Differentiating pulmonary metastasis from benign lung nodules in thyroid cancer patients using dual-energy CT parameters

Abstract

Objectives To explore the importance of quantitative characteristics of dual-energy CT (DECT) between pulmonary metastasis and benign lung nodules in thyroid cancer. Methods In this retrospective study, we identified 63 patients from our institution's database with pathologically proven thyroid cancer who underwent DECT to assess pulmonary metastasis. Among these patients, 22 had 55 pulmonary metastases, and 41 had 97 benign nodules. If nodules showed increased iodine uptake on I-131 single-photon emission computed tomography-computed tomography or increased size in follow-up CT, they were considered metastatic. We compared the clinical findings and DECT parameters of both groups and performed a receiver operating characteristic analysis to evaluate the optimal cutoff values of the DECT parameters. Results Patients with metastases were significantly older than patients with benign nodules (p = 0.048). The DECT parameters of the metastatic nodules were significantly higher than those of the benign nodules (iodine concentration [IC], 5.61 +/- 2.02 mg/mL vs. 1.61 +/- 0.98 mg/mL; normalized IC [NIC], 0.60 +/- 0.20 vs. 0.16 +/- 0.11; NIC using pulmonary artery [NICPA], 0.60 +/- 0.44 vs. 0.15 +/- 0.11; slope of the spectral attenuation curves [lambda HU], 5.18 +/- 2.54 vs. 2.12 +/- 1.39; and Z-effective value [Z(eff)], 10.0 +/- 0.94 vs. 8.79 +/- 0.75; all p < 0.001). In the subgroup analysis according to nodule size, all DECT parameters of the metastatic nodules in all subgroups were significantly higher than those of the benign nodules (all p < 0.05). The cutoff values for IC, NIC, lambda HU, NICPA, and Z(eff) for diagnosing metastases were 3.10, 0.29, 3.57, 0.28, and 9.34, respectively (all p < 0.001). Conclusions DECT parameters can help to differentiate metastatic and benign lung nodules in thyroid cancer.