Source of Support: None, Conflict of Interest: None
Delayed renal scintigraphy, beyond usual 30 min dynamic study period, is commonly used for evaluation of urographically non-opacified kidneys. However, optimum time at which these urographically 'absent' kidneys will appear on nuclear imaging is controvertial. It has been observed that if a kidney is not seen up to 4 hrs, it is unlikely that it would be seen later. Mathematical modelling of scintigraphic visualisation data using parabolic and exponential functions have been done. Parabolic function which apparently represents the best-fit model for temporal spectrum of scintigraphic visualisation reveals that the cut-off time beyond which kidneys are not seen is t = 4.535 hrs. Zeros and maxima for both the functions were calculated and the merits and demerits of these modelling functions discussed.