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Takemura H, Kruper JA, Miyata T, Rokem A. Tractometry of Human Visual White Matter Pathways in Health and Disease. Magn Reson Med Sci 2024; 23:316-340. [PMID: 38866532 PMCID: PMC11234945 DOI: 10.2463/mrms.rev.2024-0007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024] Open
Abstract
Diffusion-weighted MRI (dMRI) provides a unique non-invasive view of human brain tissue properties. The present review article focuses on tractometry analysis methods that use dMRI to assess the properties of brain tissue within the long-range connections comprising brain networks. We focus specifically on the major white matter tracts that convey visual information. These connections are particularly important because vision provides rich information from the environment that supports a large range of daily life activities. Many of the diseases of the visual system are associated with advanced aging, and tractometry of the visual system is particularly important in the modern aging society. We provide an overview of the tractometry analysis pipeline, which includes a primer on dMRI data acquisition, voxelwise model fitting, tractography, recognition of white matter tracts, and calculation of tract tissue property profiles. We then review dMRI-based methods for analyzing visual white matter tracts: the optic nerve, optic tract, optic radiation, forceps major, and vertical occipital fasciculus. For each tract, we review background anatomical knowledge together with recent findings in tractometry studies on these tracts and their properties in relation to visual function and disease. Overall, we find that measurements of the brain's visual white matter are sensitive to a range of disorders and correlate with perceptual abilities. We highlight new and promising analysis methods, as well as some of the current barriers to progress toward integration of these methods into clinical practice. These barriers, such as variability in measurements between protocols and instruments, are targets for future development.
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Affiliation(s)
- Hiromasa Takemura
- Division of Sensory and Cognitive Brain Mapping, Department of System Neuroscience, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Hayama, Kanagawa, Japan
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita, Osaka, Japan
| | - John A Kruper
- Department of Psychology and eScience Institute, University of Washington, Seattle, WA, USA
| | - Toshikazu Miyata
- Division of Sensory and Cognitive Brain Mapping, Department of System Neuroscience, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita, Osaka, Japan
| | - Ariel Rokem
- Department of Psychology and eScience Institute, University of Washington, Seattle, WA, USA
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2
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Pawar PR, Booth J, Neely A, McIlwaine G, Lueck CJ. Nerve fibre organisation in the human optic nerve and chiasm: what do we really know? Eye (Lond) 2024:10.1038/s41433-024-03137-7. [PMID: 38849598 DOI: 10.1038/s41433-024-03137-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 04/30/2024] [Accepted: 05/07/2024] [Indexed: 06/09/2024] Open
Abstract
A recent anatomical study of the human optic chiasm cast doubt on the widespread assumption that nerve fibres travelling in the human optic nerve and chiasm are arranged retinotopically. Accordingly, a scoping literature review was performed to determine what is known about the nerve fibre arrangement in these structures. Meta-analysis suggested that the average number of fibres in each optic nerve was 1.023 million with an inter-individual range of approximately 50% of the mean. Loss of nerve fibres with age (approximately 3,400 fibres/year) could not account for this variability. The review suggested that there might be a retinotopic arrangement of nerve fibres in the orbital portion of the optic nerve but that this arrangement is most likely to be lost posteriorly with a more random distribution of nerve fibres at the chiasm. Limited studies have looked at nerve fibre arrangement in the chiasm. In summary, the chiasm is more 'H-shaped' than 'X-shaped': nerve fibre crossings occur paracentrally with nerves in the centre of the chiasm travelling coronally and in parallel. There is interaction between crossed and uncrossed fibres which are widely distributed. The review supports the non-existence of Wilbrand's knee. Considerable further work is required to provide more precise anatomical information, but this review suggests that the assumed preservation of retinotopy in the human optic nerve and chiasm is probably not correct.
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Affiliation(s)
- Pratap R Pawar
- School of Engineering and Technology, University of New South Wales, Canberra, NSW, Australia
| | - Joshua Booth
- School of Medicine and Psychology, Australian National University, Canberra, NSW, Australia
| | - Andrew Neely
- School of Engineering and Technology, University of New South Wales, Canberra, NSW, Australia
| | - Gawn McIlwaine
- Department of Ophthalmology, Mater Hospital, Belfast, Northern, Ireland
| | - Christian J Lueck
- School of Medicine and Psychology, Australian National University, Canberra, NSW, Australia.
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3
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He J, Zhang F, Pan Y, Feng Y, Rushmore J, Torio E, Rathi Y, Makris N, Kikinis R, Golby AJ, O'Donnell LJ. Reconstructing the somatotopic organization of the corticospinal tract remains a challenge for modern tractography methods. Hum Brain Mapp 2023; 44:6055-6073. [PMID: 37792280 PMCID: PMC10619402 DOI: 10.1002/hbm.26497] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 09/09/2023] [Accepted: 09/13/2023] [Indexed: 10/05/2023] Open
Abstract
The corticospinal tract (CST) is a critically important white matter fiber tract in the human brain that enables control of voluntary movements of the body. The CST exhibits a somatotopic organization, which means that the motor neurons that control specific body parts are arranged in order within the CST. Diffusion magnetic resonance imaging (MRI) tractography is increasingly used to study the anatomy of the CST. However, despite many advances in tractography algorithms over the past decade, modern, state-of-the-art methods still face challenges. In this study, we compare the performance of six widely used tractography methods for reconstructing the CST and its somatotopic organization. These methods include constrained spherical deconvolution (CSD) based probabilistic (iFOD1) and deterministic (SD-Stream) methods, unscented Kalman filter (UKF) tractography methods including multi-fiber (UKF2T) and single-fiber (UKF1T) models, the generalized q-sampling imaging (GQI) based deterministic tractography method, and the TractSeg method. We investigate CST somatotopy by dividing the CST into four subdivisions per hemisphere that originate in the leg, trunk, hand, and face areas of the primary motor cortex. A quantitative and visual comparison is performed using diffusion MRI data (N = 100 subjects) from the Human Connectome Project. Quantitative evaluations include the reconstruction rate of the eight anatomical subdivisions, the percentage of streamlines in each subdivision, and the coverage of the white matter-gray matter (WM-GM) interface. CST somatotopy is further evaluated by comparing the percentage of streamlines in each subdivision to the cortical volumes for the leg, trunk, hand, and face areas. Overall, UKF2T has the highest reconstruction rate and cortical coverage. It is the only method with a significant positive correlation between the percentage of streamlines in each subdivision and the volume of the corresponding motor cortex. However, our experimental results show that all compared tractography methods are biased toward generating many trunk streamlines (ranging from 35.10% to 71.66% of total streamlines across methods). Furthermore, the coverage of the WM-GM interface in the largest motor area (face) is generally low (under 40%) for all compared tractography methods. Different tractography methods give conflicting results regarding the percentage of streamlines in each subdivision and the volume of the corresponding motor cortex, indicating that there is generally no clear relationship, and that reconstruction of CST somatotopy is still a large challenge. Overall, we conclude that while current tractography methods have made progress toward the well-known challenge of improving the reconstruction of the lateral projections of the CST, the overall problem of performing a comprehensive CST reconstruction, including clinically important projections in the lateral (hand and face areas) and medial portions (leg area), remains an important challenge for diffusion MRI tractography.
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Affiliation(s)
- Jianzhong He
- Institution of Information Processing and AutomationZhejiang University of TechnologyHangzhouChina
| | - Fan Zhang
- Department of Radiology, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
- University of Electronic Science and Technology of ChinaChengduSichuanChina
| | - Yiang Pan
- Institution of Information Processing and AutomationZhejiang University of TechnologyHangzhouChina
| | - Yuanjing Feng
- Institution of Information Processing and AutomationZhejiang University of TechnologyHangzhouChina
| | - Jarrett Rushmore
- Departments of Psychiatry, Neurology and RadiologyMassachusetts General Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of Anatomy and NeurobiologyBoston University School of MedicineBostonMassachusettsUSA
| | - Erickson Torio
- Department of NeurosurgeryBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Yogesh Rathi
- Department of Radiology, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
- Department of PsychiatryBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Nikos Makris
- Departments of Psychiatry, Neurology and RadiologyMassachusetts General Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of PsychiatryBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Ron Kikinis
- Department of Radiology, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
| | - Alexandra J. Golby
- Department of Radiology, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
- Department of NeurosurgeryBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Lauren J. O'Donnell
- Department of Radiology, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
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Li Z, Miller KL, Andersson JLR, Zhang J, Liu S, Guo H, Wu W. Sampling strategies and integrated reconstruction for reducing distortion and boundary slice aliasing in high-resolution 3D diffusion MRI. Magn Reson Med 2023; 90:1484-1501. [PMID: 37317708 PMCID: PMC10952965 DOI: 10.1002/mrm.29741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 04/14/2023] [Accepted: 05/17/2023] [Indexed: 06/16/2023]
Abstract
PURPOSE To develop a new method for high-fidelity, high-resolution 3D multi-slab diffusion MRI with minimal distortion and boundary slice aliasing. METHODS Our method modifies 3D multi-slab imaging to integrate blip-reversed acquisitions for distortion correction and oversampling in the slice direction (kz ) for reducing boundary slice aliasing. Our aim is to achieve robust acceleration to keep the scan time the same as conventional 3D multi-slab acquisitions, in which data are acquired with a single direction of blip traversal and without kz -oversampling. We employ a two-stage reconstruction. In the first stage, the blip-up/down images are respectively reconstructed and analyzed to produce a field map for each diffusion direction. In the second stage, the blip-reversed data and the field map are incorporated into a joint reconstruction to produce images that are corrected for distortion and boundary slice aliasing. RESULTS We conducted experiments at 7T in six healthy subjects. Stage 1 reconstruction produces images from highly under-sampled data (R = 7.2) with sufficient quality to provide accurate field map estimation. Stage 2 joint reconstruction substantially reduces distortion artifacts with comparable quality to fully-sampled blip-reversed results (2.4× scan time). Whole-brain in-vivo results acquired at 1.22 mm and 1.05 mm isotropic resolutions demonstrate improved anatomical fidelity compared to conventional 3D multi-slab imaging. Data demonstrate good reliability and reproducibility of the proposed method over multiple subjects. CONCLUSION The proposed acquisition and reconstruction framework provide major reductions in distortion and boundary slice aliasing for 3D multi-slab diffusion MRI without increasing the scan time, which can potentially produce high-quality, high-resolution diffusion MRI.
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Affiliation(s)
- Ziyu Li
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Karla L. Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Jesper L. R. Andersson
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Jieying Zhang
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of MedicineTsinghua UniversityBeijingChina
| | - Simin Liu
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of MedicineTsinghua UniversityBeijingChina
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of MedicineTsinghua UniversityBeijingChina
| | - Wenchuan Wu
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
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Carrozzi A, Gramegna LL, Sighinolfi G, Zoli M, Mazzatenta D, Testa C, Lodi R, Tonon C, Manners DN. Methods of diffusion MRI tractography for localization of the anterior optic pathway: A systematic review of validated methods. Neuroimage Clin 2023; 39:103494. [PMID: 37651845 PMCID: PMC10477810 DOI: 10.1016/j.nicl.2023.103494] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 06/21/2023] [Accepted: 08/07/2023] [Indexed: 09/02/2023]
Abstract
The anterior optic pathway (AOP) is a system of three structures (optic nerves, optic chiasma, and optic tracts) that convey visual stimuli from the retina to the lateral geniculate nuclei. A successful reconstruction of the AOP using tractography could be helpful in several clinical scenarios, from presurgical planning and neuronavigation of sellar and parasellar surgery to monitoring the stage of fiber degeneration both in acute (e.g., traumatic optic neuropathy) or chronic conditions that affect AOP structures (e.g., amblyopia, glaucoma, demyelinating disorders or genetic optic nerve atrophies). However, its peculiar anatomy and course, as well as its surroundings, pose a serious challenge to obtaining successful tractographic reconstructions. Several AOP tractography strategies have been adopted but no standard procedure has been agreed upon. We performed a systematic review of the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) 2020 guidelines in order to find the combinations of acquisition and reconstruction parameters that have been performed previously and have provided the highest rate of successful reconstruction of the AOP, in order to promote their routine implementation in clinical practice. For this purpose, we reviewed data regarding how the process of anatomical validation of the tractographies was performed. The Cochrane Handbook for Systematic Reviews of Interventions was used to assess the risk of bias and thus the study quality We identified thirty-nine studies that met our inclusion criteria, and only five were considered at low risk of bias and achieved over 80% of successful reconstructions. We found a high degree of heterogeneity in the acquisition and analysis parameters used to perform AOP tractography and different combinations of them can achieve satisfactory levels of anterior optic tractographic reconstruction both in real-life research and clinical scenarios. One thousand s/mm2 was the most frequently used b value, while both deterministic and probabilistic tractography algorithms performed morphological reconstruction of the tract satisfactorily, although probabilistic algorithms estimated a more realistic percentage of crossing fibers (45.6%) in healthy subjects. A wide heterogeneity was also found regarding the method used to assess the anatomical fidelity of the AOP reconstructions. Three main strategies can be found: direct visual direct visual assessment of the tractography superimposed to a conventional MR image, surgical evaluation, and computational methods. Because the latter is less dependent on a priori knowledge of the anatomy by the operator, computational methods of validation of the anatomy should be considered whenever possible.
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Affiliation(s)
- Alessandro Carrozzi
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Laura Ludovica Gramegna
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Functional and Molecular Neuroimaging Unit, Bologna, Italy.
| | - Giovanni Sighinolfi
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Matteo Zoli
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Pituitary Unit, Bologna, Italy
| | - Diego Mazzatenta
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Pituitary Unit, Bologna, Italy
| | - Claudia Testa
- Department of Physics and Astronomy, University of Bologna, Bologna, Italy
| | - Raffaele Lodi
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - Caterina Tonon
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Functional and Molecular Neuroimaging Unit, Bologna, Italy
| | - David Neil Manners
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Functional and Molecular Neuroimaging Unit, Bologna, Italy; Department for Life Quality Studies (QUVI), University of Bologna, Bologna, Italy
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Ivanov D, De Martino F, Formisano E, Fritz FJ, Goebel R, Huber L, Kashyap S, Kemper VG, Kurban D, Roebroeck A, Sengupta S, Sorger B, Tse DHY, Uludağ K, Wiggins CJ, Poser BA. Magnetic resonance imaging at 9.4 T: the Maastricht journey. MAGMA (NEW YORK, N.Y.) 2023; 36:159-173. [PMID: 37081247 PMCID: PMC10140139 DOI: 10.1007/s10334-023-01080-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 03/18/2023] [Accepted: 03/20/2023] [Indexed: 04/22/2023]
Abstract
The 9.4 T scanner in Maastricht is a whole-body magnet with head gradients and parallel RF transmit capability. At the time of the design, it was conceptualized to be one of the best fMRI scanners in the world, but it has also been used for anatomical and diffusion imaging. 9.4 T offers increases in sensitivity and contrast, but the technical ultra-high field (UHF) challenges, such as field inhomogeneities and constraints set by RF power deposition, are exacerbated compared to 7 T. This article reviews some of the 9.4 T work done in Maastricht. Functional imaging experiments included blood oxygenation level-dependent (BOLD) and blood-volume weighted (VASO) fMRI using different readouts. BOLD benefits from shorter T2* at 9.4 T while VASO from longer T1. We show examples of both ex vivo and in vivo anatomical imaging. For many applications, pTx and optimized coils are essential to harness the full potential of 9.4 T. Our experience shows that, while considerable effort was required compared to our 7 T scanner, we could obtain high-quality anatomical and functional data, which illustrates the potential of MR acquisitions at even higher field strengths. The practical challenges of working with a relatively unique system are also discussed.
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Affiliation(s)
- Dimo Ivanov
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands.
| | - Federico De Martino
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Elia Formisano
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Francisco J Fritz
- Institute of Systems Neuroscience, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Rainer Goebel
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Laurentius Huber
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Sriranga Kashyap
- Krembil Brain Institute, University Health Network, Toronto, ON, Canada
| | - Valentin G Kemper
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Denizhan Kurban
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Alard Roebroeck
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | | | - Bettina Sorger
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
| | - Desmond H Y Tse
- Scannexus BV, Oxfordlaan 55, 6229 EV, Maastricht, The Netherlands
| | - Kâmil Uludağ
- Krembil Brain Institute, Koerner Scientist in MR Imaging, University Health Network Toronto, Toronto, ON, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
- Center for Neuroscience Imaging Research, Institute for Basic Science and Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Christopher J Wiggins
- Imaging Core Facility (INM-ICF), Institut für Neurowissenschaften und Medizin, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Benedikt A Poser
- Faculty of Psychology and Neuroscience, Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands
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Horton JC, Dilbeck MD, Economides JR. Decussating axons segregate within the anterior core of the primate optic chiasm. Br J Ophthalmol 2023; 107:447-452. [PMID: 36575620 PMCID: PMC10038861 DOI: 10.1136/bjo-2022-322235] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 09/02/2022] [Indexed: 12/12/2022]
Abstract
BACKGROUND The axons of ganglion cells in the nasal retina decussate at the optic chiasm. It is unclear why tumours cause more injury to crossing nasal fibres, thereby giving rise to temporal visual field loss in each eye. To address this issue, the course of fibres through the optic chiasm was examined following injection of a different fluorescent tracer into each eye of a monkey. METHODS Under general anaesthesia, cholera toxin subunit B-Alexa Fluor 488 was injected into the right eye and cholera toxin subunit B-Alexa Fluor 594 was injected into the left eye of a single normal adult male rhesus monkey. After a week's survival for anterograde transport, serial coronal sections through the primary optic pathway were examined. RESULTS A zone within the core of the anterior and mid portions of the optic chiasm was comprised entirely of crossing fibres. This zone of decussation was delineated by segregated, interwoven sheets of green (right eye) and red (left eye) fibres. It expanded steadily to fill more of the optic chiasm as fibres coursed posteriorly towards the optic tracts. Eventually, crossed fibres became completely intermingled with uncrossed fibres, so that ocular separation was lost. CONCLUSIONS A distinct, central compartment located within the anterior two-thirds of the optic chiasm contains only crossing fibres. Sellar tumours focus their compressive force on this portion of the structure, explaining why they so often produce visual field loss in the temporal fields.
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Affiliation(s)
- Jonathan C Horton
- Department of Ophthalmology, University of California San Francisco, San Francisco, California, USA
| | - Mikayla D Dilbeck
- Department of Ophthalmology, University of California San Francisco, San Francisco, California, USA
| | - John R Economides
- Department of Ophthalmology, University of California San Francisco, San Francisco, California, USA
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Ramos-Llordén G, Lobos RA, Kim TH, Tian Q, Witzel T, Lee HH, Scholz A, Keil B, Yendiki A, Bilgiç B, Haldar JP, Huang SY. High-fidelity, high-spatial-resolution diffusion magnetic resonance imaging of ex vivo whole human brain at ultra-high gradient strength with structured low-rank echo-planar imaging ghost correction. NMR IN BIOMEDICINE 2023; 36:e4831. [PMID: 36106429 PMCID: PMC9883835 DOI: 10.1002/nbm.4831] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 08/20/2022] [Accepted: 09/11/2022] [Indexed: 06/15/2023]
Abstract
Diffusion magnetic resonance imaging (dMRI) of whole ex vivo human brain specimens enables three-dimensional (3D) mapping of structural connectivity at the mesoscopic scale, providing detailed evaluation of fiber architecture and tissue microstructure at a spatial resolution that is difficult to access in vivo. To account for the short T2 and low diffusivity of fixed tissue, ex vivo dMRI is often acquired using strong diffusion-sensitizing gradients and multishot/segmented 3D echo-planar imaging (EPI) sequences to achieve high spatial resolution. However, the combination of strong diffusion-sensitizing gradients and multishot/segmented EPI readout can result in pronounced ghosting artifacts incurred by nonlinear spatiotemporal variations in the magnetic field produced by eddy currents. Such ghosting artifacts cannot be corrected with conventional correction solutions and pose a significant roadblock to leveraging human MRI scanners with ultrahigh gradients for ex vivo whole-brain dMRI. Here, we show that ghosting-correction approaches that correct for either polarity-related ghosting or shot-to-shot variations in a separate manner are suboptimal for 3D multishot diffusion-weighted EPI experiments in fixed human brain specimens using strong diffusion-sensitizing gradients on the 3-T Connectom MRI scanner, resulting in orientationally biased dMRI estimates. We apply a recently developed advanced k-space reconstruction method based on structured low-rank matrix (SLM) modeling that handles both polarity-related ghosting and shot-to-shot variation simultaneously, to mitigate artifacts in high-angular resolution multishot dMRI data acquired in several fixed human brain specimens at 0.7-0.8-mm isotropic spatial resolution using b-values up to 10,000 s/mm2 and gradient strengths up to 280 mT/m. We demonstrate the improved mapping of diffusion tensor imaging and fiber orientation distribution functions in key neuroanatomical areas distributed across the whole brain using SLM-based EPI ghost correction compared with alternative techniques.
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Affiliation(s)
- Gabriel Ramos-Llordén
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Rodrigo A. Lobos
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA
| | - Tae Hyung Kim
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
- Computer Engineering, Hongik University, Seoul, Republic of Korea
| | - Qiyuan Tian
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Hong-Hsi Lee
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Alina Scholz
- Institute of Medical Physics and Radiation Protection, Mittelhessen University of Applied Sciences, Giessen, Germany
| | - Boris Keil
- Institute of Medical Physics and Radiation Protection, Mittelhessen University of Applied Sciences, Giessen, Germany
- Department of Diagnostic and Interventional Radiology, University Hospital Marburg, Philipps University of Marburg, Marburg, Germany
| | - Anastasia Yendiki
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Berkin Bilgiç
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Justin P. Haldar
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA
| | - Susie Y. Huang
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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9
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Grotheer M, Kubota E, Grill-Spector K. Establishing the functional relevancy of white matter connections in the visual system and beyond. Brain Struct Funct 2022; 227:1347-1356. [PMID: 34846595 PMCID: PMC9046284 DOI: 10.1007/s00429-021-02423-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 11/02/2021] [Indexed: 01/04/2023]
Abstract
For over a century, researchers have examined the functional relevancy of white matter bundles. Consequently, many large-scale bundles spanning several centimeters have been associated in their entirety with specific brain functions, such as language or attention. However, these coarse structural-functional relationships are at odds with modern understanding of the fine-grained functional organization of human cortex, such as the mosaic of category-selective regions in ventral temporal cortex. Here, we review a multimodal approach that combines fMRI to define functional regions of interest within individual's brains with dMRI tractography to identify the white matter bundles of the same individual. Combining these data allows to determine which subsets of streamlines within a white matter bundle connect to specific functional regions in each individual. That is, this approach identifies the functionally defined white matter sub-bundles of the brain. We argue that this approach not only enhances the accuracy of interpreting the functional relevancy of white matter bundles, but also enables segmentation of these large-scale bundles into meaningful functional units, which can then be linked to behavior with enhanced precision. Importantly, this approach has the potential for making new discoveries of the fine-grained functional relevancy of white matter connections in the visual system and the brain more broadly, akin to the flurry of research that has identified functional regions in cortex.
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Affiliation(s)
- Mareike Grotheer
- Department of Psychology, Philipps-Universität Marburg, 35032, Marburg, Germany.
- Center for Mind, Brain and Behavior-CMBB, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, 35037, Marburg, Germany.
| | - Emily Kubota
- Psychology Department, Stanford University, Stanford, CA, 94305, USA
| | - Kalanit Grill-Spector
- Psychology Department, Stanford University, Stanford, CA, 94305, USA
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, 94305, USA
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10
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Novello L, Henriques RN, Ianuş A, Feiweier T, Shemesh N, Jovicich J. In vivo Correlation Tensor MRI reveals microscopic kurtosis in the human brain on a clinical 3T scanner. Neuroimage 2022; 254:119137. [PMID: 35339682 DOI: 10.1016/j.neuroimage.2022.119137] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 02/17/2022] [Accepted: 03/22/2022] [Indexed: 12/15/2022] Open
Abstract
Diffusion MRI (dMRI) has become one of the most important imaging modalities for noninvasively probing tissue microstructure. Diffusional Kurtosis MRI (DKI) quantifies the degree of non-gaussian diffusion, which in turn has been shown to increase sensitivity towards, e.g., disease and orientation mapping in neural tissue. However, the specificity of DKI is limited as different sources can contribute to the total intravoxel diffusional kurtosis, including: variance in diffusion tensor magnitudes (Kiso), variance due to diffusion anisotropy (Kaniso), and microscopic kurtosis (μK) related to restricted diffusion, microstructural disorder, and/or exchange. Interestingly, μK is typically ignored in diffusion MRI signal modeling as it is assumed to be negligible in neural tissues. However, recently, Correlation Tensor MRI (CTI) based on Double-Diffusion-Encoding (DDE) was introduced for kurtosis source separation, revealing non negligible μK in preclinical imaging. Here, we implemented CTI for the first time on a clinical 3T scanner and investigated the sources of total kurtosis in healthy subjects. A robust framework for kurtosis source separation in humans is introduced, followed by estimation of μK (and the other kurtosis sources) in the healthy brain. Using this clinical CTI approach, we find that μK significantly contributes to total diffusional kurtosis both in gray and white matter tissue but, as expected, not in the ventricles. The first μK maps of the human brain are presented, revealing that the spatial distribution of μK provides a unique source of contrast, appearing different from isotropic and anisotropic kurtosis counterparts. Moreover, group average templates of these kurtosis sources have been generated for the first time, which corroborated our findings at the underlying individual-level maps. We further show that the common practice of ignoring μK and assuming the multiple gaussian component approximation for kurtosis source estimation introduces significant bias in the estimation of other kurtosis sources and, perhaps even worse, compromises their interpretation. Finally, a twofold acceleration of CTI is discussed in the context of potential future clinical applications. We conclude that CTI has much potential for future in vivo microstructural characterizations in healthy and pathological tissue.
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Affiliation(s)
- Lisa Novello
- Center for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, Italy.
| | | | - Andrada Ianuş
- Champalimaud Research, Champalimaud Foundation, Lisbon, Portugal
| | | | - Noam Shemesh
- Champalimaud Research, Champalimaud Foundation, Lisbon, Portugal
| | - Jorge Jovicich
- Center for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto, Italy
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11
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Pang Y, Tan Z, Mo W, Chen X, Wei J, Guo Q, Zhong Q, Zhong J. A pilot study of combined optical coherence tomography and diffusion tensor imaging method for evaluating microstructural change in the visual pathway of pituitary adenoma patients. BMC Ophthalmol 2022; 22:115. [PMID: 35279128 PMCID: PMC8917617 DOI: 10.1186/s12886-022-02320-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 02/19/2022] [Indexed: 02/06/2023] Open
Abstract
Background RNFL thickness measured by optical coherence tomography (OCT) and visual pathway measured by diffusion tensor imaging (DTI) can be used to predict visual field recovery, respectively. However, the relationship between RNFL thickness and visual pathway injury in patients with pituitary adenoma (PA) remains unclear. This study aims to evaluate the combining DTI and OCT methods in observing the microstructural change in the visual pathway in patients with PA. Methods Twenty-nine patients who were diagnosed with PA were included in the study group, and 29 healthy subjects were included as the control group. OCT detected the thickness of circumpapillary retinal nerve fiber layer (CP-RNFL) and ganglion cell layer (GCL). DTI measured the values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Correlation between CP-RNFL and GCL thickness and FA and ADC values was analyzed in the study group. Results Compared with the control group, the FA values of the bilateral optic nerve, chiasma, bilateral optic tract, and left optic radiation in the study group were reduced, and the ADC values of the bilateral optic nerve and optic chiasma were increased. Correlation analysis showed that the FA value of the optic chiasma was positively correlated with the average thickness of RNFL, the CP-RNFL thickness in the nasal and temporal retinal quadrants in both eyes, as well as the thickness of macular ring GCL in the nasal, supra, and inferior quadrants. The FA values of the optic nerve, optic chiasma, optic tract, and optic radiation were positively correlated with CP-RNFL thickness in the nasal and temporal quadrants. Conclusion Combined DTI and OCT can provide a comprehensive understanding of the microscopic changes in the structure and function of the whole visual pathway in patients with PA.
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12
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Moerel M, Yacoub E, Gulban OF, Lage-Castellanos A, De Martino F. Using high spatial resolution fMRI to understand representation in the auditory network. Prog Neurobiol 2021; 207:101887. [PMID: 32745500 PMCID: PMC7854960 DOI: 10.1016/j.pneurobio.2020.101887] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/27/2020] [Accepted: 07/15/2020] [Indexed: 12/23/2022]
Abstract
Following rapid methodological advances, ultra-high field (UHF) functional and anatomical magnetic resonance imaging (MRI) has been repeatedly and successfully used for the investigation of the human auditory system in recent years. Here, we review this work and argue that UHF MRI is uniquely suited to shed light on how sounds are represented throughout the network of auditory brain regions. That is, the provided gain in spatial resolution at UHF can be used to study the functional role of the small subcortical auditory processing stages and details of cortical processing. Further, by combining high spatial resolution with the versatility of MRI contrasts, UHF MRI has the potential to localize the primary auditory cortex in individual hemispheres. This is a prerequisite to study how sound representation in higher-level auditory cortex evolves from that in early (primary) auditory cortex. Finally, the access to independent signals across auditory cortical depths, as afforded by UHF, may reveal the computations that underlie the emergence of an abstract, categorical sound representation based on low-level acoustic feature processing. Efforts on these research topics are underway. Here we discuss promises as well as challenges that come with studying these research questions using UHF MRI, and provide a future outlook.
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Affiliation(s)
- Michelle Moerel
- Maastricht Centre for Systems Biology, Maastricht University, Maastricht, the Netherlands; Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht, the Netherlands.
| | - Essa Yacoub
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, USA.
| | - Omer Faruk Gulban
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht, the Netherlands; Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, USA; Brain Innovation B.V., Maastricht, the Netherlands.
| | - Agustin Lage-Castellanos
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht, the Netherlands; Department of NeuroInformatics, Cuban Center for Neuroscience, Cuba.
| | - Federico De Martino
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, the Netherlands; Maastricht Brain Imaging Center (MBIC), Maastricht, the Netherlands; Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, USA.
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13
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Abstract
We describe a collection of T1-, diffusion- and functional T2*-weighted magnetic resonance imaging data from human individuals with albinism and achiasma. This repository can be used as a test-bed to develop and validate tractography methods like diffusion-signal modeling and fiber tracking as well as to investigate the properties of the human visual system in individuals with congenital abnormalities. The MRI data is provided together with tools and files allowing for its preprocessing and analysis, along with the data derivatives such as manually curated masks and regions of interest for performing tractography.
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14
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Mapping degeneration of the visual system in long-term follow-up after childhood hemispherectomy - A series of four cases. Epilepsy Res 2021; 178:106808. [PMID: 34801940 DOI: 10.1016/j.eplepsyres.2021.106808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 10/18/2021] [Accepted: 11/02/2021] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Although hemidisconnection surgery may eliminate or reduce seizure activity in patients with epilepsy, there are visual, cognitive and motor deficits which affect patients' function post-operatively, with varying severity and according to pathology. Consequently, there is a need to map microstructural changes over long time periods and develop/apply methods that work with legacy data. METHODS In this study, we applied the novel single shell 3-Tissue method to data from a cohort of 4 patients who were scanned 20-years following childhood hemidisconnection surgery and presented with variable clinical outcomes. We have successfully reconstructed tractography of the whole visual pathway from single shell diffusion data with reduced number of gradient directions. RESULTS All patients presented with degeneration of the visual system characterised by low fractional anisotropy and high mean diffusivity. There were no apparent microstructural differences between both optic nerves that could explain the different level of visual function across patients. However, we provide evidence suggesting an association between the level of visual function and DTI metrics within the remaining components of the visual system, particularly the optic tract, of the contralateral hemisphere post-surgery. SIGNIFICANCE We believe this study suggests that diffusion MRI can be used to monitor the integrity of the visual system following hemispherectomy and if extended to larger cohorts and a greater number of time-points, including pre-surgically, can provide a clearer picture of the natural history of visual system degeneration. This knowledge may in turn help to identify patients at greatest risk of poor visual outcomes that might benefit from rehabilitation therapies.
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15
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He J, Zhang F, Xie G, Yao S, Feng Y, Bastos DCA, Rathi Y, Makris N, Kikinis R, Golby AJ, O'Donnell LJ. Comparison of multiple tractography methods for reconstruction of the retinogeniculate visual pathway using diffusion MRI. Hum Brain Mapp 2021; 42:3887-3904. [PMID: 33978265 PMCID: PMC8288095 DOI: 10.1002/hbm.25472] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/24/2021] [Accepted: 04/25/2021] [Indexed: 12/31/2022] Open
Abstract
The retinogeniculate visual pathway (RGVP) conveys visual information from the retina to the lateral geniculate nucleus. The RGVP has four subdivisions, including two decussating and two nondecussating pathways that cannot be identified on conventional structural magnetic resonance imaging (MRI). Diffusion MRI tractography has the potential to trace these subdivisions and is increasingly used to study the RGVP. However, it is not yet known which fiber tracking strategy is most suitable for RGVP reconstruction. In this study, four tractography methods are compared, including constrained spherical deconvolution (CSD) based probabilistic (iFOD1) and deterministic (SD-Stream) methods, and multi-fiber (UKF-2T) and single-fiber (UKF-1T) unscented Kalman filter (UKF) methods. Experiments use diffusion MRI data from 57 subjects in the Human Connectome Project. The RGVP is identified using regions of interest created by two clinical experts. Quantitative anatomical measurements and expert anatomical judgment are used to assess the advantages and limitations of the four tractography methods. Overall, we conclude that UKF-2T and iFOD1 produce the best RGVP reconstruction results. The iFOD1 method can better quantitatively estimate the percentage of decussating fibers, while the UKF-2T method produces reconstructed RGVPs that are judged to better correspond to the known anatomy and have the highest spatial overlap across subjects. Overall, we find that it is challenging for current tractography methods to both accurately track RGVP fibers that correspond to known anatomy and produce an approximately correct percentage of decussating fibers. We suggest that future algorithm development for RGVP tractography should take consideration of both of these two points.
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Affiliation(s)
- Jianzhong He
- Institute of Information Processing and Automation, College of Information Engineering, Zhejiang University of TechnologyHangzhouChina
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Fan Zhang
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Guoqiang Xie
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of NeurosurgeryNuclear Industry 215 Hospital of Shaanxi ProvinceXianyangChina
| | - Shun Yao
- Department of Neurosurgery, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
- Center for Pituitary Tumor Surgery, Department of NeurosurgeryThe First Affiliated Hospital, Sun Yat‐sen UniversityGuangzhouChina
| | - Yuanjing Feng
- Institute of Information Processing and Automation, College of Information Engineering, Zhejiang University of TechnologyHangzhouChina
| | - Dhiego C. A. Bastos
- Department of Neurosurgery, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
| | - Yogesh Rathi
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of Psychiatry, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
| | - Nikos Makris
- Department of Psychiatry, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
- Departments of Psychiatry, Neurology and Radiology, Massachusetts General HospitalHarvard Medical SchoolBostonMassachusettsUSA
| | - Ron Kikinis
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Alexandra J. Golby
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of Neurosurgery, Brigham and Women's HospitalHarvard Medical SchoolBostonMassachusettsUSA
| | - Lauren J. O'Donnell
- Department of RadiologyBrigham and Women's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
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16
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Bosler NSI, Ashton D, Neely AJ, Lueck CJ. Variation in the Anatomy of the Normal Human Optic Chiasm: An MRI Study. J Neuroophthalmol 2021; 41:194-199. [PMID: 32141976 DOI: 10.1097/wno.0000000000000907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Compression of the optic chiasm typically leads to bitemporal hemianopia. This implies that decussating nasal fibers are selectively affected, but the precise mechanism is unclear. Stress on nasal fibers has been investigated using finite element modeling but requires accurate anatomical data to generate a meaningful output. The precise shape of the chiasm is unclear: A recent photomicrographic study suggested that nasal fibers decussate paracentrally and run parallel to each other in the central arm of an "H." This study aimed to determine the population variation in chiasmal shape to inform future models. METHODS Sequential MRI scans of 68 healthy individuals were selected. 2D images of each chiasm were created and analyzed to determine the angle of elevation of the chiasm, the width of the chiasm, and the offset between the points of intersection of lines drawn down the centers of the optic nerves and contralateral optic tracts. RESULTS The mean width of the chiasm was 12.0 ± 1.5 mm (SD), and the mean offset was 4.7 ± 1.4 mm generating a mean offset:width ratio of 0.38 ± 0.09. No chiasm had an offset of zero. The mean incident angle of optic nerves was 56 ± 7°, and for optic tracts, it was 51 ± 7°. CONCLUSIONS The human optic chiasm is "H" shaped, not "X" shaped. The findings are consistent with nasal fibers decussating an average of 2.4 mm lateral to the midline before travelling in parallel across the midline. This information will inform future models of chiasmal compression.
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Affiliation(s)
- Nicholas S I Bosler
- Australian National University Medical School (NSIB, DA, CJL), Canberra, Australia ; Departments of Neurology (NSIB, CJL) and Radiology (DA), The Canberra Hospital, Canberra, Australia; and School of Engineering and Information Technology (AJN), University of New South Wales, Canberra, Australia
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17
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Mohammadi S, Callaghan MF. Towards in vivo g-ratio mapping using MRI: Unifying myelin and diffusion imaging. J Neurosci Methods 2021; 348:108990. [PMID: 33129894 PMCID: PMC7840525 DOI: 10.1016/j.jneumeth.2020.108990] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 09/21/2020] [Accepted: 10/20/2020] [Indexed: 12/19/2022]
Abstract
BACKGROUND The g-ratio, quantifying the comparative thickness of the myelin sheath encasing an axon, is a geometrical invariant that has high functional relevance because of its importance in determining neuronal conduction velocity. Advances in MRI data acquisition and signal modelling have put in vivo mapping of the g-ratio, across the entire white matter, within our reach. This capacity would greatly increase our knowledge of the nervous system: how it functions, and how it is impacted by disease. NEW METHOD This is the second review on the topic of g-ratio mapping using MRI. RESULTS This review summarizes the most recent developments in the field, while also providing methodological background pertinent to aggregate g-ratio weighted mapping, and discussing pitfalls associated with these approaches. COMPARISON WITH EXISTING METHODS Using simulations based on recently published data, this review reveals caveats to the state-of-the-art calibration methods that have been used for in vivo g-ratio mapping. It highlights the need to estimate both the slope and offset of the relationship between these MRI-based markers and the true myelin volume fraction if we are really to achieve the goal of precise, high sensitivity g-ratio mapping in vivo. Other challenges discussed in this review further evidence the need for gold standard measurements of human brain tissue from ex vivo histology. CONCLUSIONS We conclude that the quest to find the most appropriate MRI biomarkers to enable in vivo g-ratio mapping is ongoing, with the full potential of many novel techniques yet to be investigated.
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Affiliation(s)
- Siawoosh Mohammadi
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
| | - Martina F Callaghan
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, UK
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18
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Kaneko T, Takemura H, Pestilli F, Silva AC, Ye FQ, Leopold DA. Spatial organization of occipital white matter tracts in the common marmoset. Brain Struct Funct 2020; 225:1313-1326. [PMID: 32253509 PMCID: PMC7577349 DOI: 10.1007/s00429-020-02060-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 03/18/2020] [Indexed: 11/30/2022]
Abstract
The primate brain contains a large number of interconnected visual areas, whose spatial organization and intracortical projections show a high level of conservation across species. One fiber pathway of recent interest is the vertical occipital fasciculus (VOF), which is thought to support communication between dorsal and ventral visual areas in the occipital lobe. A recent comparative diffusion MRI (dMRI) study reported that the VOF in the macaque brain bears a similar topology to that of the human, running superficial and roughly perpendicular to the optic radiation. The present study reports a comparative investigation of the VOF in the common marmoset, a small New World monkey whose lissencephalic brain is approximately tenfold smaller than the macaque and 150-fold smaller than the human. High-resolution ex vivo dMRI of two marmoset brains revealed an occipital white matter structure that closely resembles that of the larger primate species, with one notable difference. Namely, unlike in the macaque and the human, the VOF in the marmoset is spatially fused with other, more anterior vertical tracts, extending anteriorly between the parietal and temporal cortices. We compare several aspects of this continuous structure, which we term the VOF complex (VOF +), and neighboring fasciculi to those of macaques and humans. We hypothesize that the essential topology of the VOF+ is a conserved feature of the posterior cortex in anthropoid primates, with a clearer fragmentation into multiple named fasciculi in larger, more gyrified brains.
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Affiliation(s)
- Takaaki Kaneko
- RIKEN Center for Brain Science (CBS), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
- Systems Neuroscience Section, Primate Research Institute, Kyoto University, 41 Kanrin, Inuyamas-shi, Aichi, 484-8506, Japan.
| | - Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, and Osaka University, 1-4 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
- Graduate School of Frontier Biosciences, Osaka University, 1-4 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
| | - Franco Pestilli
- Department of Psychological and Brain Sciences, Indiana University, 1101 E 10th Street, Bloomington, IN, 47405, USA
| | - Afonso C Silva
- Department of Neurobiology, University of Pittsburgh Brain Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Frank Q Ye
- Neurophysiology Imaging Facility, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - David A Leopold
- Neurophysiology Imaging Facility, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
- Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
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19
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Rushmore RJ, Bouix S, Kubicki M, Rathi Y, Yeterian EH, Makris N. How Human Is Human Connectional Neuroanatomy? Front Neuroanat 2020; 14:18. [PMID: 32351367 PMCID: PMC7176274 DOI: 10.3389/fnana.2020.00018] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/23/2020] [Indexed: 01/16/2023] Open
Abstract
The structure of the human brain has been studied extensively. Despite all the knowledge accrued, direct information about connections, from origin to termination, in the human brain is extremely limited. Yet there is a widespread misperception that human connectional neuroanatomy is well-established and validated. In this article, we consider what is known directly about human structural and connectional neuroanatomy. Information on neuroanatomical connections in the human brain is derived largely from studies in non-human experimental models in which the entire connectional pathway, including origins, course, and terminations, is directly visualized. Techniques to examine structural connectivity in the human brain are progressing rapidly; nevertheless, our present understanding of such connectivity is limited largely to data derived from homological comparisons, particularly with non-human primates. We take the position that an in-depth and more precise understanding of human connectional neuroanatomy will be obtained by a systematic application of this homological approach.
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Affiliation(s)
- R Jarrett Rushmore
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, United States.,Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Center for Morphometric Analysis, Department of Psychiatry and Neurology, A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Sylvain Bouix
- Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States
| | - Marek Kubicki
- Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Center for Morphometric Analysis, Department of Psychiatry and Neurology, A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Yogesh Rathi
- Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Center for Morphometric Analysis, Department of Psychiatry and Neurology, A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Edward H Yeterian
- Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Center for Morphometric Analysis, Department of Psychiatry and Neurology, A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.,Department of Psychology, Colby College, Waterville, ME, United States
| | - Nikos Makris
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, United States.,Psychiatric Neuroimaging Laboratory, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Center for Morphometric Analysis, Department of Psychiatry and Neurology, A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
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20
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Puzniak RJ, Ahmadi K, Kaufmann J, Gouws A, Morland AB, Pestilli F, Hoffmann MB. Quantifying nerve decussation abnormalities in the optic chiasm. NEUROIMAGE-CLINICAL 2019; 24:102055. [PMID: 31722288 PMCID: PMC6849426 DOI: 10.1016/j.nicl.2019.102055] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 10/14/2019] [Accepted: 10/22/2019] [Indexed: 12/26/2022]
Abstract
Diffusion MRI is capable of detecting structural abnormalities of the optic chiasm. Quantification of crossing strength in optic chiasm is of promise for albinism diagnostics. Optic chiasm is a powerful test model for neuroimaging methods resolving crossing fibers.
Objective The human optic chiasm comprises partially crossing optic nerve fibers. Here we used diffusion MRI (dMRI) for the in-vivo identification of the abnormally high proportion of crossing fibers found in the optic chiasm of people with albinism. Methods In 9 individuals with albinism and 8 controls high-resolution 3T dMRI data was acquired and analyzed with a set of methods for signal modeling [Diffusion Tensor (DT) and Constrained Spherical Deconvolution (CSD)], tractography, and streamline filtering (LiFE, COMMIT, and SIFT2). The number of crossing and non-crossing streamlines and their weights after filtering entered ROC-analyses to compare the discriminative power of the methods based on the area under the curve (AUC). The dMRI results were cross-validated with fMRI estimates of misrouting in a subset of 6 albinotic individuals. Results We detected significant group differences in chiasmal crossing for both unfiltered DT (p = 0.014) and CSD tractograms (p = 0.0009) also reflected by AUC measures (for DT and CSD: 0.61 and 0.75, respectively), underlining the discriminative power of the approach. Estimates of crossing strengths obtained with dMRI and fMRI were significantly correlated for CSD (R2 = 0.83, p = 0.012). The results show that streamline filtering methods in combination with probabilistic tracking, both optimized for the data at hand, can improve the detection of crossing in the human optic chiasm. Conclusions Especially CSD-based tractography provides an efficient approach to detect structural abnormalities in the optic chiasm. The most realistic results were obtained with filtering methods with parameters optimized for the data at hand. Significance Our findings demonstrate a novel anatomy-driven approach for the individualized diagnostics of optic chiasm abnormalities.
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Affiliation(s)
- Robert J Puzniak
- Department of Ophthalmology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Khazar Ahmadi
- Department of Ophthalmology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Jörn Kaufmann
- Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Andre Gouws
- York Neuroimaging Centre, Department of Psychology, University of York, York, United Kingdom
| | - Antony B Morland
- York Neuroimaging Centre, Department of Psychology, University of York, York, United Kingdom; York Biomedical Research Institute, University of York, York, United Kingdom
| | - Franco Pestilli
- Department of Psychological and Brain Sciences, Program in Neuroscience and Program in Cognitive Science, Indiana University, Bloomington, USA
| | - Michael B Hoffmann
- Department of Ophthalmology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany; Center for Behavioral Brain Sciences, Magdeburg, Germany.
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21
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Visual loss and recovery in chiasmal compression. Prog Retin Eye Res 2019; 73:100765. [DOI: 10.1016/j.preteyeres.2019.06.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 06/05/2019] [Accepted: 06/12/2019] [Indexed: 12/18/2022]
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22
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Ultra-high resolution and multi-shell diffusion MRI of intact ex vivo human brains using kT-dSTEAM at 9.4T. Neuroimage 2019; 202:116087. [DOI: 10.1016/j.neuroimage.2019.116087] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 08/08/2019] [Indexed: 01/07/2023] Open
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23
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Takemura H, Pestilli F, Weiner KS. Comparative neuroanatomy: Integrating classic and modern methods to understand association fibers connecting dorsal and ventral visual cortex. Neurosci Res 2019; 146:1-12. [PMID: 30389574 PMCID: PMC6491271 DOI: 10.1016/j.neures.2018.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 10/19/2018] [Accepted: 10/25/2018] [Indexed: 12/13/2022]
Abstract
Comparative neuroanatomy studies improve understanding of brain structure and function and provide insight regarding brain development, evolution, and also what features of the brain are uniquely human. With modern methods such as diffusion MRI (dMRI) and quantitative MRI (qMRI), we are able to measure structural features of the brain with the same methods across human and non-human primates. In this review article, we discuss how recent dMRI measurements of vertical occipital connections in humans and macaques can be compared with previous findings from invasive anatomical studies that examined connectivity, including relatively forgotten classic strychnine neuronography studies. We then review recent progress in understanding the neuroanatomy of vertical connections within the occipitotemporal cortex by combining modern quantitative MRI and classical histological measurements in human and macaque. Finally, we a) discuss current limitations of dMRI and tractography and b) consider potential paths for future investigations using dMRI and tractography for comparative neuroanatomical studies of white matter tracts between species. While we focus on vertical association connections in visual cortex in the present paper, this same approach can be applied to other white matter tracts. Similar efforts are likely to continue to advance our understanding of the neuroanatomical features of the brain that are shared across species, as well as to distinguish the features that are uniquely human.
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Affiliation(s)
- Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, and Osaka University, Suita, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.
| | - Franco Pestilli
- Departments of Psychological and Brain Sciences, Computer Science and Intelligent Systems Engineering, Programs in Neuroscience and Cognitive Science, School of Optometry, Indiana University, Bloomington, IN, USA
| | - Kevin S Weiner
- Department of Psychology, University of California, Berkeley, CA, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA
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24
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Caspers S, Axer M. Decoding the microstructural correlate of diffusion MRI. NMR IN BIOMEDICINE 2019; 32:e3779. [PMID: 28858413 DOI: 10.1002/nbm.3779] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 06/28/2017] [Accepted: 07/05/2017] [Indexed: 06/07/2023]
Abstract
Diffusion imaging has evolved considerably over the past decade. While it provides valuable information about the structural connectivity at the macro- and mesoscopic scale, bridging the gap to the microstructure at the level of single nerve fibers poses an enormous challenge. This is particularly true for the human brain with its large size, its large white-matter volume and availability of histological techniques for studying human whole-brain sections and subsequent 3D reconstruction. Classic post-mortem techniques for studying the fiber architecture of the brain, such as myeloarchitectonic staining or dye tracing, are complemented by novel histological approaches, such as 3D polarized light imaging or optical coherence tomography, enabling unique insight into the fiber architecture from large fiber bundles within deep white matter to single nerve fibers in the cortex. The present review discusses the benefits and challenges of these latest developments in comparison with the classic techniques, with particular focus on the mutual exchange between in vivo and post-mortem diffusion imaging and post-mortem microstructural approaches for understanding the wiring of the brain across different scales.
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Affiliation(s)
- Svenja Caspers
- C. and O. Vogt Institute for Brain Research, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany
- JARA-BRAIN, Jülich-Aachen Research Alliance, Jülich, Germany
| | - Markus Axer
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany
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25
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Roebroeck A, Miller KL, Aggarwal M. Ex vivo diffusion MRI of the human brain: Technical challenges and recent advances. NMR IN BIOMEDICINE 2019; 32:e3941. [PMID: 29863793 PMCID: PMC6492287 DOI: 10.1002/nbm.3941] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 04/17/2018] [Accepted: 04/17/2018] [Indexed: 05/23/2023]
Abstract
This review discusses ex vivo diffusion magnetic resonance imaging (dMRI) as an important research tool for neuroanatomical investigations and the validation of in vivo dMRI techniques, with a focus on the human brain. We review the challenges posed by the properties of post-mortem tissue, and discuss state-of-the-art tissue preparation methods and recent advances in pulse sequences and acquisition techniques to tackle these. We then review recent ex vivo dMRI studies of the human brain, highlighting the validation of white matter orientation estimates and the atlasing and mapping of large subcortical structures. We also give particular emphasis to the delineation of layered gray matter structure with ex vivo dMRI, as this application illustrates the strength of its mesoscale resolution over large fields of view. We end with a discussion and outlook on future and potential directions of the field.
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Affiliation(s)
- Alard Roebroeck
- Department of Cognitive Neuroscience, Faculty of Psychology & NeuroscienceMaastricht UniversityMaastrichtthe Netherlands
| | | | - Manisha Aggarwal
- Department of RadiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
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26
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Sani I, McPherson BC, Stemmann H, Pestilli F, Freiwald WA. Functionally defined white matter of the macaque monkey brain reveals a dorso-ventral attention network. eLife 2019; 8:e40520. [PMID: 30601116 PMCID: PMC6345568 DOI: 10.7554/elife.40520] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 12/20/2018] [Indexed: 12/18/2022] Open
Abstract
Classical studies of attention have identified areas of parietal and frontal cortex as sources of attentional control. Recently, a ventral region in the macaque temporal cortex, the posterior infero-temporal dorsal area PITd, has been suggested as a third attentional control area. This raises the question of whether and how spatially distant areas coordinate a joint focus of attention. Here we tested the hypothesis that parieto-frontal attention areas and PITd are directly interconnected. By combining functional MRI with ex-vivo high-resolution diffusion MRI, we found that PITd and dorsal attention areas are all directly connected through three specific fascicles. These results ascribe a new function, the communication of attention signals, to two known fiber-bundles, highlight the importance of vertical interactions across the two visual streams, and imply that the control of endogenous attention, hitherto thought to reside in macaque dorsal cortical areas, is exerted by a dorso-ventral network.
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Affiliation(s)
- Ilaria Sani
- Laboratory of Neural SystemsThe Rockefeller UniversityNew YorkUnited States
| | - Brent C McPherson
- Department of Psychological and Brain SciencesIndiana UniversityBloomingtonUnited States
| | - Heiko Stemmann
- Institute for Brain Research and Center for Advanced ImagingUniversity of BremenBremenGermany
| | - Franco Pestilli
- Department of Psychological and Brain SciencesIndiana UniversityBloomingtonUnited States
| | - Winrich A Freiwald
- Laboratory of Neural SystemsThe Rockefeller UniversityNew YorkUnited States
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27
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Mohammadi S, Weiskopf N. [Computational neuroanatomy and microstructure imaging using magnetic resonance imaging]. DER NERVENARZT 2017; 88:839-849. [PMID: 28721539 DOI: 10.1007/s00115-017-0373-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Current computational neuroanatomy focuses on morphological measurements of the brain using standard magnetic resonance imaging (MRI) techniques. In comparison quantitative MRI (qMRI) typically provides a better tissue contrast and also greatly improves the sensitivity and specificity with respect to the microstructural characteristics of tissue. OBJECTIVE Current methodological developments in qMRI are presented, which go beyond morphology because this provides standardized measurements of the microstructure of the brain. The concept of in-vivo histology is introduced, based on biophysical modelling of qMRI data (hMRI) for determination of quantitative histology-like markers of the microstructure. RESULTS The qMRI metrics can be used as direct biomarkers of the microstructural mechanisms driving observed morphological findings. The hMRI metrics utilize biophysical models of the MRI signal in order to determine 3‑dimensional maps of histology-like measurements in the white matter. CONCLUSION Non-invasive brain tissue characterization using qMRI or hMRI has significant implications for both scientific and clinical applications. Both approaches improve the comparability across sites and time points, facilitate multicenter and longitudinal studies as well as standardized diagnostics. The hMRI is expected to shed new light on the relationship between brain microstructure, function and behavior both in health and disease. In the future hMRI will play an indispensable role in the field of computational neuroanatomy.
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Affiliation(s)
- S Mohammadi
- Institut für systemische Neurowissenschaften, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
- Max-Planck-Institut für Kognitions- und Neurowissenschaften, Stephanstr. 1a, 04103, Leipzig, Deutschland
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London, Großbritannien
| | - N Weiskopf
- Max-Planck-Institut für Kognitions- und Neurowissenschaften, Stephanstr. 1a, 04103, Leipzig, Deutschland.
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London, Großbritannien.
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28
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Schaeffer DJ, Adam R, Gilbert KM, Gati JS, Li AX, Menon RS, Everling S. Diffusion-weighted tractography in the common marmoset monkey at 9.4T. J Neurophysiol 2017; 118:1344-1354. [PMID: 28615334 DOI: 10.1152/jn.00259.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/08/2017] [Accepted: 06/08/2017] [Indexed: 11/22/2022] Open
Abstract
The common marmoset (Callithrix jacchus) is a small New World primate that is becoming increasingly popular in the neurosciences as an animal model of preclinical human disease. With several major disorders characterized by alterations in neural white matter (e.g., multiple sclerosis, Alzheimer's disease, schizophrenia), proposed to be transgenically modeled using marmosets, the ability to isolate and characterize reliably major white matter fiber tracts with MRI will be of use for evaluating structural brain changes related to disease processes and symptomatology. Here, we propose protocols for isolating major white matter fiber tracts in the common marmoset using in vivo ultrahigh-field MRI (9.4T) diffusion-weighted imaging (DWI) data. With the use of a high angular-resolution DWI (256 diffusion-encoding directions) sequence, collected on four anesthetized marmosets, we provide guidelines for manually drawing fiber-tracking regions of interest, based on easily identified anatomical landmarks in DWI native space. These fiber-tract isolation protocols are expected to be experimentally useful for visualization and quantification of individual white matter fiber tracts in both control and experimental groups of marmosets (e.g., transgenic models). As disease models in the marmoset advance, the determination of how macroscopic white matter anatomy is altered as a function of disease state will be relevant in bridging the existing translational gap between preclinical rodent models and human patients.NEW & NOTEWORTHY Although significant progress has been made in mapping white matter connections in the marmoset brain using ex vivo tracing techniques, the application of in vivo virtual dissection of major white matter fiber tracts has been established by few studies in the marmoset literature. Here, we demonstrate the feasibility of whole-brain diffusion-weighted tractography in anesthetized marmosets at ultrahigh-field MRI (9.4T) and propose protocols for isolating nine major white matter fiber tracts in the marmoset brain.
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Affiliation(s)
- David J Schaeffer
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
| | - Ramina Adam
- Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada
| | - Kyle M Gilbert
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
| | - Joseph S Gati
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
| | - Alex X Li
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
| | - Ravi S Menon
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
| | - Stefan Everling
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; and
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29
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Takemura H, Pestilli F, Weiner KS, Keliris GA, Landi SM, Sliwa J, Ye FQ, Barnett MA, Leopold DA, Freiwald WA, Logothetis NK, Wandell BA. Occipital White Matter Tracts in Human and Macaque. Cereb Cortex 2017; 27:3346-3359. [PMID: 28369290 PMCID: PMC5890896 DOI: 10.1093/cercor/bhx070] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Revised: 03/01/2017] [Accepted: 03/04/2017] [Indexed: 12/17/2022] Open
Abstract
We compare several major white-matter tracts in human and macaque occipital lobe using diffusion magnetic resonance imaging. The comparison suggests similarities but also significant differences in the tracts. There are several apparently homologous tracts in the 2 species, including the vertical occipital fasciculus (VOF), optic radiation, forceps major, and inferior longitudinal fasciculus (ILF). There is one large human tract, the inferior fronto-occipital fasciculus, with no corresponding fasciculus in macaque. We could identify the macaque VOF (mVOF), which has been little studied. Its position is consistent with classical invasive anatomical studies by Wernicke. VOF homology is supported by similarity of the endpoints in V3A and ventral V4 across species. The mVOF fibers intertwine with the dorsal segment of the ILF, but the human VOF appears to be lateral to the ILF. These similarities and differences between the occipital lobe tracts will be useful in establishing which circuitry in the macaque can serve as an accurate model for human visual cortex.
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Affiliation(s)
- Hiromasa Takemura
- Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, and Osaka University, Suita-shi, Osaka 565-0871, Japan
- Graduate School of Frontier Biosciences, Osaka University, Suita-shi, Osaka 565-0871, Japan
| | - Franco Pestilli
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | - Kevin S. Weiner
- Department of Psychology, Stanford University, Stanford, CA 94305, USA
| | - Georgios A. Keliris
- Max Planck Institute for Biological Cybernetics, 72072 Tübingen, Germany
- Bio-Imaging Laboratory, Department of Biomedical Sciences, University of Antwerp, Wilrijk 2610, Belgium
| | - Sofia M. Landi
- Laboratory of Neural Systems, The Rockefeller University, New York, NY 10065, USA
| | - Julia Sliwa
- Laboratory of Neural Systems, The Rockefeller University, New York, NY 10065, USA
| | - Frank Q. Ye
- Neurophysiology Imaging Facility, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Eye Institute, National Institutes of Health, Bethesda, MD 20814, USA
| | | | - David A. Leopold
- Neurophysiology Imaging Facility, National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, National Eye Institute, National Institutes of Health, Bethesda, MD 20814, USA
| | - Winrich A. Freiwald
- Laboratory of Neural Systems, The Rockefeller University, New York, NY 10065, USA
| | | | - Brian A. Wandell
- Department of Psychology, Stanford University, Stanford, CA 94305, USA
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30
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Sengupta S, Fritz FJ, Harms RL, Hildebrand S, Tse DHY, Poser BA, Goebel R, Roebroeck A. High resolution anatomical and quantitative MRI of the entire human occipital lobe ex vivo at 9.4T. Neuroimage 2017; 168:162-171. [PMID: 28336427 PMCID: PMC5862655 DOI: 10.1016/j.neuroimage.2017.03.039] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 03/17/2017] [Accepted: 03/19/2017] [Indexed: 11/06/2022] Open
Abstract
Several magnetic resonance imaging (MRI) contrasts are sensitive to myelin content in gray matter in vivo which has ignited ambitions of MRI-based in vivo cortical histology. Ultra-high field (UHF) MRI, at fields of 7 T and beyond, is crucial to provide the resolution and contrast needed to sample contrasts over the depth of the cortex and get closer to layer resolved imaging. Ex vivo MRI of human post mortem samples is an important stepping stone to investigate MRI contrast in the cortex, validate it against histology techniques applied in situ to the same tissue, and investigate the resolutions needed to translate ex vivo findings to in vivo UHF MRI. Here, we investigate key technology to extend such UHF studies to large human brain samples while maintaining high resolution, which allows investigation of the layered architecture of several cortical areas over their entire 3D extent and their complete borders where architecture changes. A 16 channel cylindrical phased array radiofrequency (RF) receive coil was constructed to image a large post mortem occipital lobe sample (~80×80×80 mm3) in a wide-bore 9.4 T human scanner with the aim of achieving high-resolution anatomical and quantitative MR images. Compared with a human head coil at 9.4 T, the maximum Signal-to-Noise ratio (SNR) was increased by a factor of about five in the peripheral cortex. Although the transmit profile with a circularly polarized transmit mode at 9.4 T is relatively inhomogeneous over the large sample, this challenge was successfully resolved with parallel transmit using the kT-points method. Using this setup, we achieved 60μm anatomical images for the entire occipital lobe showing increased spatial definition of cortical details compared to lower resolutions. In addition, we were able to achieve sufficient control over SNR, B0 and B1 homogeneity and multi-contrast sampling to perform quantitative T2* mapping over the same volume at 200 μm. Markov Chain Monte Carlo sampling provided maximum posterior estimates of quantitative T2* and their uncertainty, allowing delineation of the stria of Gennari over the entire length and width of the calcarine sulcus. We discuss how custom RF receive coil arrays built to specific large post mortem sample sizes can provide a platform for UHF cortical layer-specific quantitative MRI over large fields of view. Custom-built 16 channel 9.4 T RF-coil to image large post mortem samples at high resolution. Parallel transmit techniques allow homogenization of B1+ for 3D GRE imaging at UHF. 60 μm anatomical MRI of the entire human occipital lobe. 200 μm isotropic quantitative T2* mapping of the entire human occipital lobe. A platform for future UHF cortical layer specific qMRI over large FoVs.
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Affiliation(s)
- S Sengupta
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
| | - F J Fritz
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - R L Harms
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - S Hildebrand
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - D H Y Tse
- Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - B A Poser
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - R Goebel
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - A Roebroeck
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
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31
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van de Vijver I, Ridderinkhof KR, Harsay H, Reneman L, Cavanagh JF, Buitenweg JIV, Cohen MX. Frontostriatal anatomical connections predict age- and difficulty-related differences in reinforcement learning. Neurobiol Aging 2016; 46:1-12. [PMID: 27460144 DOI: 10.1016/j.neurobiolaging.2016.06.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 06/07/2016] [Indexed: 12/12/2022]
Abstract
Reinforcement learning (RL) is supported by a network of striatal and frontal cortical structures that are connected through white-matter fiber bundles. With age, the integrity of these white-matter connections declines. The role of structural frontostriatal connectivity in individual and age-related differences in RL is unclear, although local white-matter density and diffusivity have been linked to individual differences in RL. Here we show that frontostriatal tract counts in young human adults (aged 18-28), as assessed noninvasively with diffusion-weighted magnetic resonance imaging and probabilistic tractography, positively predicted individual differences in RL when learning was difficult (70% valid feedback). In older adults (aged 63-87), in contrast, learning under both easy (90% valid feedback) and difficult conditions was predicted by tract counts in the same frontostriatal network. Furthermore, network-level analyses showed a double dissociation between the task-relevant networks in young and older adults, suggesting that older adults relied on different frontostriatal networks than young adults to obtain the same task performance. These results highlight the importance of successful information integration across striatal and frontal regions during RL, especially with variable outcomes.
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Affiliation(s)
- Irene van de Vijver
- Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands; Behavioural Science Institute, Radboud University, Nijmegen, The Netherlands.
| | | | - Helga Harsay
- Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands; Nieuw Unicum, Zandvoort, The Netherlands
| | - Liesbeth Reneman
- Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - James F Cavanagh
- Department of Psychology, University of New Mexico, Albuquerque, NM, USA
| | | | - Michael X Cohen
- Department of Psychology, University of Amsterdam, Amsterdam, The Netherlands
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32
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Sotiropoulos SN, Hernández-Fernández M, Vu AT, Andersson JL, Moeller S, Yacoub E, Lenglet C, Ugurbil K, Behrens TEJ, Jbabdi S. Fusion in diffusion MRI for improved fibre orientation estimation: An application to the 3T and 7T data of the Human Connectome Project. Neuroimage 2016; 134:396-409. [PMID: 27071694 PMCID: PMC6318224 DOI: 10.1016/j.neuroimage.2016.04.014] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 02/24/2016] [Accepted: 04/07/2016] [Indexed: 11/21/2022] Open
Abstract
Determining the acquisition parameters in diffusion magnetic resonance imaging (dMRI) is governed by a series of trade-offs. Images of lower resolution have less spatial specificity but higher signal to noise ratio (SNR). At the same time higher angular contrast, important for resolving complex fibre patterns, also yields lower SNR. Considering these trade-offs, the Human Connectome Project (HCP) acquires high quality dMRI data for the same subjects at different field strengths (3T and 7T), which are publically released. Due to differences in the signal behavior and in the underlying scanner hardware, the HCP 3T and 7T data have complementary features in k- and q-space. The 3T dMRI has higher angular contrast and resolution, while the 7T dMRI has higher spatial resolution. Given the availability of these datasets, we explore the idea of fusing them together with the aim of combining their benefits. We extend a previously proposed data-fusion framework and apply it to integrate both datasets from the same subject into a single joint analysis. We use a generative model for performing parametric spherical deconvolution and estimate fibre orientations by simultaneously using data acquired under different protocols. We illustrate unique features from each dataset and how they are retained after fusion. We further show that this allows us to complement benefits and improve brain connectivity analysis compared to analyzing each of the datasets individually.
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Affiliation(s)
- Stamatios N Sotiropoulos
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, Oxford, UK.
| | | | - An T Vu
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Jesper L Andersson
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, Oxford, UK
| | - Steen Moeller
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Essa Yacoub
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Christophe Lenglet
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Kamil Ugurbil
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Timothy E J Behrens
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, Oxford, UK; Wellcome Trust Centre for Neuroimaging, University College London, London, UK
| | - Saad Jbabdi
- Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, Oxford, UK
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33
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Correlation of the measurements of optical coherence tomography and diffuse tension imaging of optic pathways in amblyopia. Int Ophthalmol 2016; 37:85-93. [PMID: 27068828 DOI: 10.1007/s10792-016-0229-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 04/04/2016] [Indexed: 10/22/2022]
Abstract
The aim of this study was to investigate whether a correlation exists between optical coherence tomography (OCT) of retina and diffusion tensor imaging (DTI) of the optic pathway measurements. All subjects underwent OCT measurements of optic nerve head, retinal nerve fiber layer, and macula. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of optic pathways were analyzed using DTI. Prechiasmatic FA values were significantly decreased in unilateral amblyopic group in both affected and sound fellow eyes (p = 0.019 and 0.013), but not in bilateral amblyopic group (p = 0.221) when compared with the control group. ADC values were significantly greater in sound eye in unilateral amblyopic group in prechiasmatic and postchiasmatic regions (p = 0.001 and 0.049). ADC values were also significantly greater in bilateral amblyopic group in postchiasmatic region (p = 0.037). There were no significant differences between the affected eye and sound eye side DTI measurements. There was no significant correlation between prechiasmatic DTI and OCT measurements in affected and sound eyes of unilateral amblyopia group. DTI results demonstrated that there is a functional underdevelopment of the anterior and posterior visual pathways in both affected and sound eye of unilateral amblyopic patients. Significantly reduced FA values in prechiasmatic region where OCT values of retina were normal can be explained by possible micro-structural changes.
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Non Local Spatial and Angular Matching: Enabling higher spatial resolution diffusion MRI datasets through adaptive denoising. Med Image Anal 2016; 32:115-30. [PMID: 27082655 DOI: 10.1016/j.media.2016.02.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/23/2015] [Accepted: 02/29/2016] [Indexed: 11/24/2022]
Abstract
Diffusion magnetic resonance imaging (MRI) datasets suffer from low Signal-to-Noise Ratio (SNR), especially at high b-values. Acquiring data at high b-values contains relevant information and is now of great interest for microstructural and connectomics studies. High noise levels bias the measurements due to the non-Gaussian nature of the noise, which in turn can lead to a false and biased estimation of the diffusion parameters. Additionally, the usage of in-plane acceleration techniques during the acquisition leads to a spatially varying noise distribution, which depends on the parallel acceleration method implemented on the scanner. This paper proposes a novel diffusion MRI denoising technique that can be used on all existing data, without adding to the scanning time. We first apply a statistical framework to convert both stationary and non stationary Rician and non central Chi distributed noise to Gaussian distributed noise, effectively removing the bias. We then introduce a spatially and angular adaptive denoising technique, the Non Local Spatial and Angular Matching (NLSAM) algorithm. Each volume is first decomposed in small 4D overlapping patches, thus capturing the spatial and angular structure of the diffusion data, and a dictionary of atoms is learned on those patches. A local sparse decomposition is then found by bounding the reconstruction error with the local noise variance. We compare against three other state-of-the-art denoising methods and show quantitative local and connectivity results on a synthetic phantom and on an in-vivo high resolution dataset. Overall, our method restores perceptual information, removes the noise bias in common diffusion metrics, restores the extracted peaks coherence and improves reproducibility of tractography on the synthetic dataset. On the 1.2 mm high resolution in-vivo dataset, our denoising improves the visual quality of the data and reduces the number of spurious tracts when compared to the noisy acquisition. Our work paves the way for higher spatial resolution acquisition of diffusion MRI datasets, which could in turn reveal new anatomical details that are not discernible at the spatial resolution currently used by the diffusion MRI community.
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García-Gomar MG, Soto-Abraham J, Velasco-Campos F, Concha L. Anatomic characterization of prelemniscal radiations by probabilistic tractography: implications in Parkinson's disease. Brain Struct Funct 2016; 222:71-81. [PMID: 26902343 DOI: 10.1007/s00429-016-1201-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 02/09/2016] [Indexed: 12/19/2022]
Abstract
To characterize the anatomical connectivity of the prelemniscal radiations (Raprl), a white matter region within the posterior subthalamic area (PSA) that is an effective neurosurgical target for treating motor symptoms of Parkinson's disease (PD). Diffusion-weighted images were acquired from twelve healthy subjects using a 3T scanner. Constrained spherical deconvolution, a method that allows the distinction of crossing fibers within a voxel, was used to compute track-density images with sufficient resolution to accurately delineate distinct PSA regions and probabilistic tractography of Raprl in both hemispheres. Raprl connectivity was reproducible across all subjects and showed fibers traversing through this region towards primary and supplementary motor cortices, the orbitofrontal cortex, ventrolateral thalamus, and the globus pallidus, cerebellum and dorsal brainstem. All brain regions reached by Raprl fibers are part of motor circuits involved in the pathophysiology of PD; while these fiber systems converge at the level of the PSA, they can be spatially segregated. Fibers of distinct and specific motor control networks are identified within Raprl. The description of this anatomical crossroad suggests that, in the future, tractography could allow deep brain stimulation or lesional therapies in white matter targets according to individual patient's symptoms.
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Affiliation(s)
| | - Julian Soto-Abraham
- Unit for Stereotactic and Functional Neurosurgery and Radiosurgery, Mexico General Hospital, Mexico City, Mexico
| | - Francisco Velasco-Campos
- Unit for Stereotactic and Functional Neurosurgery and Radiosurgery, Mexico General Hospital, Mexico City, Mexico
| | - Luis Concha
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, México.
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Mohammadi S, Carey D, Dick F, Diedrichsen J, Sereno MI, Reisert M, Callaghan MF, Weiskopf N. Whole-Brain In-vivo Measurements of the Axonal G-Ratio in a Group of 37 Healthy Volunteers. Front Neurosci 2015; 9:441. [PMID: 26640427 PMCID: PMC4661323 DOI: 10.3389/fnins.2015.00441] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/03/2015] [Indexed: 12/13/2022] Open
Abstract
The g-ratio, quantifying the ratio between the inner and outer diameters of a fiber, is an important microstructural characteristic of fiber pathways and is functionally related to conduction velocity. We introduce a novel method for estimating the MR g-ratio non-invasively across the whole brain using high-fidelity magnetization transfer (MT) imaging and single-shell diffusion MRI. These methods enabled us to map the MR g-ratio in vivo across the brain's prominent fiber pathways in a group of 37 healthy volunteers and to estimate the inter-subject variability. Effective correction of susceptibility-related distortion artifacts was essential before combining the MT and diffusion data, in order to reduce partial volume and edge artifacts. The MR g-ratio is in good qualitative agreement with histological findings despite the different resolution and spatial coverage of MRI and histology. The MR g-ratio holds promise as an important non-invasive biomarker due to its microstructural and functional relevance in neurodegeneration.
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Affiliation(s)
- Siawoosh Mohammadi
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf Hamburg, Germany ; Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, UK
| | - Daniel Carey
- Birkbeck/UCL Centre for NeuroImaging, Birkbeck College London, UK
| | - Fred Dick
- Birkbeck/UCL Centre for NeuroImaging, Birkbeck College London, UK
| | - Joern Diedrichsen
- UCL Institute of Cognitive Neurology, University College London London, UK
| | - Martin I Sereno
- Birkbeck/UCL Centre for NeuroImaging, Birkbeck College London, UK
| | - Marco Reisert
- Medical Physics, Department of Radiology, University Medical Center Freiburg Freiburg, Germany
| | - Martina F Callaghan
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, UK
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, UK ; Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany
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Aquilina K, Daniels DJ, Spoudeas H, Phipps K, Gan HW, Boop FA. Optic pathway glioma in children: does visual deficit correlate with radiology in focal exophytic lesions? Childs Nerv Syst 2015; 31:2041-9. [PMID: 26277358 DOI: 10.1007/s00381-015-2855-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 07/28/2015] [Indexed: 11/25/2022]
Abstract
PURPOSE Unlike pilocytic astrocytomas in other parts of the brain, optic pathway gliomas (OPG) are usually diffuse lesions involving the anterior optic pathways and hypothalamus. Their infiltrative nature often precludes complete surgical resection. We sought to determine whether careful magnetic resonance (MR) analysis, correlated with visual deficits, could be sufficient to identify those focal lesions that may be amenable to more aggressive surgical resection at presentation. METHODS We retrospectively reviewed the medical records of patients from two sites: children under 20 years of age treated for OPG between 1985 and 2009 at St Jude's Children's Research Hospital and children under 16 years of age treated at Great Ormond Street Hospital, London, UK, between 1984 and 2011. Patients with isolated optic nerve tumors were excluded. Visual acuity and visual field data at presentation were reviewed and correlated with MR characteristics, including extent of optic pathway involvement, symmetry, and lateral extension. RESULTS Two hundred and one children were treated for OPG between 1984 and 2011 in the two institutions; 74 had neurofibromatosis 1 (NF1). At presentation, visual loss was symmetrical in 132 patients and asymmetrical in 69. Potential correlation between pattern of visual loss and tumor characteristics on routine MRI was found in only 13 patients with asymmetrical vision. There was no difference between patients with and without NF1. CONCLUSION The decision for aggressive surgical resection for optic pathway gliomas should be based on clinical criteria, particularly in children with good vision in one eye and poor vision in the other, as current MRI results do not reliably predict visual field deficits.
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Affiliation(s)
- Kristian Aquilina
- Department of Neurosurgery, Great Ormond Street Hospital, London, UK
| | - David J Daniels
- Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, TN, USA.,Division of Pediatric Neurosurgery, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Helen Spoudeas
- Developmental Endocrinology Research Group, Clinical & Molecular Genetics Unit, University College London Institute of Child Health, London, UK
| | - Kim Phipps
- Department of Neurosurgery, Great Ormond Street Hospital, London, UK
| | - Hoong-Wei Gan
- Developmental Endocrinology Research Group, Clinical & Molecular Genetics Unit, University College London Institute of Child Health, London, UK
| | - Frederick A Boop
- Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, TN, USA. .,Division of Pediatric Neurosurgery, St Jude Children's Research Hospital, Memphis, TN, USA. .,Semmes Murphey Clinic, 6325 Humphreys Blvd., Memphis, TN, 38120, USA.
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Seehaus A, Roebroeck A, Bastiani M, Fonseca L, Bratzke H, Lori N, Vilanova A, Goebel R, Galuske R. Histological validation of high-resolution DTI in human post mortem tissue. Front Neuroanat 2015; 9:98. [PMID: 26257612 PMCID: PMC4511840 DOI: 10.3389/fnana.2015.00098] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
Diffusion tensor imaging (DTI) is amongst the simplest mathematical models available for diffusion magnetic resonance imaging, yet still by far the most used one. Despite the success of DTI as an imaging tool for white matter fibers, its anatomical underpinnings on a microstructural basis remain unclear. In this study, we used 65 myelin-stained sections of human premotor cortex to validate modeled fiber orientations and oft used microstructure-sensitive scalar measures of DTI on the level of individual voxels. We performed this validation on high spatial resolution diffusion MRI acquisitions investigating both white and gray matter. We found a very good agreement between DTI and myelin orientations with the majority of voxels showing angular differences less than 10°. The agreement was strongest in white matter, particularly in unidirectional fiber pathways. In gray matter, the agreement was good in the deeper layers highlighting radial fiber directions even at lower fractional anisotropy (FA) compared to white matter. This result has potentially important implications for tractography algorithms applied to high resolution diffusion MRI data if the aim is to move across the gray/white matter boundary. We found strong relationships between myelin microstructure and DTI-based microstructure-sensitive measures. High FA values were linked to high myelin density and a sharply tuned histological orientation profile. Conversely, high values of mean diffusivity (MD) were linked to bimodal or diffuse orientation distributions and low myelin density. At high spatial resolution, DTI-based measures can be highly sensitive to white and gray matter microstructure despite being relatively unspecific to concrete microarchitectural aspects.
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Affiliation(s)
- Arne Seehaus
- Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Systems Neurophysiology, Technische Universität Darmstadt Darmstadt, Germany
| | - Alard Roebroeck
- Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands
| | - Matteo Bastiani
- Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Jülich Research Centre, Institute of Neuroscience and Medicine (INM-4) Jülich, Germany
| | - Lúcia Fonseca
- Department of Biomedical Engineering, Eindhoven University of Technology Eindhoven, Netherlands
| | | | - Nicolás Lori
- Visual Neuroscience Laboratory, Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra Coimbra, Portugal
| | - Anna Vilanova
- Department of Biomedical Engineering, Eindhoven University of Technology Eindhoven, Netherlands
| | - Rainer Goebel
- Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands
| | - Ralf Galuske
- Systems Neurophysiology, Technische Universität Darmstadt Darmstadt, Germany
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Dohmen M, Menzel M, Wiese H, Reckfort J, Hanke F, Pietrzyk U, Zilles K, Amunts K, Axer M. Understanding fiber mixture by simulation in 3D Polarized Light Imaging. Neuroimage 2015; 111:464-75. [PMID: 25700950 DOI: 10.1016/j.neuroimage.2015.02.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 02/04/2015] [Accepted: 02/10/2015] [Indexed: 02/04/2023] Open
Abstract
3D Polarized Light Imaging (3D-PLI) is a neuroimaging technique that has opened up new avenues to study the complex architecture of nerve fibers in postmortem brains. The spatial orientations of the fibers are derived from birefringence measurements of unstained histological brain sections that are interpreted by a voxel-based analysis. This, however, implies that a single fiber orientation vector is obtained for each voxel and reflects the net effect of all comprised fibers. The mixture of various fiber orientations within an individual voxel is a priori not accessible by a standard 3D-PLI measurement. In order to better understand the effects of fiber mixture on the measured 3D-PLI signal and to improve the interpretation of real data, we have developed a simulation method referred to as SimPLI. By means of SimPLI, it is possible to reproduce the entire 3D-PLI analysis starting from synthetic fiber models in user-defined arrangements and ending with measurement-like tissue images. For the simulation, each synthetic fiber is considered as an optical retarder, i.e., multiple fibers within one voxel are described by multiple retarder elements. The investigation of different synthetic crossing fiber arrangements generated with SimPLI demonstrated that the derived fiber orientations are strongly influenced by the relative mixture of crossing fibers. In case of perpendicularly crossing fibers, for example, the derived fiber direction corresponds to the predominant fiber direction. The derived fiber inclination turned out to be not only influenced by myelin density but also systematically overestimated due to signal attenuation. Similar observations were made for synthetic models of optic chiasms of a human and a hooded seal which were opposed to experimental 3D-PLI data sets obtained from the chiasms of both species. Our study showed that SimPLI is a powerful method able to test hypotheses on the underlying fiber structure of brain tissue and, therefore, to improve the reliability of the extraction of nerve fiber orientations with 3D-PLI.
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Affiliation(s)
- Melanie Dohmen
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany.
| | - Miriam Menzel
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany
| | - Hendrik Wiese
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany
| | - Julia Reckfort
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany
| | - Frederike Hanke
- Institute of Biosciences, Sensory and Cognitive Ecology, University of Rostock, Germany
| | - Uwe Pietrzyk
- Institute of Neuroscience and Medicine (INM-4), Research Centre Jülich, Germany; Faculty of Mathematics and Natural Sciences, University of Wuppertal, Germany
| | - Karl Zilles
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany; Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH University Aachen, 52074 Aachen, Germany and JARA Jülich-Aachen Research Alliance, Translational Brain Medicine, 52425 Jülich, Germany
| | - Katrin Amunts
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany; C. and O. Vogt Institute of Brain Research, University of Düsseldorf, Germany
| | - Markus Axer
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Germany
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Mohammadi S, Tabelow K, Ruthotto L, Feiweier T, Polzehl J, Weiskopf N. High-resolution diffusion kurtosis imaging at 3T enabled by advanced post-processing. Front Neurosci 2015; 8:427. [PMID: 25620906 PMCID: PMC4285740 DOI: 10.3389/fnins.2014.00427] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 12/05/2014] [Indexed: 12/13/2022] Open
Abstract
Diffusion Kurtosis Imaging (DKI) is more sensitive to microstructural differences and can be related to more specific micro-scale metrics (e.g., intra-axonal volume fraction) than diffusion tensor imaging (DTI), offering exceptional potential for clinical diagnosis and research into the white and gray matter. Currently DKI is acquired only at low spatial resolution (2–3 mm isotropic), because of the lower signal-to-noise ratio (SNR) and higher artifact level associated with the technically more demanding DKI. Higher spatial resolution of about 1 mm is required for the characterization of fine white matter pathways or cortical microstructure. We used restricted-field-of-view (rFoV) imaging in combination with advanced post-processing methods to enable unprecedented high-quality, high-resolution DKI (1.2 mm isotropic) on a clinical 3T scanner. Post-processing was advanced by developing a novel method for Retrospective Eddy current and Motion ArtifacT Correction in High-resolution, multi-shell diffusion data (REMATCH). Furthermore, we applied a powerful edge preserving denoising method, denoted as multi-shell orientation-position-adaptive smoothing (msPOAS). We demonstrated the feasibility of high-quality, high-resolution DKI and its potential for delineating highly myelinated fiber pathways in the motor cortex. REMATCH performs robustly even at the low SNR level of high-resolution DKI, where standard EC and motion correction failed (i.e., produced incorrectly aligned images) and thus biased the diffusion model fit. We showed that the combination of REMATCH and msPOAS increased the contrast between gray and white matter in mean kurtosis (MK) maps by about 35% and at the same time preserves the original distribution of MK values, whereas standard Gaussian smoothing strongly biases the distribution.
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Affiliation(s)
- Siawoosh Mohammadi
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London London, UK ; Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf Hamburg, Germany
| | - Karsten Tabelow
- Stochastic Algorithms and Nonparametric Statistics, Weierstrass Institute for Applied Analysis and Stochastics Berlin, Germany
| | - Lars Ruthotto
- Department of Earth, Ocean and Atmospheric Sciences, The University of British Columbia Vancouver, BC, Canada
| | | | - Jörg Polzehl
- Stochastic Algorithms and Nonparametric Statistics, Weierstrass Institute for Applied Analysis and Stochastics Berlin, Germany
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London London, UK
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Anatomical accuracy of brain connections derived from diffusion MRI tractography is inherently limited. Proc Natl Acad Sci U S A 2014; 111:16574-9. [PMID: 25368179 DOI: 10.1073/pnas.1405672111] [Citation(s) in RCA: 507] [Impact Index Per Article: 50.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Tractography based on diffusion-weighted MRI (DWI) is widely used for mapping the structural connections of the human brain. Its accuracy is known to be limited by technical factors affecting in vivo data acquisition, such as noise, artifacts, and data undersampling resulting from scan time constraints. It generally is assumed that improvements in data quality and implementation of sophisticated tractography methods will lead to increasingly accurate maps of human anatomical connections. However, assessing the anatomical accuracy of DWI tractography is difficult because of the lack of independent knowledge of the true anatomical connections in humans. Here we investigate the future prospects of DWI-based connectional imaging by applying advanced tractography methods to an ex vivo DWI dataset of the macaque brain. The results of different tractography methods were compared with maps of known axonal projections from previous tracer studies in the macaque. Despite the exceptional quality of the DWI data, none of the methods demonstrated high anatomical accuracy. The methods that showed the highest sensitivity showed the lowest specificity, and vice versa. Additionally, anatomical accuracy was highly dependent upon parameters of the tractography algorithm, with different optimal values for mapping different pathways. These results suggest that there is an inherent limitation in determining long-range anatomical projections based on voxel-averaged estimates of local fiber orientation obtained from DWI data that is unlikely to be overcome by improvements in data acquisition and analysis alone.
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Mo Y, Chao F, Song M, Liu CR, Liu HL, Qian XY, Zhao XD. Parameter comparison of white matter diffusion tensor imaging (DTI) in rhesus macaques (Macaca mulatta). DONG WU XUE YAN JIU = ZOOLOGICAL RESEARCH 2014; 35:182-5. [PMID: 24866488 DOI: 10.11813/j.issn.0254-5853.2014.3.182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, we analyzed diffusion tensor imaging (DTI) results of brain white matter in rhesus macaques (Macaca mulatta) with four different parameter settings and found that the sequence A (b=1 000 s/mm(2), spatial resolution=1.25 mm×1.25 mm× 1.25 mm, numbers of direction=33, NSA=3) and B (b=800 s/mm(2), spatial resolution=1.25 mm×1.25 mm×1.25 mm, numbers of direction=33, NSA=3) could accurately track coarse fibers. The fractional anisotropy (FA) derived from sequence C (b=1 000s/mm(2), spatial resolution=0.55 mm×0.55 mm×2.5 mm, direction number=33, NSA=3) was too fuzzy to be used in tracking white matter fibers. By comparison, the high resolution and the FA with high contrast of gray matter and white matter derived from sequence D (b=800 s/mm(2), spatial resolution=1.0 mm×1.0 mm ×1.0 mm, numbers of direction=33, NSA=3) qualified in its application in tracking both thick and thin fibers, making it an optimal DTI setting for rhesus macaques.
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Affiliation(s)
- Yin Mo
- Department of Medical Imaging, the First Affiliated Hospital of Kunming Medical University, Kunming 650032, China
| | - Fang Chao
- Department of Medical Imaging, the First Affiliated Hospital of Kunming Medical University, Kunming 650032, China
| | - Ming Song
- National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Ci-Rong Liu
- National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Hui-Lang Liu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
| | - Xi-Ying Qian
- Department of Neurology, the First Yunnan Provincial Hospital, Kunming 650032, China.
| | - Xu-Dong Zhao
- Laboratory of Primate Neuroscience, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
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Segmentation of the canine corpus callosum using diffusion-tensor imaging tractography. AJR Am J Roentgenol 2014; 202:W19-25. [PMID: 24370161 DOI: 10.2214/ajr.12.9791] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
OBJECTIVE We set out to determine functional white matter (WM) connections passing through the canine corpus callosum; these WM connections would be useful for subsequent studies of canine brains that serve as models for human WM pathway disease. Based on prior studies, we anticipated that the anterior corpus callosum would send projections to the anterior cerebral cortex whereas progressively posterior segments would send projections to more posterior cortex. MATERIALS AND METHODS A postmortem canine brain was imaged using a 7-T MRI system producing 100-μm-isotropic-resolution diffusion-tensor imaging analyzed by tractography. Using regions of interest (ROIs) within cortical locations, which were confirmed by a Nissl stain that identified distinct cortical architecture, we successfully identified six important WM pathways. We also compared fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity, and axial diffusivity in tracts passing through the genu and splenium. RESULTS Callosal fibers were organized on the basis of cortical destination (e.g., fibers from the genu project to the frontal cortex). Histologic results identified the motor cortex on the basis of cytoarchitectonic criteria that allowed placement of ROIs to discriminate between frontal and parietal lobes. We also identified cytoarchitecture typical of the orbital frontal, anterior frontal, and occipital regions and placed ROIs accordingly. FA, ADC, radial diffusivity, and axial diffusivity values were all higher in posterior corpus callosum fiber tracts. CONCLUSION Using six cortical ROIs, we identified six major WM tracts that reflect major functional divisions of the cerebral hemispheres, and we derived quantitative values that can be used for study of canine models of human WM pathologic states.
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Tobisch A, Neher PF, Rowe MC, Maier-Hein KH, Zhang H. Model-Based Super-Resolution of Diffusion MRI. MATHEMATICS AND VISUALIZATION 2014. [DOI: 10.1007/978-3-319-02475-2_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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45
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Distinct parietal and temporal connectivity profiles of ventrolateral frontal areas involved in language production. J Neurosci 2013; 33:16846-52. [PMID: 24133284 DOI: 10.1523/jneurosci.2259-13.2013] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Broca's region, which in the language-dominant hemisphere of the human brain plays a major role in language production, includes two distinct cytoarchitectonic areas: 44 and 45. The unique connectivity patterns of these two areas have not been well established. In a resting-state functional connectivity study, we tested predictions about these areas from invasive tract-tracing studies of the connectivity of their homologs in the macaque monkey. We demonstrated their distinct connectivity profiles as well as their differences from the caudally adjacent ventral parts of the premotor cortex and the primary motor cortical region that represent the orofacial musculature. Area 45 is strongly connected with the superior temporal sulcus and the cortex on the adjacent superior and middle temporal gyri. In the parietal region, area 45 is connected with the angular gyrus, whereas area 44 is connected with the supramarginal gyrus. The primary motor cortical region in the caudal precentral gyrus is not connected with the posterior parietal region, which lies outside the confines of the postcentral gyrus, whereas the ventrorostral premotor cortical area 6VR, in the most anterior part of the precentral gyrus, has strong connections with the rostral supramarginal gyrus. Thus, area 44, which has stronger connections to the posterior supramarginal gyrus, can be distinguished from both the adjacent area 6VR and area 45. These findings provide a major improvement in understanding the connectivity of the areas in the ventrolateral frontal region that are involved in language production.
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Optimal short-time acquisition schemes in high angular resolution diffusion-weighted imaging. Int J Biomed Imaging 2013; 2013:658583. [PMID: 23554808 PMCID: PMC3608261 DOI: 10.1155/2013/658583] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Accepted: 01/18/2013] [Indexed: 11/17/2022] Open
Abstract
This work investigates the possibilities of applying high-angular-resolution-diffusion-imaging- (HARDI-) based methods in a clinical setting by investigating the performance of non-Gaussian diffusion probability density function (PDF) estimation for a range of b-values and diffusion gradient direction tables. It does so at realistic SNR levels achievable in limited time on a high-performance 3T system for the whole human brain in vivo. We use both computational simulations and in vivo brain scans to quantify the angular resolution of two selected reconstruction methods: Q-ball imaging and the diffusion orientation transform. We propose a new analytical solution to the ODF derived from the DOT. Both techniques are analytical decomposition approaches that require identical acquisition and modest postprocessing times and, given the proposed modifications of the DOT, can be analyzed in a similar fashion. We find that an optimal HARDI protocol given a stringent time constraint (<10 min) combines a moderate b-value (around 2000 s/mm2) with a relatively low number of acquired directions (>48). Our findings generalize to other methods and additional improvements in MR acquisition techniques.
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Leuze CWU, Anwander A, Bazin PL, Dhital B, Stüber C, Reimann K, Geyer S, Turner R. Layer-specific intracortical connectivity revealed with diffusion MRI. Cereb Cortex 2012; 24:328-39. [PMID: 23099298 PMCID: PMC3888365 DOI: 10.1093/cercor/bhs311] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
In this work, we show for the first time that the tangential diffusion component is orientationally coherent at the human cortical surface. Using diffusion magnetic resonance imaging (dMRI), we have succeeded in tracking intracortical fiber pathways running tangentially within the cortex. In contrast with histological methods, which reveal little regarding 3-dimensional organization in the human brain, dMRI delivers additional understanding of the layer dependence of the fiber orientation. A postmortem brain block was measured at very high angular and spatial resolution. The dMRI data had adequate resolution to allow analysis of the fiber orientation within 4 notional cortical laminae. We distinguished a lamina at the cortical surface where diffusion was tangential along the surface, a lamina below the surface where diffusion was mainly radial, an internal lamina covering the Stria of Gennari, where both strong radial and tangential diffusion could be observed, and a deep lamina near the white matter, which also showed mainly radial diffusion with a few tangential compartments. The measurement of the organization of the tangential diffusion component revealed a strong orientational coherence at the cortical surface.
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Affiliation(s)
- Christoph W U Leuze
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
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Human cortical connectome reconstruction from diffusion weighted MRI: The effect of tractography algorithm. Neuroimage 2012; 62:1732-49. [PMID: 22699045 DOI: 10.1016/j.neuroimage.2012.06.002] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 06/01/2012] [Accepted: 06/03/2012] [Indexed: 11/21/2022] Open
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Zhang Y, Wan SH, Wu GJ, Zhang XL. Magnetic resonance diffusion tensor imaging and diffusion tensor tractography of human visual pathway. Int J Ophthalmol 2012; 5:452-8. [PMID: 22937504 DOI: 10.3980/j.issn.2222-3959.2012.04.09] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Accepted: 06/20/2012] [Indexed: 11/02/2022] Open
Abstract
AIM To investigate the visual pathway in normal subjects and patients with lesion involved by diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT). METHODS Thirty normal volunteers, 3 subjects with orbital tumors involved the optic nerve (ON) and 33 subjects with occipital lobe tumors involved the optic radiation (OR) (10 gliomas, 6 meningiomas and 17 cerebral metastases) undertook routine cranium magnetic resonance imaging (MRI), DTI and DTT. Visual pathway fibers were analyzed by DTI and DTT images. Test fractional anisotropy (FA) and mean diffusivity (MD) values in different part of the visual pathway. RESULTS The whole visual pathway but optic chiasm manifested as hyperintensity in FA maps and homogenous green signal in the direction encoded color maps. The optic chiasm did not display clearly. There was no significant difference between the bilateral FA values and MD values of normal visual pathway but optic chiasm, which the FA values tested were much too low (all P>0.05). The ONs of subjects with orbital tumors were compressed and displaced. Only one subject had lower FA values and higher MD values. OR of 9 gliomas subjects were infiltrated, with displacement in 2 and disruption in 7 subjects. All OR in 6 meniongiomas subjects were displaced. OR in 17 cerebral metastases subjects all developed displacement while 7 of them had disruption also. CONCLUSION MR-DTI is highly sensitive in manifesting visual pathway. Visual pathway can be analyzed quantitatively in FA and MD values. DTT supplies accurate three dimensional conformations of visual pathway. But optic chiasm's manifestation still needs to improve.
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Affiliation(s)
- Yan Zhang
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, Guangdong Province, China
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Goebel R. BrainVoyager — Past, present, future. Neuroimage 2012; 62:748-56. [PMID: 22289803 DOI: 10.1016/j.neuroimage.2012.01.083] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 01/10/2012] [Accepted: 01/16/2012] [Indexed: 11/20/2022] Open
Affiliation(s)
- Rainer Goebel
- Dept of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, The Netherlands.
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