Table 2.

Recommendations for the technical performance of prospective real-time motion and shim correction for various required levels of precision in MRS. Note: 1) precision has been derived for either pure translation or rotation considering the case of an isotropic SVS voxel; 2) for MRSI, similar precision thresholds are hard to derive theoretically and the acceptable performance level for motion correction should be empirically evaluated by test-retest. An SVS voxel of 10 mm × 10 mm × 10 mm and anterior-posterior brain diameter of 220 mm were considered. Translation for any voxel and rotation angle for a frontal pole voxel, which is displaced the most by rotation around an axis through the center of the atlanto-axial joint are calculated according to the formulas given above. All reported real-time methods have higher translation and rotation precisions than the values listed in the table. The guidelines for homogeneity of the B₀ field are the same as recommended in the B₀ shimming consensus paper.³

Basic	Moderate	Advanced
20% error in estimation of metabolite concentration 0.7 mm translation 1.0° rotation frequency update	10% error in estimation of metabolite concentrations 0.4 mm translation 0.5° rotation frequency update shim update	5% error in estimation of metabolite concentrations 0.2 mm translation 0.3° rotation frequency update shim update reacquisition