MODIFIED PRONY METHOD TO RESOLVE AND QUANTIFY IN-VIVO P-31 NMR-SPECTRA OF TUMORS

Prony's method, successfully used in processing NMR signals, performs poorly at low signal-to-noise ratios. To overcome this problem, a stat istical approach has been adopted by using Prony's method as a samplin g device from the distribution associated with the true spectrum. Spec ifically, Prony's method is applied for each regression order p and nu mber of data points n, both considered in a suitable range, and the es timates of frequencies, amplitudes, and decay factors are pooled separ ately. A histogram of the pooled frequencies is computed and, looking at the histogram, a lower and an upper frequency bound for each line o f interest is determined. All frequency estimates in each of the deter mined intervals as well as associated decay factors and amplitudes are considered to be independent normal variates. A mean value and a corr esponding 95% confidence interval are computed for each parameter. P-3 1 NMR signals from MCF7 human breast cancer cells, inoculated into ath ymic mice and which developed into tumors, have been processed with tr aditional methods and with this modified Prony's method. The main comp onents of the phosphomonoester peak, namely those deriving from phosph orylcholine and phosphorylethanolamine, are always well resolved with this new approach and their relative amplitudes can be consequently ev aluated. Peak intensities of these two signals show different behavior during treatment of tumors with the antiestrogenic drug tamoxifen. Th e results of this new approach are compared with those obtainable with traditional techniques. (C) 1994 Academic Press,Inc.