# MR spectroscopy (MRS)

MR spectroscopy (MRS) measures the chemistry of your tissues non-invasively, on a standard MRI scanner. It reads the slight frequency shifts in the MR signal to quantify specific metabolites, usually from one small box (voxel) or a grid of them. In the brain, 1H-MRS measures things like NAA (a marker of healthy neurons), choline, creatine, lactate, myo-inositol, glutamate/glutamine, and glutathione. Those help with grading tumors, and studying mitochondrial disease, multiple sclerosis, and neurodegeneration. In the liver, a related technique (MR-PDFF) is the most accurate non-invasive measure of liver fat. It has become the imaging endpoint of choice in fatty-liver (MASLD/MASH) trials, matching biopsy grades well. MRS uses no radiation. Its limits: long scan times, sensitivity to motion and field unevenness, modest spatial detail, and the need for specialized processing.

## Sources

- Bottomley PA. (1988). Human in vivo phosphate metabolite imaging with 31P NMR. Magnetic Resonance in Medicine. https://doi.org/10.1002/mrm.1910070309
- Caussy C, Reeder SB, Sirlin CB, Loomba R. (2018). Noninvasive, Quantitative Assessment of Liver Fat by MRI-PDFF as an Endpoint in NASH Trials. Hepatology. https://doi.org/10.1002/hep.29797
- Öz G, Alger JR, Barker PB, et al.. (2014). Clinical Proton MR Spectroscopy in Central Nervous System Disorders. Radiology. https://doi.org/10.1148/radiol.13130531

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