Abstract: uniform approach to constructing mathematical models of kinetics of the radiopharmaceuticals in human organism is developed for use in diagnostics of functional conditions of urinary system by means of radioisotope methods (renography, nephroscintigraphy). Two four-compartment mathematical models of transport of nephrotropic radiopharmaceuticals and based on them algorithms for processing quantitative data of radioisotope diagnostics of human kidneys and urinary system as a whole are presented. The simulation is based on solving a system of linear first order differential equations with constant coefficients. Various ways of identification of model parameters (transport constants) are considered on the basis of quantitative data of radionuclide diagnostics of human kidneys. It is shown that with the normalized study time (up to 20-25 min), the effect of radioactive decay of the radiopharmaceutical on the profile of activity-time kinetic curves can be neglected.
Our results of kinetic modeling are given and analysed for 39 patients with different types of renograms. The main quantitative indicators of dynamic nephroscintigraphy with the radiopharmaceutical “Pentatech-Tc-99m” and renography with the radiopharmaceutical “Hippuran-I-131” are calculated. The model renograms for both kidneys are constructed and compared with the clinical curves. Also, model curves of blood clearance and radiopharmaceutical accumulation in the urine in their absence in clinical results are restored. When comparing the identified transport constants, it was found that renograms of the afunctional type are characterized by lower values of the filtration constants and higher values of the evacuation constants compared to renograms of the normal types. The peculiarity of obstructive renograms is the equality of the evacuation constant to zero.
The features of kinetic modeling during radionuclide diagnostics of the kidneys in patients with vesicoureteral reflux are also discussed. It is shown that the presence of vesicoureteral reflux leads to a slight increase in the half-life of the radiopharmaceutical by this kidney.
Keywords: radionuclide diagnostics, radiopharmaceutical, modeling, kinetics, nephroscintigraphy, renography