Estimate of the 3d distribution of dose during the ¹³¹I treatments in hyperthyroidism

Hyperthyroidism is a common disease, which has among its most used options of I131 therapy treatment. Dosimetrically optimizing this therapy is the object of research and constant study. With the purpose of characterizing this treatment dosimetrically, a set of tools in Matlab, which allow studying the differences between the administered dose and the one prescribed with the most used 1D planning techniques, with the theoretical 3D and the calculated one by the S factors method. Data from 6 patients were used for this preliminary analysis. (SPECT and Iodine uptake). The deviations between the 3D dose distribution by S factors and the theoretical formulation. The discrepancies between the theoretical dosimetric planning of activity to be administered and that calculated by SPECT using the theoretical formulation were less than 19% and are related to differences in the determination of the thyroid uptake mass by scintigraphy and ultrasound. The average 3D doses delivered to the tissue / prescribed dose for the method theoretical and the ―S‖ factors showed maximum differences of 10%. The discrepancies between 3D dose distribution by S factors and the theoretical formulation, showed a maximum difference of dose per voxel / prescribed dose of 23%, located in the periphery of the thyroid. This analysis allowed corroborate that the non-homogeneities of the dose produced in the tissue are significant, and constitute a starting point for the introduction of new dosimetric planning models that optimize this treatment.