Correlation of CT values, iodine concentration, and histological changes in the thyroid.

PURPOSE: We have reported that in the thyroid, there is a linear correlation between iodine concentrations and CT values. However, the slope of the regression line was about three times as large as that in KI solutions. We investigated the factor(s) contributing to the increment of the slope of the regression line in the thyroid. METHOD: Solutions of NH4I and thyroid hormones were used to investigate the regression line. Thirty-six thyroids were evaluated to investigate the correlation between the iodine concentrations and the area ratio of thyroid follicles, which were measured by preoperative CT and from tissue slices, respectively. RESULTS: The slopes of the regression lines in the solutions were almost identical to those in KI solutions. In the thyroid, iodine concentrations were logarithmically correlated with the area ratio of follicles. CONCLUSION: The decrease in CT values not only revealed a decrease of iodine concentration in the thyroid but also represented an increase of follicular cells and/or interstitial structures in the volume ratio secondary to it.