title: Accuracy of two simple methods for estimation of thyroidal 131I kinetics for dosimetry-based treatment of Graves' disease.
abstract: One of the major challenges to the more widespread use of individualized, dosimetry-based radioiodine treatment of Graves' disease is the development of a reasonably fast, simple, and cost-effective method to measure thyroidal 131I kinetics in patients. Even though the fixed activity administration method does not optimize the therapy, giving often too high or too low a dose to the gland, it provides effective treatment for almost 80% of patients without consuming excessive time and resources. In this article two simple methods for the evaluation of the kinetics of 131I in the thyroid gland are presented and discussed. The first is based on two measurements 4 and 24 h after a diagnostic 131I administration and the second on one measurement 4 h after such an administration and a linear correlation between this measurement and the maximum uptake in the thyroid. The thyroid absorbed dose calculated by each of the two methods is compared to that calculated by a more complete 131I kinetics evaluation, based on seven thyroid uptake measurements for 35 patients at various times after the therapy administration. There are differences in the thyroid absorbed doses between those derived by each of the two simpler methods and the "reference" value (derived by more complete uptake measurements following the therapeutic 131I administration), with 20% median and 40% 90-percentile differences for the first method (i.e., based on two thyroid uptake measurements at 4 and 24 h after 131I administration) and 25% median and 45% 90-percentile differences for the second method (i.e., based on one measurement at 4 h post-administration). Predictably, although relatively fast and convenient, neither of these simpler methods appears to be as accurate as thyroid dose estimates based on more complete kinetic data.
authors.affiliation: Sezione di Fisica Medica, U.O. Fisica Sanitaria, Azienda Ospedaliero-Universitaria Pisana, via Roma n. 67, Pisa 56125, Italy. c.traino@ao-pisa.toscana.it
authors.forename: A C
authors.initials: AC
authors.lastname: Traino
authors.forename: B
authors.initials: B
authors.lastname: Xhafa
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D006111:Graves Disease / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D007700:Kinetics; D008297:Male; D015233:Models, Statistical; D011874:Radiometry / Q000379:methods*; D011877:Radionuclide Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013997:Time Factors
chemical_list: D007457:Iodine Radioisotopes