Dosimetric comparison between fixed and individualized activity in Graves' disease treatment with I-131

Abstract

A patient-especific method has been used to calculate the therapeutic I-131 activity to administer to patients with Graves’disease in order to obtain the optimal thyroid dose. The aim of this study was to analyze the dose variation in contrast to the fixed activity regimen. In 30 patients, biokinetic and morfological parameters were estimated from planar scintigraphic images obtained at 4, 24 and 96 hours after injection of I-123 and I-131 activities were calculated to deliver 120 Gy to the thyroid. Comparative dose calculations were carried out assuming that the individual patients had been treated according to 370 MBq activity administration. Activity (or dose) was reduced by an average factor of 2.4 and up to a factor 4.9 for an individual patient. The implemented method seeks a balance among the accuracy of the calculations, resource consumption and patient comfort.