Xiaoxuan He, Edward Auerbach, Michael Garwood, Xiaoping Wu, Gregory Metzger

In this abstract we demonstrated by simulation and phantom experiments the feasibility of designing composite refocusing pulse for spectroscopy using parallel transmission, featuring inherent 2D spatial and spectral selectivity along with improved immunity to B0 non-uniformity and B1+ heterogeneity while simultaneously providing lipid and water suppression and short echo times of ~18ms.

Karl Landheer, Michael Garwood, Ralph Noeske, Christoph Juchem

Modern magnetic resonance spectroscopic (MRS) pulse sequences which employ localization through adiabatic pulses suffer from long minimum echo times (≥≥ 19 ms). Here we developed a novel MRS pulse sequence which allows for an echo time of 8 ms with adiabatic localization in two of the three spatial dimensions, at the cost of two-shot volume localization. The sequence is highly robust to B₁ inhomogeneity and does not have any anomalous J-modulation since no slice-selective refocusing pulses are used. High spectral quality was obtained in phantom experiments, although strong lipid contamination was observed, consistent with previously reported two-shot localization methods.

Alexey Onikul Kulpanovich , Assaf Tal

Brain metabolite T₁ and T₂ have diagnostic value and per-subject knowledge of both metabolite and water reference T₁, T₂ is necessary for accurate metabolite absolute quantification. Here we optimize the excitation schedules of our recently-proposed magnetic resonance spectroscopic fingerprinting (MRSF) sequence to accurately estimate metabolite T₁ and T₂. We computationally evaluate the optimized schedules using Monte-Carlo simulations, as well as phantom and in-vivo experiments.

Yuqing Huang, Jin Yan, Chunhua Tan, Zhong Chen

Localized proton magnetic resonance spectroscopy (MRS) provides a non-invasive tool for metabolic studies on biological systems by revealing valuable biochemical information, complementary to anatomical information delivered by MRI. However, due to limited proton chemical shift range and extensive J coupling splittings, spectral congestion is generally encountered in the resulting 1D spectra acquired by conventional proton MRS techniques, such as PRESS (Point resolved spectroscopy) and STEAM (STimulated Echo Acquisition Mode). In this abstract, we present a previously-unreported proton MAS approach to obtain localized 1D pure shift spectra with spectral simplification, potentially useful for studies on biological samples.

Masoumeh Dehghani, Pierre Etienne, Jamie Near

Glucose, the main substrate for cerebral energy metabolism, serves as a metabolic precursor for both glutamate and GABA synthesis. In the current study, we employ a novel approach to investigate ¹³C-labeling of both glutamate and GABA in the human brain. Specifically, localized homonuclear (¹H) J-difference edited (MEGA-PRESS) MRS spectra were acquired dynamically (without heteronuclear decoupling or editing pulses) to detect glutamate and GABA labelling following an infusion of ¹³C labeled glucose. Despite excellent spectral quality and temporal stability, little or no GABA labeling was observed, raising some questions as to the functional status of the GABA pools detected by MEGA-PRESS.    

Belinda Ding, Mark Peterzan, Ferenc Mózes, Hannah Lake, Craig Lygate, Rana Sayeed, Mario Petrou, George Krasopoulos, Oliver Rider, Ladislav Valkovic, Christopher Rodgers

This work aimed to use cardiac 3T ¹H-MRS to quantify creatine concentration (“[Cr]”) in the human heart, because creatine plays a key role in cardiac energy metabolism. We implemented a cycled water-suppression scheme (WC) into the PRESS and STEAM pulse sequences on a Siemens 3T Prisma MRI scanner. Compared to the vendor’s product PRESS sequence, we found that PRESS-WC was able to measure [Cr] more than 2 times more reproducibly and in a shorter scan. Using PRESS WC in a 10-breathhold protocol, we were able to detect a decrease in creatine concentration in 5 patients suffering from aortic stenosis.

Adam Berrington, Michal Povazan, Peter Barker

Spurious echo artifacts appear in MRS spectra and originate from regions of unsuppressed and insufficiently crushed signal. We propose a reconstruction method to remove such artifacts using the sensitivity weighting of the receive channels at each spatial location. Data from phantom and simulations show that spurious echoes can be separated from underlying signal. The spatial distribution of unwanted signal was estimated in vivo using B₀ maps. Artifactual components of the signal were identified in sinus regions, however not entirely removed from the spectrum. Further work will aim to improve the conditioning of the SENSE reconstruction to remove spurious echo artifacts from MRS data.

Clémence Ligneul, Julia Huntenburg, Francisca Fernandes, Noam Shemesh

Functional magnetic resonance spectroscopy (fMRS) can provide insights on brain metabolism under activation, as has already been shown in humans. Assessing fMRS in mice would open interesting perspectives for understanding neural activity given mouse transgenics. We report preliminary encouraging results of fMRS in the mouse superior colliculus, during visual stimulation at 9.4 T (using a cryocoil for reception). Time courses of different metabolites concentrations notably reveal metabolite signal modulations during activation.

Tamás Borbáth, Saipavitra Murali Manohar, Anke Henning

Broad signals underlying in vivo ¹H MRS spectra are referred to in literature as macromolecules, and have been assigned to amino acids by Behar et al. These amino acids are creating proteins through chemical bonds. Depending on the protein structure and sequence of amino acids, they have different chemical shifts as published in protein NMR databases. This work uses these published chemical shifts to create a fitting model for the macromolecular baselines of human brain using amino acids. 

Maike Hoefemann, Christine Bolliger, Jan Willem van der Veen, Roland Kreis

The purpose of this study was to evaluate the need for a comprehensive description of the macromolecular baseline signal (MMBL), e.g. for MR fingerprinting and multidimensional fitting of MR spectra. Inherent J-evolution for certain signals as well as multi-component T₂-decays can cause variance of the signal shape as function of TE that is not described in a mono-exponential decay model. Two methods are described to accommodate this signal behavior when fitting a 2DJ-Inversion-Recovery dataset. In addition, the MMBLs for different TEs, as well as resulting metabolite contents, T₁s and T₂s with the conventional and alternative methods are reported.