Time activity curves are assessed from whole body szintigraphic time series for individual dose estimation to limit the applicable therapeutic dose, preventing critical organs from substantial damage during radiation therapy. Whole body scans are projective images, thus organ ROIs may overlap. After careful image registration rotated principal components analysis is applied to the time series, identifying image parts with similar dynamics. This method allows the separation of overlapping structures providing fuzzy regions, where fractions of the pixel counts are assigned to the respective accumulating morphology. The summed counts from theses fuzzy regions are modified with the physical decay constant of the considered therapeutic isotope, providing the correct time samples for further dose calculation. Mono-or bi-exponential regression yields the time activity curves for the respective morphologies, passed to a standard dose calculation program. The newly developed method allows the fuzzy separation of overlapping structures in projective planar imaging series, yielding more accurate dose calculation in individual radiation therapy.