TABLE 1.

Comparison of parameters obtained with standard vendor implemented 2SH_Box shimming alone and with the combined 2SH_Box + ACDC_{metBrain|fatScalp} shimming

Shim method		# Vox []	LW [ppm]	SNR []	Fat [%]	2HG tumor CRLB [%]	2HG tumor CNR []
2SHBox	Vol	2210	0.091 ± 0.041	16.1 ± 6.9	100 ± 158	N/A	N/A
	Pat	1475	0.098 ± 0.043	14.2 ± 6.5	100 ± 167	300 ± 430	0.11 ± 0.05
2SHBox + ACDCmetBrain|fatScalp	Vol	2210	0.074 ± 0.036	17.6 ± 6.7	79 ± 130	N/A	N/A
	Pat	1475	0.080 ± 0.041	13.9 ± 6.0	30 ± 39	39 ± 74	1.45 ± 0.74

Note: Numbers for LW, SNR, and fat contamination represent mean and std (where applicable) values averaged over either patients (Pat) or volunteers (Vol) and all brain voxels. The fat contamination was calculated relative to standard 2SH_Box shimming, which was assumed to have 100% contamination. The values for CRLB were calculated for 2HG only in the tumor areas of patients 1, 3, and 4 that have detectable 2HG levels by MRSI. Similarly, the CNR was calculated based on the patients 1, 3, and 4 with detectable 2HG levels by MRSI.

Abbreviations: 2HG, D-2-hydroxyglutarate; CNR, contrast-to-noise ratio; CRLB, Cramér–Rao lower bounds; Fat, contamination with scalp lipid signals; LW, linewidth; SNR, signal-to-noise ratio.

# Vox, the number of total voxels pooled over all considered subjects.