Accuracy and reliability of thyroid volumetry using spiral CT and thyroid volume in a healthy, non-iodine-deficient Chinese adult population.

Objective: The purpose of this study was to assess the accuracy and reliability of thyroid volumetry using spiral CT and to investigate thyroid volumes for a healthy, non-iodine-deficient adult population in southwestern region of China.

Materials And Methods: Spiral CT was performed in phantoms and adult subjects with normal thyroid, and the volumes were measured by observers with 5 years or more of CT experience. The phantom volumes and the thyroid volumes of all subjects were noted.

Results: For the thyroid phantoms, there was no significant difference between the true and CT calculated volumes (t = 0.862, P = 0.399), and the correlation was excellent (ICC = 0.9995, P = 0.000). In the subjects for reliability analysis, the intraobserver or interobserver differences for CT volumetric measurement of thyroid were not significant (P > 0.05). The intraobserver or interobserver correlations were very high (ICC > 0.99, P < 0.001). In the subjects for population analysis, the median of the thyroid volumes was 11.45 cm(3). The nonparametric Mann-Whitney U-test showed no significant difference for the thyroid volume between sexes (U = 4388.00, Z = -1.118, P = 0.264). The nonparametric Kruskall-Wallis test showed no significant difference in all age groups (χ(2) = 13.466, P = 0.062). There was a slight negative correlation between the thyroid volume and age (r(s) = -0.166, P = 0.019).

Conclusion: The accuracy and reliability of multi-slice spiral CT in measuring thyroid volume are very high. The thyroid volumes are not significantly difference between genders or among decades for the healthy, non-iodine-deficient adult population in southwestern region of China.