Metabolic imaging of atrophic muscle tissue using appropriate markers in 1H and 31P NMR spectroscopy

Abstract

Introduction: The purpose of this feasibility study was to demonstrate non-invasive metabolic imaging of human muscular atrophy using significant changes of NMR signals that are related directly or indirectly to fiber necrosis.

Methods: Single-voxel (1)H NMR spectroscopy and two-dimensional (31)P spectroscopic imaging on a 1.5-T whole-body scanner were used for in vivo mapping of areas of muscle damage in two cases of differently localized and pronounced atrophy. Spectral patterns affiliated with severe and intermediate stages of degeneration were compared to data of healthy control tissue to derive appropriate metabolic markers related to lipid infiltration or high-energy (31)P metabolism.

Results: Reliable detection of atrophic tissue was achieved by the following parameters: (1) liposclerotic turnover is related to a drastic reduction in the water/lipid (1)H signal intensity ratio (up to a factor of 74 compared to adjacent healthy tissue); (2) the (31)P resonance of phosphocreatine (PCr) is an adequate marker for differentiation of intact myocells with high-energy metabolism from regions dominated by terminal fiber necrosis (PCr signal vanished nearly completely or intensity was reduced by a factor of 3 in affected muscles). Metabolic images based on this signal allowed accurate non-invasive localization of atrophic tissue.

Conclusion: The molecular information provided by NMR spectroscopy--previously only used with poor localization in atrophy studies--enables access to both the myocell-specific high-energy metabolism and the result of lipid infiltration allowing non-invasive mapping of degenerate tissue. The ability to investigate the results of these advanced levels of atrophy would also be useful for studies of more subtle degrees of denervation.