I-131 THERAPY IN SPORADIC NONTOXIC GOITER

The effect of radioiodine in the treatment of nontoxic goiter is seldo m evaluated quantitatively. The aim of this study was threefold: (a) t o assess the effect of I-131 On goiter volume, (b) to establish a rela tionship between CT volume reduction and the amount of radioactivity t aken up by the thyroid and (b) to assess the precision of scintigraphi c thyroid volume measurements. Methods: In 27 patients with sporadic n ontoxic goiter, the thyroid volume was estimated from a [Tc-99m]pertec hnetate scintigram. Two different models (cylinder model and surface m odel) were applied, The I-131 dosage varied between 507 and 3700 MBq. In all patients, noncontrast CT scanning of the neck was performed bef ore therapy and 1 yr after therapy. Results: The mean CT thyroid volum e before therapy was 194 +/- 138 ml. A reduction was obtained in all p atients and averaged 34% +/- 17%. The volume reduction measured by CT correlated well with the amount of I-131 in the thyroid (r = 0.70). In thyroids larger than 200 mi, both scintigraphic volume estimation met hods were imprecise. For smaller volumes, the surface model was superi or. Hypothyroidism developed in 14% of the patients. No other side eff ects occurred, Conclusion: Iodine-131 therapy for volume reduction in nontoxic goiter is a safe and effective treatment. For scintigraphic e stimation of thyroid gland volumes smaller than 200 ml, the surface mo del is preferred.