Development of a five-compartmental model and software for pharmacokinetic studies

Recent reports evidence a number of new radiopharmaceuticals for diagnostic and theragnostic purposes. However, they have been only biologically characterized using biodistribution studies. A more detailed information concerning their pharmacokinetic parameters is desirable for radiopharmaceutical's complete characterization. However, easy-to-use tools to assist researchers in the assessment of the radiopharmacokinetic parameters are not available in nuclear medicine so far. In this article we present a developed five-compartmental mathematical model and a dedicated software CoKiMo, designed to calculate the radiopharmaceuticals' pharmacokinetic parameters. CoKiMo software can be used to obtain the time-activity curves of the five main organs such as blood pool distribution, kidney, liver, and other two organs of interest from the biodistribution data. The curves are obtained by interpolation of organ activity values, measured separately at different moments of time, and then can be integrated to calculate the radiopharmaceutical's biological half-life ( T _1/2) and mean residence time. The transfer rate constants in the organs are obtained as a solution of a number of linear differential equations, described by the model. The data obtained by the program provide information about the organ's uptake and clearance useful in the characterization of the radiopharmaceuticals. Key words: multi-compartmental model, radiopharmacokinetics, biodistribution