Mark Mikkelsen, Pallab Bhattacharyya, Pravat Mandal, Deepika Shukla, Anna Wang, Martin Wilson, Ulrike Dydak, James Murdoch, Jamie Near, Georg Oeltzschner, Richard Edden

Given the number of software analysis packages available to the MRS community, surprisingly little attention has been paid to comparing the performance of each, particularly with regard to multi-site and multi-vendor datasets. Standardization of MRS methods will necessarily require that processing and quantification tools also produce comparable outcomes. This abstract describes a comparison of five widely used software packages analyzing multi-site edited MRS data to quantify in vivo GABA+/Cr levels. The overall agreement between the packages was moderate, with packages showing systematic site-to-site biases. Further analysis on a larger cohort of data will aid in determining the cause of these discrepancies.

Muhammad Saleh, Daniel Rimbault, Mark Mikkelsen, Georg Oeltzschner, Anna Wang, Dengrong Jiang, Ali Alhamud, Jamie Near, Michael Schär, Ralph Noeske, James Murdoch, Lars Ersland, Alexander Craven, Gerard Dwyer, Eli Gruner, Li Pan, Sinyeob Ahn, Richard Edden

MEGA-PRESS is the most widely used pulse sequence for edited MRS of low-concentration metabolites, e.g. GABA, glutathione and lactate. However, current implementations of MEGA-PRESS are diverse across MR vendors, leading to differences in the shape and intensity of the final edited signal. We demonstrate a new universal editing sequence (with MEGA and HERMES functionality) for the major MR vendor platforms with standardized RF pulse shapes, durations, amplitudes and sequence timings. Phantom and in vivo experiments show excellent agreement among vendors, including consistency in lineshape and reduced variation in concentration measurements. 

Muhammad Saleh, Anna Wang, Mark Mikkelsen, Georg Oeltzschner, Eric Porges , Richard Edden

HERMES allows simultaneous edited detection of multiple low-concentration metabolites in the human brain. Here, HERMES editing of GABA, glutathione (GSH) and ethanol (EtOH) is demonstrated for the investigation of the effects of acute administration of EtOH on the human brain. Simulations and phantom experiments demonstrate excellent detection and separation of GABA, GSH and EtOH. In vivo data were acquired in a healthy male volunteer after oral administration of alcohol. Data were continuously acquired for 1 h and broken down into successive 4-min blocks, showing increasing levels of brain EtOH throughout the scan session. 

Norbert Lutz, Monique Bernard

The statistical distribution of a number of measurement parameter values in heterogeneous tissues can be analyzed based on MR spectra, using a paradigm recently introduced by us. However, the MR resonances in question are affected by influences on line shape other than those exerted by the measurement parameter to be analyzed, e.g., by magnetic-field inhomogeneity. We demonstrate here that desired and spurious line shape contributions can be efficiently disentangled by judiciously employing the convolution theorem. This method should facilitate future applications of our method of tissue heterogeneity assessment.

Meng Gu, Ralph Hurd, Daniel Spielman

As GABA editing is achieved by eliminating the overwhelming Cre peak using subtraction, discrepancies in Cre amplitude due to physiological noise result in variations in edited GABA. It can be observed the flip of the outer peaks of GABA triplet is in a different dimension from the Cre. It is thus possible to eliminate Cre and its associated physiological noise using principle component analysis (PCA). Simulation and phantom studies showed the physiological noise associated with Cre was eliminated using PCA editing without GABA signal loss. In vivo study demonstrated more consistent GABA measurement using PCA editing than regular editing.

Meng Gu, Ralph Hurd, Daniel Spielman

The SNR advantage of short-TE methods over long-TE editing-methods provided a compelling motivation for reliable quantification of glutathione using LCModel. In this study, we improved the accuracy of the glutathione basis by using an experimental glutathione in our otherwise synthetic LCModel basis. We further added ascorbate as a complementary measure of oxidative stress. Validation was made using a brain metabolite titration phantom with a matrix of glutathione and ascorbate. The near perfect linear regression results demonstrated that both GSH and ASC at physiological concentrations can be reliably quantified using LCModel. In vivo study also showed consistent glutathione quantification.

Jeffry Alger, Joseph O'Neill, Ronald Ly, Guldamla Kalender, Shantanu Joshi, Katherine Narr, Mary O'Connor, Jennifer Levitt

This study evaluated the performance of 9 unique methods of deriving GABA and GABA+ from J-edited-single-voxel-MRS using a set of high-quality spectra obtained from the anterior middle cingulate cortex in 34 pediatric human subjects. The results indicate that spectral integration produces the most consistent between-subject measure of GABA+ and that non-linear least-squares fitting that includes macromolecule confound spectral models together with GABA spectral models best produces the expected positive correlation between voxel gray matter content and GABA.
 

Christopher Jenkins, Max Chandler, Frank Langbein, Sophie Shermer

A calibrated series of MRS phantoms is used to compare the performance of common spectroscopy analysis tools in the quantification of GABA-edited spectroscopy data. Varied GABA concentration, and simulated spectra  provide a ground truth with which to compare.

Inbar Zohar, Inbar saraf-sinik, Ofer Yizhar, Assaf Tal

Dynamics of γ -aminobutyric acid (GABA) concentrations in the brain has been shown to vary under a variety of activation paradigms using functional magnetic resonance spectroscopy (fMRS). To provide better understanding of the underlying cellular mechanisms involved, we used fMRS on chemogenetically engineered mice at ultrahigh fields (15.2T), allowing us to investigate the dynamics of metabolites in response to activation of a specific neuronal population (GABAergic) in the reticular nucleus. fMRS data from four mice was analyzed using LCModel and did not show any significant change in GABA. 

Tiffany Bell, Elodie Boudes, Rachelle Loo, Gareth Barker, David Lythgoe, Richard Edden, R Lebel, Martin Wilson, Ashley Harris

To measure glutamate and GABA, two spectroscopy sequences are typically performed. Here we investigate the reliability of measuring Glx (glutamate+glutamine) from the same editing sequence used to measure GABA (MEGA-PRESS). We found that Glx measured using the unedited (“off”) sub-spectra of a macromolecule suppressed MEGA-PRESS sequence (MM-suppressed, TE=80ms) moderately agreed with Glx measured using a short-echo PRESS sequence. However, Glx measured using the off sub-spectra of a GABA+ (TE=68ms) MEGA-PRESS sequence and the co-edited Glx signal from the difference spectra of both GABA-edited MEGA-PRESS sequences showed poor agreement.

Diana Rotaru, Georg Oeltzschner, Richard Edden, David Lythgoe

Low-concentration metabolites like γ-aminobutyric acid (GABA) and glutathione (GSH) can be measured at 3T using spectral-editing magnetic resonance spectroscopy methods like MEGAPRESS, HERMES or HERCULES. We propose a novel analysis approach based on simultaneous modelling of HERMES difference and sum spectra in LCModel, instead of fitting the difference spectra separately. This approach uses all available spectral information. It improves the quality of the results providing high reproducibility, and lower Cramér-Rao lower bounds values (CRLB) compared to traditional analysis.

Seyedmorteza Rohani Rankouhi, Donghyun Hong, David Norris

MEGA edited 3 ppm signal can be severely contaminated with macro-molecules. Using two distinct acquisition methods of MASE-sLASER and MEGA-sLASER both at TE = 68 ms at 7T, we show the feasibility of macromolecule free estimation of GABA with LCModel. The presence of GABA line at 2.28 ppm in the spectra acquired with both techniques plays a crucial role for this.

James Murdoch, Ferdinand Schweser, Muhammad Saleh, Richard Edden

HERMES is a new Hadamard-based editing sequence that allows for the simultaneous acquisition of overlapping metabolite signals – most notably GABA and glutathione (GSH) at TE 80.  As such, HERMES is an alternative to conventional GABA measurement using TE 68 MEGA-PRESS, providing GSH information “for free.” In this work, we showed in a series of matched-voxel spectra that %SD values from LCModel were on average only slightly larger for HERMES than for MEGA-PRESS, suggesting that only a small price is paid in terms of GABA sensitivity.

Christopher Wickens, Stephen Sawiak, Keri Carpenter, Adrian Carpenter, Christopher Rodgers

Proton 1D MR spectroscopy has been used to quantify alterations in cerebral metabolite concentrations to investigate neurological diseases. However, the J-coupling found in key metabolites produce multiplets which result in highly overlapped signals, complicating signal quantification. 2D J-resolved spectroscopy (JPRESS) allows distribution of coupled signals into a second perpendicular dimension, reducing signal overlap. Unfortunately, the translation of 2D-JPRESS into a commonly used clinical tool has not been achieved due to limited post-processing strategies and long scan times. Here, a simple processing strategy to significantly enhance signal sensitivity and a technique to accelerate JPRESS by 30% are presented. 

Andreas Masek, Alexander Gussew, Jürgen Reichenbach

Taking advantage of the adiabatic inversion based macromolecule (MM) suppression approach, the MM contamination of the neurotransmitter GABA can be significantly reduced in MEGA-PRESS ¹H-MR brain spectra. In this work, the longitudinal relaxation times (T₁) of brain macromolecules were determined in posterior cortex of healthy subjects in order to adjust the inversion delays for MEGA-PRESS based measurements of pure GABA. Compared to main brain metabolites, T₁ times of MMs are significantly shorter and further reveal a very low inter-individual variation, which allows us to use the MM nulling approach without substantial T₁ weighing related attenuations of metabolite signals and further to apply fixed TI settings instead of performing individual T₁ measurements in future studies.

Hu Cheng, Sharlene Newman

We conducted a Monte-Carlo simulation to investigate the quantification of glutamate (Glu) and glutamine (Gln) using MEGA-PRESS and LCModel at 3 T. The results demonstrate that both glutamate and glutamine can be reliably quantified along with Gamma-aminobutyric acid if the spectrum linewidth is smaller than 0.06 ppm. However, our in vivo results showed a higher ratio of Glu/Gln, which is out of the physiological range measured by other methods. Our work suggests that glutamate and glutamine can be quantified at high accuracy in theory but the accuracy might be compromised in practice by other factors that affects the spectrum quality.

Yulu Song, Tao Gong, Fei Gao, Richard Edden, Weibo Chen, Guangbin Wang

Gamma-aminobutyric acid (GABA) in midbrain is insignificant to be measured. To determine the GABA+ level, we employed Mescher-Garwood point-resolved spectroscopy (MEGA-PRESS) by a small region of interest (ROI)(1.0 × 2.5 × 3.0 cm), which is a new technique that could precisely measure the level of the inhibitory neurotransmitter. The distribution is 2.47 ±0.66 (χ±SD),and it is prove that there was no correlation of GABA+ level with age in healthy volunteers.

Yan Zhang, Jun Shen

For in vivo MRS spectral fitting, a baseline is often used to model background signals. The existing algorithms including LCModel rely on the linewidth to distinguish metabolite peaks from the background signals. In this work, we show that the fitted short-TE baseline strongly depends on metabolite linewidth due to large baseline-metabolite covariances. This dependence negatively affects metabolite quantification using short-TE MRS, resulting in large errors in metabolite concentrations. We also demonstrate that this baseline problem can be largely eliminated using 1D JPRESS which benefits from its substantially reduced background signals.

Li An, Christopher Johnson, Milalynn Victorino, Jun Shen

A novel approach for determining macromolecule baselines at medium TE was proposed. Inversion recovery was combined with spectral editing to acquire six sets of MRS data using two editing frequencies and three long inversion times (TI).Macromolecule signals were essentially invariant across the three long TIs but metabolite signal amplitudes were significantly modulated by TI. By simultaneously fitting the six sets of data, metabolite and macromolecule signals were reliably separated without using empirical constraints on the amplitudes of the spline baselines. Compared to existing techniques, this approach exploits both T₁ and T₂ differences between metabolites and macromolecules.

Tamás Borbáth, Saipavitra Murali Manohar, Andrew Wright, Anke Henning

This work reports the apparent T₂ relaxation times of macromolecules measured at 9.4 T in the human brain.  The measured T₂ times are between 10 and 40ms, with longer relaxation times of around 50 ms for M2 and M3. The J-evolution of the peak at 2.7 ppm is observed at longer echo times. The full-width half-maxima of the simulated peaks are significantly broader than the T₂ component of the lineshapes.

Eva Heckova, Michal Považan, Bernhard Strasser, Stanislav Motyka, Gilbert Hangel, Lukas Hingerl, Philipp Moser, Stephan Gruber, Siegfried Trattnig, Wolfgang Bogner

This work investigates the influence of different macromolecular baseline models on the reliability and test-retest reproducibility of metabolite quantification for clinically attractive ~5min 2D-FID-MRSI with nominal voxel volume 3.4×3.4×8mm³. We confirmed that FID-MRSI with adequate MM prior knowledge provides highly reproducible (CV<11%) and reliable results (ICC>0.75) for the common metabolites even when using more flexible parameterized MM models.

David McAllindon, Chris Bowen, Denise Bernier, Philip Tibbo

Macromolecules underly the metabolites in short-TE ¹H magnetic resonance spectroscopy and must be accounted for in a quantitative analysis.  One method is to acquire a metabolite-nulled spectrum and use it to account for macromolecules in fitting; however, since metabolites have a range of T1, metabolite-nulling is incomplete and leaves residuals.  We introduce a new metabolite cleaning method with 2 metabolite-nulling schemes, single inversion and double inversion, and use it to examine the estimated metabolite residuals, finding that even with double-inversion nulling, there are substantial metabolite residuals of 10-35% in the macromolecule spectrum. 

Andrew Wright, Saipavitra Murali-Manohar, Anke Henning

In short echo time spectroscopy sequences macromolecular signals may strongly influence the quantification of metabolite spectra they underlay. In this work we present a method for simulating a MM basis set that is tailored toward chosen sequences and sequence parameters with the aim to improve the accuracy of metabolite measurements in vivo. We show that utilizing a simulated macromolecule basis set while considering the relaxation behavior of individual macromolecular resonances can produce metabolite quantification results of similar quality to that of a dedicatedly measured MM basis set when applied to the same spectra of interest.

Saipavitra Murali-Manohar, Andrew Wright, Tamas Borbath, Anke Henning

Longitudinal relaxation times of 13 Macromolecular (MM) resonances are reported for a gray matter rich voxel at 9.4 T for the first time.  In addition, a sequence was optimized based on calculated magnetizations from Bloch simulations for combinations of inversion times using a DIR MC-semiLASER. The results from this work highlight the importance of accounting for specific peak relaxations due to the ranging T_­1 relaxation times of the MM peaks.

Charles Lewis, Paul Nakonezny, Mark Frye, Balwinder Singh, Paul Croarkin, John Port

Newer spectral sequences have been developed to focus quantification of specific metabolites.  In this study, measurements of glutamatergic metabolites in a human sample (N=178) were compared between two sequences, a standard TE-optimized PRESS sequence designed to capture broad spectral resonance and a 2-dimensional J-resolved PRESS sequence developed specifically for glutamate signal acquisition at the expense of broad resonance capability.  Cho/Cr and NAA/Cr measurements had good correspondence between sequences (intraclass correlation coefficients >0.88), while glutamate and related metabolites (Glu, Glu/Cr, Glx, Glx/Cr) demonstrated poor reliability.  These findings emphasize the need to exercise caution when comparing glutamate measurements using different ¹H-MRS sequences.

Tianxiao Zhang, Tianyao Wang, Ziyu Meng, Ke Xue, Yudu Li, Rong Guo, Yibo Zhao, Jun Liu, Zheng Jin, Xin Yu, Zhi-Pei Liang, Yao Li

Disrupted metabolic activity is one of the most prominent pathophysiologic consequences of stroke. ¹H-MRSI has been recognized as a powerful tool for metabolic imaging, but its clinical applications have been limited due to long scan time and poor spatial resolution. In this study, we investigate the feasibility of rapid high-resolution metabolic imaging of stroke using SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation). We have successfully acquired metabolic maps from the whole brain at a nominal spatial resolution of 2.0×2.4×2.0 mm³ in a 5-min scan. Our experimental results clearly show metabolic alterations due to stroke.

Petr Bednarik, Alena Svatkova, Dinesh Deelchand, Rupert Lanzenberger, Wolfgang Bogner

Functional spectroscopy (fMRS) is capable of quantifying metabolite changes related to activation of brain energetic metabolism during sensory stimulation. Impaired energetic metabolism underlies pathophysiology of several neuropsychiatric diseases and therefore extension of fMRS to 3T clinical scanners is urgently needed. We evaluated feasibility of fMRS with advanced 1H-MRS based on semi-LASER localization highly optimized for 3T in 10 healthy volunteers. We observed significant changes of glutamate and glucose during short (12 min) paradigm of visual stimulation consistent with previous 7T reports. Thus, we demonstrated feasibility of 3T fMRS for clinical studies.

Peter Lally, Alan Bainbridge, Paolo Montaldo, Vânia Oliveira, Josephine Mendoza, Sudhin Thayyil

In various pathologies, changes in cerebral metabolite concentrations are accompanied by variations in the broader underlying lipid/macromolecular components. This introduces important biases in quantification at short echo times which, if unaddressed, undermine experiments which compare subjects with different injury severities.

Here we demonstrate the benefits of employing a simple two-point saturation recovery MRS experiment to reduce this bias introduced by pathology – in this case, taking the example of neonatal encephalopathy. This ability to accurately quantify spectra at all pathology severities is crucial for clinical trials, where biases would otherwise suppress sensitivity to important treatment effects.

Caigui Lin, Zhiliang Wei, Jiyang Dong , Zhong Chen

Hepatocellular carcinoma (HCC) is a subtype of liver cancer with high worldwide prevalence and mortality. Its high recurrence rate and heterogeneity have challenged effectiveness of existing therapies. Numerous researchers explore the multifaceted benefits of Vitamin C (VC) in cancer treatments. In this study, we utilized the NMR-based metabolomics approach to systematically surrogate the molecular basis underlying the anticancer property of VC in HCC cell. Moreover, combination of VC with chemotherapeutic agent was tried to investigate synergetic effects in modulating metabolic profiles of cancer cells. Our results help to reveal the molecular basis of HCC treatment and may facilitate future clinical therapy designs. 

Anouk Schrantee, Jannie Wijnen, Petra Pouwels, Niels de Joode, Wietske van der Zwaag, Liesbeth Reneman, Odile van den Heuvel, Chris Vriend

Ten volunteers performed a Go/NoGo task during MRS acquisition at 7T to assess if event-related fMRS could detect dynamic glutamate changes during response inhibition. Metabolite spectra were acquired using a semiLASER sequence (to assess task-induced fluctuations in glutamate and lactate) and were interleaved with water-unsuppressed spectra (to assess the BOLD response-induced water linewidth changes). The voxel was placed in the dorsomedial prefrontal cortex. Although an fMRI pilot confirmed the voxel location, no significant differences in metabolite concentrations or water amplitude between NoGo and Go trials was detected.    

Philipp Knopf, Jesus Pacheco-Torres, Flonne Wildes, Christoph Trautwein, Benyuan Zhou, Balaji Krishnamachary, Lars Zender, Bernd Pichler, Zaver Bhujwalla

Here we investigated the metabolic characteristics and the effect of the so called senescence associated secretory phenotype (SASP) on extracellular matrix (ECM) degradation of p53 re-activation induced senescence, using a murine liver carcinoma cell model, where p53 is silenced in the presence of doxycycline hyclate. Senescence is induced within three days after doxycycline hyclate withdrawal and subsequent p53 re-activation.  Our data revealed alterations of metabolites in p53-reactivation induced senescent H-Ras cells compared to control cells, including creatine, phosphocreatine and glycerophosphocholine indicating differences in energy and phospholipid metabolism.  Senescent H-Ras cells tended to degrade the ECM more than control cells.

Seyedmorteza Rohani Rankouhi, Donghyun Hong, David Norris

In proton spectroscopy there are reports of macro-molecules (MM) in mobile form and therefore with long T2 relaxation time in the literature. Using the novel antiphase editing technique, we demonstrate the contribution of such contaminants to J-difference edited spectra at 3ppm, with implications for editing GABA.

Ralf Mekle, Katharina Schmack, Jochen Fiebach, Heiner Stuke

Psychotic symptoms, such as delusions and hallucinations are frequently observed in schizophrenia. Converging evidence suggests a link to dompaminergic neurotransmission, although the underlying mechanisms are not well understood. In this study, dopamine levels were pharmacologically increased in healthy volunteers to investigate possible neurochemical alterations in the visual cortex measured by single volume ¹H MRS using the MEGA-PRESS sequence at 3 T. Reduced GABA and decreased glutamate concentrations were found induced by increased dopamine levels. The former might contribute to the perceptual deficits seen in schizophrenia, while the latter supports the theory of glutamate hypofunction in schizophrenia.

Tobias Winkler, Petros Martirosian, Erwin Schleicher, Thomas Benkert, Fritz Schick

Collagen is a protein physiologically abundant in cartilage, tendons, and ligaments. Pathological processes in many organs might lead to accumulation of collagen in the extracellular space (eg, in hepatic, muscular or renal fibrosis), and non-invasive assessment of fibrotic changes in parenchyma is of high clinical interest. Ultrashort echo-time (UTE) sequences provide direct assessment of the fast decaying signals of collagen. In this work collagen solutions were analyzed in vitro with inversion recovery FID and spin echo spectroscopy sequences to get a better understanding of the different spectral components of collagen signals and their behavior using a 3T whole-body scanner.

Maike Hoefemann, Malgorzata Marjanska, Edward Auerbach, Roland Kreis

The detection of Nicotinamide adenine dinucleotide (NAD⁺) proved to be challenging in ¹H Magnetic Resonance Spectroscopy, as standard water presaturation showed to lead to a strong suppression of NAD⁺ signals due to the polarization exchange between NAD⁺ and water. For the detection of such low-concentration metabolites, a high Signal-to-Noise-Ratio (SNR) is crucial. One possibility to increase the SNR is to choose a large voxel size (VS). In this study we show that optimizing acquisition parameters focusing on high SNR and increasing the VS to 75 cm³ allows the detection of NAD⁺ at 3T with a semi-LASER sequence despite water presaturation.

Wendy Oakden, Greg Stanisz

The type and dose of anaesthesia affects both cerebral blood flow and metabolism. For experiments which involve measuring small changes in neuro-chemical levels either between groups, or following treatment, any differences in experimental conditions which increase the amount of variability can either mask or alter the results. Using ¹H MRS, metabolites were quantified hourly in hippocampus and thalamus over the course of 5 hours under light isoflurane anaesthetic, in rats exposed to either a normal or a reversed light cycle. Both anaesthesia duration and light cycle had statistically significant effects on some, but not all, metabolites.

Andrei Manzhurtsev, Alexey Yakovlev, Petr Menshchikov, Maxim Ublinskiy, Tolib Akhadov, Natalia Semenova

In this research visual stimulation was used for the first functional MRS of aspartate, TE averaging – for pure glutamate and glutamine, and MEGA-PRESS for GABA- to find activation-induced changes at 3 Tesla. The results (except for glutamine) are in compliance with previously published data for 7T. The parameters behavior might reflect the manifestation of Glu neurotransmitter function predominance and metabolic character of changes in the concentrations of other parameters studied.

Yuhei Takado, Hiroyuki Takuwa, Manami Takahashi, Masafumi Shimojo, Takuya Urushihata, Nobuhiro Nitta, Sayaka Shibata, Jamie Near, Maiko Ono, Jun Maeda, Naruhiko Sahara, Yutaka Tomita, Ichio Aoki, Tetsuya Suhara, Makoto Higuchi

To clarify different temporal alterations of Glutamate (Glu) and GABA levels for excitatory/inhibitory (E/I) balance during neural activity in awake healthy mice, we performed ¹H-MRS during whisker stimulation. The short term sensory stimulation increased the level of Glu, then long term stimulation by repeating whisker stimulation increased GABA levels, resulting in an inhibitory dominant E/I ratio. It is conceivable that the decreased E/I ratio may be associated with sensory habituation. Given the significant influence of anesthesia on neural activity, awake ¹H-MRS in mice is valuable for investigating E/I balance in relation to brain function. 

Steven Zhang, Masoumeh Dehghani, Jim Gourdon, Chathura Kumaragamage, Jamie Near

Alzheimer’s disease (AD) is a neurodegenerative disorder commonly associated with neuronal metabolic deficits. In this study, we employ an indirect ¹H-[¹³C] MRS approach to investigate changes in glucose metabolism between wild type and transgenic Alzheimer rats. This method can be used to follow the labeling of downstream metabolites after [1-6,¹³C₂] glucose infusion and allows for quantitative measurements of the rate of ¹³C-label transfer from glucose into glutamate and glutamine in the brain. Preliminary comparison of ¹³C fractional enrichment time courses suggest that transgenic rats exhibit slower ¹³C metabolite labeling, indicative of a lowered glucose metabolic rate in AD pathology.

Ravi Prakash Reddy Nanga, Deepa Thakuri, Sanjeev Chawla, Dushyant Kumar, Abigail Cember, Hari Hariharan, Cynthia Epperson, Ravinder Reddy

Taurine is an important metabolite present in the pineal gland and is involved in the regulation of melatonin, which is plays a key role in regulation of sleep-wake cycle, in endocrine metabolism and in depression. However, there have been no known in vivo studies that measured neuro-metabolites in the pineal gland. In this study, for the first time, we explored the feasibility of single voxel proton spectroscopy from pineal gland in vivo in healthy human volunteers at 7.0T MRI.

Yasmin Geiger, Assaf Tal

Motor skills acquisition can manifest in changes in basal levels of metabolites in the motor cortex. We aim to study difference in metabolites basal levels in the ipsilateral and contralateral motor cortex using single voxel MRS. Our study showed significant difference only in basal GABA levels and the basal GABA/Glx ratio. This result should be kept in mind when interpreting or designing experiments studying the metabolic correlates of motor function.

Alireza Abaei, Dinesh K Deelchand, Francesca Rizzo, Tobias M. Böckers , Volker Rasche

To detect subtle changes in the neurometabolite concentrations by MRS, it is of utmost importance that the dominant contribution to the metabolic changes, is caused by the pathology of interest itself. Many studies involve surgery to interface e.g. cannulas to the brain. We investigate the impact of implanting an intracerebral cannula on the striatal neurochemical profile. MRS of the striatum from both hemisphere was performed 14d after surgery. A significant reduction of almost all metabolites was observed in the hemisphere with cannulation as well as contralateral side, indicating a dominant impact of the surgery, which might impact the sensitivity of MRS for quantification of pathologic processes.

Leo Sporn, Erin MacMillan, Ruiyang Ge, Afifa Humaira, Laura Barlow, Cornelia Laule, Fidel Vila-Rodriguez

There is interest in using MRS to study the effects of transcranial magnetic stimulation (TMS), but a major challenge is B₀ inhomogeneities introduced by the TMS coil. Phantom work showed increasing B₀ inhomogeneity as the MRS voxel was moved closer to the TMS coil. Distortions in the metabolite signals included increased noise fluctuations and spectral linewidth by ~50% when the voxel center was < 6cm away from the TMS coil B₀ inhomogeneity effects were similar whether the TMS coil was pulsing prior to the PRESS sequence or not. Our results suggest TMS/MRS may be able to resolve spectra in vivo.

Naoto Sato, Yuhei Takado, Yuta Kanbe, Moyoko Tomiyasu, Lijing Xin, Jamie Near, Kohki Yoshikawa, Tatsuya Higashi, Tetsuya Suhara, Makoto Higuchi, Takayuki Obata

The present study aimed to evaluate the association between the plasma and brain glutamine (Glu) and glutamate (Gln) using proton magnetic resonance spectroscopy (¹H-MRS) and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-MS), respectively, in 20 participants. A positive correlation between Gln to tCr(creatine +phosphocreatine) ratio in the posterior cingulate gyrus (PCC) and the plasma Gln indicates that Gln can be transferred effectively by Gln transporters at the blood-brain barrier (BBB). No correlation of Gln in the cerebellum (Cbll) may be attributed to either regional difference of Gln transport or lower reproducibility of the measurements in Cbll than in PCC.

Yohan Boillat, Lijing Xin, Olivier Reynaud, Wietske van der Zwaag, Rolf Gruetter

Using [Lac] and [Glu] as markers of glycolytic and oxidative metabolisms, respectively, we investigated the involvement of each of these pathways during a finger tapping task at different frequencies. We measured BOLD and CBF data and metabolite concentrations at 7T. BOLD and CBF signals increased for increasing finger tapping frequencies as well as [Lac]. The [Glu] changes were smaller and, with the current number of participants, did not follow the same trend.

Song-I Lim, Masoumeh Dehghani, Rolf Gruetter, Lijing Xin

Thalamus has been known as a critical hub through which bidirectional neural signals are transmitted between cortical and subcortical region and its abnormalities are related to psychiatric disorders. The purpose of the study is to investigate the neurochemical profile in the thalamus and to evaluate the reliability of the measurement at 7T for the first time. In this study, 6 volunteers were scanned twice using semi-SPECIAL sequence. 10 metabolites were detected including Glu, GABA, and GSH with accuracy. The average CoV of the metabolites was 8 ± 5%. This study provides a reference for future neurological studies in the thalamus.

Molly Charney, Eduardo Coello, Tyler Starr, Huijun Liao, Alexander Lin

There has been little consensus over the existence of sex-related neurochemical differences in the human brain. This analysis reveals a significant difference in tCho/tCr in the posterior cingulate gyrus of males and females of a large age range. These results indicate that sex should be considered in study recruitment, disease progression, and treatment following injury.

Katrina Cruickshank, Tak Pan Wong, Jamie Near

Cytokines are chemical signalling molecules released by the immune system in response to pathological insults. Cytokine upregulation is an early feature of Alzheimer’s disease (AD) and a possible contributor to downstream neuropathology and cognitive decline. Using magnetic resonance spectroscopy (MRS), cytokine-specific enzyme-linked immunosorbent assays (ELISA) and behavioural measures, we aimed to investigate the relationships between cytokine activity, early neurochemical changes and cognitive decline in an AD rodent model. Preliminary metabolic alterations suggest a paradoxical increase in synaptic activity, coinciding with cognitive deficits. This ongoing study is a step towards understanding the impact of abnormal cytokine levels on the AD brain.

Stephen Bawden, Scott Willis, Hannah Williams, James King, Guruprasad Aithal, Penny Gowland

MRI and MRS provides a powerful tool to non-invasively assess lipid deposition in vivo. In addition to fat fraction measurements, recent studies have shown that lipid composition may play an important role in health outcomes. ¹H MRS at high field strength provides good SNR of individual fat peaks and can be used to asses lipid composition (saturation, poly-unsaturation etc.). In this study a number of edible oils were scanned at 3T and 7T and MR spectra used to compare measurements of lipid composition with predicted values. An in vivo dataset was also acquired for comparison.

Jun-ichiro Enmi, Ikuhiro Kida, Seishi Itoi, Tetsuya Shimokawa, Noriaki Hattori, Yoshichika Yoshioka

The concentrations of some neurotransmitters (N–acetylaspartylglutamate (NAAG), glutamate (Glu), and γ-aminobutyric acid (GABA)) and some antioxidants (glutathione (GSH), ascorbic acid (Asc), and taurine (Tau)) were measured in human brain gray and white matters by using ¹H-MRS at 7 T. The distribution patterns of NAAG, Glu, and GABA were completely different from each other. The distribution patterns of the antioxidants had a relatively similar tendency. The concentrations of Asc and Tau were significantly higher in gray matters than in white matters, although there was no significant difference in GSH concentration between the gray and white matter.

Deepti Upadhyay, Naranamangalam Jagannathan, Govind Makharia , Siddharth Gupta, Prasenjit Das, Uma Sharma

Potential celiac disease (CeD) patients have positive CeD associated antibodies (anti-tissue tansglutaminase antibodies) and HLA-DQ2 and/or HLA-DQ8 genotype but no intestinal inflammation. NMR based metabonomic study of blood plasma of potential CeD patients demonstrated a distinct metabolic fingerprint characterized by raised histidine and proline in comparison to healthy controls. The changes in histidine suggested compromised cytoprotective mechanism while elevated arginine level indicated altered functioning of intestinal cells in potential CeD. These altered metabolic activities could be the initial event that precede the pathogenesis of CeD and may contribute to intestinal inflammation which results in villous atrophy.

Deepti Upadhyay, Prasenjit Das, Siddharth Gupta, Govind Makharia , Naranamangalam Jagannathan, Uma Sharma

NMR based metabonomics of small intestinal mucosal biopsies, blood plasma and urine samples from same set of patients demonstrated the underlying biochemical abnormalities and biomarker/s for celiac disease (CeD). Intestinal mucosa of CeD patients had higher levels of proline and allantoin while lower glycine, histidine and GPC compared to controls. Metabolome of blood plasma of CeD patients showed significantly higher concentration of proline, arginine and β-hydroxybutyrate while urine had higher proline, allantoin and β-hydroxybutyrate compared to healthy controls. These findings indicated metabolic abnormalities associated with villous atrophy seen in CeD and suggested proline, arginine and allantoin may serve as biomarker/s.

Naranamangalam Jagannathan, Pradeep Kumar, Rajeev Kumar, Virendra Kumar, S. Senthil Kumaran, Sanjay Sharma, Sanjay Thulkar, S. Datta Gupta

The present study evaluates the metabolic profile of blood plasma for distinguishing prostate cancer (PCa) patients with metastases (n=30) and without metastases (n=35) using ¹H-NMR spectroscopy. Our data showed significant lower concentration of leucine, valine, isoleucine, glycerophosphocholine, glutamine and acetoacetate in PCa patents with metastases as compared to patients without metastases. Results provided an insight into the alterations in the metabolic pathways in PCa and indicated that NMR spectroscopy may help in determining potential biomarker/s for the diagnosis of PCa patients with metastases.

William Reichert, Quoc Pham, Mark Does, Daniel Topgaard

Myelin MRI phantoms used to characterize magnetization dynamics require comparable microstructure and composition to physiological myelin for experiments to be translatable. Folch Fraction I bovine brain extract was evaluated for its phase behavior, composition, and structure through Polarization Transfer solid-state NMR (PT ssNMR), ³¹P static NMR, and small-angle X-ray scattering. Results indicate the absence of cholesterol and the coexistence of solid and liquid isotropic phases in phantoms across various solvent contents at body temperature, as opposed to physiological myelin's multi-lamellar liquid crystalline structure. Experiments aimed at characterizing myelin’s microstructure should look to other preparation methods.

Katarzyna Pierzchala, Dunja Simicic, Veronika Rackayova, Olivier Braissant, Dario Sessa, Stefanita Mitrea, Andrzej Sienkiewicz, Valérie McLin, Rolf Gruetter, Cristina Cudalbu

Oxidative stress (OS) is thought to be an important factor in chronic hepatic encephalopathy (CHE) pathogenesis. Combining in-vivo ¹H-MRS, ex-vivo ESR and histology of CNS allowed us to investigate the course and brain regional difference of cerebral OS in the rat model of CHE. Early changes in brain antioxidants (Asc and GSH, post-BDL) were validated by ESR and histology. Our results showed a stronger vulnerability of cerebellum and confirmed that the antioxidant system impairment and central OS is an early event in CHE.

Samuel Hernandez, marlon tilgner, Peter Caravan, Leo Cheng

Prostate Cancer (PCa) is the second leading cause of cancer death among men, however, in clinic at present, there is still a lack of sensitive biomarkers that can assist accurate diagnoses for PCa patients. Our laboratory has been engaged in the discovery of PCa metabolomic markers in the past decade using intact tissue high-resolution magic angle spinning magnetic resonance spectroscopy (HRMAS MRS). In this study, we further our endeavor by investigations of prostate tissue with diffusion ordered MRS to include the physical properties of cellular metabolites through evaluations of their diffusion characteristics.in the biomarker discovery.

Selin Ekici, Ren Geryak, Candace Fleischer

Gliomas are a class of aggressive brain tumors with a low survival rate. New biomarkers are needed to monitor tumor progression and response to treatment. Our goal was to compare the effectiveness of operator-independent LCModel analysis for HRMAS NMR spectra acquired from histologically confirmed glioma tissue (n=14) using both FID and CPMG pulse sequences. The CRLBs of lactate and myo-inositol were significantly lower for spectra acquired with the CPMG compared to the FID sequence. Relevant glioma metabolites were quantified with LCModel from most spectra acquired with CPMG but not FID.

James Barnett, Santosh Bharti, Balaji Krishnamachary, Flonne Wildes, Yelena Mironchik, Marie-France Penet, Zaver Bhujwalla

Cyclooxygenase-2 (COX-2) is an inducible enzyme that mediates the inflammatory response of cells. COX-2 overexpression is associated with poor prognosis in breast cancers.  Here we have investigated the effect of tumor COX-2 overexpression on spleen metabolism, using 1H magnetic resonance spectroscopy (MRS), as part of an overall focus on understanding the impact of cancers on inducing metabolic changes in critical organs. We focused on the spleen since it plays a critical role in the immune response and detected distinct differences in glutamate and lactate with COX-2 overexpression.

Stefania Acciardo, Lionel Mignion, Florian Gourgue, Céline Schoonjans, Nicolas Joudiou, Bernard Gallez, Bénédicte Jordan

The aim of this work is to identify a marker of response or resistance to BRAF inhibition in melanoma. BRAF inhibition resulted in a decrease of ¹³C label exchange between hyperpolarized [1-¹³C]pyruvate and lactate in sensitive, but not in resistant, melanoma cells. Such effect is likely to be mediated by a reduction of the lactate pool due to (i) decreased flux through glycolysis, (ii) reduced MCT1-mediated lactate uptake and (iii) increased lactate efflux via MCT4. The lactate/pyruvate ratio may help to discriminate between sensitive and resistant melanoma cells, by reflecting the different metabolic alterations that the cells undergo.

Pradeep Kumar, Rajeev Kumar, Virendra Kumar, S. Senthil Kumaran, Sanjay Sharma, Sanjay Thulkar, S. Datta Gupta, Naranamangalam R. Jagannathan

The present study demonstrates the potential of proton nuclear magnetic resonance (¹H-NMR) based metabolic profiling of urine for distinguishing prostate cancer patients (PCa; n=43) from patients with benign prostatic hyperplasia (BPH; n=30) and to determine non-invasive biomarker/s for diagnosis. A significantly lower concentration of leucine, valine, hippurate, dimethylglycine, glycerophosphocholine, glutamine, glycine, taurine and creatinine were observed in PCa patients as compared to BPH. Our result suggests metabolic alterations due to protein turnover, cell proliferation, energy demand and gut micro-biota metabolism in PCa patients.

Pradeep Kumar, Rajeev Kumar, Virendra Kumar, S. Senthil Kumaran, Sanjay Sharma, Sanjay Thulkar, S. Datta Gupta, Naranamangalam R. Jagannathan

This study investigates the metabolic profile of blood plasma for distinguishing prostate cancer (PCa) patients with high Gleason score (GS≥7) and low Gleason score (GS<7) using ¹H-NMR metabolomics. A significantly higher concentration of lactate, pyruvate, choline, dimethylamine, acetate and alanine were observed in the blood plasma of PCa patients with high Gleason score as compared to patients with low Gleason score. Our results suggested that the metabolic pathway alterations seen in amino acids, choline, glucose and ketone body may be related to changes in PCa progression.

Abderrazak Chahid, Sourav Bhaduri, Eric Achten, Taous-Meriem Laleg-Kirati, Hacene Serrai

A new user interactive platform for MRS data processing is proposed. This toolbox is based on the Semi-Classical Signal Analysis (SCSA)  for  Residual Water Suppression and MRS signal denoising. It allows MRS users to achieve water suppression and data denoising, with data fitting as an additional feature. The toolbox is easy to install and to use: 1)   visualization of spectroscopy data, 2) water suppression and denoising, 3) iterative data fitting using nonlinear least squares. This abstract demonstrates how each of these features has been incorporated and provides technical details about the implementation as a graphical user interface in MATLAB. 

Caitlin Tressler, Vinay Ayyappan, Kanchan Sonkar, Kristine Glunde

We are investigating aberrant glutamine metabolism in breast cancer to discover potential novel therapeutic targets to inhibit a critical energy source for cancer cells. We have examined glutamine and glutamate levels using 1H magnetic resonance spectroscopy (MRS) across multiple breast cancer cell types and have begun to look at the molecular mechanisms of glutamine addiction using qRT-PCR. We identified SLC38A3 to be overexpressed in nearly every breast cancer cell line examined, which may, in the future, serve as a potential target in breast cancer.

Uzi Eliav, Gil Navon, Peter Basser

Images obtained by inhomogeneous magnetization transfer were analyzed using models involving Zeeman and dipolar orders. These orders are affected by spin diffusion and relaxation. In the current study a method that enables the measurement of these processes in spinal cord by the same pulse sequence is presented. Magnetization transfer time (MT, spin diffusion) between CH₂ groups is ~0.1ms while the MT between them and CH₃ groups is much slower (~2ms).  The dipolar order is found to decay by three exponentials process (0.11, 0.86, 11.4ms). The fastest decaying component is compatible with the spin diffusion between the CH₂.

Karl Landheer, Kelley Swanberg, Christoph Juchem

Accurate density matrix simulation of nuclear spin systems is critical for quantifying magnetic resonance spectroscopy (MRS) data, as well as for simulation studies designed to optimize acquisition parameters. Although a variety of packages exist to achieve this result, no currently available software is capable of computing a large number of spatial points in a reasonable time frame. Here we present and experimentally validate a novel MATLAB-based software package able to compute complex spin systems, including those exhibiting scalar coupling like GABA, for 64³ spatial points within 25 minutes.

Hongxia Lei, Jean-Claude Martinou

¹H MRS study of embryonic brain development is feasible and offers valuable insights towards early brain development in utero.

Nastaren Abad, Jens Rosenberg, Tangi Roussel, Michael Harrington, Samuel Grant

 

To date, there is a lack of characterization of metabolic markers in migraine studies. Though numerous studies implicate cerebral dysfunction, robust biomarkers are yet to be identified in the migraine brain. It thus follows that identification of specific metabolic changes, potentially influenced by excitatory and inhibitory neurotransmitters, may improve understanding of migraine onset and propagation while opening new avenues for therapy development.

With the goal of evaluating metabolic processes, diffusion-weighed spectroscopy is used to identify longitudinal changes in the in vivo thalamus of an acute rodent of migraine model.

Samuel Ajamu, Rachel Fenner, Yulia Grigorova, James Karchner, Edward Lakatta, Mustapha Bouhrara, Richard Spencer, Olga Fedorova, Kenneth Fishbein

Central arterial stiffness (CAS) is associated with hypertension and is likely associated with stiffening of cerebral artery walls, with attendant cerebral hypoperfusion, neuronal density loss and cognitive decline. We sought to explore associations between pulse wave velocity (PWV), a marker of CAS, and hippocampal blood flow and neuronal density in hypertensive Dahl salt sensitive (Dahl-S) rats, which exhibit age-associated memory loss. We observed direct correlations between greater PWV, lower cerebral blood flow (CBF) and lower N-acetyl aspartate/total creatine ratio (NAA/tCr) in the hippocampus, supporting the role of CAS in cerebrovascular dysfunction and decline in cognitive performance with hypertension and aging.

Petra Hnilicová, Sona Bálentová, Dagmar Kalenská , Eva Hajtmanová , Peter Murín , Michal Bittšanský, Marian Adamkov , Ján Lehotský, Dušan Dobrota

We investigated the metabolic effect of a clinically relevant craniospinal irradiation on the rat spinal cord using ¹H MRS at 7T. Hundred days after the fractionated irradiation performed by radioactive isotope ⁶⁰Co (16Gy in 2 fractions), irradiated and sham-irradiated animals underwent in vivo ¹H MRS examination. Spinal cord spectra were measured by SVS sequence with voxel size of 3.5x2x7.5mm³. In spinal cord of irradiated animals was confirmed significantly reduced tNAA/tCr and increased tCho/tCr ratio, both showing demyelination and inflammatory processes. It seems that in vivo ¹H MRS of spinal cord could be useful for radiation therapy monitoring.

Guojing Wei, Yanqiu Feng

Non-invasive and quantifiable diagnosis of Parkinson’s disease is an ongoing challenge for researchers. In this study, we worked on the CEST signal at 2ppm (CEST@2ppm) in the substantia nigra of acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models at three different time points including pre and 3^rd day, 10^th day after treatment. CEST@2ppm after 5-pool lorentzian fitting showed a statistically significant difference after MPTP injection and metrics based on this fitting model ( MTR_rex and AREX) also indicated positive correlation of CEST@2ppm with the SN damages while the statistic difference of 3^rd and 10^th day was not significant. This quantifying CEST signal may reflect the pathological mechanism of PD in SN.

Aline Xavier, Flavia Zacconi , Daniel Cabrera , Marco Arese, Marcelo Andia

The idea of defining a biomarker to assess the progression of Nonalcoholic Fatty Liver Disease (NAFLD) by using Magnetic Resonance Spectroscopy (MRS) emerges due to the need to find a way to replace biopsy with a non-invasive method. The purpose of this study is to investigate the composition of the liver fatty acids based in the metabolite signals in MRS in NAFLD mice fed with a western-diet at 3 time-point during the progression of the disease. Our findings showed significant changes in the diallylic (2.8 ppm), olefinic (5.3ppm), allilic (2.0 ppm) and bulk methylene (1.3 ppm) peaks during the progression of the NAFLD by using high-resolution MRS.

Pandichelvam Veeraiah, Julian Mevenkamp, Ine Telgenkamp, Nynke Simons, Martijn Brouwers, Joachim E Wildberger, Patrick Schrauwen, Vera B Schrauwen-Hinderling, Lucas Lindeboom

 ¹H-MRS is extensively used to measure the hepatic lipid content. Conventionally, the water resonance is used as an internal reference, thereby assuming a constant T₂decay of water across individuals to estimate absolute hepatic lipid content. However, the T₂ values reported in literature for 3T vary widely, which might be due to different subject populations and/or other methodological discrepancies. The purpose of this study was to measure T₂ of water in a group of subjects with a wide range of hepatic lipid content and to evaluate whether there is a dependence of water T₂ relaxation times and hepatic lipid fraction. 

Xinqiang Yan, Rachelle Crescenzi, John Gore

A recurring need in MRI and MRS is to acquire signals from multiple nuclei, 1H proton and 23Na sodium, in the same study. However, a dual-tune volume coil implemented in a single structure leads to SNR and B₁-efficiency penalties for the X-nucleus. We numerically investigated how B₁-fields interact between either a traveling-wave coil existing outside the bore, or a local dipole array, paired with a birdcage 23Na-coil. For applications to head and knee imaging at 7T, an easily-implemented traveling-wave coil may provide sufficient proton signal for anatomical localization and B₀ shimming, without significantly reducing the performance of the X-nucleus coil.

Jiming Zhang, Claudio Arena, Afis Ajala, Luning Wang, Rajagopal Viswanatah Sekhar, Raja Muthupillai

A different level of overlap between intramyocellular and extramyocellular lipids signal (EMCL and IMCL) depends on muscle fiber orientation and interstitial/fascial muscle fat tissue. We proposed diffusion tensor imaging and Dixon reconstructed fiber orientation map and maximum intensity projection fat maps to guide MR spectroscopy acquisition by carefully positioning the voxel so as to minimize these two effects. This method can be used to improve the consistency and accuracy of using MRS to quantify the intra skeletal muscle lipids and minimize variability in longitudinal studies such as evaluating disease progression or monitoring treatment progress