Methodology for improved detection of low concentration metabolites in MRS: Optimised combination of signals from multi-element coil arrays

Adaptively optimized combination (AOC) of magnetic resonance spectroscopy data from phased array coils

“…Although the S/N weighting and S/N 2 weighting methods usually outperform the signal weighting method, it is interesting to find in our simulated experiments that extrinsic noise correlation likely degraded the performance of the S/N weighting and S/N 2 weighting methods compared with that of the signal weighting method, and more SNR would be compromised using the S/N 2 weighting method than the S/N weighting method, which were consistent with the theoretical analysis in this study. Of note, similar results were also reported in the recently published article that introduced the S/N 2 weighting method (21), but the reason underlying this interesting phenomenon was analyzed and verified in the present study for the first time.…”

“…The unsuppressed water signal was selected as the reference for computing the coil sensitivities and phase shifts of individual coil elements in this study (12)(13)(14)17,18,21), that is,…”

“…However, it is not an optimal combination method. The recently published method by weighting with the ratio of signal to the square of noise (i.e., S/N 2 weighting) represents the theoretical optimal combination if the noise on different coil elements is uncorrelated (21). Although a multi-element coil array is designed with minimal mutual coupling (22,23), residual noise correlation between coil elements is not uncommonly observed in reality (24,25).…”

Glutathione and glutamate in schizophrenia: a 7T MRS study

“…Briefly, the anatomical image was segmented into grey matter, white matter, and cerebrospinal fluid. MRS data acquired independently from the 32 channels were combined using an optimized coil combination method [50]. Metabolite concentrations were estimated using LCModel [51].…”

Self-Managed Belief as Part of the “Scientific Method”: Part II—Examples From Published Scientific Work

“…This is typically tested via appropriate phantoms, usually provided by the manufacturer and/or vendor of the scanner, or specifically manufactured in the laboratory [3]. Such tests include not only signal-to-noise ratio (SNR) measurements, but also, particularly in larger, inhomogeneous RF coils, the SNR homogeneity across the sample volume [4][5][6][7][8][9][10][11][12]. Even more challenging would be the QC of hybrid systems like, e.g., PET/MRI [13].…”