Magnetic Resonance in Medicine / Interleaved multivoxel 31P MR spectroscopy

Purpose Separate measurements are required when investigating multiple exercising muscles with singlevoxellocalized dynamic 31PMRS. With multivoxel spectroscopy, 31PMRS timeseries spectra are acquired from multiple independent regions during one exerciserecovery experiment with the same time resolution as for singlevoxel measurements. Methods Multiple independently selected volumes were localized using temporally interleaved semiLASER excitations at 7T. Signal loss caused by mutual saturation from shared excitation or refocusing slices was quantified at partial and full overlap, and potential contamination was investigated in phantom measurements. During an exerciserecovery experiment both gastrocnemius medialis and soleus of two healthy volunteers were measured using multivoxel acquisitions with a total TR of 6 s, while avoiding overlap of excitation slices. Results Signal reduction by shared adiabatic refocusing slices selected 1 s after the preceding voxel was between 10% (full overlap) and 20% (half overlap), in a phantom measurement. In vivo data were acquired from both muscles within the same exercise experiment, with 1318% signal reduction. Spectra show phosphocreatine, inorganic phosphate, adenosinetriposphate, phosphomonoesters, and phosphodiesters. Conclusion Signal decrease was relatively low compared to the 2fold increase in information. The approach could help to improve the understanding in metabolic research and is applicable to other organs and nuclei. Magn Reson Med 77:921927, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.(VLID)483933

NMR in Biomedicine / Dynamic multivoxel-localized 31P MRS during plantar flexion exercise with variable knee angle

Exercise studies investigating the metabolic response of calf muscles using 31P MRS are usually performed with a single knee angle. However, during natural movement, the distribution of workload between the main contributors to force, gastrocnemius and soleus is influenced by the knee angle. Hence, it is of interest to measure the respective metabolic response of these muscles to exercise as a function of knee angle using localized spectroscopy. Timeresolved multivoxel 31P MRS at 7 T was performed simultaneously in gastrocnemius medialis and soleus during rest, plantar flexion exercise and recovery in 12 healthy volunteers. This experiment was conducted with four different knee angles. PCr depletions correlated negatively with knee angle in gastrocnemius medialis, decreasing from 7914 % (extended leg) to 3523 %(40), and positively in soleus, increasing from 2021 % to 3625 %; differences were significant. Linear correlations were found between knee angle and endexercise PCr depletions in gastrocnemius medialis (R2=0.8) and soleus (R2=0.53). PCr recovery times and endexercise pH changes that correlated with PCr depletion were consistent with the literature in gastrocnemius medialis and differences between knee angles were significant. These effects were less pronounced in soleus and not significant for comparable PCr depletions. Maximum oxidative capacity calculated for all knee angles was in excellent agreement with the literature and showed no significant changes between different knee angles. In conclusion, these findings confirm that plantar flexion exercise with a straight leg is a suitable paradigm, when data are acquired from gastrocnemius only (using either localized MRS or small surface coils), and that activation of soleus requires the knee to be flexed. The present study comprises a systematic investigation of the effects of the knee angle on metabolic parameters, measured with dynamic multivoxel 31P MRS during muscle exercise and recovery, and the findings should be used in future study design.(VLID)340101

The Giant Radio Array for Neutrino Detection (GRAND):Science and design

International audienceThe Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 10$^{8}$ GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km$^{2}$. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND

Science and Design for the Giant Radio Array for Neutrino Detection

International audienceGRAND is a planned large-scale observatory of ultra-high energy (UHE) cosmic messengers with energies exceeding 10⁸ GeV. The ultimate goal is to solve the long-standing mystery of the origin of UHE cosmic rays. Three key features of GRAND will make this possible: its large exposure, sub-degree angular resolution, and sensitivity to UHE particles

Science and Design for the Giant Radio Array for Neutrino Detection

International audienceGRAND is a planned large-scale observatory of ultra-high energy (UHE) cosmic messengers with energies exceeding 10⁸ GeV. The ultimate goal is to solve the long-standing mystery of the origin of UHE cosmic rays. Three key features of GRAND will make this possible: its large exposure, sub-degree angular resolution, and sensitivity to UHE particles

Science and Design for the Giant Radio Array for Neutrino Detection

International audienceGRAND is a planned large-scale observatory of ultra-high energy (UHE) cosmic messengers with energies exceeding 10⁸ GeV. The ultimate goal is to solve the long-standing mystery of the origin of UHE cosmic rays. Three key features of GRAND will make this possible: its large exposure, sub-degree angular resolution, and sensitivity to UHE particles