FIGURE 6.

Summary of the differences in SNR performance of data acquired using the lactate-edited 3D MRSI sequence for both 8- (solid line) and 32- (dashed line) channel coils. A, Comparison between the combination algorithms in three volunteers using the cycle with sufficient residual water. The techniques that incorporated the assumption of spatially varying phase outperformed the RWcentral method, which assumes a constant phase variation among channels. Going from 8 to 32 channels, techniques with spatially varying phase produced a 40% increase in performance, compared with a 25% increase with constant phase variation, suggesting that voxel-by-voxel phase correction is crucial to reach the optimal combination and becomes more apparent in the 32-channel coil. B, Comparison between combination algorithms in one volunteer using the cycle with minimal residual water with different simulated levels of residual water. Modifying the sequence to leave residual water 10–15 fold higher than NAA obviated the need for a reference scan for both head coils and stabilized the performance of the techniques