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Magn Reson Med. 2016 Jun;75(6):2324-31. doi: 10.1002/mrm.25822. Epub 2015 Jun 26.

Dynamic PCr and pH imaging of human calf muscles during exercise and recovery using (31) P gradient-Echo MRI at 7 Tesla.

Author information

1
MR Centre of Excellence, Medical University of Vienna, Vienna, Austria.
2
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
3
Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria.
4
Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.
5
Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
6
Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria.
7
Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.

Abstract

PURPOSE:

Simultaneous acquisition of spatially resolved (31) P-MRI data for evaluation of muscle specific energy metabolism, i.e., PCr and pH kinetics.

METHODS:

A three-dimensional (3D) gradient-echo sequence for multiple frequency-selective excitations of the PCr and Pi signals in an interleaved sampling scheme was developed and tested at 7 Tesla (T). The pH values were derived from the chemical shift-induced phase difference between the resonances. The achieved spatial resolution was ∼2 mL with image acquisition time below 6 s. Ten healthy volunteers were studied performing plantar flexions during the delay between (31) P-MRI acquisitions, yielding a temporal resolution of 9-10 s.

RESULTS:

Signal from anatomically matched regions of interest had sufficient signal-to-noise ratio to allow single-acquisition PCr and pH quantification. The Pi signal was clearly detected in voxels of actively exercising muscles. The PCr depletions were in gastrocnemius 42 ± 14% (medialis), 48 ± 17% (lateralis) and in soleus 20 ± 11%. The end exercise pH values were 6.74 ± 0.18 and 6.65 ± 0.27 for gastrocnemius medialis and lateralis, respectively, and 6.96 ± 0.12 for soleus muscle.

CONCLUSION:

Simultaneous acquisition of PCr and Pi images with high temporal resolution, suitable for measuring PCr and pH kinetics in exercise-recovery experiments, was demonstrated at 7T. This study presents a fast alternative to MRS for quantifying energy metabolism of posterior muscle groups of the lower leg. Magn Reson Med 75:2324-2331, 2016. © 2015 Wiley Periodicals, Inc.

KEYWORDS:

X-nuclei imaging; dynamic imaging; high energy phosphate; pH; skeletal muscle

PMID:
26115021
DOI:
10.1002/mrm.25822
[Indexed for MEDLINE]

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