Aim: To test the efficacy of a practical method which allows the calculation of personalized activity in Graves' disease.
Methods: The method is based on International Commission of Radiological Protection (ICRP) 53 data. The model allows the prediction of the activity administered in order to release 300 Gy to the thyroid, once its iodine uptake and mass are known. We applied it to 289 patients investigated by clinical examination, biochemical assessment and neck ultrasonography. The method was applied considering the thyroid 131I uptake and the ultrasound mass. The patients were followed by check of TSH, FT3, FT4 and clinical examination. Finally, we evaluated the difference between our dosimetric method and the hypothetic administration of a fix amount of 131I (185, 370 and 600 Mbq respectively) in term of adsorbed dose.
Results: The average activity administered was 403.3+92.5 MBq with an average dose released to thyroid of 304.9+24.8 Gy. From a statistical point of view the administration of standard activities (185 and 600 MBq) would represent respectively a wrong estimate of the optimal dose (meanly 140.8+44.7 Gy and 473.6+142.6 Gy respectively). The administration of a standard activity (370 MBq) would release a dose close to that prescribed (291.2 Gy) with a standard deviation (86.9 Gy), which is considerably higher than the one obtained with the dosimetric model (24.8 Gy). Twenty four months after radioiodine treatment, 57.8% of patients presented hypothyroidism, 23.2% euthyroidism and 19% of hyperthyroidism. The overall therapeutic efficiency was of 81%.
Conclusion: The dosimetric method based on IRCP 53 data, is effective in controlling Graves' hyperthyroidism. Advantages in adopting this method are: dose optimization to patient, easy implementation in the clinical practice, low budget impact.