Quantifying H-1 decoupled in vivo P-31 brain spectra

Our objective was to develop a precise method for quantification of in vivo proton decoupled P-31 spectra from the human brain. This objective require d that an appropriate spectral model be created and that the quantification was performed using a non-subjective fitting technique. The precision of t he quantification was assessed using Cramer-Rao standard deviations and com pared using two different spectral models: one containing a pair of peaks r epresenting 2,3-diphosphoglycerate, the other excluding this metabolite. Th e data was quantified using a Marquardt-Levenberg (ML) algorithm incorporat ing prior knowledge with a Hankel singular value decomposition (HSVD) perfo rmed initially to provide parameter estimates for the ML algorithm. Quantif ication was performed on two different in vivo 2-D CSI P-31 data sets: the first examined II normal controls, the second examined a single individual six times. Spectra from a region in the parieto-occipital cortex were analy zed. The Cramer-Rao standard deviations were significantly lower for some m etabolites with 2,3-diphosphoglycerate in the model: in the repeat study mo bile phospholipids (p = 0.045) and phosphocholine (p = 0.034), and in the I l controls mobile phospholipids (p,= 0.003) and P-i (p= 0.002). Copyright ( C) 1999 John Wiley & Sons, Ltd.