The Collar Therapy Indicator (CoTI) (A device that is placed in collar around the neck resembling a turtle neck sweater collar with a wire and recording box) has been shown in a single small previously published experience 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. We hypothesize 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 thyroid cancer and hyperthyroidism. By providing more complete information about individual patient's exposures, it will facilitate more accurate estimation of the administered I-131 dose requirements for control of hyperthyroidism and thyroid remnant ablation while reducing the need for repeated visits to the clinic for dosimetry measurements. The aims of our project include the following: (1)To compare quantitative imaging-derived thyroid time activity curve to that obtained using the CoTI and to determine the extent to which there is variability in radiation dose predicted using conventional methods to that predicted from measurement of the full Time-Activity Curve (TAC).(2) Evaluate the uptake and clearance kinetics across the 5 patients in each category as proof of principle for a potential larger trial to investigate use of this device in optimizing the administered doses of radioactive iodine to achieve therapeutic goals while minimizing risks of comorbidities, such a post-radioiodine hypothyroidism in patients with Graves' disease.(3)Evaluate patient experience, convenience, and discomfort in using the CoTI device with a survey instrument.