspicious lung nodules. DE and DR images were acquired of each patient prior to biopsy. Image quality was assessed by means of human observer tests involving five radiologists independently rating the detection and characterization of lung nodules on a nine-point scale. Results were analyzed in terms of the fraction of cases at or above a given rating, and statistical significance was evaluated using Wilcoxon's signed-rank test. Performance was analyzed for all cases pooled as well as by stratification of nodule size, density, lung region, and chest thickness. Results: The studies demonstrated a significant performance advantage for DE imaging compared to DR imaging (P < .001) in the detection and characterization of lung nodules. DE imaging improved the detection of both small and large nodules and exhibited the most significant improvement in regions of the upper lobes, where overlying anatomic noise (ribs and clavicles) are believed to reduce nodule conspicuity on DR imaging. Conclusions: DE imaging outperformed DR imaging overall, particularly in the detection of small, solid nodules. DE imaging also performed better in regions dominated by anatomic noise, such as the lung apices. The potential for improved nodule detection and characterization at radiation doses equivalent to DR imaging is encouraging and could augment the broader use of DE imaging. Future studies will extend the initial cohort and rating scale tests to a larger cohort evaluated by receiver-operating characteristic analysis and will evaluate DE imaging in comparison and as an adjuvant to low-dose computed tomography.