124I in Differentiated Thyroid Cancer

124I was first used in 1960 by Phillips et al. (Acta Unio Int Contra Cancrum 16:1434–1438, 1960) for the treatment of differentiated thyroid carcinoma (DTC). However, because the decay of 131I was more suited for therapy and its production was easier and less expensive than 124I, 131I has remained the most frequently used radioiodine isotope for the treatment of DTC. Likewise, because the decay characteristics of 131I were more suitable for the imaging equipment at that time, 131I became the most frequently used radioiodine isotope for diagnostic imaging of the thyroid. Subsequently, 123I became available in the mid-1960s (Rhodes Isot Radiat Technol 4:275–280, 1967), and in the United States 123I is now the most frequently used radioisotope of iodine for diagnostic imaging in differentiated thyroid carcinoma (DTC).