Dosimetry in the Radioiodine Treatment of Hyperthyroidism

Abstract

Radioiodine therapy has largely replaced surgery and is nowadays commonly used because it is easy to perform and has proved to be effective in the definitive treatment of hyperthyroidism. Hundreds of thousands of patients have been treated all over the world, but still there isn’t a clear evidence about the optimal method to determine the activity to administer to reach the therapeutic objective. The discussion is still open on when to use fixed activities or to perform a pre-therapeutic dosimetric study to personalize the administered activity to the single patient’s morphological and metabolic characteristics. The rationale behind pretreatment personalized dosimetry is to determine the 131I activity that is most likely to lead to the therapeutic success but that limits the radiation exposure to the strictly necessary amount as also required by the recent European Directives about protection against the dangers due to ionizing radiation. Hyperthyroidism is a benign condition, so the aim of the treatment is to heal it in a short time with the minimum activity and, if possible, with a unique administration. Personalized dosimetry aims to tailor the therapeutic activity to be administered to the morphological and metabolic characteristics of each patient’s thyroid because there is quite a wide interpatient variability. Some indications about how to perform a personalized dosimetry are reported with a short review of literature data about the clinical results of different methods.