Second order proton traps for multi-nuclear RF coils: Applied for 13C MRS in humans at 7T

The concept of second order proton traps (consisting of an inductor and two capacitors) in coils for non-proton NMR allows control over the resonance frequency, the blocking frequency and the trap mode frequency. Effective proton traps with relatively high LTr, and thus very effective blocking, can be constructed, which impose only small degradation of the non-1H coil sensitivity

Proton traps for multi-nuclear RF coils: design analysis and practical implementation for 13C MRS in humans at 7T

Trapped coil designs allow the operation of lower-frequency coils in the presence of a proton coil. Adding a second capacitor to a trap in the non-proton RF coil allows control over the trap reactance at the low and high frequency (here 13C and 1H) and the frequency of the trap mode. We demonstrate the interdependence of the parameters controlled and show analytical and numerical solutions to fulfill the design constraints. Our experiments show that, using the simulations, it possible to construct an effective second order trap for 13C at 7T

Phosphocreatine line with changes in localised 31P MRS of exercising muscle at 7T

The aim was to investigate changes in the line width of high-energy phosphates solely originating from the intramyocellular compartment by temporally resolved localised 31P-MRS after aerobic calf muscle exercise. Semi-Laser [2] localised 31P-MRS of gastrocnemius muscle and pulse-acquire-MRS (10cm-surface coil) were performed alternatingley in three exercise bouts separated by >20min inactivity. PCr and Pi were quantified in AMARES from single acquitsitions, with TR=6s. While Pi line width is known to change due to pH, to our knowledge this is the first observation of an exercise induced line width increase of intra-myocellular PCr, which may be associated with myoglobin deoxygenation

Simultaneous and interleaved acquisition of NMR signals from different nuclei with a clinical MRI scanner

PURPOSE: Modification of a clinical MRI scanner to enable simultaneous or rapid interleaved acquisition of signals from two different nuclei. METHODS: A device was developed to modify the local oscillator signal fed to the receive channel(s) of an MRI console. This enables external modification of the frequency at which the receiver is sensitive and rapid switching between different frequencies. Use of the device was demonstrated with interleaved and simultaneous 31 P and 1 H spectroscopic acquisitions, and with interleaved 31 P and 1 H imaging. RESULTS: Signal amplitudes and signal-to-noise ratios were found to be unchanged for the modified system, compared with data acquired with the MRI system in the standard configuration. CONCLUSION: Interleaved and simultaneous 1 H and 31 P signal acquisition was successfully demonstrated with a clinical MRI scanner, with only minor modification of the RF architecture. While demonstrated with 31 P, the modification is applicable to any detectable nucleus without further modification, enabling a wide range of simultaneous and interleaved experiments to be performed within a clinical setting

31 P magnetic resonance spectroscopy in skeletal muscle: Experts' consensus recommendations.

Skeletal muscle phosphorus-31 31 P MRS is the oldest MRS methodology to be applied to in vivo metabolic research. The technical requirements of 31 P MRS in skeletal muscle depend on the research question, and to assess those questions requires understanding both the relevant muscle physiology, and how 31 P MRS methods can probe it. Here we consider basic signal-acquisition parameters related to radio frequency excitation, TR, TE, spectral resolution, shim and localisation. We make specific recommendations for studies of resting and exercising muscle, including magnetisation transfer, and for data processing. We summarise the metabolic information that can be quantitatively assessed with 31 P MRS, either measured directly or derived by calculations that depend on particular metabolic models, and we give advice on potential problems of interpretation. We give expected values and tolerable ranges for some measured quantities, and minimum requirements for reporting acquisition parameters and experimental results in publications. Reliable examination depends on a reproducible setup, standardised preconditioning of the subject, and careful control of potential difficulties, and we summarise some important considerations and potential confounders. Our recommendations include the quantification and standardisation of contraction intensity, and how best to account for heterogeneous muscle recruitment. We highlight some pitfalls in the assessment of mitochondrial function by analysis of phosphocreatine (PCr) recovery kinetics. Finally, we outline how complementary techniques (near-infrared spectroscopy, arterial spin labelling, BOLD and various other MRI and 1 H MRS measurements) can help in the physiological/metabolic interpretation of 31 P MRS studies by providing information about blood flow and oxygen delivery/utilisation. Our recommendations will assist in achieving the fullest possible reliable picture of muscle physiology and pathophysiology