Measurement of thyroid iodine by CT.

For evaluation of thyroidal iodine kinetics and thyroid nodules, we carried out quantitative in vivo measurement of thyroid iodine concentration by CT. Neuron activation analysis of iodine content was conducted on 48 thyroid fragments without calcification operatively obtained from 18 patients who had undergone CT of the thyroid without contrast enhancement. The CT attenuation values were obtained from the regions of interest in the CT image that corresponded to the analyzed fragment. When iodine concentration in the thyroid tissue was greater than 0.02 mg/g, the CT values correlated linearly with the iodine concentrations in thyroid nodules, thyroids with diffuse thyroid disease, and normal thyroids. The relationship is represented by the following formula: iodine concentration (mg/g) = (CT value-65)/104. The relationship between iodine concentration and CT value in diffuse thyroid disease, thyroid nodules, and normal thyroids was not significantly different.