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Lurie DJ, Pappas I, D'Esposito M. Cortical timescales and the modular organization of structural and functional brain networks. Hum Brain Mapp 2024; 45:e26587. [PMID: 38339903 PMCID: PMC10823764 DOI: 10.1002/hbm.26587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 12/01/2023] [Accepted: 12/21/2023] [Indexed: 02/12/2024] Open
Abstract
Recent years have seen growing interest in characterizing the properties of regional brain dynamics and their relationship to other features of brain structure and function. In particular, multiple studies have observed regional differences in the "timescale" over which activity fluctuates during periods of quiet rest. In the cerebral cortex, these timescales have been associated with both local circuit properties as well as patterns of inter-regional connectivity, including the extent to which each region exhibits widespread connectivity to other brain areas. In the current study, we build on prior observations of an association between connectivity and dynamics in the cerebral cortex by investigating the relationship between BOLD fMRI timescales and the modular organization of structural and functional brain networks. We characterize network community structure across multiple scales and find that longer timescales are associated with greater within-community functional connectivity and diverse structural connectivity. We also replicate prior observations of a positive correlation between timescales and structural connectivity degree. Finally, we find evidence for preferential functional connectivity between cortical areas with similar timescales. We replicate these findings in an independent dataset. These results contribute to our understanding of functional brain organization and structure-function relationships in the human brain, and support the notion that regional differences in cortical dynamics may in part reflect the topological role of each region within macroscale brain networks.
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Affiliation(s)
- Daniel J. Lurie
- Department of PsychologyUniversity of CaliforniaBerkeleyCaliforniaUSA
- Department of Biomedical Informatics University of Pittsburgh School of Medicine PittsburghPennsylvaniaUSA
| | - Ioannis Pappas
- Department of Neurology, Keck School of MedicineUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | - Mark D'Esposito
- Department of Psychology and Helen Wills Neuroscience InstituteUniversity of CaliforniaBerkeleyCaliforniaUSA
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2
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Lurie DJ, Pappas I, D'Esposito M. Cortical timescales and the modular organization of structural and functional brain networks. bioRxiv 2023:2023.07.12.548751. [PMID: 37502887 PMCID: PMC10370009 DOI: 10.1101/2023.07.12.548751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Recent years have seen growing interest in characterizing the properties of regional brain dynamics and their relationship to other features of brain structure and function. In particular, multiple studies have observed regional differences in the "timescale" over which activity fluctuates during periods of quiet rest. In the cerebral cortex, these timescales have been associated with both local circuit properties as well as patterns of inter-regional connectivity, including the extent to which each region exhibits widespread connectivity to other brain areas. In the current study, we build on prior observations of an association between connectivity and dynamics in the cerebral cortex by investigating the relationship between BOLD fMRI timescales and the modular organization of structural and functional brain networks. We characterize network community structure across multiple scales and find that longer timescales are associated with greater within-community functional connectivity and diverse structural connectivity. We also replicate prior observations of a positive correlation between timescales and structural connectivity degree. Finally, we find evidence for preferential functional connectivity between cortical areas with similar timescales. We replicate these findings in an independent dataset. These results contribute to our understanding of functional brain organization and structure-function relationships in the human brain, and support the notion that regional differences in cortical dynamics may in part reflect the topological role of each region within macroscale brain networks.
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Affiliation(s)
- Daniel J Lurie
- Department of Psychology, University of California, Berkeley
| | - Ioannis Pappas
- Department of Neurology, Keck School of Medicine, University of Southern California
| | - Mark D'Esposito
- Department of Psychology and Helen Wills Neuroscience Institute, University of California, Berkeley
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3
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Lurie DJ, Kessler D, Bassett DS, Betzel RF, Breakspear M, Kheilholz S, Kucyi A, Liégeois R, Lindquist MA, McIntosh AR, Poldrack RA, Shine JM, Thompson WH, Bielczyk NZ, Douw L, Kraft D, Miller RL, Muthuraman M, Pasquini L, Razi A, Vidaurre D, Xie H, Calhoun VD. Questions and controversies in the study of time-varying functional connectivity in resting fMRI. Netw Neurosci 2020; 4:30-69. [PMID: 32043043 PMCID: PMC7006871 DOI: 10.1162/netn_a_00116] [Citation(s) in RCA: 247] [Impact Index Per Article: 61.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 11/22/2019] [Indexed: 12/12/2022] Open
Abstract
The brain is a complex, multiscale dynamical system composed of many interacting regions. Knowledge of the spatiotemporal organization of these interactions is critical for establishing a solid understanding of the brain's functional architecture and the relationship between neural dynamics and cognition in health and disease. The possibility of studying these dynamics through careful analysis of neuroimaging data has catalyzed substantial interest in methods that estimate time-resolved fluctuations in functional connectivity (often referred to as "dynamic" or time-varying functional connectivity; TVFC). At the same time, debates have emerged regarding the application of TVFC analyses to resting fMRI data, and about the statistical validity, physiological origins, and cognitive and behavioral relevance of resting TVFC. These and other unresolved issues complicate interpretation of resting TVFC findings and limit the insights that can be gained from this promising new research area. This article brings together scientists with a variety of perspectives on resting TVFC to review the current literature in light of these issues. We introduce core concepts, define key terms, summarize controversies and open questions, and present a forward-looking perspective on how resting TVFC analyses can be rigorously and productively applied to investigate a wide range of questions in cognitive and systems neuroscience.
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Affiliation(s)
- Daniel J. Lurie
- Department of Psychology, University of California, Berkeley, Berkeley, CA, USA
| | - Daniel Kessler
- Departments of Statistics and Psychiatry, University of Michigan, Ann Arbor, MI, USA
| | - Danielle S. Bassett
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, PA, USA
- Department of Physics & Astronomy, College of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Electrical & Systems Engineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Richard F. Betzel
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Michael Breakspear
- University of Newcastle, Callaghan, NSW, 2308, Australia
- QIMR Berghofer, Brisbane, Australia
| | - Shella Kheilholz
- Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Aaron Kucyi
- Department of Neurology and Neurological Sciences, Stanford University, Stanford CA, USA
| | - Raphaël Liégeois
- Institute of Bioengineering, Center for Neuroprosthetics, Ecole Polytechnique Fédérale de Lausanne, Switzerland
- Department of Radiology and Medical Informatics, University of Geneva, Switzerland
| | | | - Anthony Randal McIntosh
- Rotman Research Institute - Baycrest Centre, Toronto, Canada
- Department of Psychology, University of Toronto, Toronto, Canada
| | | | - James M. Shine
- Brain and Mind Centre, University of Sydney, NSW, Australia
| | - William Hedley Thompson
- Department of Psychology, Stanford University, Stanford, CA, USA
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | | | - Linda Douw
- Department of Anatomy and Neurosciences, VU University Medical Center, Amsterdam, The Netherlands
| | - Dominik Kraft
- Department of Psychology, Goethe University Frankfurt, Frankfurt am Main, Germany
| | | | - Muthuraman Muthuraman
- Biomedical Statistics and Multimodal Signal Processing Unit, Movement Disorders and Neurostimulation, Department of Neurology, Focus Program Translational Neuroscience, Johannes-Gutenberg-University Hospital, Mainz, Germany
| | - Lorenzo Pasquini
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, CA, USA
| | - Adeel Razi
- Monash Institute of Cognitive and Clinical Neurosciences and Monash Biomedical Imaging, Monash University, Clayton, Australia
- Wellcome Centre for Human Neuroimaging, Institute of Neurology, University College London, London, United Kingdom
- Department of Electronic Engineering, NED University of Engineering and Technology, Karachi, Pakistan
| | - Diego Vidaurre
- Wellcome Trust Centre for Integrative Neuroimaging, Oxford Centre for Human Brain Activity, University of Oxford, United Kingdom
| | - Hua Xie
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - Vince D. Calhoun
- The Mind Research Network, Albuquerque, NM, USA
- Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM, USA
- Tri-institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS), Georgia State, Georgia Tech, Emory, Atlanta, Georgia, USA
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Reid AT, Headley DB, Mill RD, Sanchez-Romero R, Uddin LQ, Marinazzo D, Lurie DJ, Valdés-Sosa PA, Hanson SJ, Biswal BB, Calhoun V, Poldrack RA, Cole MW. Advancing functional connectivity research from association to causation. Nat Neurosci 2019; 22:1751-1760. [PMID: 31611705 PMCID: PMC7289187 DOI: 10.1038/s41593-019-0510-4] [Citation(s) in RCA: 142] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 09/06/2019] [Indexed: 11/09/2022]
Abstract
Cognition and behavior emerge from brain network interactions, such that investigating causal interactions should be central to the study of brain function. Approaches that characterize statistical associations among neural time series-functional connectivity (FC) methods-are likely a good starting point for estimating brain network interactions. Yet only a subset of FC methods ('effective connectivity') is explicitly designed to infer causal interactions from statistical associations. Here we incorporate best practices from diverse areas of FC research to illustrate how FC methods can be refined to improve inferences about neural mechanisms, with properties of causal neural interactions as a common ontology to facilitate cumulative progress across FC approaches. We further demonstrate how the most common FC measures (correlation and coherence) reduce the set of likely causal models, facilitating causal inferences despite major limitations. Alternative FC measures are suggested to immediately start improving causal inferences beyond these common FC measures.
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Affiliation(s)
- Andrew T Reid
- School of Psychology, University of Nottingham, Nottingham, UK
| | - Drew B Headley
- Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ, USA
| | - Ravi D Mill
- Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ, USA
| | - Ruben Sanchez-Romero
- Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ, USA
| | - Lucina Q Uddin
- Department of Psychology, University of Miami, Coral Gables, FL, USA
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL, USA
| | | | - Daniel J Lurie
- Department of Psychology, University of California, Berkeley, Berkeley, CA, USA
| | - Pedro A Valdés-Sosa
- The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China, Chengdu, China
- Cuban Neuroscience Center, La Habana, Cuba
| | | | - Bharat B Biswal
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
| | - Vince Calhoun
- Tri-institutional Center for Translational Research in Neuroimaging and Data Science (TReNDS) [Georgia State University, Georgia Institute of Technology, Emory University], Atlanta, GA, USA
| | | | - Michael W Cole
- Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ, USA.
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5
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Abbas H, Broche LM, Ezdoglian A, Li D, Yuecel R, Ross PJ, Lurie DJ, Wilson HM, Dawson DK. 4324Fast-field cycling magnetic resonance detection of intracellular iron in the nanomolar range - A pre-requisite for in-vivo study of inflammation. Eur Heart J 2019. [DOI: 10.1093/eurheartj/ehz745.0161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Background
Ultra-small superparamagnetic iron oxide (USPIO) nanoparticles are phagocytosed by macrophages and when subjected to magnetic resonance imaging (MRI) detect inflammation. We describe a novel MR technique where the magnetic field is rapidly cycled (Fast field-cycling MR, FFC-MR), assessing T1 dispersion over a range of low (100μT-0.2T) fields and offering superior T1-based iron quantification.
AIM
To quantify iron using the FFC-MR R1 (1/T1) dispersion profile and flow cytometry features of USPIO-laden cells, in comparison to colorimetric assays.
Methods
Murine J774 macrophage-like cells were incubated with 0–200μg/ml Fe as USPIO (ferumoxytol) for 16 hours, washed and suspended in 500μl PBS/2mM EDTA. Prussian blue staining confirmed USPIO phagocytosis. Relaxation was measured using a clinical, in-house built prototype 0.2T FFC-MR system with a custom test tube coil. R1 dispersion was derived from a saturation recovery sequence (Fig. 1A). R1 (s–1) values were calculated with a monoexponential curve fitting algorithm, R2 of fits were ≥0.999. R1 dispersion profiles were generated plotting R1 against the magnetic field (T). Quantification of side scatter (SCC) intensity and the USPIO-occupied fraction of total cell area was performed with imaging flow cytometry. A colorimetric assay provided validation of cell iron content. All data are mean±SEM, analysed with t-tests, Pearson correlation and linear regression; statistical significance set at p<0.05.
Results
Table 1 shows quantitative data derived by all 3 modalities with increasing USPIO exposure. FFC-MR detection of intracellular iron was excellent (p≤0.001 vs. control for all), with separation of average R1 dispersion profiles (Fig. 1B), strong correlation with colorimetry (r=0.993 p<0.001) and good fit on linear regression model (R2=0.9222, Fig 1C). Flow cytometry quantification of SCC was comparable (p≤0.001 for all), whereas USPIO-occupied area was only sensitive at exposures ≥10μg/ml USPIO (r=0.967 p<0.001 & r=0.983 p<0.001 vs. colorimetric respectively). FFC-MR detected iron at ≥1.12ng/μg protein.
USPIO exposure (μg/ml medium) 0 5 10 40 80 100 200 FFC-MR Mean R1 1x106 cell suspension (s–1) 0.308±0.014 0.356±0.013** 0.432±0.016** 0.706±0.021** 1.174±0.031** 1.239±0.033** 1.599±0.041** Flow cytometry USPIO area/cell area 0.034±0.001 0.036±0.001 0.037±0.001* 0.069±0.001** 0.085±0.001** 0.090±0.001** 0.097±0.001** Flow cytometry SSC intensity 26860 32815** 39573** 69285** 80967** 82693** 86373** Colorimetric assay Iron concentration 1x106 cells (ng/μg protein) 0.115±0.118 1.121±0.045** 2.074±0.084** 5.496±0.134** 8.421±0.269** 9.771±0.100** 12.398±0.233** SSC = side-scattered light; *p<0.05 vs. control; **p<0.001 vs. control.
Conclusion
Field-cycling MR is capable of highly accurate intracellular USPIO quantification, which has potential to non-invasively detect clinically relevant amounts of iron in inflammatory cardiovascular diseases.
Acknowledgement/Funding
NHS Grampian Endowment Fund
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Affiliation(s)
- H Abbas
- University of Aberdeen, Aberdeen Cardiovascular and Diabetes Centre, Aberdeen, United Kingdom
| | - L M Broche
- University of Aberdeen, Dept. of Bio-medical Physical, Aberdeen, United Kingdom
| | - A Ezdoglian
- University of Aberdeen, Iain Fraser Cytometry Centre, Institute of Medical Sciences, Aberdeen, United Kingdom
| | - D Li
- University of Aberdeen, Iain Fraser Cytometry Centre, Institute of Medical Sciences, Aberdeen, United Kingdom
| | - R Yuecel
- University of Aberdeen, Iain Fraser Cytometry Centre, Institute of Medical Sciences, Aberdeen, United Kingdom
| | - P J Ross
- University of Aberdeen, Dept. of Bio-medical Physical, Aberdeen, United Kingdom
| | - D J Lurie
- University of Aberdeen, Dept. of Bio-medical Physical, Aberdeen, United Kingdom
| | - H M Wilson
- University of Aberdeen, Aberdeen Cardiovascular and Diabetes Centre, Aberdeen, United Kingdom
| | - D K Dawson
- University of Aberdeen, Aberdeen Cardiovascular and Diabetes Centre, Aberdeen, United Kingdom
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6
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Yoncheva YN, Hardy KK, Lurie DJ, Somandepalli K, Yang L, Vezina G, Kadom N, Packer RJ, Milham MP, Castellanos FX, Acosta MT. Computerized cognitive training for children with neurofibromatosis type 1: A pilot resting-state fMRI study. Psychiatry Res 2017; 266:53-58. [PMID: 28605662 PMCID: PMC5582983 DOI: 10.1016/j.pscychresns.2017.06.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 06/02/2017] [Accepted: 06/03/2017] [Indexed: 12/19/2022]
Abstract
In this pilot study, we examined training effects of a computerized working memory program on resting state functional magnetic resonance imaging (fMRI) measures in children with neurofibromatosis type 1 (NF1). We contrasted pre- with post-training resting state fMRI and cognitive measures from 16 participants (nine males; 11.1 ± 2.3 years) with NF1 and documented working memory difficulties. Using non-parametric permutation test inference, we found significant regionally specific differences (family-wise error corrected) in two of four voxel-wise resting state measures: fractional amplitude of low frequency fluctuations (indexing peak-to-trough intensity of spontaneous oscillations) and regional homogeneity (indexing local intrinsic synchrony). Some cognitive task improvement was observed as well. These preliminary findings suggest that regionally specific changes in resting state fMRI indices may be associated with treatment-related cognitive amelioration in NF1. Nevertheless, current results must be interpreted with caution pending independent controlled replication.
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Affiliation(s)
- Yuliya N Yoncheva
- Department of Child and Adolescent Psychiatry, NYU Langone Medical Center, New York, NY, USA
| | - Kristina K Hardy
- Department of Pediatrics and Neurology, George Washington University, School of Medicine, Washington, DC, USA; Children's National Health System, Washington, DC, USA
| | - Daniel J Lurie
- Department of Psychology, University of California, Berkeley, Berkeley, CA, USA
| | | | - Lanbo Yang
- Department of Child and Adolescent Psychiatry, NYU Langone Medical Center, New York, NY, USA
| | - Gilbert Vezina
- Children's National Health System, Washington, DC, USA; Department of Diagnostic Imaging and Radiology, Children's National Health System, Washington, DC, USA
| | - Nadja Kadom
- Department of Radiology and Imaging Sciences, Children's Healthcare of Atlanta (Egleston), Atlanta, GA, USA
| | - Roger J Packer
- Department of Pediatrics and Neurology, George Washington University, School of Medicine, Washington, DC, USA; Children's National Health System, Washington, DC, USA
| | - Michael P Milham
- Child Mind Institute, New York, NY, USA; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, USA
| | - F Xavier Castellanos
- Department of Child and Adolescent Psychiatry, NYU Langone Medical Center, New York, NY, USA; Nathan Kline Institute for Psychiatric Research, Orangeburg, NY, USA
| | - Maria T Acosta
- Department of Pediatrics and Neurology, George Washington University, School of Medicine, Washington, DC, USA; Children's National Health System, Washington, DC, USA.
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7
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Cameron Craddock R, S Margulies D, Bellec P, Nolan Nichols B, Alcauter S, A Barrios F, Burnod Y, J Cannistraci C, Cohen-Adad J, De Leener B, Dery S, Downar J, Dunlop K, R Franco A, Seligman Froehlich C, J Gerber A, S Ghosh S, J Grabowski T, Hill S, Sólon Heinsfeld A, Matthew Hutchison R, Kundu P, R Laird A, Liew SL, J Lurie D, G McLaren D, Meneguzzi F, Mennes M, Mesmoudi S, O'Connor D, H Pasaye E, Peltier S, Poline JB, Prasad G, Fraga Pereira R, Quirion PO, Rokem A, S Saad Z, Shi Y, C Strother S, Toro R, Q Uddin L, D Van Horn J, W Van Meter J, C Welsh R, Xu T. Brainhack: a collaborative workshop for the open neuroscience community. Gigascience 2016; 5:16. [PMID: 27042293 PMCID: PMC4818387 DOI: 10.1186/s13742-016-0121-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 03/15/2016] [Indexed: 11/10/2022] Open
Abstract
Brainhack events offer a novel workshop format with participant-generated content that caters to the rapidly growing open neuroscience community. Including components from hackathons and unconferences, as well as parallel educational sessions, Brainhack fosters novel collaborations around the interests of its attendees. Here we provide an overview of its structure, past events, and example projects. Additionally, we outline current innovations such as regional events and post-conference publications. Through introducing Brainhack to the wider neuroscience community, we hope to provide a unique conference format that promotes the features of collaborative, open science.
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Affiliation(s)
- R Cameron Craddock
- The Neuro Bureau, Leipzig, 04317 Germany ; Computational Neuroimaging Lab, Center for Biomedical Imaging and Neuromodulation, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, New York, 10962 USA ; Center for the Developing Brain, Child Mind Institute, New York, New York, 10022 USA
| | - Daniel S Margulies
- The Neuro Bureau, Leipzig, 04317 Germany ; Max Planck Research Group for Neuroanatomy & Connectivity, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103 Germany
| | - Pierre Bellec
- The Neuro Bureau, Leipzig, 04317 Germany ; Département d'Informatique et de Recherche Opérationnelle, Université de Montréal, Montréal, Québec H3W 1W5, Canada ; Functional Neuroimaging Unit, Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, Québec H3W 1W5, Canada
| | - B Nolan Nichols
- The Neuro Bureau, Leipzig, 04317 Germany ; Center for Health Sciences, SRI International, Menlo Park, California, 94025 USA ; Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, California, 94305 USA
| | - Sarael Alcauter
- Instituto De Neurobiología, Universidad Nacional Autónoma de México, Querétaro, 76203 México
| | - Fernando A Barrios
- Instituto De Neurobiología, Universidad Nacional Autónoma de México, Querétaro, 76203 México
| | - Yves Burnod
- Laboratoire d'Imagerie Biomédicale, Sorbonne Universités, UPMC Université Paris 06, Paris, 75005 France ; Institut des Systèmes Complexes de Paris-Île-de-France, Paris, 75013 France
| | - Christopher J Cannistraci
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, 10029 USA
| | - Julien Cohen-Adad
- Functional Neuroimaging Unit, Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, Québec H3W 1W5, Canada ; Institute of Biomedical Engineering, Ecole Polytechnique de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Benjamin De Leener
- Institute of Biomedical Engineering, Ecole Polytechnique de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Sebastien Dery
- McConnell Brain Imaging Center, Montreal Neurological Institute, Montreal, Quebec H3A 2B4, Canada
| | - Jonathan Downar
- MRI-Guided rTMS Clinic, University Health Network, Toronto, Ontario M5T 2S8, Canada ; Department of Psychiatry, University Health Network, University of Toronto, Toronto, Ontario M5T 2S8, Canada ; Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Katharine Dunlop
- MRI-Guided rTMS Clinic, University Health Network, Toronto, Ontario M5T 2S8, Canada ; Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Alexandre R Franco
- The Neuro Bureau, Leipzig, 04317 Germany ; Faculdade de Engenharia, PUCRS, Porto Alegre, 90619 Brazil ; Instituto do Cérebro do Rio Grande do Sul, PUCRS, Porto Alegre, 90610 Brazil ; Faculdade de Medicina, PUCRS, Porto Alegre, 90619 Brazil
| | - Caroline Seligman Froehlich
- The Neuro Bureau, Leipzig, 04317 Germany ; Computational Neuroimaging Lab, Center for Biomedical Imaging and Neuromodulation, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, New York, 10962 USA
| | - Andrew J Gerber
- New York State Psychiatric Institute, New York, New York, 10032 USA ; Division of Child and Adolescent Psychiatry, Department of Psychiatry, Columbia University, New York, New York, 10032 USA
| | - Satrajit S Ghosh
- The Neuro Bureau, Leipzig, 04317 Germany ; McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 USA ; Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, 02115 USA
| | - Thomas J Grabowski
- Department of Radiology, University of Washington, Seattle, Washington, 98105 USA ; Department of Neurology, University of Washington, Seattle, Washington, 98105 USA
| | - Sean Hill
- International Neuroinformatics Coordinating Facility, Stockholm, 171 77 Sweden ; Karolinska Institutet, Stockholm, 171 77 Sweden
| | | | - R Matthew Hutchison
- The Neuro Bureau, Leipzig, 04317 Germany ; Center for Brain Science, Harvard University, Cambridge, Massachusetts, 02138 USA
| | - Prantik Kundu
- The Neuro Bureau, Leipzig, 04317 Germany ; Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, 10029 USA
| | - Angela R Laird
- Department of Physics, Florida International University, Miami, Florida, 33199 USA
| | - Sook-Lei Liew
- The Neuro Bureau, Leipzig, 04317 Germany ; Chan Division of Occupational Science and Occupational Therapy, Division of Physical Therapy and Biokinesiology, Department of Neurology, University of Southern California, Los Angeles, California, 90033 USA ; USC Mark and Mary Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, Canada, 90033 USA
| | - Daniel J Lurie
- Department of Psychology,, University of California, Berkeley, California, 94720 USA
| | - Donald G McLaren
- The Neuro Bureau, Leipzig, 04317 Germany ; Biospective, Inc., Montréal,, Québec H4P 1K6, Canada ; Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, 02114, USA
| | | | - Maarten Mennes
- The Neuro Bureau, Leipzig, 04317 Germany ; Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, Nijmegen, 6525 EN The Netherlands
| | - Salma Mesmoudi
- Institut des Systèmes Complexes de Paris-Île-de-France, Paris, 75013 France ; Sorbonne Universités, Paris-1 Université, Equipement d'Excellence MATRICE, Paris, 75005, France
| | - David O'Connor
- Center for the Developing Brain, Child Mind Institute, New York, New York, 10022 USA
| | - Erick H Pasaye
- Instituto De Neurobiología, Universidad Nacional Autónoma de México, Querétaro, 76203 México
| | - Scott Peltier
- Functional MRI Laboratory, University of Michigan, Ann Arbor, Michigan, 48109 USA
| | - Jean-Baptiste Poline
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, 94720 USA ; Henry H. Wheeler Jr. Brain Imaging Center, University of California, Berkeley, California, 94709 USA
| | - Gautam Prasad
- Laboratory of Neuro Imaging, Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of University of Southern California, Los Angeles, California, 90033 USA
| | | | - Pierre-Olivier Quirion
- Functional Neuroimaging Unit, Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, Québec H3W 1W5, Canada
| | - Ariel Rokem
- The University of Washington eScience Institute, Seattle, Washington, 98195 USA
| | - Ziad S Saad
- Scientific and Statistical Computing Core, National Institute of Mental Health, Bethesda, Maryland, 20892 USA
| | - Yonggang Shi
- Laboratory of Neuro Imaging, Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of University of Southern California, Los Angeles, California, 90033 USA
| | - Stephen C Strother
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada ; Rotman Research Institute, Baycrest Hospital, Toronto, Ontario M6A 2E1, Canada ; Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Roberto Toro
- The Neuro Bureau, Leipzig, 04317 Germany ; Human Genetics and Cognitive Functions Unit, Institut Pasteur, Paris, 75015 France ; Unité Mixte de Recherche 3571, Genes, Synapses and Cognition, Centre National de la Recherche Scientifique, Institut Pasteur, Paris, 75015 France
| | - Lucina Q Uddin
- The Neuro Bureau, Leipzig, 04317 Germany ; Department of Psychology, University of Miami, Coral Gables, Florida, 33124 USA ; Neuroscience Program, University of Miami Miller School of Medicine, Miami, Florida, 33136 USA
| | - John D Van Horn
- USC Mark and Mary Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, Canada, 90033 USA
| | - John W Van Meter
- Center for Functional and Molecular Imaging, Georgetown University Medical Center, Washington,, 20007 DC USA
| | - Robert C Welsh
- Department of Psychiatry, University of Michigan, Ann Arbor, Michigan, 48109 USA ; Department of Radiology,, University of Michigan, Ann Arbor, Michigan, 48109 USA
| | - Ting Xu
- Center for the Developing Brain, Child Mind Institute, New York, New York, 10022 USA
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8
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Abstract
A numerical model of the behaviour of the magnetization in a field-cycled dynamic nuclear polarization (DNP) experiment is presented, with the aim of optimizing pulse sequence parameters in field-cycled proton-electron double-resonance free radical imaging. The model is used to predict the observed enhancement of the NMR signal as a function of the magnetic field strength, EPR irradiation frequency and pulse sequence timing, as well as the properties of the sample including the NMR and EPR relaxation times. The model allowed optimization of parameters in the field-cycled DNP experiment, in particular the EPR irradiation frequency, to find the value which would give the largest difference between NMR signals recorded with and without EPR irradiation. Experiments to verify the model were carried out using aqueous solutions of TEMPOL, which exhibits three hyperfine lines in its EPR spectrum and triarylmethyl (TAM), which has a single, narrow line. It was found that the model predicted very well the variation in DNP enhancement with EPR irradiation power for both samples. The behaviour of the NMR signal with EPR irradiation frequency in studies using TEMPOL was also accurately modelled, with the optimum frequency lying between 60 and 80 MHz, depending on the EPR irradiation power. The optimum frequency obtained from the model also agreed with the experimental data obtained using the TAM free radical, but with this sample the theoretical curves tended to deviate from the experimental data at irradiation frequencies below 70 MHz.
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Affiliation(s)
- W Youngdee
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK
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9
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Affiliation(s)
- D J Lurie
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
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10
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Davies GR, Lurie DJ, Hutchison JM, McCallum SJ, Nicholson I. Continuous-wave magnetic resonance imaging of short T(2) materials. J Magn Reson 2001; 148:289-297. [PMID: 11237634 DOI: 10.1006/jmre.2000.2245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
There is growing interest in the use of magnetic resonance imaging (MRI) to examine solid materials where the restricted motion of the probed spins leads to broad lines and short T(2) values, rendering many interesting systems invisible to conventional 2DFT pulsed imaging methods. In EPR T(2) seldom exceeds 0.1 mus and continuous-wave methods are adopted for spectroscopy and imaging. In this paper we demonstrate the use of continuous-wave MRI to obtain 2-dimensional images of short T(2) samples. The prototype system can image samples up to 50 mm in diameter by 60 mm long and has been used to image polymers and water penetration in porous media. Typical acquisition times range between 10 and 40 min. Resolution of 1 to 2 mm has been achieved for samples with T(2) values ranging from 38 to 750 mus. There is the possibility of producing image contrast that is determined by the material properties of the sample.
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Affiliation(s)
- G R Davies
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
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11
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Khramtsov VV, Grigor'ev IA, Foster MA, Lurie DJ, Nicholson I. Biological applications of spin pH probes. Cell Mol Biol (Noisy-le-grand) 2000; 46:1361-74. [PMID: 11156481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The determination of pH is one of the most important problems in the biochemistry of living organisms, since many of the vital processes of cells and cellular organelles depend on the local pH value. Amongst currently used experimental approaches for the measurement of pH, the application of spin pH probes in combination with EPR spectroscopy is a comparatively new and rapidly developing field. In this article we describe the background, advantages and limitations of the method of spin pH probes, and discuss its recent applications. Availability of a wide variety of pH-sensitive nitroxides with different ranges of pH-sensitivity, labeling group and lipophilicity facilitates their application to a variety of biological systems from subcellular organelles to complex organisms. The recent progress in low-field EPR-based imaging and spectroscopy-based techniques allows spin pH probes to be used for non-invasive in vivo pH measurement and pH-sensitive imaging.
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Affiliation(s)
- V V Khramtsov
- Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia.
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12
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13
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Abstract
Imaging of free radicals in vivo using an interleaved field-cycled proton-electron double-resonance imaging (FC-PEDRI) pulse sequence has recently been investigated. In this work, in order to reduce the EPR (electron paramagnetic resonance) irradiation power required and the imaging time, a centric reordered snapshot FC-PEDRI pulse sequence has been implemented. This is based on the FLASH pulse sequence with a very short repetition time and the use of centric reordering of the phase-encoding gradient, allowing the most significant free induction decay (FID) signals to be collected before the signal enhancement decays significantly. A new technique of signal phaseshift correction was required to eliminate ghost artefacts caused by the instability of the main magnetic field after field cycling. An FID amplitude correction scheme has also been implemented to reduce edge enhancement artefacts caused by the rapid change of magnetization population before reaching the steady state. Using the rapid pulse sequence, the time required for acquisition of a 64 x 64 pixel FC-PEDRI image was reduced to 6 s per image compared with about 2.5 min with the conventional pulse sequence. The EPR irradiation power applied to the sample was reduced by a factor of approximately 64. Although the resulting images obtained by the rapid pulse sequence have a lower signal to noise than those obtained by a normal interleaved FC-PEDRI pulse sequence, the results show that rapid imaging of free radicals in vivo using snapshot FC-PEDRI is possible.
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Affiliation(s)
- P Puwanich
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK
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14
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Abstract
The nitrogen monoxide radical (NO*) forms paramagnetic mono- and dinitrosyl-iron complexes in biologic tissues. To establish a noninvasive technique for in vivo NO* imaging, we evaluated the suitability of these complexes as magnetic resonance (MR) contrast agents, making use of the ability of the unpaired electrons of the complexes to enter into dynamic nuclear polarization with water protons and hence produce enhancement on images generated by the technique of proton-electron-double-resonance imaging (PEDRI). Phantom solutions of synthetic nitrosyl-iron complexes (NICs) altered the signal intensity of PEDRI images. The dinitrosyl-iron complex (DNIC) with serum albumin induced a significantly larger signal alteration than the mononitrosyl-iron complex (MNIC) with dithiocarbamate. Exposure of rat liver to sodium nitroprusside (SNP) by ex vivo and in situ perfusion induced a composite X-band electron spin resonance (ESR) spectrum of the isolated liver characteristic of a MNIC and DNIC. On storage of the tissue, the MNIC signal disappeared and the DNIC signal intensity increased. Correspondingly, in cross-sectional PEDRI images taken at room temperature, the SNP-exposed livers initially exhibited a weak signal that strongly increased with time. In conclusion, NICs can be detected using PEDRI and could be exploited for in vivo NO* imaging.
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Affiliation(s)
- A Mülsch
- Institut für Kardiovaskuläre Physiologie, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt, Germany.
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15
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Abstract
EPR irradiation by a train of inverting pulses has potential advantages over continuous-wave EPR irradiation in DNP applications; however, it has previously been used only at high field (5 T). This paper presents the design and testing of an apparatus for performing pulsed DNP experiments at 10 mT with large samples (17 ml). Experimental results using pulsed DNP with an aqueous solution of a narrow-linewidth paramagnetic probe are presented. A maximum DNP enhancement of about -36 with a train of inverting pulses (width 500 ns, repetition time 4 micros) was measured. A preliminary comparison showed that, when the same enhancement value is considered, the pulsed DNP technique requires an average power that is about three times higher than that required with the CW irradiation. However, for in vivo DNP applications it is very important to minimize the average power deposited in the sample. From the experimental results reported in this work, when considering the maximum enhancement, the pulsed technique requires only 2% of the average power necessary with the CW DNP technique. We believe that this reduction in the average power can be important for future DNP studies with large biological samples.
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Affiliation(s)
- M Alecci
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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16
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Seimenis I, Foster MA, Lurie DJ, Hutchison JM, Whiting PH, Payne S. Chemically induced analgesic nephropathy in the rat monitored by proton-electron double-resonance imaging (PEDRI). Magn Reson Med 1998; 40:280-6. [PMID: 9702710 DOI: 10.1002/mrm.1910400214] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Proton-electron double-resonance imaging (PEDRI) was used to assess renal function by monitoring the flow of the exogenous nitroxide free radical proxyl carboxylic acid (PCA) through normal and injured kidneys in the living rat. Kidney damage was induced by treatment with 2-bromoethylamine (BEA), which provides a well established model for human analgesic nephropathy. PCA clearance rates for liver, abdominal blood vessels, and renal tissues were determined from serial PEDRI images of normal rats (n = 6) and rats treated with BEA (n = 21). Different groups of BEA-treated animals were imaged on day 4 (n = 6), day 6 (n = 6), and day 9 (n = 9) after treatment. In BEA-treated rats, there was an increase in PCA half-life in all tissues studied. This increase was greatest in the kidney tissues and the effect progressed with time after treatment. The effect is probably due to BEA-induced damage to the tubules in the renal cortex and may not be related to the primary lesions in the renal medulla.
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Affiliation(s)
- I Seimenis
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, Scotland
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17
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Alecci M, Seimenis I, McCallum SJ, Lurie DJ, Foster MA. Nitroxide free radical clearance in the live rat monitored by radio-frequency CW-EPR and PEDRI. Phys Med Biol 1998; 43:1899-905. [PMID: 9703053 DOI: 10.1088/0031-9155/43/7/011] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The use of RF (100 to 300 MHz) PEDRI and CW-EPR techniques allows the in vivo study of large animals such as whole rats and rabbits. Recently a PEDRI instrument was modified to also allow CW-EPR spectroscopy with samples of similar size and under the same experimental conditions. In the present study, this CW-EPR and PEDRI apparatus was used to assess the feasibility of the detection of a pyrrolidine nitroxide free radical (2,2,5,5,-tetramethylpyrrolidine-1-oxyl-3-carboxylic acid, PCA) in the abdomen of rats. In particular, we have shown that after the PCA administration (4 mmol kg(-1) b.w.): (i) the PCA EPR linewidth does not show line broadening due to concentration effects; (ii) a similar PCA up-take phase is observed by EPR and PEDRI; and (iii) the PCA half-lives in the whole abdomen of rats measured with the CW-EPR (T1/2=26+/-4 min, mean+/-sd, n=10) and PEDRI (T1/2=29+/-4 min, mean+/-sd, n=4) techniques were not significantly different (p > 0.05). These results show, for the first time, that information about PCA pharmacokinetics obtained by CW-EPR is the same as that from PEDRI under the same experimental conditions.
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Affiliation(s)
- M Alecci
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK
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18
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Abstract
The multimodality approach to in vivo detection of free radicals combines the relative benefits of three free radical detection modalities: conventional RF CW-ESR, LODESR and PEDRI. We have built apparatus capable of combining these modalities to allow sequential PEDRI and CW-ESR, sequential LODESR and proton NMR imaging and simultaneous LODESR and CW-ESR. These systems offer superior performance in terms of both the scope and quality of information over single-modality free radical detection systems.
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Affiliation(s)
- S J McCallum
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK
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19
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Abstract
Proton-electron double-resonance imaging (PEDRI) has considerable value for study of the distribution and elimination pathways of nitroxide free radicals (NFRs). This has been illustrated by its use in studies of kidney function in the living rat in which the NFR proxyl carboxylic acid (PCA) has been employed as a 'tracer'. The technique, at its present stage of development, can demonstrate location of PCA in enough detail to observe the passage through kidney cortex and medulla differentially, and to see the NFR within the major abdominal blood vessels. These studies are helping towards an understanding of the metabolic fate of PCA, as well as providing information about kidney performance after challenge with a nephrotoxin. In addition, nitric oxide complexes, formed in vivo by providing rats with a nitrite-rich diet, have been observed ex vivo using PEDRI and field-cycled DNP.
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Affiliation(s)
- M A Foster
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK.
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20
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Abstract
The design, construction and use of a large-scale field-cycled proton-electron double-resonance imaging (FC-PEDRI) imager is described. The imager is based on a whole-body sized, vertical field, 59 mT permanent magnet. Field cycling is accomplished by the field compensation method, and uses a secondary, resistive magnet with an internal diameter of 52 cm. The magnetic field can be switched from zero to 59 mT or vice versa in 40 ms. It is used with a double-resonance coil assembly (NMR/EPR) comprising a solenoidal NMR transmit/receive coil and a coaxial, external birdcage resonator for EPR irradiation. Experiments to image the distribution of an exogenous nitroxide free radical in anaesthetized rabbits are described.
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Affiliation(s)
- D J Lurie
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK
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21
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Abstract
We have designed and constructed RF coil assemblies and the appropriate instrumentation for combining proton NMR imaging with LODESR imaging. This has enabled us to collect sequential images from the same sample using both methods. The coil assembly consists of a crossed ellipse coil for LODESR and proton NMR signal detection and a saddle coil for excitation of the ESR resonance. Images have been collected of phantoms containing copper sulphate and Tempol solutions. NMR images were collected (4.3 min) and within 30 s LODESR data collection started (collection time 2.5 min). Only the Tempol solutions are visible in the LODESR images.
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Affiliation(s)
- I Nicholson
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK
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22
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Seimenis I, Foster MA, Lurie DJ, Hutchison JM, Whiting PH, Payne S. The excretion mechanism of the spin label proxyl carboxylic acid (PCA) from the rat monitored by X-band ESR and PEDRI. Magn Reson Med 1997; 37:552-8. [PMID: 9094077 DOI: 10.1002/mrm.1910370413] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Proton electron double resonance imaging (PEDRI) was used for monitoring in vivo the distribution, metabolism and, in particular, the excretion mechanism of the exogenous nitroxide free radical proxyl carboxylic acid (PCA) in the rat. PCA clearance half-lives through liver, abdominal vessels, and renal tissues were determined from a series of PEDRI images for normal rats (n = 5) and rats treated with probenecid (n = 5), a competitive inhibitor of the tubular secretion process. The approximately doubled renal half-lives of the treated animals suggest that tubular secretion accounts for about 50% of PCA renal loss in the normal rat and reabsorption is insignificant. PCA binding to bovine serum albumin was investigated by X-band ESR and the bound fraction was found to be less than 10% of the total PCA. Most probably, PCA binds to hydrophilic sites. Blood PCA concentration investigated by X-band ESR exhibited biphasic behavior and PEDRI results confirmed the in vivo metabolic reduction of PCA by rat liver cells.
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Affiliation(s)
- I Seimenis
- Department of Biomedical Physics and Bioengineering, University of Aberdeen, Foresterhill, UK
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23
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Nicholson I, Foster MA, Robb FJ, Hutchison JM, Lurie DJ. In vivo imaging of nitroxide-free-radical clearance in the rat, using radiofrequency longitudinally detected ESR imaging. J Magn Reson B 1996; 113:256-61. [PMID: 8995845 DOI: 10.1006/jmrb.1996.0185] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- I Nicholson
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, United Kingdom
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24
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Affiliation(s)
- D J Lurie
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK
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25
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Alecci M, Lurie DJ, Nicholson I, Placidi G, Sotgiu A. Young Investigator Award presentation at the 13th Annual Meeting of the ESMRMB, September 1996, Prague. A proton-electron double-resonance imaging apparatus with simultaneous multiple electron paramagnetic resonance irradiation at 10 mT. MAGMA 1996; 4:187-93. [PMID: 9220407 DOI: 10.1007/bf01772006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The detection of free radicals in vivo is very important for the study of many physiologic and pathologic conditions. Free radicals have been implicated in a number of diseases such as ischemia, inflammation, kidney damage, and cancer. Proton-electron double-resonance imaging (PEDRI) allows the indirect detection of free radicals via the Overhauser effect. Nitroxide free radicals used for in vivo PEDRI studies present spectra with two or three lines, but most PEDRI experiments performed to date have used only single-line electron paramagnetic resonance (EPR) irradiation. There is theoretical evidence that simultaneous irradiation of multiple EPR transitions could increase the maximum achievable PEDRI enhancement. From the experimental point of view, this requires the combined use of a suitable multiple-frequency EPR source and a multiple-tuned EPR resonator. A novel radiofrequency (RF) triple-tuned loop-gap resonator for use in PEDRI has recently been developed, and dynamic nuclear polarization (DNP) data were reported. In the present study we describe a new PEDRI apparatus, equipped with a triple-tuned resonator, that is suitable for simultaneous double- or triple-EPR irradiation of nitroxide free radicals. In particular, the details of the EPR hardware used to generate the two or three EPR frequencies are given, and PEDRI images obtained with simultaneous multiple EPR irradiation are shown. Moreover, DNP experimental results showing the increase of the enhancement as a function of the EPR power for single and simultaneous double EPR irradiation are presented. The main goal of this apparatus is to improve the sensitivity and/or to reduce EPR irradiation power in a PEDRI experiment. This is likely to be particularly important in future biologic applications of PEDRI where the applied power must be optimized to reduce sample heating.
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Affiliation(s)
- M Alecci
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK
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26
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Abstract
Current pulsed nuclear magnetic resonance methods of imaging samples such as solids with short spin-spin relaxation times are restricted to use with T2 values longer than approximately 10 microseconds. In the present study a method of imaging ultra-short T2 samples using continuous- wave, swept-field NMR is presented that, in principle, will be able to overcome this restriction. The technique is identical to that used in continuous-wave electron paramagnetic resonance imaging of paramagnetic species and involves irradiating the sample continuously with a radiofrequency excitation in the presence of a strong stationary magnetic field gradient. When the main magnetic field is swept over a suitable range, the variation of the NMR absorption signal with applied magnetic field yields a one-dimensional projection of the object under study along the gradient direction. Two- or three-dimensional image data sets may be reconstructed from projections that are obtained by applying the gradient in different directions. Signal-to-noise ratio can be improved by modulating the magnetic field and employing a lock-in amplifier to recover signal variations at the audio modulation frequency. Preliminary experiments were performed using a 7 Tesla magnet and a 300 MHz continuous-wave radiofrequency bridge with lock-in detection. The apparatus is described and the results of pilot experiments that employed vulcanized rubber samples are presented. The ability of the technique to detect short T2 samples was demonstrated by the presence of a background signal from the Perspex former of the birdcage resonator used for signal reception.
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Affiliation(s)
- D J Lurie
- Department of Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Foresterhill, UK
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27
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Yeung D, Hutchison JM, Lurie DJ. An efficient birdcage resonator at 2.5 MHz using a novel multilayer self-capacitance construction technique. MAGMA 1995; 3:163-8. [PMID: 8749735 DOI: 10.1007/bf01771702] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The birdcage resonator, well appreciated for its high signal-to-noise ratio and its magnetic field uniformity characteristics, operates efficiently in mid- to high-field MRI systems but, unfortunately not for low-field (< 0.4 T) applications. The inherently low inductance of the birdcage architecture is the main obstacle to achieving low-frequency resonance because of the need to use very high-value capacitors for the tuning. Small-case-size, high-value ceramic capacitors are known to have high dissipation factors which when used in the fabrication of RF coils could result in poor efficiency. To overcome this limitation, a novel technique known as multilayer self-capacitance (MLSC) construction has been developed and a prototype 2.5 MHz bird-cage resonator of length 25 cm and diameter 20 cm has been built. The technique involves the modification of the leg sections of the conductors constituting the bird cage into integrated capacitors using very low-loss materials as dielectrics. The observed unloaded Q-factor was 267 using the MLSC construction, and when loaded with a 16-cm-diameter bottle of 0.45% saline, its Q dropped to 246. The RF field uniformity plots have demonstrated that the MLSC technique has no adverse effects on the magnetic field homogeneity of the bird-cage resonator.
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Affiliation(s)
- D Yeung
- Department of Bio-medical Physics and Bio-engineering, University of Aberdeen, Aberdeen Royal Hospitals, Foresterhill, UK
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28
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Lurie DJ, Smith FA, Shukri A. The dissociation of some 111In chelates in the presence of transferrin and haemoglobin studied by PAC. Int J Appl Radiat Isot 1985; 36:57-62. [PMID: 3918943 DOI: 10.1016/0020-708x(85)90055-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The interaction of [111In]Tris-chelates with protein molecules in aqueous solution at room temperature has been studied using time-integral and time-differential PAC. Increasing amounts of apo-transferrin were added to solutions of [111In]tropolonate, -acetylacetonate, -oxinate and -oxine sulphate, and of haemoglobin to [111In]tropolonate. The transfer of 111In from chelate to protein was monitored by time-integral PAC measurements. Analysis of these data in erms of stability constants showed that with added transferrin complete dissociation of each 111In chelate occurred with increasing protein concentration, the radiolabel being sequestered by the protein molecules. Confirmation of this was provided by time-differential PAC measurements at four tropolone:transferrin relative concentrations, and in the pure systems. A value for the first stability constant of transferrin is presented. Analysis of time-integral PAC data showed that added haemoglobin did not cause complete dissociation of [111In]tropolonate, a [111In]tropolone-haemoglobin complex being formed. Time-differential PAC studies of the [111In]tropolonate:haemoglobin and [111In]haemoglobin systems at 77 K and 295 K supported this conclusion, revealing quadrupole frequencies of 14.0 +/- 0.6 MHz in [111In]haemoglobin and 9.1 +/- 1.1 MHz in the mixed system.
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29
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Abstract
Spectral tailoring of an amplitude-modulated radio-frequency (RF) pulse may be used to modify the slice-profile produced by a selective excitation sequence. Optimisation of the profile by intuitive means is difficult, however, due to the non-linearity of the magnetisation's response. A design procedure is presented which uses computer-simulation to calculate the response to an arbitrary RF envelope, and alters systematically the shape of the envelope in order to optimise the slice-profile. Two forms of modulation function are suggested, both based on a truncated-sinc, and the simulated response to optimised 90 degrees and 180 degrees pulses is shown. The effect on the slice-profile of RF magnetic field inhomogeneity is discussed.
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30
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Smith FA, Lurie DJ, Brady F, Danpure HJ, Kensett MJ, Osman S, Silvester DJ, Waters SL. PAC studies of 111In binding to transferrin, tropolone and acetylacetone in aqueous solutions. Int J Appl Radiat Isot 1984; 35:501-6. [PMID: 6735495 DOI: 10.1016/0020-708x(84)90171-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Time integral and time-differential PAC measurements have been made over a wide temperature range in aqueous solutions of [111In]tropolonate and [111In]acetylacetonate. The quadrupole frequency in the latter is approximately 30% higher than that in the former and the molecular volumes derived from rotational correlation times show the expected differences. Apo-transferrin was separately added to the two 111In-chelates and the transfer of activity from chelate to transferrin followed as a function of relative molar concentrations. Very much larger molar ratios of transferrin to tropolone than of transferrin to acetylacetone were required before substantial transfer of 111In from chelate to transferrin took place. This difference in affinity for transferrin could be one significant factor in explaining the enhanced ability of [111In]tropolonate to label blood cells in the presence of plasma. The determination of PAC parameters in [111In]transferrin over a range of temperatures showed that the values of quadrupole frequency obtained depended on the number of binding sites assumed. For only one 111In site per molecule, the quadrupole frequency increases by over 50% as the temperature is reduced below the freezing point of the solution. If two 111In sites are assumed there appears to be a change in the percentage occupancy of the two sites on either side of the transition.
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