Fig. 1.

Schematic overview of the workflow. Based on existing activity measurements, a reference and reduced sampling schedule (“case”) were generated. The reference sampling schedule includes all available biokinetic data for a given patient. To describe the biokinetics, the parameters of the employed PBPK model were fitted. After parameter fitting (standard or iterative approach), the areas under the time-activity curves were determined and subsequently, the time-integrated activity coefficients were calculated. The same methodology is applied to the sampling schedules omitting alternated numbers of measurement points. At the end, the derived time-integrated activity coefficients (TIACs) are quantitatively compared and evaluated for treatment planning accuracy by calculating the relative deviation (Eq. (1))