The value of a tracer dose in predicting the kinetics of therapeutic doses of 131I in thyrotoxicosis.

The kinetics of tracer doses of 131I, assessed by measuring uptake and effective half-life, correlate well with the kinetics of therapy doses. The effective half-life was measured using thermoluminescent discs fixed to the patients' anterior neck surface. This method gives results comparable with those obtained using an uptake probe, and met with a good response by the patients. Using the kinetics of the tracer dose to assist prescription of radioiodine therapy would considerably reduce the spread of absorbed doses to the glands of a group of patients. The case for attempting more exact dosimetry in this field is reviewed.