Fast Methods for Fitting Biexponentials Especially Applicable to Mri Multiecho Data

A sequence of decaying data, uniformly spaced in time, may be rapidly analysed as a sum of two monoexponential decays by multiplying the amplitudes by four Poisson distributions and summing. The resulting four sums form a system of equations which is easily solved for the parameters of the decays. On simulated noisy data, the method showed precision comparable with the established eigenfunction expansion method (DISCRETE). The method is so fast that it may be applied pixel by pixel to MR images. A faster but less exact variant of the method was also investigated. The method may also be extended to sums of more than two exponentials, but at a considerable cost in speed.