Journal Highlight: Interrelations of muscle functional MRI, diffusion-weighted MRI and 31P-MRS in exercised lower back muscles

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  • Published: Sep 22, 2014
  • Author: spectroscopyNOW
  • Channels: MRI Spectroscopy
thumbnail image: Journal Highlight: Interrelations of muscle functional MRI, diffusion-weighted MRI and <sup>31</sup>P-MRS in exercised lower back muscles
Exercise-induced changes of transverse proton relaxation time, tissue perfusion and metabolic turnover were investigated in the lower back muscles of volunteers by applying muscle functional MRI and diffusion-weighted imaging before and after exercise as well as dynamic 31P-MRS during exercise.



Interrelations of muscle functional MRI, diffusion-weighted MRI and 31P-MRS in exercised lower back muscles

NMR in Biomedicine, 2014, 27, 958-970
Patrick Hiepe, Alexander Gussew, Reinhard Rzanny, Christoph Anders, Mario Walther, Hans-Christoph Scholle and Jürgen R. Reichenbach

Abstract: Exercise-induced changes of transverse proton relaxation time (T2), tissue perfusion and metabolic turnover were investigated in the lower back muscles of volunteers by applying muscle functional MRI (mfMRI) and diffusion-weighted imaging (DWI) before and after as well as dynamic 31P-MRS during the exercise. Inner (M. multifidus, MF) and outer lower back muscles (M. erector spinae, ES) were examined in 14 healthy young men performing a sustained isometric trunk-extension. Significant phosphocreatine (PCr) depletions ranging from 30% (ES) to 34% (MF) and Pi accumulations between 95% (left ES) and 120%–140% (MF muscles and right ES) were observed during the exercise, which were accompanied by significantly decreased pH values in all muscles (∆pH ≈ –0.05). Baseline T2 values were similar across all investigated muscles (approximately 27 ms at 3 T), but revealed right–left asymmetric increases (T2,inc) after the exercise (right ES/MF: T2,inc = 11.8/9.7%; left ES/MF: T2,inc = 4.6/8.9%). Analyzed muscles also showed load-induced increases in molecular diffusion D (p = .007) and perfusion fraction f (p = .002). The latter parameter was significantly higher in the MF than in the ES muscles both at rest and post exercise. Changes in PCr (p = .03), diffusion (p < .01) and perfusion (p = .03) were strongly associated with T2,inc, and linear mixed model analysis revealed that changes in PCr and perfusion both affect T2,inc (p < .001). These findings support previous assumptions that T2 changes are not only an intra-cellular phenomenon resulting from metabolic stress but are also affected by increased perfusion in loaded muscles.

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