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Moore JE, Robison RK, Hu J, Sengupta ST, Mahdi OS, Anderson AW, Luo LY, Mohler AC, Merrell RT, Choi C. Optimization of the flip angles of narrow-band editing pulses in J-difference edited MRS of lactate at 3T. Magn Reson Med 2024; 91:886-895. [PMID: 38010083 PMCID: PMC10929535 DOI: 10.1002/mrm.29933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/25/2023] [Accepted: 11/01/2023] [Indexed: 11/29/2023]
Abstract
PURPOSE Application of highly selective editing RF pulses provides a means of minimizing co-editing of contaminants in J-difference MRS (MEGA), but it causes reduction in editing yield. We examined the flip angles (FAs) of narrow-band editing pulses to maximize the lactate edited signal with minimal co-editing of threonine. METHODS The effect of editing-pulse FA on the editing performance was examined, with numerical and phantom analyses, for bandwidths of 17.6-300 Hz in MEGA-PRESS editing of lactate at 3T. The FA and envelope of 46 ms Gaussian editing pulses were tailored to maximize the lactate edited signal at 1.3 ppm and minimize co-editing of threonine. The optimized editing-pulse FA MEGA scheme was tested in brain tumor patients. RESULTS Simulation and phantom data indicated that the optimum FA of MEGA editing pulses is progressively larger than 180° as the editing-pulse bandwidth decreases. For 46 ms long 17.6 Hz bandwidth Gaussian pulses and other given sequence parameters, the lactate edited signal was maximum at the first and second editing-pulse FAs of 241° and 249°, respectively. The edit-on and difference-edited lactate peak areas of the optimized FA MEGA were greater by 43% and 25% compared to the 180°-FA MEGA, respectively. In-vivo data confirmed the simulation and phantom results. The lesions of the brain tumor patients showed elevated lactate and physiological levels of threonine. CONCLUSION The lactate MEGA editing yield is significantly increased with editing-pulse FA much larger than 180° when the editing-pulse bandwidth is comparable to the lactate quartet frequency width.
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Affiliation(s)
- Jason E. Moore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ryan K. Robison
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Philips, Nashville, TN, USA
| | - Jie Hu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Saikat T. Sengupta
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Olaimatu S. Mahdi
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Adam W. Anderson
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Leo Y. Luo
- Department of Radiation Oncology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Alexander C. Mohler
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ryan T. Merrell
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Changho Choi
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
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Bang JW, Parra C, Yu K, Wollstein G, Schuman JS, Chan KC. GABA decrease is associated with degraded neural specificity in the visual cortex of glaucoma patients. Commun Biol 2023; 6:679. [PMID: 37386293 PMCID: PMC10310759 DOI: 10.1038/s42003-023-04918-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 05/05/2023] [Indexed: 07/01/2023] Open
Abstract
Glaucoma is an age-related neurodegenerative disease of the visual system, affecting both the eye and the brain. Yet its underlying metabolic mechanisms and neurobehavioral relevance remain largely unclear. Here, using proton magnetic resonance spectroscopy and functional magnetic resonance imaging, we investigated the GABAergic and glutamatergic systems in the visual cortex of glaucoma patients, as well as neural specificity, which is shaped by GABA and glutamate signals and underlies efficient sensory and cognitive functions. Our study shows that among the older adults, both GABA and glutamate levels decrease with increasing glaucoma severity regardless of age. Further, our study shows that the reduction of GABA but not glutamate predicts the neural specificity. This association is independent of the impairments on the retina structure, age, and the gray matter volume of the visual cortex. Our results suggest that glaucoma-specific decline of GABA undermines neural specificity in the visual cortex and that targeting GABA could improve the neural specificity in glaucoma.
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Affiliation(s)
- Ji Won Bang
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA.
| | - Carlos Parra
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA
| | - Kevin Yu
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA
- Center for Neural Science, College of Arts and Science, New York University, New York, New York, 10003, USA
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, New York, 11201, USA
| | - Joel S Schuman
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA
- Center for Neural Science, College of Arts and Science, New York University, New York, New York, 10003, USA
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, New York, 11201, USA
- Neuroscience Institute, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10016, USA
| | - Kevin C Chan
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10017, USA.
- Center for Neural Science, College of Arts and Science, New York University, New York, New York, 10003, USA.
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, New York, 11201, USA.
- Neuroscience Institute, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10016, USA.
- Department of Radiology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, New York, 10016, USA.
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Peek AL, Rebbeck TJ, Leaver AM, Foster SL, Refshauge KM, Puts NA, Oeltzschner G. A comprehensive guide to MEGA-PRESS for GABA measurement. Anal Biochem 2023; 669:115113. [PMID: 36958511 PMCID: PMC10805000 DOI: 10.1016/j.ab.2023.115113] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 03/06/2023] [Accepted: 03/07/2023] [Indexed: 03/25/2023]
Abstract
The aim of this guideline is to provide a series of evidence-based recommendations that allow those new to using MEGA-PRESS to produce high-quality data for the measurement of GABA levels using edited magnetic resonance spectroscopy with the MEGA-PRESS sequence at 3T. GABA is the main inhibitory neurotransmitter of the central nervous system and has been increasingly studied due to its relevance in many clinical disorders of the central nervous system. MEGA-PRESS is the most widely used method for quantification of GABA at 3T, but is technically challenging and operates at a low signal-to-noise ratio. Therefore, the acquisition of high-quality MRS data relies on avoiding numerous pitfalls and observing important caveats. The guideline was developed by a working party that consisted of experts in MRS and experts in guideline development and implementation, together with key stakeholders. Strictly following a translational framework, we first identified evidence using a systematically conducted scoping literature review, then synthesized and graded the quality of evidence that formed recommendations. These recommendations were then sent to a panel of 21 world leaders in MRS for feedback and approval using a modified-Delphi process across two rounds. The final guideline consists of 23 recommendations across six domains essential for GABA MRS acquisition (Parameters, Practicalities, Data acquisition, Confounders, Quality/reporting, Post-processing). Overall, 78% of recommendations were formed from high-quality evidence, and 91% received agreement from over 80% of the expert panel. These 23 expert-reviewed recommendations and accompanying extended documentation form a readily useable guideline to allow those new to using MEGA-PRESS to design appropriate MEGA-PRESS study protocols and generate high-quality data.
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Affiliation(s)
- A L Peek
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, 2141, Australia; NHMRC Centre of Research Excellence in Road Traffic Injury Recovery, Queensland, Australia.
| | - T J Rebbeck
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, 2141, Australia; NHMRC Centre of Research Excellence in Road Traffic Injury Recovery, Queensland, Australia.
| | - A M Leaver
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, 2141, Australia.
| | - S L Foster
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, 2141, Australia; Department of Radiology, Westmead Hospital, Hawkesbury Road, Westmead, New South Wales, 2145, Australia.
| | - K M Refshauge
- Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales, 2141, Australia.
| | - N A Puts
- Department of Forensic and Neurodevelopmental Sciences, Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology, and Neuroscience, Kings College London, UK.
| | - G Oeltzschner
- Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, 21287, United States; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, 21205, United States.
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Durazzo TC, McNerney MW, Hansen AM, Gu M, Sacchet MD, Padula CB. BDNF rs6265 Met carriers with alcohol use disorder show greater age-related decline of N-acetylaspartate in left dorsolateral prefrontal cortex. Drug Alcohol Depend 2023; 248:109901. [PMID: 37146499 DOI: 10.1016/j.drugalcdep.2023.109901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 04/04/2023] [Accepted: 04/25/2023] [Indexed: 05/07/2023]
Abstract
BACKGROUND Brain-derived neurotrophic factor (BDNF) is implicated in neuronal and glial cell growth and differentiation, synaptic plasticity, and apoptotic mechanisms. A single-nucleotide polymorphism of the BDNF rs6265 gene may contribute to the pattern and magnitude of brain metabolite abnormalities apparent in those with an Alcohol Use Disorder (AUD). We predicted that Methionine (Met) carriers would demonstrate lower magnetic resonance spectroscopy (MRS) measures of N-acetylaspartate level (NAA) and greater age-related decline in NAA than Valine (Val) homozygotes. METHODS Veterans with AUD (n=95; 46±12 years of age, min = 25, max = 71) were recruited from VA Palo Alto residential treatment centers. Single voxel MRS, at 3 Tesla, was used to obtain NAA, choline (Cho) and creatine (Cr) containing compounds from the left dorsolateral prefrontal cortex (DLPFC). Metabolite spectra were fit with LC Model and NAA and Cho were standardized to total Cr level and NAA was also standardized to Cho. RESULTS Val/Met (n=35) showed markedly greater age-related decline in left DLPFC NAA/Cr level than Val/Val (n=60); no differences in mean metabolite levels were observed between Val/Met and Val/Val. Val/Met demonstrated greater frequency of history of MDD and higher frequency of cannabis use disorder over 12 months prior to study. CONCLUSIONS The greater age-related decline in left DLPFC NAA/Cr and the higher frequency of MDD history and Cannabis Use disorder in BDNF rs6265 Met carriers with AUD are novel and may have implications for non-invasive brain stimulation targeting the left DLFPC and other psychosocial interventions typically utilized in the treatment of AUD.
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Affiliation(s)
- Timothy C Durazzo
- Palo Alto Veterans Affairs Health Care System, Mental Illness Research and Education Clinical Centers (MIRECC) Palo Alto, CA, USA; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA.
| | - M Windy McNerney
- Palo Alto Veterans Affairs Health Care System, Mental Illness Research and Education Clinical Centers (MIRECC) Palo Alto, CA, USA; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Annika M Hansen
- Palo Alto Veterans Affairs Health Care System, Mental Illness Research and Education Clinical Centers (MIRECC) Palo Alto, CA, USA
| | - Meng Gu
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Matthew D Sacchet
- Meditation Research Program, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Claudia B Padula
- Palo Alto Veterans Affairs Health Care System, Mental Illness Research and Education Clinical Centers (MIRECC) Palo Alto, CA, USA; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
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5
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Gozdas E, Hinkley L, Fingerhut H, Dacorro L, Gu M, Sacchet MD, Hurd R, Hosseini SMH. 1H-MRS neurometabolites and associations with neurite microstructures and cognitive functions in amnestic mild cognitive impairment. Neuroimage Clin 2022; 36:103159. [PMID: 36063758 PMCID: PMC9450331 DOI: 10.1016/j.nicl.2022.103159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 08/04/2022] [Accepted: 08/18/2022] [Indexed: 01/16/2023]
Abstract
Alzheimer's disease (AD) pathogenesis is associated with alterations in neurometabolites and cortical microstructure. However, our understanding of alterations in neurochemicals in the prefrontal cortex and their relationship with changes in cortical microstructure in AD remains unclear. Here, we studied the levels of neurometabolites in the left dorsolateral prefrontal cortex (DLPFC) in healthy older adults and patients with amnestic Mild Cognitive Impairments (aMCI) using single-voxel proton-magnetic resonance spectroscopy (1H-MRS). N-acetyl aspartate (NAA), glutamate+glutamate (Glx), Myo-inositol (mI), and γ-aminobutyric acid (GABA) brain metabolite levels were quantified relative to total creatine (tCr = Cr + PCr). aMCI had significantly decreased NAA/tCr, Glx/tCr, NAA/mI, and increased mI/tCr levels compared with healthy controls. Further, we leveraged advanced diffusion MRI to extract neurite properties in the left DLPFC and found a significant positive correlation between NAA/tCr, related to neuronal intracellular compartment, and neurite density (ICVF, intracellular volume fraction), and a negative correlation between mI/tCr and neurite orientation (ODI) only in healthy older adults. These data suggest a potential decoupling in the relationship between neurite microstructures and NAA and mI concentrations in DLPFC in the early stage of AD. Together, our results confirm altered DLPFC neurometabolites in prodromal phase of AD and provide unique evidence regarding the imbalance in the association between neurometabolites and neurite microstructure in early stage of AD.
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Affiliation(s)
- Elveda Gozdas
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA.
| | - Lauren Hinkley
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Hannah Fingerhut
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Lauren Dacorro
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Meng Gu
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Matthew D Sacchet
- Center for Depression, Anxiety, and Stress Research, McLean Hospital, Harvard Medical School, Belmont, MA, USA
| | - Ralph Hurd
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - S M Hadi Hosseini
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
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6
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Lim S, Xin L. γ-aminobutyric acid measurement in the human brain at 7 T: Short echo-time or Mescher-Garwood editing. NMR IN BIOMEDICINE 2022; 35:e4706. [PMID: 35102618 PMCID: PMC9285498 DOI: 10.1002/nbm.4706] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 01/21/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
The purposes of the current study were to introduce a Mescher-Garwood (MEGA) semi-adiabatic spin-echo full-intensity localization (MEGA-sSPECIAL) sequence with macromolecule (MM) subtraction and to compare the test-retest reproducibility of γ-aminobutyric acid (GABA) measurements at 7 T using the sSPECIAL and MEGA-sSPECIAL sequences. The MEGA-sSPECIAL editing scheme using asymmetric adiabatic and highly selective Gaussian pulses was used to compare its GABA measurement reproducibility with that of short echo-time (TE) sSPECIAL. Proton magnetic resonance spectra were acquired in the motor cortex (M1) and medial prefrontal cortex (mPFC) using the sSPECIAL (TR/TE = 4000/16 ms) and MEGA-sSPECIAL sequences (TR/TE = 4000/80 ms). The metabolites were quantified using LCModel with unsuppressed water spectra. The concentrations are reported in institutional units. The test-retest reproducibility was evaluated by scanning each subject twice. Between-session reproducibility was assessed using coefficients of variation (CVs), Pearson's r correlation coefficients, and intraclass correlation coefficients (ICCs). Intersequence agreement was evaluated using Pearson's r correlation coefficients and Bland-Altman plots. Regarding GABA measurements by sSPECIAL, the GABA concentrations were 0.92 ± 0.31 (IU) in the M1 and 1.56 ± 0.49 (IU) in the mPFC. This demonstrated strong between-session correlation across both regions (r = 0.81, p < 0.01; ICC = 0.82). The CVs between the two scans were 21.8% in the M1 and 10.2% in the mPFC. On the other hand, the GABA measurements by MEGA-sSPECIAL were 0.52 ± 0.04 (IU) in the M1 and 1.04 ± 0.24 (IU) in the mPFC. MEGA-sSPECIAL demonstrated strong between-session correlation across the two regions (r = 0.98, p < 0.001; ICC = 0.98) and lower CVs than sSPECIAL, providing 4.1% in the M1 and 5.8% in the mPFC. The MEGA-editing method showed better reproducibility of GABA measurements in both brain regions compared with the short-TE sSPECIAL method. Thus it is a more sensitive method with which to detect small changes in areas with low GABA concentrations. In GABA-rich brain regions, GABA measurements can be achieved reproducibly using both methods.
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Affiliation(s)
- Song‐I Lim
- Laboratory of Functional and Metabolic ImagingÉcole polytechnique fédérale de Lausanne (EPFL)LausanneSwitzerland
- Animal Imaging and TechnologyEcole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
| | - Lijing Xin
- CIBM Center for Biomedical ImagingSwitzerland
- Animal Imaging and TechnologyEcole Polytechnique Fédérale de Lausanne (EPFL)LausanneSwitzerland
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7
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Krishnamurthy V, Paredes Spir I, Mammino KM, Nocera JR, McGregor KM, Crosson BA, Krishnamurthy LC. The Relationship Between Resting Cerebral Blood Flow, Neurometabolites, Cardio-Respiratory Fitness and Aging-Related Cognitive Decline. Front Psychiatry 2022; 13:923076. [PMID: 35757218 PMCID: PMC9218954 DOI: 10.3389/fpsyt.2022.923076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 05/18/2022] [Indexed: 01/06/2023] Open
Abstract
Older adults typically experience a decline in cognitive function, but improvements in physical health and lifestyle can be neuroprotective across the human lifespan. The primary objective of this study is to advance our basic understanding of how cardiorespiratory fitness and neurophysiological attributes relate to cognitive decline. While cerebral blood flow (CBF) is critical for the supply of nutrients to the tissue, the brain's major neurotransmitters (i.e., gamma-aminobutyric acid, GABA, and glutamate-glutamine complex, Glx) are closely linked to oxidative metabolism. Within the context of flow-metabolism coupling, the critical question is how these neurophysiological parameters interplay, resulting in cognitive decline. Further, how cardiorespiratory fitness may impact aging neurophysiology and cognition is not well understood. To address these questions, we recruited 10 younger and 12 older cognitively intact participants to collect GABA and Glx using magnetic resonance spectroscopy (MRS), CBF using pseudo-continuous arterial spin labeling Magnetic Resonance Imaging (MRI), VO2max as a measure of cardiorespiratory fitness using the YMCA submax test, and cognitive and motor-cognitive measures using a battery of behavioral assessments. We observed expected differences in GABA+, Glx, and CBF between younger and older participants in pre-SMA, a frontal domain-general region. When GABA+ and Glx were related to CBF via multiple linear regression, Glx was identified as the main contributor to the model. For higher-order executive function (i.e., inhibition versus color naming), GABA*Glx*CBF interaction was critical in younger, while only Glx was involved in older participants. For unimanual motor dexterity, GABA*Glx interaction was the common denominator across both groups, but younger participants' brain also engages CBF. In terms of selective motor inhibition, CBF from younger participants was the only major neurophysiological factor. In terms of fitness, cardiorespiratory fitness was significantly related to GABA, Glx, and motor performance when combining cohorts, but no group-specific relationships were observed. Taken together, our results indicate that Glx and CBF coupling decreases with aging, perhaps due to altered glial oxidative metabolism. Our data suggest that GABA, Glx, and CBF are engaged and weighted differently for different cognitive measures sensitized to aging, and higher fitness allows for a more efficient metabolic shift that facilitates improved performance on cognitive-motor tasks.
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Affiliation(s)
- Venkatagiri Krishnamurthy
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
- Department of Neurology, Emory University, Atlanta, GA, United States
- Division of Geriatrics and Gerontology, Department of Medicine, Emory University, Atlanta, GA, United States
| | - Isabella Paredes Spir
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
| | - Kevin M. Mammino
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
| | - Joe R. Nocera
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
- Department of Neurology, Emory University, Atlanta, GA, United States
- Department of Rehabilitation Medicine, Emory University, Atlanta, GA, United States
| | - Keith M. McGregor
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
- Department of Clinical and Diagnostic Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
- Birmingham/Atlanta VA GRECC, Birmingham, AL, United States
| | - Bruce A. Crosson
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
- Department of Neurology, Emory University, Atlanta, GA, United States
| | - Lisa C. Krishnamurthy
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, United States
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, United States
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States
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8
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Deelchand DK, Marjańska M, Henry PG, Terpstra M. MEGA-PRESS of GABA+: Influences of acquisition parameters. NMR IN BIOMEDICINE 2021; 34:e4199. [PMID: 31658398 PMCID: PMC7186154 DOI: 10.1002/nbm.4199] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/11/2019] [Accepted: 09/15/2019] [Indexed: 05/13/2023]
Abstract
γ-aminobutyric acid (GABA) was the first molecule that was edited with MEGA-PRESS. GABA edited spectroscopy is challenged by limited selectivity of editing pulses. Coediting of resonances from macromolecules (MM) is the greatest single limitation of GABA edited spectroscopy. In this contribution, relative signal contributions from GABA, MM and homocarnosine to the total MEGA-PRESS edited signal at ~3 ppm, i.e., GABA+, are simulated at 3 tesla using several acquisition schemes. The base scheme is modeled after those currently supplied by vendors: it uses typical pulse shapes and lengths, it minimizes the first echo time (TE), and the delay between the editing pulses is kept at TE/2. Edited spectra are simulated for imperfect acquisition parameters such as incorrect frequency, larger chemical shift displacement, incorrect transmit B1 -field calibration for localization and editing pulses, and longer TE. An alternative timing scheme and longer editing pulses are also considered. Additional simulations are performed for symmetric editing around the MM frequency to suppress the MM signal. The relative influences of these acquisition parameters on the constituents of GABA+ are examined from the perspective of modern experimental designs for investigating brain GABA concentration differences in healthy and diseased humans. Other factors that influence signal contributions, such as T1 and T2 relaxation times are also considered.
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Affiliation(s)
- Dinesh K Deelchand
- Center for Magnetic Resonance Research and Department of Radiology, University of, Minnesota, Minneapolis, MN, USA
| | - Małgorzata Marjańska
- Center for Magnetic Resonance Research and Department of Radiology, University of, Minnesota, Minneapolis, MN, USA
| | - Pierre-Gilles Henry
- Center for Magnetic Resonance Research and Department of Radiology, University of, Minnesota, Minneapolis, MN, USA
| | - Melissa Terpstra
- Center for Magnetic Resonance Research and Department of Radiology, University of, Minnesota, Minneapolis, MN, USA
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9
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Ho TC, Teresi GI, Segarra JR, Ojha A, Walker JC, Gu M, Spielman DM, Sacchet MD, Jiang F, Rosenberg-Hasson Y, Maecker H, Gotlib IH. Higher Levels of Pro-inflammatory Cytokines Are Associated With Higher Levels of Glutamate in the Anterior Cingulate Cortex in Depressed Adolescents. Front Psychiatry 2021; 12:642976. [PMID: 33935833 PMCID: PMC8081972 DOI: 10.3389/fpsyt.2021.642976] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 02/26/2021] [Indexed: 12/14/2022] Open
Abstract
Animal models of stress and related conditions, including depression, have shown that elevated peripheral levels of inflammatory cytokines have downstream consequences on glutamate (Glu) in the brain. Although studies in human adults with depression have reported evidence of higher inflammation but lower Glu in the anterior cingulate cortex (ACC), the extent to which peripheral inflammation contributes to glutamatergic abnormalities in adolescents with depression is not well-understood. It is also unclear whether antioxidants, such as ascorbate (Asc), may buffer against the effects of inflammation on Glu metabolism. Fifty-five depressed adolescents were recruited in the present cross-sectional study and provided blood samples, from which we assayed pro-inflammatory cytokines, and underwent a short-TE proton magnetic spectroscopy scan at 3T, from which we estimated Glu and Asc in the dorsal ACC. In the 31 adolescents with usable cytokine and Glu data, we found that IL-6 was significantly positively associated with dorsal ACC Glu (β = 0.466 ± 0.199, p = 0.029). Of the 16 participants who had usable Asc data, we found that at higher levels of dorsal ACC Asc, there was a negative association between IL-6 and Glu (interaction effect: β = -0.906 ± 0.433, p = 0.034). Importantly, these results remained significant when controlling for age, gender, percentage of gray matter in the dorsal ACC voxel, BMI, and medication (antidepressant and anti-inflammatory) usage. While preliminary, our results underscore the importance of examining both immune and neural contributors to depression and highlight the potential role of anti-inflammatory compounds in mitigating the adverse effects of inflammation (e.g., glutamatergic neuroexcitotoxicity). Future studies that experimentally manipulate levels of inflammation, and of ascorbate, and that characterize these effects on cortical glutamate concentrations and subsequent behavior in animals and in humans are needed.
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Affiliation(s)
- Tiffany C Ho
- Department of Psychiatry and Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
| | - Giana I Teresi
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Jillian R Segarra
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Amar Ojha
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
| | - Johanna C Walker
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Meng Gu
- Department of Radiology, Stanford University, Stanford, CA, United States
| | - Daniel M Spielman
- Department of Radiology, Stanford University, Stanford, CA, United States
| | - Matthew D Sacchet
- Center for Depression, Anxiety, and Stress Research, McLean Hospital and Harvard Medical School, Belmont, MA, United States
| | - Fei Jiang
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, United States
| | - Yael Rosenberg-Hasson
- Department of Microbiology and Immunology, Stanford University, Stanford, CA, United States
| | - Holden Maecker
- Department of Microbiology and Immunology, Stanford University, Stanford, CA, United States
| | - Ian H Gotlib
- Department of Psychology, Stanford University, Stanford, CA, United States
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10
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Thalamic and prefrontal GABA concentrations but not GABA A receptor densities are altered in high-functioning adults with autism spectrum disorder. Mol Psychiatry 2021; 26:1634-1646. [PMID: 32376999 PMCID: PMC7644591 DOI: 10.1038/s41380-020-0756-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 03/11/2020] [Accepted: 04/23/2020] [Indexed: 01/04/2023]
Abstract
The gamma aminobutyric acid (GABA) neurotransmission system has been implicated in autism spectrum disorder (ASD). Molecular neuroimaging studies incorporating simultaneous acquisitions of GABA concentrations and GABAA receptor densities can identify objective molecular markers in ASD. We measured both total GABAA receptor densities by using [18F]flumazenil positron emission tomography ([18F]FMZ-PET) and GABA concentrations by using proton magnetic resonance spectroscopy (1H-MRS) in 28 adults with ASD and 29 age-matched typically developing (TD) individuals. Focusing on the bilateral thalami and the left dorsolateral prefrontal cortex (DLPFC) as our regions of interest, we found no differences in GABAA receptor densities between ASD and TD groups. However, 1H-MRS measurements revealed significantly higher GABA/Water (GABA normalized by water signal) in the left DLPFC of individuals with ASD than that of TD controls. Furthermore, a significant gender effect was observed in the thalami, with higher GABA/Water in males than in females. Hypothesizing that thalamic GABA correlates with ASD symptom severity in gender-specific ways, we stratified by diagnosis and investigated the interaction between gender and thalamic GABA/Water in predicting Autism-Spectrum Quotient (AQ) and Ritvo Autism Asperger's Diagnostic Scale-Revised (RAADS-R) total scores. We found that gender is a significant effect modifier of thalamic GABA/Water's relationship with AQ and RAADS-R scores for individuals with ASD, but not for TD controls. When we separated the ASD participants by gender, a negative correlation between thalamic GABA/Water and AQ was observed in male ASD participants. Remarkably, in female ASD participants, a positive correlation between thalamic GABA/Water and AQ was found.
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11
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Walker JC, Teresi GI, Weisenburger RL, Segarra JR, Ojha A, Kulla A, Sisk L, Gu M, Spielman DM, Rosenberg-Hasson Y, Maecker HT, Singh MK, Gotlib IH, Ho TC. Study Protocol for Teen Inflammation Glutamate Emotion Research (TIGER). Front Hum Neurosci 2020; 14:585512. [PMID: 33192421 PMCID: PMC7604389 DOI: 10.3389/fnhum.2020.585512] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/03/2020] [Indexed: 12/19/2022] Open
Abstract
This article provides an overview of the study protocol for the Teen Inflammation Glutamate Emotion Research (TIGER) project, a longitudinal study in which we plan to recruit 60 depressed adolescents (ages 13–18 years) and 30 psychiatrically healthy controls in order to examine the inflammatory and glutamatergic pathways that contribute to the recurrence of depression in adolescents. TIGER is the first study to examine the effects of peripheral inflammation on neurodevelopmental trajectories by assessing changes in cortical glutamate in depressed adolescents. Here, we describe the scientific rationale, design, and methods for the TIGER project. This article is intended to serve as an introduction to this project and to provide details for investigators who may be seeking to replicate or extend these methods for other related research endeavors.
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Affiliation(s)
- Johanna C Walker
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Giana I Teresi
- Department of Psychology, Stanford University, Stanford, CA, United States
| | | | - Jillian R Segarra
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Amar Ojha
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
| | - Artenisa Kulla
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Lucinda Sisk
- Department of Psychology, Yale University, New Haven, CT, United States
| | - Meng Gu
- Department of Radiology, Stanford University, Stanford, CA, United States
| | - Daniel M Spielman
- Department of Radiology, Stanford University, Stanford, CA, United States.,Department of Electrical Engineering, Stanford University, Stanford, CA, United States
| | - Yael Rosenberg-Hasson
- Human Immune Monitoring Center, Stanford University, Stanford, CA, United States.,Department of Microbiology and Immunology, Stanford University, Stanford, CA, United States
| | - Holden T Maecker
- Human Immune Monitoring Center, Stanford University, Stanford, CA, United States.,Department of Microbiology and Immunology, Stanford University, Stanford, CA, United States
| | - Manpreet K Singh
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, United States
| | - Ian H Gotlib
- Department of Psychology, Stanford University, Stanford, CA, United States
| | - Tiffany C Ho
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States.,Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, San Francisco, CA, United States
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12
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Landheer K, Prinsen H, Petroff OA, Rothman DL, Juchem C. Elevated homocarnosine and GABA in subject on isoniazid as assessed through 1H MRS at 7T. Anal Biochem 2020; 599:113738. [PMID: 32302606 DOI: 10.1016/j.ab.2020.113738] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/09/2020] [Accepted: 04/11/2020] [Indexed: 12/27/2022]
Abstract
Typical magnetic resonance spectroscopy J-editing methods designed to quantify GABA suffer from contamination of both overlapping macromolecules and homocarnosine signal, introducing potential confounds. The aim of this study was to develop a novel method to assess accurately both the relative concentrations of homocarnosine as well as GABA free from overlapping creatine, homocarnosine and macromolecule signal. A novel method which utilized the combination of echo time STEAM and MEGA-sLASER magnetic resonance spectroscopy experiments at 7T were used to quantify the concentration of GABA and homocarnsoine independently, which are typically quantified in tandem. The metabolites GABA and homocarnosine were measured in brain of 6 healthy control subjects, and in a single subject medicated with isoniazid. It was found that (16.6±10.2)% of the supposed GABA signal in the brain originated from homocarnosine, and that isoniazid caused significantly elevated concentration of GABA and homocarnosine in a single subject compared to controls.
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Affiliation(s)
- Karl Landheer
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, NY, USA.
| | - Hetty Prinsen
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA
| | - Ognen A Petroff
- Department of Neurology, Yale University, New Haven, CT, USA
| | - Douglas L Rothman
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA
| | - Christoph Juchem
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, NY, USA; Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA; Department of Neurology, Yale University, New Haven, CT, USA; Department of Radiology, Columbia University College of Physicians and Surgeons, New York, NY, USA
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13
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Landheer K, Noeske R, Garwood M, Juchem C. UTE-SPECIAL for3D localization at an echo time of 4 ms on a clinical 3 T scanner. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 311:106670. [PMID: 31927513 PMCID: PMC7045707 DOI: 10.1016/j.jmr.2019.106670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 12/04/2019] [Accepted: 12/13/2019] [Indexed: 05/08/2023]
Abstract
Reducing the echo time of magnetic resonance spectroscopy experiments is appealing because it increases the available signal and reduces J-evolution of coupled metabolites. In this manuscript a novel sequence, referred to as Ultrashort echo TimE, SPin ECho, full Intensity Acquired Localized (UTE-SPECIAL), is described which is able to achieve ultrashort echo times (4 ms) on a standard clinical 3 T MR system while recovering the entirety of the available magnetization. UTE-SPECIAL obtains full 3D spatial localization through a 2D adiabatic inversion pulse which is cycled "on" and "off" every other repetition, in combination with a slice-selective excitation pulse. In addition to an ultrashort echo time, UTE-SPECIAL has negligible chemical shift displacement artefact and, because it uses no slice-selective refocusing pulse, has no signal cancellation at the borders for J-coupled metabolites. Spectra with an ultrashort echo time of 4 ms are demonstrated in vivo at 3 T, as well as J-resolved spectra obtained in a phantom and a healthy volunteer.
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Affiliation(s)
- Karl Landheer
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, NY, United States.
| | | | - Michael Garwood
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
| | - Christoph Juchem
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, NY, United States; Radiology, Columbia University College of Physicians and Surgeons, New York, NY, United States
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14
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Landheer K, Juchem C. Simultaneous optimization of crusher and phase cycling schemes for magnetic resonance spectroscopy: an extension of dephasing optimization through coherence order pathway selection. Magn Reson Med 2019; 83:391-402. [PMID: 31529647 DOI: 10.1002/mrm.27952] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 12/20/2022]
Abstract
PURPOSE To extend the dephasing optimization through coherence order pathway selection (DOTCOPS) algorithm, originally designed solely for gradient crusher schemes, to include tailored phase cycling schemes for arbitrary pulse sequences and arbitrary number of coupled spins. THEORY AND METHODS The effects all possible nested and cogwheel phase cycling schemes have on the coherence order pathways for an arbitrary experiment are considered. The DOTCOPS algorithm uses a cost function to maximally eliminate unwanted coherence pathways, with schemes preferentially eliminating unwanted coherence pathways that are less affected by the crusher scheme. Efficacy was demonstrated experimentally in 2 separate MR spectroscopy (MRS) sequences: semi-localized adiabatic selective refocusing (sLASER) and MEscher-GArwood sLASER both with phantom and in vivo experiments. RESULTS For all sequences investigated, cogwheel was found to theoretically outperform typical nested phase cycling schemes. The chosen cogwheel phase cycling schemes through DOTCOPS were found to outperform a typical 2-step phase cycling scheme in both phantom and in vivo experiments. Both crusher schemes and phase cycling schemes with 8, 16, or 32 steps are presented for 6 of the most common advanced MRS sequences. CONCLUSION The DOTCOPS algorithm has been extended to provide optimal crusher and phase cycling schemes considered in tandem. DOTCOPS can be applied to any pulse sequence of interest for any number of coupled spins. DOTCOPS is now able to alleviate the long-standing issue of designing effective crusher and phase cycling schemes for complex MRS modern sequences and, as a result, is expected to improve the data quality of virtually all applications.
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Affiliation(s)
- Karl Landheer
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, New York
| | - Christoph Juchem
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science, New York, New York.,Radiology, Columbia University College of Physicians and Surgeons, New York, New York
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15
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Landheer K, Schulte RF, Treacy MS, Swanberg KM, Juchem C. Theoretical description of modern1H in Vivo magnetic resonance spectroscopic pulse sequences. J Magn Reson Imaging 2019; 51:1008-1029. [DOI: 10.1002/jmri.26846] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/14/2019] [Accepted: 06/17/2019] [Indexed: 01/20/2023] Open
Affiliation(s)
- Karl Landheer
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science New York New York USA
| | | | - Michael S. Treacy
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science New York New York USA
| | - Kelley M. Swanberg
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science New York New York USA
| | - Christoph Juchem
- Biomedical Engineering, Columbia University Fu Foundation School of Engineering and Applied Science New York New York USA
- Radiology, Columbia University College of Physicians and Surgeons New York New York USA
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16
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Chan KL, Oeltzschner G, Saleh MG, Edden RAE, Barker PB. Simultaneous editing of GABA and GSH with Hadamard-encoded MR spectroscopic imaging. Magn Reson Med 2019; 82:21-32. [PMID: 30793803 DOI: 10.1002/mrm.27702] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 01/28/2019] [Accepted: 01/30/2019] [Indexed: 12/23/2022]
Abstract
PURPOSE To evaluate the feasibility of simultaneous MR spectroscopic imaging (MRSI) of gamma-aminobutyric acid (GABA) and glutathione (GSH) in the human brain using Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy (HERMES). METHODS Point RESolved Spectroscopy (PRESS)-localized MRSI was performed in GABA and GSH phantoms and in the human brain (n = 3) using HERMES editing and compared to conventional MEGA editing of each metabolite. Multiplet patterns, signal intensities, and metabolite crosstalk were compared between methods. GABA+ and GSH levels were compared between methods for bias and variability. Linear regression of HERMES-MRSI GABA+/H2 O and GSH/H2 O versus gray matter (GM) fraction were performed to assess differences between GM and white matter (WM). RESULTS Phantom HERMES-MRSI scans gave comparable GABA+ and GSH signals to MEGA-MRSI across the PRESS-localized volume. In vivo, HERMES-reconstructed GABA+ and GSH values had minimal measurement bias and variability relative to MEGA-MRSI. Intersubject coefficients of variation (CV) from two regions within the PRESS-localized volume for HERMES and MEGA were 6-12% for GABA+ and 6-19% for GSH. Interregion CVs were 5-15% for GABA+ and 3-17% for GSH. The GABA+/H2 O and GSH/H2 O ratios were ~1.8 times higher and ~1.9 times higher, respectively, in GM than in WM. CONCLUSION HERMES-MRSI of GABA+ and GSH was found to be practical in the human brain with minimal measurement bias and comparable variability to separate MEGA-edited acquisitions of each metabolite performed in double the scan time. The HERMES-MRSI is a promising method for simultaneously mapping the distribution of multiple low-concentration metabolites.
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Affiliation(s)
- Kimberly L Chan
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Georg Oeltzschner
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Muhammad G Saleh
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Richard A E Edden
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
| | - Peter B Barker
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
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