A useful correlation between maximum thyroid uptake and radioiodine urine levels at different times after exposure was developed in order to determine when the intervention with an adequate blocking agent might still be effective.
In an animal model (dog), six different doses were administered in the range of 100-600 kBq.
The best correlation was found between the 125I uptake after 48 h (T-48) and urine radioactivity 4-6 h (U-4, U-5, U-6) after exposure.
For the case of U-4, the equation YT-48=0.790 XU-4+2.973 (r=0.974 with a level of significance of p<0.001) was obtained.
An analogous study, carried out in humans (n=20) to whom 131I was administered, showed a similar correlation and level of significance : YT-24=1.162 XU-4+3.263 (r=0.926 ; p<0.001).
The validity of this correlation was confirmed in four volunteers who received small doses of 125I (25-100 kBq), with good agreement between measured and extrapolated thyroid uptake and a mean difference of less than 10% (CV=16.2%). Three different blocking agents were then tested in the same dog : potassium iodide, potassium perchlorate, and a thionamide (Tapazole).
The blocking action of the first two compounds was about 90%, as opposed to only 48% for the third compound.
Potassium iodide was chosen for its limited side effects and more universal utilization.
The final study, carried out with four different doses, indicated that 25 mg of KI is the ideal amount to be administered to the dog. (...)
Mots-clés Pascal : Radioprotection, Thyroïde, Iode, Captation, Distribution dose, Blocage, Urine, Modèle animal, Chien, Fissipedia, Carnivora, Mammalia, Vertebrata, Excrétion, Dépendance du temps
Mots-clés Pascal anglais : Radioprotection, Thyroid gland, Iodine, Uptake, Dose repartition, Blocking, Urine, Animal model, Dog, Fissipedia, Carnivora, Mammalia, Vertebrata, Excretion, Time dependence
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 99-0085558
Code Inist : 002A08F04. Création : 31/05/1999.