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    Interpretable surface-based detection of focal cortical dysplasias: a Multi-centre Epilepsy Lesion Detection study
    Spitzer, H ; Ripart, M ; Whitaker, K ; D'Arco, F ; Mankad, K ; Chen, AA ; Napolitano, A ; De Palma, L ; De Benedictis, A ; Foldes, S ; Humphreys, Z ; Zhang, K ; Hu, W ; Mo, J ; Likeman, M ; Davies, S ; Guttler, C ; Lenge, M ; Cohen, NT ; Tang, Y ; Wang, S ; Chari, A ; Tisdall, M ; Bargallo, N ; Conde-Blanco, E ; Pariente, JC ; Pascual-Diaz, S ; Delgado-Martinez, I ; Perez-Enriquez, C ; Lagorio, I ; Abela, E ; Mullatti, N ; O'Muircheartaigh, J ; Vecchiato, K ; Liu, Y ; Caligiuri, ME ; Sinclair, B ; Vivash, L ; Willard, A ; Kandasamy, J ; McLellan, A ; Sokol, D ; Semmelroch, M ; Kloster, AG ; Opheim, G ; Ribeiro, L ; Yasuda, C ; Rossi-Espagnet, C ; Hamandi, K ; Tietze, A ; Barba, C ; Guerrini, R ; Gaillard, WD ; You, X ; Wang, I ; Gonzalez-Ortiz, S ; Severino, M ; Striano, P ; Tortora, D ; Kalviainen, R ; Gambardella, A ; Labate, A ; Desmond, P ; Lui, E ; O'Brien, T ; Shetty, J ; Jackson, G ; Duncan, JS ; Winston, GP ; Pinborg, LH ; Cendes, F ; Theis, FJ ; Shinohara, RT ; Cross, JH ; Baldeweg, T ; Adler, S ; Wagstyl, K (OXFORD UNIV PRESS, 2022-11-21)
    One outstanding challenge for machine learning in diagnostic biomedical imaging is algorithm interpretability. A key application is the identification of subtle epileptogenic focal cortical dysplasias (FCDs) from structural MRI. FCDs are difficult to visualize on structural MRI but are often amenable to surgical resection. We aimed to develop an open-source, interpretable, surface-based machine-learning algorithm to automatically identify FCDs on heterogeneous structural MRI data from epilepsy surgery centres worldwide. The Multi-centre Epilepsy Lesion Detection (MELD) Project collated and harmonized a retrospective MRI cohort of 1015 participants, 618 patients with focal FCD-related epilepsy and 397 controls, from 22 epilepsy centres worldwide. We created a neural network for FCD detection based on 33 surface-based features. The network was trained and cross-validated on 50% of the total cohort and tested on the remaining 50% as well as on 2 independent test sites. Multidimensional feature analysis and integrated gradient saliencies were used to interrogate network performance. Our pipeline outputs individual patient reports, which identify the location of predicted lesions, alongside their imaging features and relative saliency to the classifier. On a restricted 'gold-standard' subcohort of seizure-free patients with FCD type IIB who had T1 and fluid-attenuated inversion recovery MRI data, the MELD FCD surface-based algorithm had a sensitivity of 85%. Across the entire withheld test cohort the sensitivity was 59% and specificity was 54%. After including a border zone around lesions, to account for uncertainty around the borders of manually delineated lesion masks, the sensitivity was 67%. This multicentre, multinational study with open access protocols and code has developed a robust and interpretable machine-learning algorithm for automated detection of focal cortical dysplasias, giving physicians greater confidence in the identification of subtle MRI lesions in individuals with epilepsy.
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    Structural network alterations in focal and generalized epilepsy assessed in a worldwide ENIGMA study follow axes of epilepsy risk gene expression
    Lariviere, S ; Royer, J ; Rodriguez-Cruces, R ; Paquola, C ; Caligiuri, ME ; Gambardella, A ; Concha, L ; Keller, SS ; Cendes, F ; Yasuda, CL ; Bonilha, L ; Gleichgerrcht, E ; Focke, NK ; Domin, M ; von Podewills, F ; Langner, S ; Rummel, C ; Wiest, R ; Martin, P ; Kotikalapudi, R ; O'Brien, TJ ; Sinclair, B ; Vivash, L ; Desmond, PM ; Lui, E ; Vaudano, AE ; Meletti, S ; Tondelli, M ; Alhusaini, S ; Doherty, CP ; Cavalleri, GL ; Delanty, N ; Kalviainen, R ; Jackson, GD ; Kowalczyk, M ; Mascalchi, M ; Semmelroch, M ; Thomas, RH ; Soltanian-Zadeh, H ; Davoodi-Bojd, E ; Zhang, J ; Winston, GP ; Griffin, A ; Singh, A ; Tiwari, VK ; Kreilkamp, BAK ; Lenge, M ; Guerrini, R ; Hamandi, K ; Foley, S ; Ruber, T ; Weber, B ; Depondt, C ; Absil, J ; Carr, SJA ; Abela, E ; Richardson, MP ; Devinsky, O ; Severino, M ; Striano, P ; Tortora, D ; Kaestner, E ; Hatton, SN ; Vos, SB ; Caciagli, L ; Duncan, JS ; Whelan, CD ; Thompson, PM ; Sisodiya, SM ; Bernasconi, A ; Labate, A ; McDonald, CR ; Bernasconi, N ; Bernhardt, BC (NATURE PORTFOLIO, 2022-07-27)
    Epilepsy is associated with genetic risk factors and cortico-subcortical network alterations, but associations between neurobiological mechanisms and macroscale connectomics remain unclear. This multisite ENIGMA-Epilepsy study examined whole-brain structural covariance networks in patients with epilepsy and related findings to postmortem epilepsy risk gene expression patterns. Brain network analysis included 578 adults with temporal lobe epilepsy (TLE), 288 adults with idiopathic generalized epilepsy (IGE), and 1328 healthy controls from 18 centres worldwide. Graph theoretical analysis of structural covariance networks revealed increased clustering and path length in orbitofrontal and temporal regions in TLE, suggesting a shift towards network regularization. Conversely, people with IGE showed decreased clustering and path length in fronto-temporo-parietal cortices, indicating a random network configuration. Syndrome-specific topological alterations reflected expression patterns of risk genes for hippocampal sclerosis in TLE and for generalized epilepsy in IGE. These imaging-transcriptomic signatures could potentially guide diagnosis or tailor therapeutic approaches to specific epilepsy syndromes.
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    Topographic divergence of atypical cortical asymmetry and atrophy patterns in temporal lobe epilepsy
    Park, B-Y ; Lariviere, S ; Rodriguez-Cruces, R ; Royer, J ; Tavakol, S ; Wang, Y ; Caciagli, L ; Caligiuri, ME ; Gambardella, A ; Concha, L ; Keller, SS ; Cendes, F ; Alvim, MKM ; Yasuda, C ; Bonilha, L ; Gleichgerrcht, E ; Focke, NK ; Kreilkamp, BAK ; Domin, M ; von Podewils, F ; Langner, S ; Rummel, C ; Rebsamen, M ; Wiest, R ; Martin, P ; Kotikalapudi, R ; Bender, B ; O'Brien, TJ ; Law, M ; Sinclair, B ; Vivash, L ; Kwan, P ; Desmond, PM ; Malpas, CB ; Lui, E ; Alhusaini, S ; Doherty, CP ; Cavalleri, GL ; Delanty, N ; Kalviainen, R ; Jackson, GD ; Kowalczyk, M ; Mascalchi, M ; Semmelroch, M ; Thomas, RH ; Soltanian-Zadeh, H ; Davoodi-Bojd, E ; Zhang, J ; Lenge, M ; Guerrini, R ; Bartolini, E ; Hamandi, K ; Foley, S ; Weber, B ; Depondt, C ; Absil, J ; Carr, SJA ; Abela, E ; Richardson, MP ; Devinsky, O ; Severino, M ; Striano, P ; Parodi, C ; Tortora, D ; Hatton, SN ; Vos, SB ; Duncan, JS ; Galovic, M ; Whelan, CD ; Bargallo, N ; Pariente, J ; Conde-Blanco, E ; Vaudano, AE ; Tondelli, M ; Meletti, S ; Kong, X-Z ; Francks, C ; Fisher, SE ; Caldairou, B ; Ryten, M ; Labate, A ; Sisodiya, SM ; Thompson, PM ; McDonald, CR ; Bernasconi, A ; Bernasconi, N ; Bernhardt, BC (OXFORD UNIV PRESS, 2022-03-25)
    Temporal lobe epilepsy, a common drug-resistant epilepsy in adults, is primarily a limbic network disorder associated with predominant unilateral hippocampal pathology. Structural MRI has provided an in vivo window into whole-brain grey matter structural alterations in temporal lobe epilepsy relative to controls, by either mapping (i) atypical inter-hemispheric asymmetry; or (ii) regional atrophy. However, similarities and differences of both atypical asymmetry and regional atrophy measures have not been systematically investigated. Here, we addressed this gap using the multisite ENIGMA-Epilepsy dataset comprising MRI brain morphological measures in 732 temporal lobe epilepsy patients and 1418 healthy controls. We compared spatial distributions of grey matter asymmetry and atrophy in temporal lobe epilepsy, contextualized their topographies relative to spatial gradients in cortical microstructure and functional connectivity calculated using 207 healthy controls obtained from Human Connectome Project and an independent dataset containing 23 temporal lobe epilepsy patients and 53 healthy controls and examined clinical associations using machine learning. We identified a marked divergence in the spatial distribution of atypical inter-hemispheric asymmetry and regional atrophy mapping. The former revealed a temporo-limbic disease signature while the latter showed diffuse and bilateral patterns. Our findings were robust across individual sites and patients. Cortical atrophy was significantly correlated with disease duration and age at seizure onset, while degrees of asymmetry did not show a significant relationship to these clinical variables. Our findings highlight that the mapping of atypical inter-hemispheric asymmetry and regional atrophy tap into two complementary aspects of temporal lobe epilepsy-related pathology, with the former revealing primary substrates in ipsilateral limbic circuits and the latter capturing bilateral disease effects. These findings refine our notion of the neuropathology of temporal lobe epilepsy and may inform future discovery and validation of complementary MRI biomarkers in temporal lobe epilepsy.
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    Atlas of lesion locations and postsurgical seizure freedom in focal cortical dysplasia: A MELD study
    Wagstyl, K ; Whitaker, K ; Raznahan, A ; Seidlitz, J ; Vertes, PE ; Foldes, S ; Humphreys, Z ; Hu, W ; Mo, J ; Likeman, M ; Davies, S ; Lenge, M ; Cohen, NT ; Tang, Y ; Wang, S ; Ripart, M ; Chari, A ; Tisdall, M ; Bargallo, N ; Conde-Blanco, E ; Carlos Pariente, J ; Pascual-Diaz, S ; Delgado-Martinez, I ; Perez-Enriquez, C ; Lagorio, I ; Abela, E ; Mullatti, N ; O'Muircheartaigh, J ; Vecchiato, K ; Liu, Y ; Caligiuri, M ; Sinclair, B ; Vivash, L ; Willard, A ; Kandasamy, J ; McLellan, A ; Sokol, D ; Semmelroch, M ; Kloster, A ; Opheim, G ; Yasuda, C ; Zhang, K ; Hamandi, K ; Barba, C ; Guerrini, R ; Gaillard, WD ; You, X ; Wang, I ; Gonzalez-Ortiz, S ; Severino, M ; Striano, P ; Tortora, D ; Kalviainen, R ; Gambardella, A ; Labate, A ; Desmond, P ; Lui, E ; O'Brien, T ; Shetty, J ; Jackson, G ; Duncan, JS ; Winston, GP ; Pinborg, L ; Cendes, F ; Cross, JH ; Baldeweg, T ; Adler, S (WILEY, 2022-01)
    OBJECTIVE: Drug-resistant focal epilepsy is often caused by focal cortical dysplasias (FCDs). The distribution of these lesions across the cerebral cortex and the impact of lesion location on clinical presentation and surgical outcome are largely unknown. We created a neuroimaging cohort of patients with individually mapped FCDs to determine factors associated with lesion location and predictors of postsurgical outcome. METHODS: The MELD (Multi-centre Epilepsy Lesion Detection) project collated a retrospective cohort of 580 patients with epilepsy attributed to FCD from 20 epilepsy centers worldwide. Magnetic resonance imaging-based maps of individual FCDs with accompanying demographic, clinical, and surgical information were collected. We mapped the distribution of FCDs, examined for associations between clinical factors and lesion location, and developed a predictive model of postsurgical seizure freedom. RESULTS: FCDs were nonuniformly distributed, concentrating in the superior frontal sulcus, frontal pole, and temporal pole. Epilepsy onset was typically before the age of 10 years. Earlier epilepsy onset was associated with lesions in primary sensory areas, whereas later epilepsy onset was associated with lesions in association cortices. Lesions in temporal and occipital lobes tended to be larger than frontal lobe lesions. Seizure freedom rates varied with FCD location, from around 30% in visual, motor, and premotor areas to 75% in superior temporal and frontal gyri. The predictive model of postsurgical seizure freedom had a positive predictive value of 70% and negative predictive value of 61%. SIGNIFICANCE: FCD location is an important determinant of its size, the age at epilepsy onset, and the likelihood of seizure freedom postsurgery. Our atlas of lesion locations can be used to guide the radiological search for subtle lesions in individual patients. Our atlas of regional seizure freedom rates and associated predictive model can be used to estimate individual likelihoods of postsurgical seizure freedom. Data-driven atlases and predictive models are essential for evidence-based, precision medicine and risk counseling in epilepsy.
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    Assessment of the DTI-ALPS Parameter Along the Perivascular Space in Older Adults at Risk of Dementia
    Steward, CE ; Venkatraman, VK ; Lui, E ; Malpas, CB ; Ellis, KA ; Cyarto, EV ; Vivash, L ; O'Brien, TJ ; Velakoulis, D ; Ames, D ; Masters, CL ; Lautenschlager, NT ; Bammer, R ; Desmond, PM (WILEY, 2021-05)
    BACKGROUND AND PURPOSE: Recently, there has been growing interest in the glymphatic system (the functional waste clearance pathway for the central nervous system and its role in flushing solutes (such as amyloid ß and tau), metabolic, and other cellular waste products in the brain. Herein, we investigate a recent potential biomarker for glymphatic activity (the diffusion tensor imaging along the perivascular space [DTI-ALPS] parameter) using diffusion MRI imaging in an elderly cohort comprising 10 cognitively normal, 10 mild cognitive impairment (MCI), and 16 Alzheimer's disease (AD). METHODS: All 36 participants imaged on a Siemens 3.0T Tim Trio. Single-SE diffusion weighted Echo-planar imaging scans were acquired as well as T1 magnetization prepared rapid gradient echo, T2 axial, and susceptibility weighted imaging. Three millimeter regions of interest were drawn in the projection and association fibers adjacent to the medullary veins at the level of the lateral ventricle. The DTI-ALPS parameter was calculated in these regions and correlated with cognitive status, Mini-Mental State Examination (MMSE), and ADASCog11 measures. RESULTS: Significant correlations were found between DTI-ALPS and MMSE and ADASCog11 in the right hemisphere adjusting for age, sex, and APoE ε4 status. Significant differences were also found in the right DTI-ALPS indices between cognitively normal and AD groups (P < .026) and MCI groups (P < .025) in a univariate general linear model corrected for age, sex, and APoE ε4. Significant differences in apparent diffusion coefficient between cognitively normal and AD groups were found in the right projection fibers (P = .028). CONCLUSION: Further work is needed to determine the utility of DTI-ALPS index in larger elderly cohorts and whether it measures glymphatic activity.
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    Artificial intelligence for classification of temporal lobe epilepsy with ROI-level MRI data: A worldwide ENIGMA-Epilepsy study
    Gleichgerrcht, E ; Munsell, BC ; Alhusaini, S ; Alvim, MKM ; Bargallo, N ; Bender, B ; Bernasconi, A ; Bernasconi, N ; Bernhardt, B ; Blackmon, K ; Caligiuri, ME ; Cendes, F ; Concha, L ; Desmond, PM ; Devinsky, O ; Doherty, CP ; Domin, M ; Duncan, JS ; Focke, NK ; Gambardella, A ; Gong, B ; Guerrini, R ; Hatton, SN ; Kalviainen, R ; Keller, SS ; Kochunov, P ; Kotikalapudi, R ; Kreilkamp, BAK ; Labate, A ; Langner, S ; Lariviere, S ; Lenge, M ; Lui, E ; Martin, P ; Mascalchi, M ; Meletti, S ; O'Brien, TJ ; Pardoe, HR ; Pariente, JC ; Rao, JX ; Richardson, MP ; Rodriguez-Cruces, R ; Ruber, T ; Sinclair, B ; Soltanian-Zadeh, H ; Stein, DJ ; Striano, P ; Taylor, PN ; Thomas, RH ; Vaudano, AE ; Vivash, L ; von Podewills, F ; Vos, SB ; Weber, B ; Yao, Y ; Yasuda, CL ; Zhang, J ; Thompson, PM ; Sisodiya, SM ; McDonald, CR ; Bonilha, L (ELSEVIER SCI LTD, 2021)
    Artificial intelligence has recently gained popularity across different medical fields to aid in the detection of diseases based on pathology samples or medical imaging findings. Brain magnetic resonance imaging (MRI) is a key assessment tool for patients with temporal lobe epilepsy (TLE). The role of machine learning and artificial intelligence to increase detection of brain abnormalities in TLE remains inconclusive. We used support vector machine (SV) and deep learning (DL) models based on region of interest (ROI-based) structural (n = 336) and diffusion (n = 863) brain MRI data from patients with TLE with ("lesional") and without ("non-lesional") radiographic features suggestive of underlying hippocampal sclerosis from the multinational (multi-center) ENIGMA-Epilepsy consortium. Our data showed that models to identify TLE performed better or similar (68-75%) compared to models to lateralize the side of TLE (56-73%, except structural-based) based on diffusion data with the opposite pattern seen for structural data (67-75% to diagnose vs. 83% to lateralize). In other aspects, structural and diffusion-based models showed similar classification accuracies. Our classification models for patients with hippocampal sclerosis were more accurate (68-76%) than models that stratified non-lesional patients (53-62%). Overall, SV and DL models performed similarly with several instances in which SV mildly outperformed DL. We discuss the relative performance of these models with ROI-level data and the implications for future applications of machine learning and artificial intelligence in epilepsy care.
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    7T Magnetic Resonance Imaging Quantification of Brain Glutamate in Acute Ischaemic Stroke
    Nicolo, J-P ; Moffat, B ; Wright, DK ; Sinclair, B ; Neal, A ; Lui, E ; Desmond, P ; Glarin, R ; Davis, KA ; Reddy, R ; Yan, B ; O'Brien, TJ ; Kwan, P (Korean Stroke Society, 2021-05-01)
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    Seven-tesla quantitative magnetic resonance spectroscopy of glutamate, γ-aminobutyric acid, and glutathione in the posterior cingulate cortex/precuneus in patients with epilepsy
    Gonen, OM ; Moffat, BA ; Desmond, PM ; Lui, E ; Kwan, P ; O'Brien, TJ (WILEY, 2020-12)
    OBJECTIVE: The posterior cingulate cortex (PCC)/precuneus is a key hub of the default mode network, whose function is known to be altered in epilepsy. Glutamate and γ-aminobutyric acid (GABA) are the main excitatory and inhibitory neurotransmitters in the central nervous system, respectively. Glutathione (GSH) is the most important free radical scavenging compound in the brain. Quantification of these molecules by magnetic resonance spectroscopy (MRS) up to 4 T is limited by overlapping resonances from other molecules. In this study, we used ultra-high-field (7 T) MRS to quantify their concentrations in patients with different epilepsy syndromes. METHODS: Nineteen patients with temporal lobe epilepsy (TLE) and 16 with idiopathic generalized epilepsy (IGE) underwent magnetic resonance imaging scans using a 7-T research scanner. Single-voxel (8 cm3 ) MRS, located in the PCC/precuneus, was acquired via stimulated echo acquisition mode. Their results were compared to 10 healthy volunteers. RESULTS: Mean concentrations of glutamate, GABA, and the glutamate/GABA ratio did not differ between the IGE, TLE, and healthy volunteer groups. The mean ± SD concentration of GSH was 1.9 ± 0.3 mmol·L-1 in healthy controls, 2.0 ± 0.2 mmol·L-1 in patients with TLE, and 2.2 ± 0.4 mmol·L-1 in patients with IGE. One-way analysis of variance with post hoc Tukey-Kramer test revealed a significant difference in the concentration of GSH between patients with IGE and controls (P = .03). Short-term seizure freedom in patients with epilepsy was predicted by an elevated concentration of glutamate in the PCC/precuneus (P = .01). In patients with TLE, the concentration of GABA declined with age (P = .03). SIGNIFICANCE: Patients with IGE have higher concentrations of GSH in the PCC/precuneus than healthy controls. There is no difference in the concentrations of glutamate and GABA, or their ratio, in the PCC/precuneus between patients with IGE, patients with TLE, and healthy controls. Measuring the concentration of glutamate in the PCC/precuneus may assist with predicting drug response.
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    Resting-state functional connectivity and quantitation of glutamate and GABA of the PCC/precuneus by magnetic resonance spectroscopy at 7T in healthy individuals
    Gonen, OM ; Moffat, BA ; Kwan, P ; O'Brien, TJ ; Desmond, PM ; Lui, E ; Stamatakis, EA (PUBLIC LIBRARY SCIENCE, 2020-12-29)
    The default mode network (DMN) is the main large-scale network of the resting brain and the PCC/precuneus is a major hub of this network. Glutamate and GABA (γ-amino butyric acid) are the main excitatory and inhibitory neurotransmitters in the CNS, respectively. We studied glutamate and GABA concentrations in the PCC/precuneus via magnetic resonance spectroscopy (MRS) at 7T in relation to age and correlated them with functional connectivity between this region and other DMN nodes in ten healthy right-handed volunteers ranging in age between 23-68 years. Mean functional connectivity of the PCC/precuneus to the other DMN nodes and the glutamate/GABA ratio significantly correlated with age (r = 0.802, p = 0.005 and r = 0.793, p = 0.006, respectively) but not with each other. Glutamate and GABA alone did not significantly correlate with age nor with functional connectivity within the DMN. The glutamate/GABA ratio and functional connectivity of the PCC/precuneus are, therefore, independent age-related biomarkers of the DMN and may be combined in a multimodal pipeline to study DMN alterations in various disease states.
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    Reproducibility of Glutamate, Glutathione, and GABA Measurementsin vivoby Single-Voxel STEAM Magnetic Resonance Spectroscopy at 7-Tesla in Healthy Individuals
    Gonen, OM ; Moffat, BA ; Kwan, P ; O'Brien, TJ ; Desmond, PM ; Lui, E (FRONTIERS MEDIA SA, 2020-09-15)
    BACKGROUND AND PURPOSE: Derangements in brain glutamate, glutathione, and γ-amino butyric acid (GABA) are implicated in a range of neurological disorders. Reliable methods to measure these compounds non-invasively in vivo are needed. We evaluated the reproducibility of their measurements in brain regions involved in the default mode network using quantitative MRS at 7-Tesla in healthy individuals. METHODS: Ten right-handed healthy volunteers underwent 7-Tesla MRI scans on 2 separate days, not more than 2 weeks apart. On each day two scanning sessions took place, with a re-positioning break in between. High-resolution isotropic anatomical scans were acquired prior to each scan, followed by single-voxel 1H-MRS using the STEAM pulse sequence on an 8 mL midline cubic voxel, positioned over the posterior cingulate and precuneus regions. Concentrations were corrected for partial-volume effects. RESULTS: Maximal Cramér-Rao lower bounds for glutamate, glutathione, and GABA were 2.0, 8.0, and 14.0%, respectively. Mean coefficients of variation within sessions were 5.9 ± 4.8%, 9.3 ± 7.6%, and 11.5 ± 8.8%, and between sessions were 4.6 ± 4.5%, 8.3 ± 5.7%, and 9.2 ± 8.7%, respectively. The mean (±SD) Dice's coefficient for voxel overlap was 90 ± 4% within sessions and 86 ± 7% between sessions. CONCLUSION: Glutamate, glutathione, and GABA can be reliably quantified using STEAM MRS at 7-Tesla from the posterior cingulate and precuneus cortices of healthy human subjects. STEAM MRS at 7-Tesla may be used to study the metabolic behavior of this important resting-state hub in various disease states.