2.5. SNR and quantification

Spectra were fitted within the Oxford Spectroscopy Analysis (OXSA) toolbox⁴⁵ using AMARES methods. Metabolite peak SNRs were calculated according to Eq. (3), with noise variance calculated from a residual region lacking metabolite signals. As an additional signal quantification metric, “raw SNR” (Eq. (4)) was estimated by dividing the highest absolute peak point by the noise variance in an off-spectrum region; this method carries the advantage of consistently assessing signal strength regardless of any interfering spectral phase.

Data acquisition, reconstruction, processing, and analysis workflow is summarized in Figs. 2 and ​and33.

Workflow of data acquisition, reconstruction, processing, and analysis. Subjects were positioned feet-first supine with both quadriceps positioned between the 30-cm phased array coil plates. Raw data were exported, appropriately reconstructed, coil-combined, and phased prior to fitting and quantification.

(A) Signal intensity and selected central axial slices for Subject 3’s rosette UTE acquisition. (B) Visualization of “raw SNR” calculation on ³¹P-MRS muscle spectrum in one voxel. (C) Results for quantifiable (SNR >3) voxels within selection.