Dual energy computed tomography of lung nodules: Differentiation of iodine and calcium in artificial pulmonary nodules in vitro

Background: Iodine enhancement is a marker for malignancy in pulmonary nodules. The purpose of this in vitro study was to assess whether dual energy computed tomography (DECT) can be used to detect iodine and to distinguish iodine from disperse calcifications in artificial pulmonary nodules. Materials and methods: Small, medium, and large artificial nodules (n = 54), with increasing concentrations of iodine or calcium corresponding to an increase in Hounsfield Units (HU) of 15, 30, 45, and 90 at 120 kV, were scanned in a chest phantom with DECT at 80 and 140 kV. Attenuation values of each nodule were measured using semi-automated volumetric analysis. The mean DE ratio with 95% confidence intervals (CI) was calculated for each nodule. Results: The mean maximum diameter of the 18 small nodules was 12 mm (standard deviation: 0.4), 16 mm (0.4) for the 18 medium nodules, and 30 mm (1.1) for the 18 large nodules. There was no overlap of 95% CI of DE ratios of iodine and calcium in nodules >= 16 mm. In nodules <16 mm, there was an overlap of DE ratios in low contrast lesions. Conclusion: DECT can distinguish iodine from calcium in artificial nodules >= 16 mm in vitro. In smaller lesions, a clear differentiation is not possible. (C) 2010 Elsevier Ireland Ltd. All rights reserved.