SAT-417 Personalized Treatment Planning for Radioiodine Therapy of Graves’ Disease;The Collar Therapy Indicator(CoTI)

Introduction Since its introduction 80 years ago, the therapeutic I-131 dosage has usually been tailored to individual patient requirements based on the uptake of a tracer radio-iodine(RAI) dose. Estimated exposure has typically been extrapolated from the results of activity measurements at one or two time points, e.g., at 4 and 24 hours. We now know that treatment of hyperthyroid Graves disease with these methods lead to a 13–25% rate of failure to cure hyperthyroidism and a 46–80% rate of long-term hypothyroidism in cured patients. There is a need for a much more personalized approach to RAI dosing based on individual RAI tissue uptake, kinetics. This can be achieved only after including multiple data points during the evaluation of tissue uptake. The Collar Therapy Indicator (CoTI), a device placed in cloth collar around the neck resembling a turtle neck sweater collar with a connecting wire and recording box, has been shown in small feasibility studies to provide data regarding radioiodine exposure that correlates with conventional methods of measuring I-123 and I-131 uptakes after diagnostic dose administration and/or therapy for thyroid disorders Methods; We hypothesized that the device’s continuous measurement capability will permit more accurate estimates of radiation exposure to thyroid tissue than conventionally employed methods assessing fractional uptake at one or a few time points. It may also provide information about the extent of variability in the absorbed radiation dose among patients with hyperthyroidism. We performed a feasibility study in a patient with graves’ disease to see the difference between tradition methods of I-123 uptake and the CoTI; (1) We compared the conventional quantitative uptake-derived thyroid time activity curve (TAC) as well as the Area Under the Curve (AUC)(based on percent uptake at 6 hour and 24 hour time points) to that obtained using the CoTI.(2) We evaluated the uptake and clearance kinetics of diagnostic I-123 administered.(3) We also evaluated patient experience in using the CoTI device with a survey instrument. Results; The CoTI plotted TAC and AUC offered a different approach from the conventional methods of calculation (6 hr and 24 hr % uptake) of I-123 TAC and AUC. The patient reported no difficulty in using the device and the device itself was not inconvenient. Conclusions; The calculation of % uptake as well as rate of uptake within the thyroid by CoTI might help us, in achieving a more personalized approach to I-131 RAI dose calculation for treatment of Graves’ disease. The preliminary research findings that we have generated will help us investigate different aspects of RAI uptake within the thyroid and will hopefully lead to solutions, for some of the common issues and problems arising out of random dosing of RAI.