Arnaud Le Troter - Academia.edu (original) (raw)

Papers by Arnaud Le Troter

Lecture Notes in Computer Science, 2011

In the context of inter-subject brain surface matching, we present a parameterization of the cort... more In the context of inter-subject brain surface matching, we present a parameterization of the cortical surface constrained by a model of cortical organization. The parameterization is defined via an harmonic mapping of each hemisphere surface to a rectangular planar domain that integrates a representation of the model. As opposed to previous conformal mapping methods we do not match folds between individuals but instead optimize the fit between cortical sulci and specific iso-coordinate axis in the model. Experiments on both hemispheres of 34 subjects are presented and results are very promising.

HAL (Le Centre pour la Communication Scientifique Directe), 2013

National audienceno abstrac

IEEE Transactions on Medical Imaging, May 1, 2013

In the context of inter subject brain surface matching, we present a parameterization of the cort... more In the context of inter subject brain surface matching, we present a parameterization of the cortical surface constrained by a model of cortical organization. The parameterization is defined via an harmonic mapping of each hemisphere surface to a rectangular planar domain that integrates a representation of the model. As opposed to previous landmark-based registration methods we do not match folds between individuals but instead optimize the fit between cortical sulci and specific iso-coordinate axis in the model. This strategy overcomes some limitation to sulcus-based registration techniques such as topological variability in sulcal landmarks across subjects. Experiments on 62 subjects with manually traced sulci are presented and compared with the result of the Freesurfer software. The evaluation involves a measure of dispersion of sulci with both angular and area distortions. We show that the model-based strategy can lead to a natural, efficient and very fast (less than 5 min per hemisphere) method for defining inter subjects correspondences. We discuss how this approach also reduces the problems inherent to anatomically defined landmarks and open the way to the investigation of cortical organization through the notion of orientation and alignment of structures across the cortex.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 26, 2005

International audienceNon disponibl

Ugly duckling (UD) concept is widely admitted as major criteria for malignant melanoma (MM) detec... more Ugly duckling (UD) concept is widely admitted as major criteria for malignant melanoma (MM) detection. It demonstrates that nevi in the same individual tend to resemble one another and human brain can identify a few similarity clusters, which include all nevi sharing the same morphological features. UD is the nevus that does not fit into any of the clusters of the individual, likely to be suspicious (i.e. MM). Our research program was to modeling the perceived similarity clusters (PSC) as a basis for a computer-aided diagnosis system. In the present part of the study, nine observers (dermatologists) participated to do the clustering of nevi and to identify the UDs using dermoscopic images of nevi of 80 individuals (2089 nevi with 7 histologically confirmed melanomas). Observers identified all confirmed melanomas as UDs (100% sensitivity and 98% specificity). The observers tend to be concordant about the identification of PSCs. We combined the multiple clusterings of experts to find the consensus clustering, which yields a stable and robust final clustering that is in agreement with the multiple clusterings of experts. We demonstrated the limited variability of nevi patterns per individual (2.45 PSCs in average), whatever the number of nevi, which human brain has a natural intuitive ability to perceive

NeuroImage

Background: To investigate the association of ihMT (inhom signals with the demyelination and remy... more Background: To investigate the association of ihMT (inhom signals with the demyelination and remyelination phases of the acute cuprizone mouse model in comparison with histology, and to assess the extent of tissue damage and repair from MRI data. Methods: Acute demyelination by feeding 0.2% cuprizone for five weeks, followed by a four-week remyelination period was applied on genetically modified plp-GFP mice. Animals were scanned at different time points of the demyelination and remyelination phases of the cuprizone model using a multimodal MRI protocol, including ihMT T 1D-filters, MPF (Macromolecular Proton Fraction) and R 1 (longitudinal relaxation rate). For histology, plp-GFP (proteolipid protein-Green Fluorescent Protein) microscopy and LFB (Luxol Fast Blue) staining were employed as references for the myelin content. Comparison of MRI with histology was performed in the medial corpus callosum (mCC) and cerebral cortex (CTX) at two brain levels whereas ROI-wise and voxel-based analyses of the MRI metrics allowed investigating in vivo the spatial extent of myelin alterations. Results: IhMT high-pass T 1D-filters, targeted toward long T 1D components, showed significant temporal variations in the mCC consistent with the effects induced by the cuprizone toxin. In addition, the corresponding signals correlated strongly and significantly with the myelin content assessed by GFP fluorescence and LFB staining over the demyelination and the remyelination phases. The signal of the band-pass T 1D-filter, which isolates short T 1D components, showed changes over time that were poorly correlated with histology, hence suggesting a sensitivity to pathological processes possibly not related to myelin. Although MPF was also highly correlated to histology, ihMT high-pass T 1D-filters showed better capability to characterize the spatial-temporal patterns during the demyelination and remyelination phases of the acute cuprizone model (e.g., rostro-caudal gradient of demyelination in the mCC previously described in the literature). Conclusions: IhMT sequences selective for long T 1D components are specific and sensitive in vivo markers of demyelination and remyelination and have successfully captured the spatially heterogeneous pattern of the demyelination and remyelination mechanisms in the cuprizone model. Interestingly, differences in signal variations between the ihMT high-pass and band-pass T 1D-filter, suggest a sensitivity of the ihMT sequences targeted to short T 1D s to alterations other than those of myelin. Future studies will need to further address these differences by examining more closely the origin of the short T 1D components and the variation of each T 1D component in pathology.

Focal epilepsy is characterized by repeated spontaneous seizures that originate from cortical epi... more Focal epilepsy is characterized by repeated spontaneous seizures that originate from cortical epileptogenic zone networks (EZN). More recently, analysis of intracerebral recordings showed that subcortical structures, and in particular the thalamus, play an important role in facilitating and/or propagating epileptic activity. This supports previously reported structural alterations of these structures. Nonetheless, between-patient differences in EZN (e.g., temporal vs. non-temporal lobe epilepsy) as well as other clinical features (e.g., number of epileptogenic regions) might impact the magnitude as well as spatial distribution of subcortical structural changes. Here we used 7 Tesla MRI T1data to provide a comprehensive description of subcortical morphological (volume, tissue deformation, and shape) and longitudinal relaxation (T1) changes in focal epilepsy patients to evaluate the impact of the EZN and patient-specific clinical features. Our results showed widespread morphometric an...

2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2017

Manual and automated segmentation of individual muscles in magnetic resonance images have been re... more Manual and automated segmentation of individual muscles in magnetic resonance images have been recognized as challenging given the high variability of shapes between muscles and subjects and the discontinuity or lack of visible boundaries between muscles. In the present study, we proposed an original algorithm allowing a semi-automatic transversal propagation of manually-drawn masks. Our strategy was based on several ascending and descending non-linear registration approaches which is similar to the estimation of a Lagrangian trajectory applied to manual masks. Using several manually-segmented slices, we have evaluated our algorithm on the four muscles of the quadriceps femoris group. We mainly showed that our 3D propagated segmentation was very accurate with an averaged Dice similarity coefficient value higher than 0.91 for the minimal manual input of only two manually-segmented slices.

National audienceno abstrac

ArXiv, 2021

The spinal cord (SC), which conveys information between the brain and the peripheral nervous syst... more The spinal cord (SC), which conveys information between the brain and the peripheral nervous system, plays a key role in various neurological disorders such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS), in which both gray matter (GM) and white matter (WM) may be impaired. While automated methods for WM/GM segmentation are now largely available, these techniques, developed for conventional systems (3T or lower) do not necessarily perform well on 7T MRI data, which feature finer details, contrasts, but also different artifacts or signal dropout. The primary goal of this study is thus to propose a new deep learning model that allows robust SC/GM multi-class segmentation based on ultra-high resolution 7T T2*-w MR images. The second objective is to highlight the relevance of implementing a specific data augmentation (DA) strategy, in particular to generate a generic model that could be used for multi-center studies at 7T.

NMR in Biomedicine, 2021

Quantitative analysis of abdominal organs motion and deformation is crucial to better understand ... more Quantitative analysis of abdominal organs motion and deformation is crucial to better understand biomechanical alterations undermining respiratory, digestive or perineal pathophysiology. In particular, biomechanical characterization of the antero‐lateral abdominal wall is central in the diagnosis of abdominal muscle deficiency. Here, we present a dedicated semiautomatic dynamic MRI postprocessing method enabling the quantification of spatial and temporal deformations of the antero‐lateral abdominal wall muscles. Ten healthy participants were imaged during a controlled breathing session at the L3–L4 disc level using real‐time dynamic MRI at 3 T. A coarse feature‐tracking step allowed the selection of the inhalation cycle of maximum abdominal excursion. Over this image series, the described method combines (1) a supervised 2D+t segmentation procedure of the abdominal wall muscles, (2) the quantification of muscle deformations based on masks registration, and (3) the mapping of deforma...

PurposeTo propose an efficient retrospective image-based method for motion correction of multi-co... more PurposeTo propose an efficient retrospective image-based method for motion correction of multi-contrast acquisitions with a low number of available images (MC-MoCo) and evaluate its use in 3D inhomogeneous Magnetization Transfer (ihMT) experiments in the human brain.MethodsA framework for motion correction, including image pre-processing enhancement and rigid registration to an iteratively improved target image, was developed. The proposed method was compared to Motion Correction with FMRIB’s Linear Image Registration Tool (MCFLIRT) function in FSL over 13 subjects. Native (pre-correction) and residual (post-correction) motions were evaluated by means of markers positioned at well-defined anatomical regions over each image.ResultsBoth motion correction strategies significantly reduced inter-image misalignment, and the MC-MoCo method yielded significantly better results than MCFLIRT.ConclusionMC-MoCo is a high-performance method for motion correction of multi-contrast volumes as in 3...

Dynamic Functional Connectivity (dFC) in the resting state (rs) is considered as a correlate of c... more Dynamic Functional Connectivity (dFC) in the resting state (rs) is considered as a correlate of cognitive processing. Describing dFC as a flow across morphing connectivity configurations, our notion of dFC speed quantifies the rate at which FC networks evolve in time. Here we probe the hypothesis that variations of rs dFC speed and cognitive performance are selectively interrelated within specific functional subnetworks.In particular, we focus on Sleep Deprivation (SD) as a reversible model of cognitive dysfunction. We found that whole-brain level (global) dFC speed significantly slows down after 24h of SD. However, the reduction in global dFC speed does not correlate with variations of cognitive performance in individual tasks, which are subtle and highly heterogeneous. On the contrary, we found strong correlations between performance variations in individual tasks –including Rapid Visual Processing (RVP, assessing sustained visual attention)– and dFC speed quantified at the level ...

Clinical Oncology and Research, 2020

Background and objectives: Sarcoma preoperative planning critically depends on MRI, sometimes uni... more Background and objectives: Sarcoma preoperative planning critically depends on MRI, sometimes uninformative when compartments barriers or critical structures are involved. objective: to prospectively assess the feasibility and the potential of 7T MRI in sarcoma. Methods: Two patients with femoral chondrosarcoma were CT and MRI (1.5 and 7T) scanned with T1W, T2W, GRE and DTI sequences. Image quality and characteristics of the tumors were compared between these modalities. Results: In-plane resolution was higher at 7T as compared to 1.5T MRI, tumor delineation was more reliable and soft tissue involvement was clearer. DT imaging and corresponding ADC mapping allowed a clear distinction between edema and tumor and identified tumor involvement of collateral ligament allowing healthy structures sparing with histopathology confirmation. 7T MRI was also able to define cortical reaction as precisely as CT imaging. Conclusion: Musculoskeletal tumours UHF-MRI is promising. Higher resolution a...

The Journal of the Acoustical Society of America, 2019

In-ear devices are used in a wide range of applications for which the device's usability and/... more In-ear devices are used in a wide range of applications for which the device's usability and/or efficiency is strongly related to comfort aspects that are influenced by the mechanical interaction between the device and the walls of the earcanal. Although the displacement of the earcanal walls due to the insertion of the device is an important characteristic of this interaction, existing studies on this subject are very limited. This paper proposes a method to estimate this displacement in vivo using a registration technique on magnetic resonance images. The amplitude, the location and the direction of the earcanal wall displacement are computed for four types of earplugs used by one participant. These displacements give indications on how each earplug deforms the earcanal for one specific earcanal geometry and one specific earplug insertion. Although the displacement due to a specific earplug family cannot be generalized using the results of this paper, the latter help to unders...

Abstracts Accepted for Publication, 2019

microarchitecture parameters were correlated to each other but not correlated with BMD. Multiple ... more microarchitecture parameters were correlated to each other but not correlated with BMD. Multiple regression analysis demonstrated that the combination of the microarchitecture parameters and BMD improved the prediction of the failure load with for example an improved fracture risk prediction from R² = 0.418 to 0.688 when combining BMD and Euler Ch. Overall, femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of BMD and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients. Conclusion: We demonstrated that femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of bone mineral density and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients.

PloS one, 2017

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disor... more Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disorders. Currently FSHD has no known effective treatment and detailed data on the natural history are lacking. Determination of the efficacy of a given therapeutic approach might be difficult in FSHD given the slow and highly variable disease progression. Magnetic resonance imaging (MRI) has been widely used to qualitatively and quantitatively evaluate in vivo the muscle alterations in various neuromuscular disorders. The main aim of the present study was to investigate longitudinally the time-dependent changes occurring in thigh muscles of FSHD patients using quantitative MRI and to assess the potential relationships with the clinical findings. Thirty-five FSHD1 patients (17 females) were enrolled. Clinical assessment tools including manual muscle testing using medical research council score (MRC), and motor function measure (MFM) were recorded each year for a period ranging from 1 to 2 ye...

Frontiers in Human Neuroscience, 2016

Longitudinal Changes in Alien Hand Connectomics This also raises the possibility that changes to ... more Longitudinal Changes in Alien Hand Connectomics This also raises the possibility that changes to large-scale functional architecture revealed by resting-state functional magnetic resonance imaging (fMRI) (rs-fMRI) may provide relevant information on the evolution of behavioral syndromes in addition to that provided by structural and task-based functional imaging.

Scientific Reports, 2015

In the present study, we proposed an original and robust methodology which combines the spatial n... more In the present study, we proposed an original and robust methodology which combines the spatial normalization of skeletal muscle images, the statistical parametric mapping (SPM) analysis and the use of a specific parcellation in order to accurately localize and quantify the extent of skeletal muscle damage within the four heads of the quadriceps femoris. T2 maps of thigh muscles were characterized before, two (D2) and four (D4) days after 40 maximal isometric electrically-evoked contractions in 25 healthy young males. On the basis of SPM analysis of coregistrated T2 maps, the alterations were similarly detected at D2 and D4 in the superficial and distal regions of the vastus medialis (VM) whereas the proportion of altered muscle was higher in deep muscle regions of the vastus lateralis at D4 (deep: 35 ± 25%, superficial: 23 ± 15%) as compared to D2 (deep: 18 ± 13%, superficial: 17 ± 13%). The present methodology used for the first time on skeletal muscle would be of utmost interest ...

Lecture Notes in Computer Science, 2011

In the context of inter-subject brain surface matching, we present a parameterization of the cort... more In the context of inter-subject brain surface matching, we present a parameterization of the cortical surface constrained by a model of cortical organization. The parameterization is defined via an harmonic mapping of each hemisphere surface to a rectangular planar domain that integrates a representation of the model. As opposed to previous conformal mapping methods we do not match folds between individuals but instead optimize the fit between cortical sulci and specific iso-coordinate axis in the model. Experiments on both hemispheres of 34 subjects are presented and results are very promising.

HAL (Le Centre pour la Communication Scientifique Directe), 2013

National audienceno abstrac

IEEE Transactions on Medical Imaging, May 1, 2013

In the context of inter subject brain surface matching, we present a parameterization of the cort... more In the context of inter subject brain surface matching, we present a parameterization of the cortical surface constrained by a model of cortical organization. The parameterization is defined via an harmonic mapping of each hemisphere surface to a rectangular planar domain that integrates a representation of the model. As opposed to previous landmark-based registration methods we do not match folds between individuals but instead optimize the fit between cortical sulci and specific iso-coordinate axis in the model. This strategy overcomes some limitation to sulcus-based registration techniques such as topological variability in sulcal landmarks across subjects. Experiments on 62 subjects with manually traced sulci are presented and compared with the result of the Freesurfer software. The evaluation involves a measure of dispersion of sulci with both angular and area distortions. We show that the model-based strategy can lead to a natural, efficient and very fast (less than 5 min per hemisphere) method for defining inter subjects correspondences. We discuss how this approach also reduces the problems inherent to anatomically defined landmarks and open the way to the investigation of cortical organization through the notion of orientation and alignment of structures across the cortex.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 26, 2005

International audienceNon disponibl

Ugly duckling (UD) concept is widely admitted as major criteria for malignant melanoma (MM) detec... more Ugly duckling (UD) concept is widely admitted as major criteria for malignant melanoma (MM) detection. It demonstrates that nevi in the same individual tend to resemble one another and human brain can identify a few similarity clusters, which include all nevi sharing the same morphological features. UD is the nevus that does not fit into any of the clusters of the individual, likely to be suspicious (i.e. MM). Our research program was to modeling the perceived similarity clusters (PSC) as a basis for a computer-aided diagnosis system. In the present part of the study, nine observers (dermatologists) participated to do the clustering of nevi and to identify the UDs using dermoscopic images of nevi of 80 individuals (2089 nevi with 7 histologically confirmed melanomas). Observers identified all confirmed melanomas as UDs (100% sensitivity and 98% specificity). The observers tend to be concordant about the identification of PSCs. We combined the multiple clusterings of experts to find the consensus clustering, which yields a stable and robust final clustering that is in agreement with the multiple clusterings of experts. We demonstrated the limited variability of nevi patterns per individual (2.45 PSCs in average), whatever the number of nevi, which human brain has a natural intuitive ability to perceive

NeuroImage

Background: To investigate the association of ihMT (inhom signals with the demyelination and remy... more Background: To investigate the association of ihMT (inhom signals with the demyelination and remyelination phases of the acute cuprizone mouse model in comparison with histology, and to assess the extent of tissue damage and repair from MRI data. Methods: Acute demyelination by feeding 0.2% cuprizone for five weeks, followed by a four-week remyelination period was applied on genetically modified plp-GFP mice. Animals were scanned at different time points of the demyelination and remyelination phases of the cuprizone model using a multimodal MRI protocol, including ihMT T 1D-filters, MPF (Macromolecular Proton Fraction) and R 1 (longitudinal relaxation rate). For histology, plp-GFP (proteolipid protein-Green Fluorescent Protein) microscopy and LFB (Luxol Fast Blue) staining were employed as references for the myelin content. Comparison of MRI with histology was performed in the medial corpus callosum (mCC) and cerebral cortex (CTX) at two brain levels whereas ROI-wise and voxel-based analyses of the MRI metrics allowed investigating in vivo the spatial extent of myelin alterations. Results: IhMT high-pass T 1D-filters, targeted toward long T 1D components, showed significant temporal variations in the mCC consistent with the effects induced by the cuprizone toxin. In addition, the corresponding signals correlated strongly and significantly with the myelin content assessed by GFP fluorescence and LFB staining over the demyelination and the remyelination phases. The signal of the band-pass T 1D-filter, which isolates short T 1D components, showed changes over time that were poorly correlated with histology, hence suggesting a sensitivity to pathological processes possibly not related to myelin. Although MPF was also highly correlated to histology, ihMT high-pass T 1D-filters showed better capability to characterize the spatial-temporal patterns during the demyelination and remyelination phases of the acute cuprizone model (e.g., rostro-caudal gradient of demyelination in the mCC previously described in the literature). Conclusions: IhMT sequences selective for long T 1D components are specific and sensitive in vivo markers of demyelination and remyelination and have successfully captured the spatially heterogeneous pattern of the demyelination and remyelination mechanisms in the cuprizone model. Interestingly, differences in signal variations between the ihMT high-pass and band-pass T 1D-filter, suggest a sensitivity of the ihMT sequences targeted to short T 1D s to alterations other than those of myelin. Future studies will need to further address these differences by examining more closely the origin of the short T 1D components and the variation of each T 1D component in pathology.

Focal epilepsy is characterized by repeated spontaneous seizures that originate from cortical epi... more Focal epilepsy is characterized by repeated spontaneous seizures that originate from cortical epileptogenic zone networks (EZN). More recently, analysis of intracerebral recordings showed that subcortical structures, and in particular the thalamus, play an important role in facilitating and/or propagating epileptic activity. This supports previously reported structural alterations of these structures. Nonetheless, between-patient differences in EZN (e.g., temporal vs. non-temporal lobe epilepsy) as well as other clinical features (e.g., number of epileptogenic regions) might impact the magnitude as well as spatial distribution of subcortical structural changes. Here we used 7 Tesla MRI T1data to provide a comprehensive description of subcortical morphological (volume, tissue deformation, and shape) and longitudinal relaxation (T1) changes in focal epilepsy patients to evaluate the impact of the EZN and patient-specific clinical features. Our results showed widespread morphometric an...

2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2017

Manual and automated segmentation of individual muscles in magnetic resonance images have been re... more Manual and automated segmentation of individual muscles in magnetic resonance images have been recognized as challenging given the high variability of shapes between muscles and subjects and the discontinuity or lack of visible boundaries between muscles. In the present study, we proposed an original algorithm allowing a semi-automatic transversal propagation of manually-drawn masks. Our strategy was based on several ascending and descending non-linear registration approaches which is similar to the estimation of a Lagrangian trajectory applied to manual masks. Using several manually-segmented slices, we have evaluated our algorithm on the four muscles of the quadriceps femoris group. We mainly showed that our 3D propagated segmentation was very accurate with an averaged Dice similarity coefficient value higher than 0.91 for the minimal manual input of only two manually-segmented slices.

National audienceno abstrac

ArXiv, 2021

The spinal cord (SC), which conveys information between the brain and the peripheral nervous syst... more The spinal cord (SC), which conveys information between the brain and the peripheral nervous system, plays a key role in various neurological disorders such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS), in which both gray matter (GM) and white matter (WM) may be impaired. While automated methods for WM/GM segmentation are now largely available, these techniques, developed for conventional systems (3T or lower) do not necessarily perform well on 7T MRI data, which feature finer details, contrasts, but also different artifacts or signal dropout. The primary goal of this study is thus to propose a new deep learning model that allows robust SC/GM multi-class segmentation based on ultra-high resolution 7T T2*-w MR images. The second objective is to highlight the relevance of implementing a specific data augmentation (DA) strategy, in particular to generate a generic model that could be used for multi-center studies at 7T.

NMR in Biomedicine, 2021

Quantitative analysis of abdominal organs motion and deformation is crucial to better understand ... more Quantitative analysis of abdominal organs motion and deformation is crucial to better understand biomechanical alterations undermining respiratory, digestive or perineal pathophysiology. In particular, biomechanical characterization of the antero‐lateral abdominal wall is central in the diagnosis of abdominal muscle deficiency. Here, we present a dedicated semiautomatic dynamic MRI postprocessing method enabling the quantification of spatial and temporal deformations of the antero‐lateral abdominal wall muscles. Ten healthy participants were imaged during a controlled breathing session at the L3–L4 disc level using real‐time dynamic MRI at 3 T. A coarse feature‐tracking step allowed the selection of the inhalation cycle of maximum abdominal excursion. Over this image series, the described method combines (1) a supervised 2D+t segmentation procedure of the abdominal wall muscles, (2) the quantification of muscle deformations based on masks registration, and (3) the mapping of deforma...

PurposeTo propose an efficient retrospective image-based method for motion correction of multi-co... more PurposeTo propose an efficient retrospective image-based method for motion correction of multi-contrast acquisitions with a low number of available images (MC-MoCo) and evaluate its use in 3D inhomogeneous Magnetization Transfer (ihMT) experiments in the human brain.MethodsA framework for motion correction, including image pre-processing enhancement and rigid registration to an iteratively improved target image, was developed. The proposed method was compared to Motion Correction with FMRIB’s Linear Image Registration Tool (MCFLIRT) function in FSL over 13 subjects. Native (pre-correction) and residual (post-correction) motions were evaluated by means of markers positioned at well-defined anatomical regions over each image.ResultsBoth motion correction strategies significantly reduced inter-image misalignment, and the MC-MoCo method yielded significantly better results than MCFLIRT.ConclusionMC-MoCo is a high-performance method for motion correction of multi-contrast volumes as in 3...

Dynamic Functional Connectivity (dFC) in the resting state (rs) is considered as a correlate of c... more Dynamic Functional Connectivity (dFC) in the resting state (rs) is considered as a correlate of cognitive processing. Describing dFC as a flow across morphing connectivity configurations, our notion of dFC speed quantifies the rate at which FC networks evolve in time. Here we probe the hypothesis that variations of rs dFC speed and cognitive performance are selectively interrelated within specific functional subnetworks.In particular, we focus on Sleep Deprivation (SD) as a reversible model of cognitive dysfunction. We found that whole-brain level (global) dFC speed significantly slows down after 24h of SD. However, the reduction in global dFC speed does not correlate with variations of cognitive performance in individual tasks, which are subtle and highly heterogeneous. On the contrary, we found strong correlations between performance variations in individual tasks –including Rapid Visual Processing (RVP, assessing sustained visual attention)– and dFC speed quantified at the level ...

Clinical Oncology and Research, 2020

Background and objectives: Sarcoma preoperative planning critically depends on MRI, sometimes uni... more Background and objectives: Sarcoma preoperative planning critically depends on MRI, sometimes uninformative when compartments barriers or critical structures are involved. objective: to prospectively assess the feasibility and the potential of 7T MRI in sarcoma. Methods: Two patients with femoral chondrosarcoma were CT and MRI (1.5 and 7T) scanned with T1W, T2W, GRE and DTI sequences. Image quality and characteristics of the tumors were compared between these modalities. Results: In-plane resolution was higher at 7T as compared to 1.5T MRI, tumor delineation was more reliable and soft tissue involvement was clearer. DT imaging and corresponding ADC mapping allowed a clear distinction between edema and tumor and identified tumor involvement of collateral ligament allowing healthy structures sparing with histopathology confirmation. 7T MRI was also able to define cortical reaction as precisely as CT imaging. Conclusion: Musculoskeletal tumours UHF-MRI is promising. Higher resolution a...

The Journal of the Acoustical Society of America, 2019

In-ear devices are used in a wide range of applications for which the device's usability and/... more In-ear devices are used in a wide range of applications for which the device's usability and/or efficiency is strongly related to comfort aspects that are influenced by the mechanical interaction between the device and the walls of the earcanal. Although the displacement of the earcanal walls due to the insertion of the device is an important characteristic of this interaction, existing studies on this subject are very limited. This paper proposes a method to estimate this displacement in vivo using a registration technique on magnetic resonance images. The amplitude, the location and the direction of the earcanal wall displacement are computed for four types of earplugs used by one participant. These displacements give indications on how each earplug deforms the earcanal for one specific earcanal geometry and one specific earplug insertion. Although the displacement due to a specific earplug family cannot be generalized using the results of this paper, the latter help to unders...

Abstracts Accepted for Publication, 2019

microarchitecture parameters were correlated to each other but not correlated with BMD. Multiple ... more microarchitecture parameters were correlated to each other but not correlated with BMD. Multiple regression analysis demonstrated that the combination of the microarchitecture parameters and BMD improved the prediction of the failure load with for example an improved fracture risk prediction from R² = 0.418 to 0.688 when combining BMD and Euler Ch. Overall, femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of BMD and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients. Conclusion: We demonstrated that femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of bone mineral density and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients.

PloS one, 2017

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disor... more Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disorders. Currently FSHD has no known effective treatment and detailed data on the natural history are lacking. Determination of the efficacy of a given therapeutic approach might be difficult in FSHD given the slow and highly variable disease progression. Magnetic resonance imaging (MRI) has been widely used to qualitatively and quantitatively evaluate in vivo the muscle alterations in various neuromuscular disorders. The main aim of the present study was to investigate longitudinally the time-dependent changes occurring in thigh muscles of FSHD patients using quantitative MRI and to assess the potential relationships with the clinical findings. Thirty-five FSHD1 patients (17 females) were enrolled. Clinical assessment tools including manual muscle testing using medical research council score (MRC), and motor function measure (MFM) were recorded each year for a period ranging from 1 to 2 ye...

Frontiers in Human Neuroscience, 2016

Longitudinal Changes in Alien Hand Connectomics This also raises the possibility that changes to ... more Longitudinal Changes in Alien Hand Connectomics This also raises the possibility that changes to large-scale functional architecture revealed by resting-state functional magnetic resonance imaging (fMRI) (rs-fMRI) may provide relevant information on the evolution of behavioral syndromes in addition to that provided by structural and task-based functional imaging.

Scientific Reports, 2015

In the present study, we proposed an original and robust methodology which combines the spatial n... more In the present study, we proposed an original and robust methodology which combines the spatial normalization of skeletal muscle images, the statistical parametric mapping (SPM) analysis and the use of a specific parcellation in order to accurately localize and quantify the extent of skeletal muscle damage within the four heads of the quadriceps femoris. T2 maps of thigh muscles were characterized before, two (D2) and four (D4) days after 40 maximal isometric electrically-evoked contractions in 25 healthy young males. On the basis of SPM analysis of coregistrated T2 maps, the alterations were similarly detected at D2 and D4 in the superficial and distal regions of the vastus medialis (VM) whereas the proportion of altered muscle was higher in deep muscle regions of the vastus lateralis at D4 (deep: 35 ± 25%, superficial: 23 ± 15%) as compared to D2 (deep: 18 ± 13%, superficial: 17 ± 13%). The present methodology used for the first time on skeletal muscle would be of utmost interest ...