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Kim S, Jo Y, Im GH, Lee C, Oh C, Kook G, Kim SG, Lee HJ. Miniaturized MR-compatible ultrasound system for real-time monitoring of acoustic effects in mice using high-resolution MRI. Neuroimage 2023; 276:120201. [PMID: 37269955 DOI: 10.1016/j.neuroimage.2023.120201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 05/24/2023] [Accepted: 05/26/2023] [Indexed: 06/05/2023] Open
Abstract
Visualization of focused ultrasound in high spatial and temporal resolution is crucial for accurately and precisely targeting brain regions noninvasively. Magnetic resonance imaging (MRI) is the most widely used noninvasive tool for whole-brain imaging. However, focused ultrasound studies employing high-resolution (> 9.4 T) MRI in small animals are limited by the small size of the radiofrequency (RF) volume coil and the noise sensitivity of the image to external systems such as bulky ultrasound transducers. This technical note reports a miniaturized ultrasound transducer system packaged directly above a mouse brain for monitoring ultrasound-induced effects using high-resolution 9.4 T MRI. Our miniaturized system integrates MR-compatible materials with electromagnetic (EM) noise reduction techniques to demonstrate echo-planar imaging (EPI) signal changes in the mouse brain at various ultrasound acoustic intensities. The proposed ultrasound-MRI system will enable extensive research in the expanding field of ultrasound therapeutics.
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Affiliation(s)
- Subeen Kim
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Yehhyun Jo
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Geun Ho Im
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon 16419, South Korea
| | - Chanhee Lee
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon 16419, South Korea
| | - Chaerin Oh
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Geon Kook
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon 16419, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon 16419, South Korea; Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon 16419, South Korea.
| | - Hyunjoo J Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea; KAIST Institute for Nano Century (KINC), Daejeon 34141, South Korea.
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Bidirectional alterations in brain temperature profoundly modulate spatiotemporal neurovascular responses in-vivo. Commun Biol 2023; 6:185. [PMID: 36797344 PMCID: PMC9935519 DOI: 10.1038/s42003-023-04542-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/31/2023] [Indexed: 02/18/2023] Open
Abstract
Neurovascular coupling (NVC) is a mechanism that, amongst other known and latent critical functions, ensures activated brain regions are adequately supplied with oxygen and glucose. This biological phenomenon underpins non-invasive perfusion-related neuroimaging techniques and recent reports have implicated NVC impairment in several neurodegenerative disorders. Yet, much remains unknown regarding NVC in health and disease, and only recently has there been burgeoning recognition of a close interplay with brain thermodynamics. Accordingly, we developed a novel multi-modal approach to systematically modulate cortical temperature and interrogate the spatiotemporal dynamics of sensory-evoked NVC. We show that changes in cortical temperature profoundly and intricately modulate NVC, with low temperatures associated with diminished oxygen delivery, and high temperatures inducing a distinct vascular oscillation. These observations provide novel insights into the relationship between NVC and brain thermodynamics, with important implications for brain-temperature related therapies, functional biomarkers of elevated brain temperature, and in-vivo methods to study neurovascular coupling.
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Serrano ME, Kim E, Petrinovic MM, Turkheimer F, Cash D. Imaging Synaptic Density: The Next Holy Grail of Neuroscience? Front Neurosci 2022; 16:796129. [PMID: 35401097 PMCID: PMC8990757 DOI: 10.3389/fnins.2022.796129] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/15/2022] [Indexed: 12/19/2022] Open
Abstract
The brain is the central and most complex organ in the nervous system, comprising billions of neurons that constantly communicate through trillions of connections called synapses. Despite being formed mainly during prenatal and early postnatal development, synapses are continually refined and eliminated throughout life via complicated and hitherto incompletely understood mechanisms. Failure to correctly regulate the numbers and distribution of synapses has been associated with many neurological and psychiatric disorders, including autism, epilepsy, Alzheimer’s disease, and schizophrenia. Therefore, measurements of brain synaptic density, as well as early detection of synaptic dysfunction, are essential for understanding normal and abnormal brain development. To date, multiple synaptic density markers have been proposed and investigated in experimental models of brain disorders. The majority of the gold standard methodologies (e.g., electron microscopy or immunohistochemistry) visualize synapses or measure changes in pre- and postsynaptic proteins ex vivo. However, the invasive nature of these classic methodologies precludes their use in living organisms. The recent development of positron emission tomography (PET) tracers [such as (18F)UCB-H or (11C)UCB-J] that bind to a putative synaptic density marker, the synaptic vesicle 2A (SV2A) protein, is heralding a likely paradigm shift in detecting synaptic alterations in patients. Despite their limited specificity, novel, non-invasive magnetic resonance (MR)-based methods also show promise in inferring synaptic information by linking to glutamate neurotransmission. Although promising, all these methods entail various advantages and limitations that must be addressed before becoming part of routine clinical practice. In this review, we summarize and discuss current ex vivo and in vivo methods of quantifying synaptic density, including an evaluation of their reliability and experimental utility. We conclude with a critical assessment of challenges that need to be overcome before successfully employing synaptic density biomarkers as diagnostic and/or prognostic tools in the study of neurological and neuropsychiatric disorders.
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Affiliation(s)
- Maria Elisa Serrano
- Department of Neuroimaging, The BRAIN Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.,Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, United Kingdom
| | - Eugene Kim
- Department of Neuroimaging, The BRAIN Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.,Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, United Kingdom
| | - Marija M Petrinovic
- Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.,MRC Centre for Neurodevelopmental Disorders, King's College London, London, United Kingdom
| | - Federico Turkheimer
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, United Kingdom
| | - Diana Cash
- Department of Neuroimaging, The BRAIN Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.,Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, Kings College London, London, United Kingdom
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Cortex senses environmental temperature earlier than the hypothalamus in awake rats. J Therm Biol 2020; 91:102652. [DOI: 10.1016/j.jtherbio.2020.102652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/14/2020] [Accepted: 06/16/2020] [Indexed: 11/24/2022]
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Albers F, Wachsmuth L, Schache D, Lambers H, Faber C. Functional MRI Readouts From BOLD and Diffusion Measurements Differentially Respond to Optogenetic Activation and Tissue Heating. Front Neurosci 2019; 13:1104. [PMID: 31708721 PMCID: PMC6821691 DOI: 10.3389/fnins.2019.01104] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 10/01/2019] [Indexed: 12/12/2022] Open
Abstract
Functional blood-oxygenation-level-dependent (BOLD) MRI provides a brain-wide readout that depends on the hemodynamic response to neuronal activity. Diffusion fMRI has been proposed as an alternative to BOLD fMRI and has been postulated to directly rely on neuronal activity. These complementary functional readouts are versatile tools to be combined with optogenetic stimulation to investigate networks of the brain. The cell-specificity and temporal precision of optogenetic manipulations promise to enable further investigation of the origin of fMRI signals. The signal characteristics of the diffusion fMRI readout vice versa may better resolve network effects of optogenetic stimulation. However, the light application needed for optogenetic stimulation is accompanied by heat deposition within the tissue. As both diffusion and BOLD are sensitive to temperature changes, light application can lead to apparent activations confounding the interpretation of fMRI data. The degree of tissue heating, the appearance of apparent activation in different fMRI sequences and the origin of these phenomena are not well understood. Here, we disentangled apparent activations in BOLD and diffusion measurements in rats from physiological activation upon sensory or optogenetic stimulation. Both, BOLD and diffusion fMRI revealed similar signal shapes upon sensory stimulation that differed clearly from those upon heating. Apparent activations induced by high-intensity light application were dominated by T2∗-effects and resulted in mainly negative signal changes. We estimated that even low-intensity light application used for optogenetic stimulation reduces the BOLD response close to the fiber by up to 0.4%. The diffusion fMRI signal contained T2, T2∗ and diffusion components. The apparent diffusion coefficient, which reflects the isolated diffusion component, showed negative changes upon both optogenetic and electric forepaw stimulation. In contrast, positive changes were detected upon high-intensity light application and thus ruled out heating as a major contributor to the diffusion fMRI signal.
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Affiliation(s)
- Franziska Albers
- Translational Research Imaging Center, Department of Clinical Radiology, University Hospital Münster, Münster, Germany
| | - Lydia Wachsmuth
- Translational Research Imaging Center, Department of Clinical Radiology, University Hospital Münster, Münster, Germany
| | - Daniel Schache
- Translational Research Imaging Center, Department of Clinical Radiology, University Hospital Münster, Münster, Germany
| | - Henriette Lambers
- Translational Research Imaging Center, Department of Clinical Radiology, University Hospital Münster, Münster, Germany
| | - Cornelius Faber
- Translational Research Imaging Center, Department of Clinical Radiology, University Hospital Münster, Münster, Germany
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Yamato H, Jin T, Nomura Y. Near infrared imaging of intrinsic signals in cortical spreading depression observed through the intact scalp in hairless mice. Neurosci Lett 2019; 701:213-217. [PMID: 30797869 DOI: 10.1016/j.neulet.2019.02.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 02/19/2019] [Accepted: 02/20/2019] [Indexed: 01/15/2023]
Abstract
Brain cooling was inevitable in both thinned and intact skull windows in neuroimaging in vivo of mice. Thus we proposed the novel imaging method leaving intact scalp on the skull using the light at 670, 785, and 975 nm. In this study, we used hairless mice (Hos:HR-1) since the deterioration of image quality was resulted from the hair. Cortical spreading depression was induced by KCl application through small incision and burr hole on the frontal bone. Intrinsic optical signals through the intact scalp in the observation area were detected. Time course of the signal showed a triphasic feature which was consistent with the intrinsic optical signals through the intact skull. In three pairs of signal amplitudes at the different wavelengths, no significant differences were observed. Although the intact scalp weakened the amplitudes significantly, e.g., 4.0 from 6.9 at 975 nm, the signals during cortical spreading depression were sufficient to be detected.
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Affiliation(s)
- Hiro Yamato
- Department of Systems Life Engineering, Maebashi Institute of Technology, 460-1, Kamisadori, Maebashi, Gunma 371-0816, Japan
| | - Takashi Jin
- Laboratory for Nano-Bio Probes, RIKEN Quantitative Biology Center, Furuedai 6-2-3, Suita, Osaka 565-0874, Japan
| | - Yasutomo Nomura
- Department of Systems Life Engineering, Maebashi Institute of Technology, 460-1, Kamisadori, Maebashi, Gunma 371-0816, Japan; Laboratory for Nano-Bio Probes, RIKEN Quantitative Biology Center, Furuedai 6-2-3, Suita, Osaka 565-0874, Japan.
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Low frequency pulse stimulation of Schaffer collaterals in Trpm4 -/- knockout rats differently affects baseline BOLD signals in target regions of the right hippocampus but not BOLD responses at the site of stimulation. Neuroimage 2018; 188:347-356. [PMID: 30553915 DOI: 10.1016/j.neuroimage.2018.12.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/21/2018] [Accepted: 12/11/2018] [Indexed: 11/22/2022] Open
Abstract
Electrical stimulation of right Schaffer collateral in Trpm4-/- knockout and wild type rats were used to study the role of Trpm4 channels for signal processing in the hippocampal formation. Stimulation induced neuronal activity was simultaneously monitored in the CA1 region by in vivo extracellular field recordings and in the entire brain by BOLD fMRI measurements. In wild type and Trpm4-/- knockout rats, consecutive 5 Hz pulse trains elicited similar neuronal responses in the CA1 region and similar BOLD responses in the stimulated right hippocampus. Stimulus-related positive BOLD responses were also found in the left dorsal hippocampus. In contrast to the right dorsal hippocampus, baseline BOLD signals in the left hippocampus significantly decreased during consecutive stimulation trains. Similarly, slowly developing significant declines in baseline BOLD signals, in absence of any positive BOLD responses, were also observed in the right entorhinal, right piriform cortex, right basolateral amygdala and right dorsal striatum whereas baseline BOLD signals remained almost stable in the corresponding left regions. Furthermore, significant declines in baseline BOLD signals were found in the prefrontal cortex and prelimbic/infralimbic cortex. Because significant baseline BOLD declines were only observed in target regions of the right dorsal hippocampus, it might reflect functional connectivity between these regions. In all observed regions the decline in baseline BOLD signals was significantly delayed and less pronounced in Trpm4-/- knockout rats when compared to wild type rats. Thus, either Trpm4 channels are involved in mediating these baseline BOLD shifts or functional connectivity of the hippocampus is impaired in Trpm4-/- knockout rats.
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