131I effective half-life (Teff) for patients with thyroid cancer.

Nuclear medicine procedures that use I activity represent significant sources of potential absorbed dose to medical staff, volunteers, and the general public. The potential exposures are due principally from exposures to excreted and retained activities in the patients' bodies. In general, exposure rate decreases in a simple exponential manner. The average effective half-life found for all patients in the study reported here is 11.41 +/- 0.02 h; this information may be used in guidelines on the management of patients in thyroid cancer therapy and for general radioprotection practice.