Can dual-energy CT evaluate contrast enhancement of ground-glass attenuation? Phantom and preliminary clinical studies.

Evaluation of contrast enhancement of pulmonary lesions with ground-glass attenuation (GGA) is difficult with conventional techniques but might be possible using contrast-mapping images (CMIs) obtained by dual-energy computed tomography. To address this issue, a phantom study was conducted, and this technique was then applied to clinical cases. Phantoms made of agarose gel and those made of hollow resin clay, containing various concentrations of iodine or calcium, were used to simulate soft tissue and GGA, respectively. They were scanned using a dual-energy computed tomographic scanner, and the relationship between iodine concentration and calculated iodine value on CMIs was examined. The influence of calcium was also evaluated. In addition, contrast enhancement of 24 GGA lesions was evaluated on CMIs. There was a good correlation between iodine value and iodine concentration in the soft-tissue models (r(2) = 0.996). In the GGA models, the former tended to exceed the latter when default parameters for calculating CMIs were used, but this could be corrected by modifying the parameters (r(2) = 0.998). The iodine value increased with calcium concentration in both models. On CMIs, contrast enhancement was visible in 22 adenocarcinomas but not in a pulmonary hemorrhage and an inflammatory change. Dual-energy computed tomography can evaluate contrast enhancement of GGA lesions.