Excess radiation absorbed doses from non-optimised radioiodine treatment of hyperthyroidism

Radioiodine therapy is often the method of choice for treatment of hyperthyroidism because it is considered safe, is relatively inexpensive, and is convenient for the patient and except for occasional hypothyroidism, almost without side effects. Even though radioiodine treatment has been performed for over 50 years, the method of treatment differs from country to country and even from hospital to hospital within the same country. To illuminate such differences 187 radioiodine treatments for Graves' disease at Malmö University Hospital in Sweden have been analysed. Comparative dose calculations were carried out assuming that the individual patients had also been treated according to a number of other protocols in current use. The results show that the protocol used for calculating the administered activity in radioiodine therapy is far from optimised in many hospitals. Following the protocols where the absorbed dose to the thyroid is calculated without any uptake measurements after administration of a test activity, most of the patients were treated with an unnecessarily high activity, as a mean factor of 2.5 times too high and in individual patients up to eight times too high, leading to an unnecessary radiation exposure both for the patient, the family and the public. This is not in accordance with generally accepted radiation protection principles. Using higher activity than necessary will also prolong the patient's stay at the hospital and thus increase the costs for the care. Unnecessarily high activity will also necessitate more long-lasting radiation protection restriction relative to family members when the patient is back home.