Analysis of influence of dosimetric factors on the outcome of I-131 therapy in patients with hyperthyroidism

The influence of dosimetric factors on the outcome of 131I therapy has been examined in hyperthyroid patients submitted to 131I treatment. The following factors - which could have influence on the effects of therapy with radioiodine - were analysed: the goitre volume, the thyroid radioiodine uptake after 24 h, and the effective half-life time of 131I (EHL). Five hundred (500) randomly selected patients with hyperthyroidism, treated with 131I, were studied. They were divided into three groups (based on clinical examination, hormonal and immunological tests, thyroid scintigraphy and ultrasound imaging). The study shows that the effectiveness of 131I therapy depends on the thyroid volume and absorbed dose in all the groups of patients and on the thyroid radioiodine uptake and EHL in patients with a single autonomously functioning thyroid nodule. We have failed to determine the borderline D, distinguishing between effective and ineffective therapy. The treatment outcome can be predicted with approximately 70% accuracy, based on minimal absorbed dose