Table 1:

SNR and metabolite ratios

	SNR_ROI (%)	SNR_voxel (%)	SNR_theory (%)	Scan Time (%) (24 × 24 Scan)	Cho/NAA	Cr/NAA
ETL = 1	100	100	100	100	0.39	0.35
ETL = 2	84	90	71	51	0.38	0.31
ETL = 6	54	62	48	23	0.30	0.27
SENSE, ETL = 2	50	51	38	15	0.37	0.33
SENSE, ETL = 6	32	32	29	8	0.42	0.33

NOTE:—SNR indicates signal intensity-to-noise ratio; ETL, echo-train length; SENSE, sensitivity encoding; Cho, choline; Cr, creatine; NAA, N-acetylaspartate. SNR, averaged over SNR_NAA, SNR_Cr, SNR_Cho, was averaged once over a region of interest (ROI) containing 105 voxels and once only for the voxel depicted in FIg 4. SNR_theory gives only the theoretical SNR reduction with the square root of total scan time. The metabolite ratios are given for the voxel depicted in Fig 4 and show the variability over the different acquisition techniques.