Should we reconsider blocking the thyroid for 123 I-Ioflupane studies in elderly patients: quantifying radiation dose to the unblocked thyroid and implications for clinical practice.

Objectives: To measure the absorbed dose to the thyroid in patients injected with 123 I-Ioflupane where the thyroid was not blocked with prophylaxis to investigate whether thyroid blocking should be limited to younger patients. This risk from the additional absorbed dose to the thyroid was then compared to the risk from iodine overdose through ingestion of the iodide prophylaxis, resulting in iodine-induced hyper/hypothyroidism (IIH).

Methods: A cohort of patients (n = 30) who did not receive thyroid prophylaxis underwent static thyroid imaging 3 h after 123 I-Ioflupane administration.