Maximum entropy method for frequency-domain fluorescence lifetime analysis. 2. Timing, mismatched intensity, and reference lifetime errors.

The maximum entropy method (MEM) provides a robust and unbiased solution to fluorescence lifetime data through the use of a broad window of decay terms fit by simultaneous minimization of the chi 2 goodness-of-fit parameter and maximization of a statistical entropy function. This work investigated the effects of three systematic errors, common in frequency-domain measurements, on fluorescence lifetime recovery by MEM. Through real and simulated data, the expression of the systematic errors in lifetime distributions recovered by MEM was compared to that in standard nonlinear least-squares (NLLS) analysis. Reference lifetime errors in the presence of random noise had similar effects on both MEM and NLLS results. Characteristic changes in the recovered lifetimes, fractional intensities, and peak shapes were related to the identification of the true reference lifetime. Compared to NLLS, MEM afforded significant improvements for the recovery of lifetimes and fractional intensities from data containing timing or mismatched intensity errors. These improvements are linked to the dynamic, self-modeling approach of MEM and the direction provided by the entropy criterion. These results speak to the utility of the maximum entropy approach in frequency-domain fluorescence lifetime recovery as well as in other applications.