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TASO Manuel

PhD Student
tel : +33 4 91 38 84 65
Key Words
- Spinal Cord multi-parametric MRI
- MRI processing
- Biomechanics
- Finite element analysis
- Multiphysics approach

Current Research Interest and projects

PhD project (2013-2016) : Multiphysics characterization of Spinal Cord compressive pathologies by coupling MRI and biomechanical modeling

Supervisors : Pierre-Jean Arnoux (LBA UMRT 24 IFSTTAR/AMU) and Virginie Callot (CRMBM)

My PhD project, developed at the CRMBM and at the Laboratoire de Biomécanique Appliquée (LBA UMRT 24 IFSTTAR/AMU), in collaboration with the departments of Radiology (Pr. Chaumoître) and Neurosurgery (Pr. PH. Roche) of Marseille North’s Hospital (AP-HM), aims at introducing a new methodology for an accurate characterization of spinal cord (SC) compressive pathologies (with a focus on cervical spondylotic myelopathy), by combining advanced multi-parametric Magnetic Resonance Imaging techniques (high-resolution anatomical imaging, DTI, MT ...) and biomechanical modeling using finite element modeling (FEM) of the cervical spine. By doing so, the goal is to link the mechanical cause of the disease to its consequences (micro and macrostructural alterations assessed by MRI and functional alterations revealed by clinical symptoms).

Multi-parametric MRI for an accuracte characterization of the healthy and pathological SC

To achieve this project, intense work has been directed towards an accurate characterization of the morphology (Taso et al., MAGMA, 2014 and Taso et al., NeuroImage, 2015) and microstructure of the spinal cord using mp-MRI combined by proper post-processing tools (Taso et al., NMR in Biomedicine, 2016). Those post-processing tools include probabilistic WM/GM atlases (the AMU40 atlas) and T2*-w template providing a framework for automated WM/GM segmentation and morphological analysis using TBM (Taso et al., NeuroImage, 2015).

This is now currently used to conduct region-specific analysis of structural impairments encountered in patients suffering from cervical myelopathy to have a better understanding of the physiopathological chain of events from diagnosis to surgical decompression (Taso et al., ISMRM, 2015)

Biomechanical analysis using Finite Element Modeling (FEM) of SC compressive pathologies

The developments made at the CRMBM, and especially the probabilistic atlases provided a biofidel medullary component to a finite element model of the entire spine (SM2S – Spine Model for Safety and Surgery) which is currently used for simulation of the SC behaviour under compression as encountered in cervical spondylotic myelopathy (Taso et al., CMBBE, 2015). This should bridge the gap between the mechanical cause of the pathology and the macro/microstructural consequences observed with mp-MRI.


-  Combining biomechanical finite element analysis and multi-parametric MRI to assess the mechanical and structural damage in cervical spondylotic myelopathy. M. Taso, PJ. Arnoux, L. Fradet, A. Le Troter, JP. Ranjeva, K. Chaumoître, PH. Roche, V. Callot. ISMRM Merit Award, Magna Cum Laude . ISMRM, Singapore, 2016.
-  Regional and age-related variations of the healthy spinal cord structure assessed by multimodal MRI (diffusion, inhomogeneous magnetization transfer). M. Taso, O. Girard, G. Duhamel, A. Le Troter, G. Ribeiro, T. Feiweier, M. Guye, JP. Ranjeva, V. Callot. ISMRM Merit Award, Magna Cum Laude . ISMRM, Toronto, 2015.
-  Cervical myelopathy patient follow-up after decompressive surgery using diffusion tensor imaging (DTI) and inhomogeneous magnetization transfer (ihMT): preliminary application and results. M. Taso, O. Girard, G. Duhamel, T. Feiweier, PJ. Arnoux, M. Guye, JP. Ranjeva, K.Chaumoître, PH. Roche, V. Callot. ISMRM Merit Award, Magna Cum Laude . ISMRM, Toronto, 2015.
-  Validation of a 2D spinal cord probabilistic atlas. Application to FA measurement and VBM study of the GM atrophy occuring with age. M. Taso, A. Le Troter, M. Sdika, V. Fonov, J. Cohen-Adad, M. Guye, JP. Ranjeva, V. Callot. ISMRM Merit Award, Magna Cum Laude . ISMRM, Milan, 2014.
-  SCHIVA: construction of a Spinal Cord Human In Vivo Atlas based on high resolution MR images at cervical and thoracic levels : preliminary results. M.Taso, A. Le Troter, M. Sdika, JP. Ranjeva, M. Bernard, V. Callot. Young Investigator Award . ESMRMB 2013.



Journal Article

  • Dupont, SM, De Leener, B, Taso, M, Le Troter, A, Nadeau, S, Stikov, N, Callot, V & Cohen-Adad, J 2017, “Fully-integrated framework for the segmentation and registration of the spinal cord white and gray matter”, NeuroImage, vol. 150, p. 358-372.
    Résumé : The spinal cord white and gray matter can be affected by various pathologies such as multiple sclerosis, amyotrophic lateral sclerosis or trauma. Being able to precisely segment the white and gray matter could help with MR image analysis and hence be useful in further understanding these pathologies, and helping with diagnosis/prognosis and drug development. Up to date, white/gray matter segmentation has mostly been done manually, which is time consuming, induces a bias related to the rater and prevents large-scale multi-center studies. Recently, few methods have been proposed to automatically segment the spinal cord white and gray matter. However, no single method exists that combines the following criteria: (i) fully automatic, (ii) works on various MRI contrasts, (iii) robust towards pathology and (iv) freely available and open source. In this study we propose a multi-atlas based method for the segmentation of the spinal cord white and gray matter that addresses the previous limitations. Moreover, to study the spinal cord morphology, atlas-based approaches are increasingly used. These approaches rely on the registration of a spinal cord template to an MR image, however the registration usually doesn't take into account the spinal cord internal structure and thus lacks accuracy. In this study, we propose a new template registration framework that integrates the white and gray matter segmentation to account for the specific gray matter shape of each individual subject. Validation of segmentation was performed in 24 healthy subjects using T2*-weighted images, in 8 healthy subjects using diffusion weighted images (exhibiting inverted white-to-gray matter contrast compared to T2*-weighted), and in 5 patients with spinal cord injury. The template registration was validated in 24 subjects using T2*-weighted data. Results of automatic segmentation on T2*-weighted images was in close correspondence with the manual segmentation (Dice coefficient in the white/gray matter of 0.91/0.71 respectively). Similarly, good results were obtained in data with inverted contrast (diffusion-weighted image) and in patients. When compared to the classical template registration framework, the proposed framework that accounts for gray matter shape significantly improved the quality of the registration (comparing Dice coefficient in gray matter: p=9.5×10-6). While further validation is needed to show the benefits of the new registration framework in large cohorts and in a variety of patients, this study provides a fully-integrated tool for quantitative assessment of white/gray matter morphometry and template-based analysis. All the proposed methods are implemented in the Spinal Cord Toolbox (SCT), an open-source software for processing spinal cord multi-parametric MRI data.

  • Girard, OM, Callot, V, Prevost, VH, Robert, B, Taso, M, Ribeiro, G, Varma, G, Rangwala, N, Alsop, DC & Duhamel, G 2017, “Magnetization transfer from inhomogeneously broadened lines (ihMT): Improved imaging strategy for spinal cord applications”, Magnetic Resonance in Medicine, vol. 77, p. 581-591, viewed 10March,2016, .
    Résumé : Purpose Inhomogeneous magnetization transfer (ihMT) shows great promise for specific imaging of myelinated tissues. Whereas the ihMT technique has been previously applied in brain applications, the current report presents a strategy for cervical spinal cord (SC) imaging free of cerebrospinal fluid (CSF) pulsatility artifacts. Methods A pulsed ihMT preparation was combined with a single-shot HASTE readout. Electrocardiogram (ECG) synchronization was used to acquire all images during the quiescent phase of SC motion. However ihMT signal quantification errors may occur when a variable recovery delay is introduced in the sequence as a consequence of variable cardiac cycle. A semiautomatic retrospective correction algorithm, based on repetition time (TR) -matching, is proposed to correct for signal variations of long T1-components (e.g., CSF). Results The proposed strategy combining ECG synchronization and retrospective data pairing led to clean SC images free of CSF artifacts. Lower variability of the ihMT metrics were obtained with the correction algorithm, and allowed for shorter TR to be used, hence improving signal-to-noise ratio efficiency. Conclusion The proposed methodology enabled faster acquisitions, while offering robust ihMT quantification and exquisite SC image quality. This opens great perspectives for widening the in vivo characterization of SC physiopathology using MRI, such as studying white matter tracts microstructure or impairment in degenerative pathologies. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.
    Mots-clés : crmbm, CSF pulsatility, ECG synchronization, ihMT, inhomogeneous magnetization transfer, motion correction, myelin, snc, Spinal cord, White Matter.


Journal Article

  • De Leener, B, Taso, M, Cohen-Adad, J & Callot, V 2016, “Segmentation of the human spinal cord”, Magma (New York, N.Y.), vol. 29, no. 2, p. 125-153.
    Résumé : Segmenting the spinal cord contour is a necessary step for quantifying spinal cord atrophy in various diseases. Delineating gray matter (GM) and white matter (WM) is also useful for quantifying GM atrophy or for extracting multiparametric MRI metrics into specific WM tracts. Spinal cord segmentation in clinical research is not as developed as brain segmentation, however with the substantial improvement of MR sequences adapted to spinal cord MR investigations, the field of spinal cord MR segmentation has advanced greatly within the last decade. Segmentation techniques with variable accuracy and degree of complexity have been developed and reported in the literature. In this paper, we review some of the existing methods for cord and WM/GM segmentation, including intensity-based, surface-based, and image-based methods. We also provide recommendations for validating spinal cord segmentation techniques, as it is important to understand the intrinsic characteristics of the methods and to evaluate their performance and limitations. Lastly, we illustrate some applications in the healthy and pathological spinal cord. One conclusion of this review is that robust and automatic segmentation is clinically relevant, as it would allow for longitudinal and group studies free from user bias as well as reproducible multicentric studies in large populations, thereby helping to further our understanding of the spinal cord pathophysiology and to develop new criteria for early detection of subclinical evolution for prognosis prediction and for patient management. Another conclusion is that at the present time, no single method adequately segments the cord and its substructure in all the cases encountered (abnormal intensities, loss of contrast, deformation of the cord, etc.). A combination of different approaches is thus advised for future developments, along with the introduction of probabilistic shape models. Maturation of standardized frameworks, multiplatform availability, inclusion in large suite and data sharing would also ultimately benefit to the community.

  • Massire, A, Taso, M, Besson, P, Guye, M, Ranjeva, J-P & Callot, V 2016, “High-resolution multi-parametric quantitative magnetic resonance imaging of the human cervical spinal cord at 7T”, NeuroImage, vol. 143, p. 58-69.
    Résumé : Quantitative MRI techniques have the potential to characterize spinal cord tissue impairments occurring in various pathologies, from both microstructural and functional perspectives. By enabling very high image resolution and enhanced tissue contrast, ultra-high field imaging may offer further opportunities for such characterization. In this study, a multi-parametric high-resolution quantitative MRI protocol is proposed to characterize in vivo the human cervical spinal cord at 7T. Multi-parametric quantitative MRI acquizitions including T1, T2(*) relaxometry mapping and axial diffusion MRI were performed on ten healthy volunteers with a whole-body 7T system using a commercial prototype coil-array dedicated to cervical spinal cord imaging. Automatic cord segmentation and multi-parametric data registration to spinal cord templates enabled robust regional studies within atlas-based WM tracts and GM horns at the C3 cervical level. T1 value, cross-sectional area and GM/WM ratio evolutions along the cervical cord were also reported. An original correction method for B1(+)-biased T1 mapping sequence was additionally proposed and validated on phantom. As a result, relaxometry and diffusion parameters derived from high-resolution quantitative MRI acquizitions were reported at 7T for the first time. Obtained images, with unmatched resolutions compared to lower field investigations, provided exquisite anatomical details and clear delineation of the spinal cord substructures within an acquisition time of 30min, compatible with clinical investigations. Regional statistically significant differences were highlighted between WM and GM based on T1 and T2* maps (p<10(-3)), as well as between sensory and motor tracts based on diffusion tensor imaging maps (p<0.05). The proposed protocol demonstrates that ultra-high field spinal cord high-resolution quantitative MRI is feasible and lays the groundwork for future clinical investigations of degenerative spinal cord pathologies.
    Mots-clés : crmbm, diffusion tensor imaging, Quantitative MRI, Relaxometry mapping, snc, Spinal cord, Template-based segmentation, Ultra-high field.

  • Taso, M, Girard, OM, Duhamel, G, Le Troter, A, Feiweier, T, Guye, M, Ranjeva, J-P & Callot, V 2016, “Tract-specific and age-related variations of the spinal cord microstructure: a multi-parametric MRI study using diffusion tensor imaging (DTI) and inhomogeneous magnetization transfer (ihMT)”, NMR in biomedicine, vol. 29, no. 6, p. 817-832.
    Résumé : Being able to finely characterize the spinal cord (SC) microstructure and its alterations is a key point when investigating neural damage mechanisms encountered in different central nervous system (CNS) pathologies, such as multiple sclerosis, amyotrophic lateral sclerosis or myelopathy. Based on novel methods, including inhomogeneous magnetization transfer (ihMT) and dedicated SC probabilistic atlas post-processing, the present study focuses on the in vivo characterization of the healthy SC tissue in terms of regional microstructure differences between (i) upper and lower cervical vertebral levels and (ii) sensory and motor tracts, as well as differences attributed to normal aging. Forty-eight healthy volunteers aged from 20 to 70 years old were included in the study and scanned at 3 T using axial high-resolution T2 *-w imaging, diffusion tensor imaging (DTI) and ihMT, at two vertebral levels (C2 and C5). A processing pipeline with minimal user intervention, SC segmentation and spatial normalization into a reference space was implemented in order to assess quantitative morphological and structural parameters (cross-sectional areas, scalar DTI and MT/ihMT metrics) in specific white and gray matter regions of interest. The multi-parametric MRI metrics collected allowed upper and lower cervical levels to be distinguished, with higher ihMT ratio (ihMTR), higher axial diffusivity (λ∥ ) and lower radial diffusivity (λ⊥ ) at C2 compared with C5. Significant differences were also observed between white matter fascicles, with higher ihMTR and lower λ∥ in motor tracts compared with posterior sensory tracts. Finally, aging was found to be associated with significant metric alterations (decreased ihMTR and λ∥ ). The methodology proposed here, which can be easily transferred to the clinic, provides new insights for SC characterization. It bears great potential to study focal and diffuse SC damage in neurodegenerative and demyelinating diseases. Copyright © 2016 John Wiley & Sons, Ltd.
    Mots-clés : aging, crmbm, diffusion tensor imaging (DTI), ihMT, inhomogeneous magnetization transfer (ihMT), microstructure, Multi-parametric MRI, snc, Spinal cord.


Journal Article

  • Taso, M, Fradet, L, Callot, V & Arnoux, PJ 2015, “Anteroposterior compression of the spinal cord leading to cervical myelopathy: a finite element analysis”, Computer Methods in Biomechanics and Biomedical Engineering, vol. 18 Suppl 1, p. 2070-2071.
    Mots-clés : anterior compression, Cervical myelopathy, crmbm, finite element analysis, snc, Spinal cord.
    Attachment Snapshot 52.3 kb (source)

  • Taso, M, Le Troter, A, Sdika, M, Cohen-Adad, J, Arnoux, P-J, Guye, M, Ranjeva, J-P & Callot, V 2015, “A reliable spatially normalized template of the human spinal cord - Applications to automated white matter/gray matter segmentation and tensor-based morphometry (TBM) mapping of gray matter alterations occurring with age”, NeuroImage, vol. 117, p. 20-28.
    Résumé : Recently, a T2*-weighted template and probabilistic atlas of the white and gray matter (WM, GM) of the spinal cord (SC) have been reported. Such template can be used as tissue-priors for automated WM/GM segmentation but can also provide a common reference and normalized space for group studies. Here, a new template has been created (AMU40), and accuracy of automatic template-based WM/GM segmentation was quantified. The feasibility of tensor-based morphometry (TBM) for studying voxel-wise morphological differences of SC between young and elderly healthy volunteers was also investigated. Sixty-five healthy subjects were divided into young (n=40, age<40years old, mean age 28±5years old) and elderly (n=25, age>50years old, mean age 57±5years old) groups and scanned at 3T using an axial high-resolution T2*-weighted sequence. Inhomogeneity correction and affine intensity normalization of the SC and cerebrospinal fluid (CSF) signal intensities across slices were performed prior to both construction of the AMU40 template and WM/GM template-based segmentation. The segmentation was achieved using non-linear spatial normalization of T2*-w MR images to the AMU40 template. Validation of WM/GM segmentations was performed with a leave-one-out procedure by calculating DICE similarity coefficients between manual and automated WM/GM masks. SC morphological differences between young and elderly healthy volunteers were assessed using the same non-linear spatial normalization of the subjects' MRI to a common template, derivation of the Jacobian determinant maps from the warping fields, and a TBM analysis. Results demonstrated robust WM/GM automated segmentation, with mean DICE values greater than 0.8. Concerning the TBM analysis, an anterior GM atrophy was highlighted in elderly volunteers, demonstrating thereby, for the first time, the feasibility of studying local structural alterations in the SC using tensor-based morphometry. This holds great promise for studies of morphological impairment occurring in several central nervous system pathologies.
    Mots-clés : crmbm, snc.


Journal Article

  • Fonov, VS, Le Troter, A, Taso, M, De Leener, B, Lévêque, G, Benhamou, M, Sdika, M, Benali, H, Pradat, P-F, Collins, DL, Callot, V & Cohen-Adad, J 2014, “Framework for integrated MRI average of the spinal cord white and gray matter: The MNI-Poly-AMU template”, NeuroImage, vol. 102 Pt 2, p. 817-827.
    Résumé : The field of spinal cord MRI is lacking a common template, as existing for the brain, which would allow extraction of multi-parametric data (diffusion-weighted, magnetization transfer, etc.) without user bias, thereby facilitating group analysis and multi-center studies. This paper describes a framework to produce an unbiased average anatomical template of the human spinal cord. The template was created by co-registering T2-weighted images (N=16 healthy volunteers) using a series of pre-processing steps followed by non-linear registration. A white and gray matter probabilistic template was then merged to the average anatomical template, yielding the MNI-Poly-AMU template, which currently covers vertebral levels C1 to T6. New subjects can be registered to the template using a dedicated image processing pipeline. Validation was conducted on 16 additional subjects by comparing an automatic template-based segmentation and manual segmentation, yielding a median Dice coefficient of 0.89. The registration pipeline is rapid (~15min), automatic after one C2/C3 landmark manual identification, and robust, thereby reducing subjective variability and bias associated with manual segmentation. The template can notably be used for measurements of spinal cord cross-sectional area, voxel-based morphometry, identification of anatomical features (e.g., vertebral levels, white and gray matter location) and unbiased extraction of multi-parametric data.
    Mots-clés : crmbm.

  • Taso, M, Le Troter, A, Sdika, M, Ranjeva, J-P, Guye, M, Bernard, M & Callot, V 2014, “Construction of an in vivo human spinal cord atlas based on high-resolution MR images at cervical and thoracic levels: preliminary results”, Magma (New York, N.Y.), vol. 27, no. 3, p. 257-267.
    Résumé : OBJECT: Our goal was to build a probabilistic atlas and anatomical template of the human cervical and thoracic spinal cord (SC) that could be used for segmentation algorithm improvement, parametric group studies, and enrichment of biomechanical modelling. MATERIALS AND METHODS: High-resolution axial T2*-weighted images were acquired at 3T on 15 healthy volunteers using a multi-echo-gradient-echo sequence (1 slice per vertebral level from C1 to L2). After manual segmentation, linear and affine co-registrations were performed providing either inter-individual morphometric variability maps, or substructure probabilistic maps [CSF, white and grey matter (WM/GM)] and anatomical SC template. RESULTS: The larger inter-individual morphometric variations were observed at the thoraco-lumbar levels and in the posterior GM. Mean SC diameters were in agreement with the literature and higher than post-mortem measurements. A representative SC MR template was generated and values up to 90 and 100% were observed on GM and WM-probability maps. CONCLUSION: This work provides a probabilistic SC atlas and a template that could offer great potentialities for parametrical MRI analysis (DTI/MTR/fMRI) and group studies, similar to what has already been performed using a brain atlas. It also offers great perspective for biomechanical models usually based on post-mortem or generic data. Further work will consider integration into an automated SC segmentation pipeline.
    Mots-clés : award_ESMRMB13, crmbm.
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