Effect of Gut Retention on the Effective Whole Body Half-Time of Iodine-131 in Thyroid Cancer Patients

Abstract

The whole body radiation dose resulting from iodine-131 (¹³¹ I) therapy in patients with thyroid cancer is directly related to the effective whole body half-time of ¹³¹I in those patients. In 101 studies on 64 patients referred for quantitative whole body radioiodine scans for thyroid cancer; the effective whole body half-time was found to be significantly greater (p < 0.05) when gut retention was maximal. These results indicate that gut retention is a significant contributor to the whole body half-time of ¹³¹I. The routine use of non-iodine-containing laxatives at the time of ¹³¹I studies and therapy may be useful in decreasing whole body ¹³¹I retention times and, therefore, in decreasing whole body radiation doses, and should be considered in such patients.