Clinical values of of gemstone spectral CT in diagnosing thyroid disease

OBJECTIVE: To quantitatively evaluate the diagnostic value of gemstone spectral CT in thyroid disease.

PATIENTS and METHODS: A total of 123 patients with thyroid diseases were enrolled in the retrospective study. All the patients underwent spectral CT scan, and 39 of them underwent dual-phase enhanced scan. Iodine concentration (IC) and normalized IC (NIC) were compared between benign and malignant nodules. The optimal threshold to predict malignancy was obtained by receiver operating characteristic curve (ROC). Multivariate ROC analysis was performed to evaluate the efficacy of combining the IC (NIC) and conventional morphological characteristics.

RESULTS: Ten diffuse diseases and 113 nodular diseases were confirmed by clinical laboratory examination and histopathology. In total, 122 nodules (87 benign and 35 malignant) were detected, 41 nodules in enhanced cases. The IC and NIC $_{VP}$ of malignant nodules were significantly lower than benign nodules in noncontrast and venous phase (VP) (P=0.000). The optimal IC and NIC $_{VP}$ threshold was 0.68 mg/mL and 0.38, achieving 74.3% and 76.9% sensitivity, 66.7% and 80.0% specificity, respectively. For multivariate analysis, the area under ROC (AUC) was 0.88 and 0.94 in noncontrast and VP, respectively. Sensitivities of 77.1% and 84.6%, and specificities of 84.5% and 88.0% were achieved.

CONCLUSION: Gemstone spectral CT can generally evaluate the abnormal iodine content in thyroid disease. Lower iodine can help differentiating malignant from benign nodules. A comprehensive analysis combining spectrum parameters and morphological characteristics is suggested in differential diagnosis.