Biophysical inputs into the software "MIRDose".

Administered amount of activity decides on absorbed dose in thyroid gland during therapy of thyroid cancer tumors by 131I. Medical Internal Radiation Dose (MIRD) methodology estimates this dose as well as influence on other organs. MIRDose--the software implementation of MIRD--is permanently improving and has reached a substantial degree of maturity. Thus the reliability of the results depends predominantly on quality of the input data. The residence time and functional volume of the thyroid gland of a particular patient are the key inputs. Here we concentrate on the former one. We found that the traditionally used mono-exponential model, characterized by the effective half-life, introduces non-negligible modelling error. It cannot be improved by any data processing. For this reason, we proposed a novel accumulation model. Now we inspect influences of differences in the guessed residence time on the outputs of MIRDose. We briefly characterize MIRDose software, recall the improved model and present illustrative results of evaluations.