Table 2.

SNR comparisons between PRESS and MRSF, in both the phantom and in-vivo, based on numerical 3D Bloch spin simulations. Simulations were run for each singlet (NAA, Cr, Cho), using its mean measured T₁ and T₂ values, and averaged over all singlets. Note that, on average, T₁ values in the phantom are shorter than in-vivo, while T₂ values are longer. The SNR per unit time of the TR=1500 ms PRESS was normalized to one. The table demonstrates that using just the short echo time (TE=35 ms) scans of MRSF for metabolite quantification yields approximately 60% of the optimal PRESS SNR. However, since T₁ is often unknown in-vivo, acquisitions with prolonged TRs are preferred, such as a PRESS with TR=5000 ms; relative to such an acquisition, the TE=35 MRSF scans yield approximately 0.61/0.78≈80% of the SNR.

	Normalized Voxel Volume	Weighted Voxel Volume	SNR per unit time
Phantom (average over all singlets)
PRESS (TR/TE=1500/35 ms)	0.87	0.48	1.00
PRESS (TR/TE=5000/35 ms)	0.87	0.54	0.59
MRSF (All TEs)	0.67	0.34	0.70
MRSF (TE=35 ms)	0.64	0.32	0.57
In-vivo (average over all singlets)
PRESS (TR/TE=1500/35 ms)	0.87	0.48	1.00
PRESS (TR/TE=5000/35 ms)	0.87	0.68	0.78
MRSF (All TEs)	0.67	0.31	0.67
MRSF (TE=35 ms)	0.64	0.32	0.61