Publications of Christophe Phillips
Bookmark and Share    
Full Text
See detailRepeatability of ultra-high-resolution Multi-Parametric Mapping across five 7T sites
Sherif, Siya ULiege; Aghaeifar, Ali; pine., Kerrin et al

Conference (2022)

Detailed reference viewed: 44 (2 ULiège)
See detailTimely sleep coupling: phase locked slow wave - spindle pairing is linked to AD neuropathology and forecasts cognitive decline
Chylinski, Daphné ULiege; Van Egroo, Maxime; Narbutas, Justinas ULiege et al

Conference (2021, November 19)

Alteration of sleep quality is a hallmark of the ageing process. The fine-tuned coalescence of elements of sleep microstructure seems to play a pivotal role in cognitive trajectories in ageing. This may ... [more ▼]

Alteration of sleep quality is a hallmark of the ageing process. The fine-tuned coalescence of elements of sleep microstructure seems to play a pivotal role in cognitive trajectories in ageing. This may be of prime clinical importance as a bidirectional detrimental relationship between sleep quality and Alzheimer’s disease (AD) neuropathology emerges in the literature and holds promise for novel sleep related interventions. However, sleep is not yet established as a true risk factor for AD, most likely because the understanding of its core associations with AD neuropathology remains insufficient. In this context, we focused on the timely coupling of two key graphoelements of Non-Rapid Eye Movement (NREM) sleep that is slow waves and spindles, and their associations with AD neuropathology and cognition. We show, in a detailed large dataset (N=100; 68 woman) of undisturbed sleep recorded in late middle-aged healthy individuals (50 to 70y; 60 +- 5), that the precise coupling of sleep spindles with a specific category of sleep slow waves, those deemed most important for memory consolidation, is associated to lower medial prefrontal cortex PET-scan β-Amyloid burden, a landmark of AD neuropathology (F1,96=6.2, p=0.014). Cruder aspects of sleep macrostructure and sleep intensity were, however, not significantly linked to β-Amyloid burden in this relatively young sample with low β-Amyloid deposit. We further show that this specific coupling is predictive of a lower memory decline, assessed over 2 years using a task highly sensitive to the first signs of memory impairment (F1,54=4.67, p=0.035). These findings unravel early links between sleep, AD-related and cognitive trajectories in ageing and suggest that altered coupling of sleep microstructure elements key to its functions could constitute the first association with AD neuropathology and that less refined measures of sleep macrostructure or sleep intensity may only be significantly associated to AD neuropathology later in life, when β-amyloid burden is higher. Sleep microstructure integrity could therefore constitute a potential indicator of a less successful ageing trajectory. [less ▲]

Detailed reference viewed: 51 (8 ULiège)
Full Text
See detailQuantitative MRI, EM head modelling and more: practical considerations and applications
Phillips, Christophe ULiege

Scientific conference (2021, November 03)

Detailed reference viewed: 22 (3 ULiège)
Full Text
See detailqMRI-BIDS: an extension to the brain imaging data structure for quantitative magnetic resonance imaging data
Karakuzu, Agah; Appelhoff, Stefan; Auer, Tibor et al

E-print/Working paper (2021)

The Brain Imaging Data Structure (BIDS) established community consensus on the organization of data and metadata for several neuroimaging modalities. Traditionally, BIDS had a strong focus on functional ... [more ▼]

The Brain Imaging Data Structure (BIDS) established community consensus on the organization of data and metadata for several neuroimaging modalities. Traditionally, BIDS had a strong focus on functional magnetic resonance imaging (MRI) datasets and lacked guidance on how to store multimodal structural MRI datasets. Here, we present and describe the BIDS Extension Proposal 001 (BEP001), which adds a range of quantitative MRI (qMRI) applications to the BIDS. In general, the aim of qMRI is to characterize brain microstructure by quantifying the physical MR parameters of the tissue via computational, biophysical models. By proposing this new standard, we envision standardization of qMRI which makes multicenter dissemination of interoperable data possible. As a result, BIDS can act as a catalyst of convergence between qMRI methods development and application-driven neuroimaging studies that can help develop quantitative biomarkers for neural tissue characterization. Finally, our BIDS extension offers a common ground for developers to exchange novel imaging data and tools, reducing the practical barriers to standardization that is currently lacking in the field of neuroimaging. [less ▲]

Detailed reference viewed: 25 (4 ULiège)
Full Text
See detailAlzheimer’s disease genetic risk and sleep phenotypes: association with more slow-waves and daytime sleepiness
Muto, Vincenzo ULiege; Koshmanova, Ekaterina ULiege; Ghaemmaghami Tabrizi, Pouya ULiege et al

in Sleep (2021), 44(1), 137

Study objectives: Sleep disturbances and genetic variants have been identified as risk factors for Alzheimer's disease. Our goal was to assess whether genome-wide polygenic risk scores (PRS) for AD ... [more ▼]

Study objectives: Sleep disturbances and genetic variants have been identified as risk factors for Alzheimer's disease. Our goal was to assess whether genome-wide polygenic risk scores (PRS) for AD associate with sleep phenotypes in young adults, decades before typical AD symptom onset. Methods: We computed whole-genome Polygenic Risk Scores (PRS) for AD and extensively phenotyped sleep under different sleep conditions, including baseline sleep, recovery sleep following sleep deprivation and extended sleep opportunity, in a carefully selected homogenous sample of healthy 363 young men (22.1 y ± 2.7) devoid of sleep and cognitive disorders. Results: AD PRS was associated with more slow wave energy, i.e. the cumulated power in the 0.5-4 Hz EEG band, a marker of sleep need, during habitual sleep and following sleep loss, and potentially with large slow wave sleep rebound following sleep deprivation. Furthermore, higher AD PRS was correlated with higher habitual daytime sleepiness. Conclusions: These results imply that sleep features may be associated with AD liability in young adults, when current AD biomarkers are typically negative, and the notion that quantifying sleep alterations may be useful in assessing the risk for developing AD. [less ▲]

Detailed reference viewed: 111 (33 ULiège)
Full Text
See detailParkinson’s disease multimodal imaging: F-DOPA PET, neuromelanin-sensitive and quantitative iron-sensitive MRI
DEPIERREUX, Frédérique ULiege; PARMENTIER, Eric ULiege; MACKELS, Laurane ULiege et al

in NPJ Parkinson's Disease (2021)

Parkinson’s disease is a neurodegenerative synucleinopathy characterized by the degeneration of neuromelanin-containing dopaminergic neurons and deposition of iron in the substantia nigra (SN). How ... [more ▼]

Parkinson’s disease is a neurodegenerative synucleinopathy characterized by the degeneration of neuromelanin-containing dopaminergic neurons and deposition of iron in the substantia nigra (SN). How regional neuromelanin (NM) loss and iron accumulation within specific areas of SN relates to nigro-striatal dysfunction needs to be clarified. We measured dopaminergic function in pre- and post-commissural putamen by [18F]DOPA PET in twenty-three Parkinson’s disease (PD) patients and 23 healthy control (HC) participants in whom NM content and iron load was assessed in medial and lateral SN, respectively by neuromelanin-sensitive and quantitative R2* MRI. Data analysis consisted of voxelwise regressions testing the group effect and its interaction with NM or iron signals. In PD patients, R2* was selectively increased in left lateral SN as compared to healthy participants, suggesting a local accumulation of iron in Parkinson’s disease. By contrast, NM signal differed between PD and HC, without specific regional specificity within SN. Dopaminergic function in posterior putamen decreased as R2* increased in lateral SN, indicating that dopaminergic function impairment progresses with iron accumulation in the SN. Dopaminergic function was also positively correlated with NM signal in lateral SN, indicating that dopaminergic function impairment progresses with depigmentation in the SN. A complex relationship was detected between R2* in the lateral SN and NM signal in the medial substantia nigra. In conclusion, multimodal imaging reveals regionally-specific relationships between iron accumulation and depigmentation within the SN of Parkinson’s disease and provides in vivo insights in its neuropathology. [less ▲]

Detailed reference viewed: 63 (17 ULiège)
See detailNODDI singularity
Sherif, Siya ULiege; Grignard, Martin ULiege; Phillips, Christophe ULiege

Software (2021)

Singularity containerized version of the NODDI toolbox. NODDI matlab toolbox is a MatLab based toolbox developed by Prof Gary Zang for fitting NODDI data. Since the tool requires MatLab, it cannot be ... [more ▼]

Singularity containerized version of the NODDI toolbox. NODDI matlab toolbox is a MatLab based toolbox developed by Prof Gary Zang for fitting NODDI data. Since the tool requires MatLab, it cannot be deplyed on High-Performance Computing (HPC) clusters that do not have MatLab installed on it. This NODDI singularity container provides an alternative option to run NODDI without MATLAB and can be readily deployed in most HCP clusters. For this container, we are using the single thread option of the NODDI matlab toolbox because the Parallel Computing Toolbox implementation requires an additional Matlab licence. The single thread version takes more than the parallel version. However, this delay could be compensated when deployed in HPC where many images could be processed in parallel. (Eg. NODDI processing using Parallel Computing Toolbox to fit NODDI data with 220454 voxels in local machine using 8 parallel core takes ~ 3 hours. Thats 300 Hours for 100 subjets. The single thread version takes ~18 hours per subject. However, 100 subjects could be launched parallely in the HCP parallely.) [less ▲]

Detailed reference viewed: 31 (3 ULiège)
Full Text
See detailExploratory radiomic analysis of conventional versus quantitative brain MRI: Towards automatic diagnosis of early multiple sclerosis
Lavrova, Elizaveta ULiege; LOMMERS, Emilie ULiege; WOODRUFF, Henry et al

in Frontiers in Neuroscience (2021)

Conventional magnetic resonance imaging (cMRI) is poorly sensitive to pathological changes related to multiple sclerosis (MS) in normal-appearing white matter (NAWM) and grey matter (GM), with the added ... [more ▼]

Conventional magnetic resonance imaging (cMRI) is poorly sensitive to pathological changes related to multiple sclerosis (MS) in normal-appearing white matter (NAWM) and grey matter (GM), with the added difficulty of not being very reproducible. Quantitative MRI (qMRI) on the other hand attempts to represent physical properties of tissues, making it an ideal candidate for quantitative medical image analysis, or radiomics. We therefore hypothesized that qMRI-based radiomic features have added diagnostic value in MS compared to cMRI. This study investigated the ability of cMRI (T1w) and qMRI features extracted from WM, NAWM, and GM to distinguish between MS patients (MSP) and healthy control subjects (HCS). We developed exploratory radiomic classification models on a dataset comprising 36 MSP and 36 HCS recruited in CHU Liege, Belgium, acquired with cMRI and qMRI. For each image type and region of interest, qMRI radiomic models for MS diagnosis were developed on a training subset and validated on a testing subset. Radiomic models based on cMRI were developed on the entire training dataset and externally validated on open-source datasets with 167 HCS and 10 MSP. Ranked by region of interest, the best diagnostic performance was achieved in the whole WM. Here the model based on magnetization transfer imaging (a type of qMRI) features yielded a median area under the receiver operating characteristic curve (AUC) of 1.00 in the testing sub-cohort. Ranked by image type, the best performance was achieved by the magnetization transfer models, with median AUCs of 0.79 (0.69-0.90 90% CI) in NAWM and 0.81 (0.71-0.90) in GM. External validation of the T1w models yielded an AUC of 0.78 (0.47-1.00) in whole WM, demonstrating a large 95% CI and low sensitivity of 0.30 (0.10-0.70). This exploratory study indicates that qMRI Radiomics could provide efficient diagnostic information using NAWM and GM analysis in MSP. T1w radiomics could be useful for a fast and automated check of conventional MRI for WM abnormalities once acquisition and reconstruction heterogeneities have been overcome. Further prospective validation is needed involving more data for better interpretation and generalization of the results. [less ▲]

Detailed reference viewed: 54 (9 ULiège)
Full Text
See detailShamo v1.0 - Stochastic electromagnetic head modelling made easy
Grignard, Martin ULiege; Geuzaine, Christophe ULiege; Phillips, Christophe ULiege

Poster (2021, June)

We introduce a Python 3 package: “shamo”. It can perform mesh generation, electromagnetic simulations and sensitivity analysis.

Detailed reference viewed: 21 (2 ULiège)
Full Text
See detailTime course of cortical response complexity during extended wakefulness and its differential association with vigilance in young and older individuals
Gaggioni, Giulia ULiege; Shumbayawonda, Elizabeth; Montanaro, Umberto et al

in Biochemical Pharmacology (2021), epub ahead of print

Detailed reference viewed: 35 (10 ULiège)
Full Text
See detailVoxel-Based quantitative MRI reveals spatial patterns of grey matter alteration in multiple sclerosis
LOMMERS, Emilie ULiege; Guillemin, Camille ULiege; REUTER, Gilles ULiege et al

in Human Brain Mapping (2021), 42(4), 1003-1012

Despite robust postmortem evidence and potential clinical importance of gray matter (GM) pathology in multiple sclerosis (MS), assessing GM damage by conventional magnetic resonance imaging (MRI) remains ... [more ▼]

Despite robust postmortem evidence and potential clinical importance of gray matter (GM) pathology in multiple sclerosis (MS), assessing GM damage by conventional magnetic resonance imaging (MRI) remains challenging. This prospective cross-sectional study aimed at characterizing the topography of GM microstructural and volumetric alteration in MS using, in addition to brain atrophy measures, three quantitative MRI (qMRI) parameters—magnetization transfer (MT) saturation, longitudinal (R1), and effective transverse (R2*) relaxation rates, derived from data acquired during a single scanning session. Our study involved 35 MS patients (14 relapsing–remitting MS; 21 primary or secondary progressive MS) and 36 age-matched healthy controls (HC). The qMRI maps were computed and segmented in different tissue classes. Voxel-based quantification (VBQ) and voxelbased morphometry (VBM) statistical analyses were carried out using multiple linear regression models. In MS patients compared with HC, three configurations of GM microstructural/volumetric alterations were identified. (a) Co-localization of GM atrophy with significant reduction of MT, R1, and/or R2*, usually observed in primary cortices. (b) Microstructural modifications without significant GM loss: hippocampus and paralimbic cortices, showing reduced MT and/or R1 values without significant atrophy. (c) Atrophy without significant change in microstructure, identified in deep GM nuclei. In conclusion, this quantitative multiparametric voxel-based approach reveals three different spatially-segregated combinations of GM microstructural/volumetric alterations in MS that might be associated with different neuropathology. [less ▲]

Detailed reference viewed: 105 (37 ULiège)
Full Text
See detailshamo: A tool for electromagnetic modelling, simulation and sensitivity analysis of the head
Grignard, Martin ULiege; Geuzaine, Christophe ULiege; Phillips, Christophe ULiege

E-print/Working paper (2021)

Accurate electromagnetic modelling of the head of a subject is of main interest in the fields of source reconstruction and brain stimulation. Those processes rely heavily on the quality of the model and ... [more ▼]

Accurate electromagnetic modelling of the head of a subject is of main interest in the fields of source reconstruction and brain stimulation. Those processes rely heavily on the quality of the model and, even though the geometry of the tissues can be extracted from magnetic resonance images (MRI) or computed tomography (CT), their physical properties such as the electrical conductivity are hard to measure with non intrusive techniques. In this paper, we propose a tool to assess the uncertainty in the model parameters as well as compute a parametric electroencephalography (EEG) forward solution and current distribution for transcranial direct current stimulation (tDCS). [less ▲]

Detailed reference viewed: 34 (5 ULiège)
Full Text
See detailIncidental Verbal Semantic Processing Recruits the Fronto-temporal Semantic Control Network
JEDIDI, Zayd ULiege; Manard, Marine ULiege; Balteau, Evelyne ULiege et al

in Cerebral Cortex (2021), 31

The frontoparietal semantic network, encompassing the inferior frontal gyrus and the posterior middle temporal cortex, is considered to be involved in semantic control processes. The explicit versus ... [more ▼]

The frontoparietal semantic network, encompassing the inferior frontal gyrus and the posterior middle temporal cortex, is considered to be involved in semantic control processes. The explicit versus implicit nature of these control processes remains however poorly understood. The present study examined this question by assessing regional brain responses to the semantic attributes of an unattended stream of auditory words while participants’ top–down attentional control processes were absorbed by a demanding visual search task. Response selectivity to semantic aspects of verbal stimuli was assessed via a functional magnetic resonance imaging response adaptation paradigm. We observed that implicit semantic processing of an unattended verbal stream recruited not only unimodal and amodal cortices in posterior supporting semantic knowledge areas, but also inferior frontal and posterior middle temporal areas considered to be part of the semantic control network. These results indicate that frontotemporal semantic networks support incidental semantic (control) processes. [less ▲]

Detailed reference viewed: 49 (12 ULiège)
Full Text
See detailRestoring statistical validity in group analyses of motion-corrupted MRI data
Lutti, Antoine; Corbin, Nadège; Ashburner, John et al

E-print/Working paper (2021)

Motion during the acquisition of magnetic resonance imaging (MRI) data degrades image quality, hindering our capacity to characterize disease in patient populations. Quality control procedures allow the ... [more ▼]

Motion during the acquisition of magnetic resonance imaging (MRI) data degrades image quality, hindering our capacity to characterize disease in patient populations. Quality control procedures allow the exclusion of the most affected images from analysis. However, the criterion for exclusion is difficult to determine objectively and exclusion can lead to a suboptimal compromise between image quality and sample size. We provide an alternative, data-driven solution that assigns weights to each image, computed from an index of image quality using restricted maximum likelihood. We illustrate this method through the analysis of brain MRI data. The proposed method restores the validity of statistical tests, and performs near optimally in all brain regions, despite local effects of head motion. This method is amenable to the analysis of a broad type of MRI data and can accommodate any measure of image quality. [less ▲]

Detailed reference viewed: 20 (2 ULiège)
Full Text
See detailPositive Effect of Cognitive Reserve on Episodic Memory, Executive and Attentional Functions Taking Into Account Amyloid-Beta, Tau, and Apolipoprotein E Status
Narbutas, Justinas ULiege; Chylinski, Daphné ULiege; Van Egroo, Maxime et al

in Frontiers in Aging Neuroscience (2021), 13

Studies exploring the simultaneous influence of several physiological and environmental factors on domain-specific cognition in late middle-age remain scarce. Therefore, our objective was to determine the ... [more ▼]

Studies exploring the simultaneous influence of several physiological and environmental factors on domain-specific cognition in late middle-age remain scarce. Therefore, our objective was to determine the respective contribution of modifiable risk/protective factors (cognitive reserve and allostatic load) on specific cognitive domains (episodic memory, executive functions, and attention), taking into account non-modifiable factors [sex, age, and genetic risk for Alzheimer’s disease (AD)] and AD-related biomarker amount (amyloid-beta and tau/neuroinflammation) in a healthy late-middle-aged population. One hundred and one healthy participants (59.4 ± 5 years; 68 women) were evaluated for episodic memory, executive and attentional functioning via neuropsychological test battery. Cognitive reserve was determined by the National Adult Reading Test. The allostatic load consisted of measures of lipid metabolism and sympathetic nervous system functioning. The amyloid-beta level was assessed using positron emission tomography in all participants, whereas tau/neuroinflammation positron emission tomography scans and apolipoprotein E genotype were available for 58 participants. Higher cognitive reserve was the main correlate of better cognitive performance across all domains. Moreover, age was negatively associated with attentional functioning, whereas sex was a significant predictor for episodic memory, with women having better performance than men. Finally, our results did not show clear significant associations between performance over any cognitive domain and apolipoprotein E genotype and AD biomarkers. This suggests that domain-specific cognition in late healthy midlife is mainly determined by a combination of modifiable (cognitive reserve) and non-modifiable factors (sex and age) rather than by AD biomarkers and genetic risk for AD. [less ▲]

Detailed reference viewed: 52 (9 ULiège)