Planning of 131I therapy for graves disease based on the radiation dose to thyroid follicular cells.
We evaluated the effects on the absorbed dose to thyroid follicular cells of self-absorption of (131)I radiation (specifically, beta-rays) in the follicular colloid.


METHODS
Thyroid follicles were modeled as colloid-filled spheres, containing a uniform concentration of (131)I and surrounded by a concentric monolayer of cells. Assuming close packing of identical follicles, we used Monte Carlo simulation to assess the absorbed dose to follicular cells.


RESULTS
Because of beta-ray self-absorption in colloidal spheres with radii larger than 50 mum, the absorbed dose to follicular cells is less than the average thyroid absorbed dose.


CONCLUSIONS
For the same thyroid mass, radioiodine thyroid uptake, and effective half-life, patients with follicles with colloidal sphere radii of 100, 200, 300, and 400 microm should be administered 9%, 15%, 21%, and 30% more (131)I, respectively, than patients with colloidal sphere radii of less than 50 microm, to yield the same absorbed dose to follicular cells.
Eterovic
Davor
D
Department of Nuclear Medicine, University Hospital Split, University of Split Medical Faculty, Split, Croatia. eterovic@bsb.mefst.hr
Antunovic
Zeljko
Z
Markovic
Vinko
V
Grosev
Darko
D
D003198:Computer Simulation; D006111:Graves Disease / Q000503:physiopathology* / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008954:Models, Biological; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013961:Thyroid Gland / Q000503:physiopathology* / Q000528:radiation effects*
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals