Sigrun Goluch

Dynamic ASL and T2*‐weighted MRI in exercising calf muscle at 7 T: A feasibility study

The aim of this study was to develop a measurement protocol for noninvasive simultaneous perfusion quantification and T2*‐weighted MRI acquisition in the exercising calf muscle at 7 Tesla.

Exercising calf muscle T₂∗ changes correlate with pH, PCr recovery and maximum oxidative phosphorylation.

Skeletal muscle metabolism is impaired in disorders like diabetes mellitus or peripheral vascular disease. The skeletal muscle echo planar imaging (EPI) signal (SEPI) and its relation to energy metabolism are still debated.

A form-fitted three channel 31P, two channel 1H transceiver coil array for calf muscle studies at 7 T

To enhance sensitivity and coverage for calf muscle studies, a novel, form‐fitted, three‐channel phosphorus‐31 (31P), two‐channel proton (1H) transceiver coil array for 7 T MR imaging and spectroscopy is presented.

Power Balance and Loss Mechanism Analysis in RF Transmit Coil Arrays

To establish a framework for transmit array power balance calculations based on power correlation matrices to accurately quantify the loss contributions from different mechanisms such as coupling, lumped components, and radiation.

Combining phase images from array coils using a short echo time reference scan (COMPOSER).

To develop a simple method for combining phase images from multichannel coils that does not require a reference coil and does not entail phase unwrapping, fitting or iterative procedures.

Novel inductive decoupling technique for flexible transceiver arrays of monolithic transmission line resonators.

This article presents a novel inductive decoupling technique for form‐fitting coil arrays of monolithic transmission line resonators, which target biomedical applications requiring high signal‐to‐noise ratio over a large field of view to image anatomical structures varying in size and shape from patient to patient.

Skeletal muscle ATP synthesis and cellular H(+) handling measured by localized (31)P-MRS during exercise and recovery.

31P magnetic resonance spectroscopy (MRS) is widely used for non-invasive investigation of muscle metabolism dynamics. This study aims to extend knowledge on parameters derived from these measurements in detail and comprehensiveness: proton (H+) efflux, buffer capacity and the contributions of glycolytic (L) and oxidative (Q) rates to ATP synthesis were calculated from the evolutions of phosphocreatine (PCr) and pH. Data are reported for two muscles in the human calf, for each subject and over a wide range of exercise intensities. 22 subjects performed plantar flexions in a 7T MR-scanner, leading to PCr changes ranging from barely noticeable to almost complete depletion, depending on exercise protocol and muscle studied by localized MRS. Cytosolic buffer capacity was quantified for the first time non-invasively and individually, as was proton efflux evolution in early recovery. Acidification started once PCr depletion reached 60–75%. Initial and end-exercise L correlated with end-exercise levels of PCr and approximately linear with pH. Q calculated directly from PCr and pH derivatives was plausible, requiring fewer assumptions than the commonly used ADP-model. In conclusion, the evolution of parameters describing cellular energy metabolism was measured over a wide range of exercise intensities, revealing a relatively complete picture of muscle metabolism.

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

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

Interleaved multivoxel31P MR spectroscopy: Multivoxel31P MRS

Separate measurements are required when investigating multiple exercising muscles with singlevoxel‐localized dynamic 31P‐MRS. With multivoxel spectroscopy, 31P‐MRS time‐series spectra are acquired from multiple independent regions during one exercise‐recovery experiment with the same time resolution as for singlevoxel measurements.

Proton-decoupled carbon magnetic resonance spectroscopy in human calf muscles at 7 T using a multi-channel radiofrequency coil

Abstract13C magnetic resonance spectroscopy is a viable, non-invasive method to study cell metabolism in skeletal muscles. However, MR sensitivity of 13C is inherently low, which can be overcome by applying a higher static magnetic field strength together with radiofrequency coil arrays instead of single loop coils or large volume coils, and 1H decoupling, which leads to a simplified spectral pattern. 1H-decoupled 13C-MRS requires RF coils which support both, 1H and 13C, Larmor frequencies with sufficient electromagnetic isolation between the pathways of the two frequencies. We present the development, evaluation, and first in vivo measurement with a 7 T 3-channel 13C and 4-channel 1H transceiver array optimized for 1H-decoupled 13C-MRS in the posterior human calf muscles. To ensure minimal cross-coupling between 13C and 1H arrays, several strategies were combined: mutual magnetic flux was minimized by coil geometry, two LCC traps were inserted into each 13C element, and band-pass and low-pass filters were integrated along the signal pathways. The developed coil array was successfully tested in phantom and in vivo MR experiments, showing a simplified spectral pattern and increase in signal-to-noise ratio of approximately a factor 2 between non-decoupled and 1H-decoupled spectra in a glucose phantom and the human calf muscle.