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A dosimetric approach to patient‐specific radioiodine treatment of Graves' disease with incorporation of treatment‐induced changes in thyroid mass
Author(s) -
Traino A. Claudio,
Di Martino Fabio,
Lazzeri Mauro
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1763411
Subject(s) - absorbed dose , thyroid , medicine , nuclear medicine , dosimetry , radioiodine therapy , reduction (mathematics) , radiation therapy , graves' disease , effective dose (radiation) , endocrinology , mathematics , thyroid cancer , geometry
The traditional algorithms (Marinelli–Quimby and MIRD) used for the absorbed dose calculation in radionuclide therapy generally assume that the mass of the target organs does not change with time. In radioiodine therapy for Graves' disease this approximation may not be valid. In this paper a mathematical model of thyroid mass reduction during the clearance phase (30–35 days) after131 I administration to patients with Graves' disease is presented. A new algorithm for the absorbed dose calculation is derived, taking into account the reduction of the mass of the gland resulting from the131 I therapy. It is demonstrated that thyroid mass reduction has a considerable effect on the calculated radiation dose. Either the model of the thyroid mass reduction or the new equation for the absorbed dose calculation depend on a parameter k for each patient. This parameter can be calculated after the administration of a diagnostic amount of radioiodine activity (0.37–1.85 MBq). Thus, thyroid absorbed dose and thyroid mass reduction during the first month after therapy can be predicted before therapy administration. The absorbed dose values calculated by the new algorithm are compared to those calculated by the traditional Marinelli–Quimby and MIRD algorithms.