Table 2.

2D-MRSI acquisition and preprocessing consensus summary.

Aspect	Consensus
Pre-localization method	Chemical shift displacement less than 2% per ppm. 3 T: semi-LASER with OVS (preferred) or OVERPRESS with VSS. 1.5 T: semi-LASER with OVS (preferred) or PRESS with VSS.
Echo and repetition time	TE as short as possible (typically 30 ms). Longer TEs may be preferred for lactate detection (144 or 288 ms) and enhanced lipid suppression. TR 1.5 s at 1.5 T, 2.0 s at 3 T.
Matrix dimensions, nominal voxel dimensions and sampling parameters	16x16 matrix with 10 mm in-plane resolution and 15 mm slice thickness. 1 average per phase encoding step. Spectral sampling of 1024 complex data points at 2000 Hz spectral width at 1.5 T or 3 T.
k-space sampling and preprocessing	2D phase-encoded Cartesian sampling over an elliptical or circular k-space mask. K-space zero-filling (interpolation) to twice the acquired number of points. Hamming filter. Reduction of subcutaneous lipid contamination (e.g. Papoulis-Gerchberg algorithm).
Water reference acquisition	Should be acquired where possible. Collect with the same sequence parameters as the water-suppressed scan, but without water suppression. Typically, to reduce scan time, a lower resolution scan is acceptable and interpolated post-acquisition to match the metabolite resolution
B0 shimming hardware	2nd order shim coils with adequately powered amplifiers are recommended at 1.5 T and 3 T.
B0 shimming algorithm	Methods incorporating shim strength limits and instability counter-measures are preferred over unconstrained approaches.