BACKGROUNDThe incidence of thyroid cancer has been increasing. Our aim was to evaluate the efficacy of low-dose dual-phase helical computed tomography (CT) in the characterization of thyroid lesions, and to discuss the relationship between image characteristics and their pathology.

METHODSOne hundred and six patients with thyroid lesions underwent low-dose dual-phase helical CT after the injection of contrast material. CT scans were obtained at arterial and venous phase with delays of 25 and 65 seconds, and tube current of 60 and 120 mA, respectively. The attenuation change in the lesion between the arterial and venous phase was analyzed and categorized as "increased," "decreased," "mixed" or "no change."

RESULTSHistopathologic diagnosis was obtained by surgery in 106 patients (115 lesions). Of the 106 patients, 45 had nodular goiter, 5 thyroid adenoma, 6 thyroiditis, and 50 papillary thyroid carcinoma (PTC) (59 lesions). The attenuation value showed a significant difference (P < 0.05) between the arterial and venous phase for the high attenuation area. There was statistical significant difference in terms of attenuation value in high attenuation areas at both phases and in low attenuation areas on arterial phase between nodular goiter and PTC (P < 0.05). However, there was no significant difference in attenuation value between adenoma and PTC. Twenty-nine cases (76.3%) of goiter manifested mixed type, 3 cases (3/5) of adenoma showed decreased type, 6 cases (6/6) of thyroiditis showed increased type, and 55 cases (93.2%) of PTC showed decreased type attenuation. The sensitivity, specificity for thyroid carcinoma by dual-phase CT were 94.9% and 80.4% respectively. The overall diagnostic accuracy for thyroid lesions by dual-phase CT was 87.8%.

CONCLUSIONSThe performance of dual-phase helical CT is related to the pathological structure of the lesions. The analysis of enhancement patterns by using dual-phase helical CT will be helpful in the differential diagnosis of thyroid lesions.