DEPARTMENTS Letters to the Editor Improved Planning of Radioiodine Therapy for Thyroid Cancer TO THE EDITOR: In regard to the prolonged measurements

and frequent data sampling performed after both diagnostic and therapeutic administration of radioiodine in thyroid cancer pa-tients, the recent work of Hermanska et al. (1) has the potential of shedding more light on radiobiological effects of 131I radiation. In their paper (1), the authors proposed an alternative to a monoex-ponential model of radioiodine kinetics to assess more accurately time–activity curves over thyroid remnants. The ratio of residence times (d/t) of diagnostic (70–75 MBq) versus therapeutic (4.2 1.4 GBq) activity of 131I found to be 1.5 (1). Every time–activity curve is generally characterized by 3 pa-rameters: the effective half-life of an uptake phase (TU), the maximum uptake (UMAX), and the effective half-life of a clearance phase (TC). The latter parameters can be derived by fitting the time–activity curve, in order to calculate the residence time by curve integration. Apart from the obvious need of having appro