PT - JOURNAL ARTICLE AU - Haruna Ikeda AU - Yoshinori Ito AU - Tomohiro Tada AU - Rina Murayama AU - Yuka Ochi AU - MIka Tamura AU - Yoshinori Tsutsumi AU - Katsuhiko Kato TI - Correlation between thyroid computed tomography density and thyroid function in hyperthyroidism DP - 2020 May 01 TA - Journal of Nuclear Medicine PG - 3081--3081 VI - 61 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/61/supplement_1/3081.short 4100 - http://jnm.snmjournals.org/content/61/supplement_1/3081.full SO - J Nucl Med2020 May 01; 61 AB - 3081Objectives: In general, three methods are available to determine the activity of radioiodine used in I-131 therapy for hyperthyroidism: i) a fixed activity is determined for all patients; ii) an activity is determined depending on patient’s thyroid size; and iii) an activity is calculated from the Marinelli-Quimby formula based on the 24-h radioiodine uptake rate, effective half-life, and weight of the thyroid gland. Despite the long history of using radioiodine therapy for hyperthyroidism, controversy persists regarding the optimal method used to determine the activity required for restoring thyroid function. Thyroid computed tomography (CT) density is significantly lower in patients with hyperthyroidism than in individuals with normal thyroid levels and may be associated with thyroid function. If there is a correlation between thyroid CT density and thyroid function, the optimal radioiodine activity used in I-131 therapy can be determined by using thyroid CT density. This study aimed to investigate the relationship between thyroid CT density and thyroid function or morphology by exploring factors influencing changes in thyroid CT density in hyperthyroidism. Methods: Forty patients with Graves' disease and 10 patients with Plummers' disease were recruited and retrospectively evaluated in this study. The region of interest was set over the entire thyroid gland for X-ray CT with Syngo VE 32B (Siemens) to obtain the mean thyroid CT density and weight of the thyroid gland. A test activity of I-131 (3.7 MBq) was administered before I-131 therapy, and the radioiodine uptake was measured after 3, 24, 96, and 167 h. An approximate curve was plotted based on the obtained uptake rate, and the effective half-life was calculated. We examined whether the mean thyroid CT density correlated with the weight of the thyroid gland, 24-h iodine uptake rate, effective half-life, free tri-iodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), TSH receptor antibody (TRAb), or urinary iodine concentration. Patients with Graves' disease and those with Plummers' disease were separately examined. Results: In patients with Graves' disease, thyroid CT density did not correlate with the thyroid weight, 24-h iodine uptake rate, fT3, fT4, TSH, TRAb, and urinary iodine concentration. However, thyroid CT density had a significant positive correlation with the effective half-life (r = 0.589, p < 0.0001). In patients with Plummers' disease, the thyroid CT density did not correlate with any investigated parameters. Conclusions: In patients with Graves' disease, thyroid CT density has a significant positive correlation with the effective half-life.