Table 3.

In-vivo quantification results. Mean±standard deviations are taken over all 14 subjects, and represent inter-subject statistics. The inter-scan, intra-subject coefficient of variation for each quantity – corresponding to the precision of our method – is shown in parentheses. Concentrations were calculated by fitting the summed TE=35 ms acquisitions using LCModel. CRLBs output by LCModel are averaged over all subjects. Shown are only those metabolites for which CRLB<20%. As with the phantom, T1 and T2 were only quantified for the singlets; B1+ was quantified using the reference water scan and used to constrain dictionary fitting for all other metabolites. To perform absolute quantification for coupled metabolites, average literature values for T1 and T2 were used, indicated by daggers (†). The transverse relaxation time of GSH was not found in the literature and a T2=100 ms was assumed (indicated by a double dagger). Table 3 shows that coupled metabolites can be successfully fit using the proposed method.

Metabolite	Conc (mM)	CRLB	T1 (ms)	T2 (ms)	B1+
NAA (2.01 ppm)	12.5±1.1 (3.2%)	3.6%	1409±91 (4%)	168±13 (3%)	N/A
Cr (3 ppm)	7.4±0.7 (3.4%)	4.3%	1353±160 (5%)	126±12 (5%)	N/A
Cho (3.2 ppm)	2.4±0.3 (3.7%)	6.3%	1260±112 (5%)	174±20 (6%)	N/A
Glx	7.9±0.9 (5.4%)	8.7%	1200†	180†	N/A
GSH	1.8±0.5 (13%)	13.1%	397†	100††	N/A
mI	3.7±0.7 (6.4%)	8.6%	920†	196†	N/A
Water	N/A	N/A	1035±100 (2%)	70±4 (1%)	1.01±0.03 (0.4%)