Next Breakfast & Science Seminar
May 25th, 10 am, CHUV, BH08-Salle séminaire 2, Lausanne, Add to my calendar
“Beyond Fiber Orientations: Microstructure Informed Tractography” by Gabriel Girard from Signal Processing core of CIBM and LTS5, EPFL.
2017/11/17: “Combining EEG and fMRI to study human brain function: insights and developments at ultra-high field" by J. Jorge
Abstract: Scalp electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are valuable non-invasive neuroscience tools, which can complement each other remarkably. Combined EEG-fMRI recordings can offer rich descriptions of brain function and dysfunction, at both electrical and vascular levels, with high temporal and spatial specificity. However, this combination carries important challenges for signal quality, many of which remain open problems in research. This seminar will cover the fundamentals of EEG-fMRI acquisition and applications, followed by an overview of our most recent developments and experiences at an ultra-high field strength of 7 Tesla, at EPFL, Lausanne. 7T EEG-fMRI may offer novel insights into brain activity at unprecedented temporal and spatial resolution (down to the level of cortical columns and cortical layers). The inherent issues of EEG-fMRI are accentuated at 7T, yet can be substantially mitigated, while revealing new artifact properties of general importance to signal analysis, for this as well as lower field strengths.
Dr. J. Jorge post-doc researcher at MIAL core.
2017/12/15: "Whole-brain functional networks" by K. Glomb
Abstract: The last years have seen an unprecedented increase in studies on connectomics. This is largely due to progress in methods for whole-brain imaging – fMRI allows to image whole-brain activity with a decent spatial resolution, diffusion imaging provides us with detailed accounts of anatomical connectivity, and lately, high-density EEG has led to remarkable improvements of source localization for data with excellent temporal resolution. Often, the so-called resting state experimental paradigm is used to record spontaneous activity that can be used to probe “intrinsic” functional connectivity of the brain. This is based on the concept that the brain contains more or less fixed pathways that are flexibly engaged depending on task demands. In other words, we study brain activity as the result of signals propagating through a complex network. I will present two distinct but complementary approaches that explain whole-brain signals as generated by multiple networks overlapping in space and time, namely tensor decomposition and functional harmonics.
Dr K. Glomb is post-doc researcher at Radiology Department, CHUV.
2018/01/19: "EEG resting states: from scalp potentials to sources" by A. Custo
Abstract: Using electroencephalography (EEG) to elucidate the spontaneous activation of brain resting-state networks (RSNs) is nontrivial as the signal of interest is of low amplitude and it is difficult to distinguish the underlying neural sources. Using the principles of electric field topographical analysis, it is possible to estimate the meta-stable states of the brain (i.e., the resting-state topographies, so-called microstates). We estimated seven resting-state topographies explaining the EEG data set with k-means clustering (N = 164, 256 electrodes). Using a method specifically designed to localize the sources of broadband EEG scalp topographies by matching sensor and source space temporal patterns, we demonstrated that we can estimate the EEG RSNs reliably by measuring the reproducibility of our findings. After subtracting their mean from the seven EEG RSNs, we identified seven state-specific networks. The mean map includes regions known to be densely anatomically and functionally connected (superior frontal, superior parietal, insula, and anterior cingulate cortices). While the mean map can be interpreted as a ‘‘router,’’ crosslinking multiple functional networks, the seven state-specific RSNs partly resemble and extend previous functional magnetic reso- nance imaging-based networks estimated as the hemodynamic correlates of four canonical EEG microstates.
Dr A. Custo is senior research at the EEG-HUG core of the CIBM.
2018/02/09: "Magnetic resonance imaging of the lungs for the evaluation of cystic fibrosis patients" by J. Delacoste
Time and Place: 10 am at EPFL, CH F1 614, Add to my calendar
Abstract: Lung disease is the main cause of mortality in cystic fibrosis patients. Imaging studies, in particular using computed tomography (CT), deliver valuable clinical information. However, repeated exposure to ionizing radiation increases the lifetime risk of cancer. Magnetic resonance imaging (MRI) methods are therefore increasingly investigated as an alternative free of ionizing radiation.
However, several technical challenges remain. First, the abundance of air-tissue interfaces within the organ results in very short T2*, of the order of 2 ms in the lung parenchyma at 1.5 Tesla, which may result in images with low signal-to-noise ratio. An additional issue is that motion corruption of the images must be avoided, while ensuring coverage of the whole lungs. Self-navigation and compressed sensing can be used to obtain motion resolved images of the lung without requiring breath holds or respiratory gating hardware. These technical developments, and their applications for imaging of cystic fibrosis patients will be introduced in this presentation.
Dr. J. Delacoste is senior researcher with CIBM MRI-CHUV core.
2018/03/09: "From beside to classroom: The added value of electrical neuroimaging in understanding sensory, brain and cogntive development in naturalistic settings" by Dr P. Matusz
Time and Place: 10 am at HUG, Radiology Department, Salle de colloque 3 (level P), Add to my calendar
Abstract: Fundamental principles of perception and functional brain organisation have been established by research utilising well-controlled but simplified paradigms with basic stimuli. While it employed nascent neuroscientific methods, the last thirty years ushered a revolution in computational power, brain mapping and signal-processing techniques. Drawing on those theoretical and methodological advances, recently there’s been a rapidly growing interest in studying and explaining brain-cognitive processes as they occur in naturalistic environments, in both healthy and atypical individuals. In this context, EEG has the potential of becoming a prominent tool to measure brain activity, due to its elevated cost-effectiveness and ease of administration compared to other similar methods.These advantages become magnified by using advanced EEG analyses, such as a locally developed electrical neuroimaging (EN) approach (Lehmann & Skrandies 1980; Murray et al. 2008; Michel & Murray 2008). EN provides results that are directly interpretable in terms of neurophysiological mechanisms as well as robust and thus replicable. I will discuss two lines of developmental research in naturalistic settings where these combined advantages are directly visible. First, I will discuss insights into early typical and atypical tactile processing and their interactions with experience (e.g., the ration of positive/negative tactile experiences; constraint-based treatments) in pre-term born infants at NICUs and in young children with cerebral palsy. Second, I will present new findings on the role of brain and behavioural markers of attentional control towards visual and multisensory stimuli in shaping educational outcomes in healthy children at the very beginning (i.e., “1P”) and following substantial amount of school instruction (i.e., “3P”). These findings will highlight how synergies across experimental psychology, neuroscience, and brain imaging provide a better understanding of sensory and cognitive functions in everyday contexts where this knowledge is most pertinent: education and paediatric clinical practice.
Dr P. Matusz is a senior researcher at Institute of Information Systems, HES-SO Valais, Sierre and The Laboratory for Investigative Neurophysiology, Department of Radiology, Centre of Research in Radiology RC7, CHUV – UNIL.
2018/03/23: "Development of a phase-contrast clinical mammography prototype for the in-vivo investigation of breast cancer" by Dr. C. Arboleda Clavijois
Abstract: Breast cancer is the second leading cause of cancer death in women. Detecting it in early stages increases the survival rate and thus contributes to the life quality of the patient. Currently, attenuation-based mammography is the most used screening technique. Notwithstanding, it is not capable of detecting some important malignant formations, due to small differences in X-ray attenuation between them and healthy tissue. Phase contrast X-ray imaging has proven to ameliorate soft tissue contrast and, therefore, to be useful for breast cancer detection. However, it generally requires the utilization of highly-coherent sources, like synchrotrons, which are difficult to access and therefore transfer to the clinical environment.
The advent of X-ray grating interferometry has paved the way for the transfer of the
phase-contrast technology to the clinics, since it can be performed with a regular X-ray tube. Although there have been several investigative works on grating-based phase contrast mammography, none of them has really managed to address all the issues that imply the commissioning of such a technique in a hospital, like the minimum required field-of-view, maximum allowed exposure time, dose limitation and geometrical constraints.
In this presentation, I will talk about the X-ray grating interferometry technique basics and the design, development and implementation of a fully clinically-compatible X-ray grating-based mammography device. Furthermore, I will summarize the outcomes of an extensive investigation of the scattering properties of breast microcalcifications and how they can be exploited to non-invasively diagnose malignant breast lesions.
Dr. Carolina Arboleda Clavijois senior researcher with CIBM Phase contrast X-ray imaging core.
2018/04/20: "fMRI data analysis: from temporal deconvolution to dynamics" by Dr. Younes Farouj
Time and Place: 10 am at CHUV, to be determined, Add to my calendar
Abstract: Functional Magnetic Resonance Imaging (fMRI) offers a window on brain activity over time, and on its dynamics at rest or upon cognitive challenge. Deciphering the complex brain organization from fMRI data requires, however, advanced data processing and analysis tools. In this presentation, I will give an overview of some of the works that have been conducted at the MIPLAB-EPFL to unravel complex dynamic interactions between brain region. First, I will present a framework that combines temporal and spatial regularization to deconvolve the fMRI blood oxygen-level dependent (BOLD) signals; i.e., undo them from the influence of the hemodynamic response and thus reveal exact moments of sustained activity in the brain. Second, I will show how these recovered signals can be further exploited by temporal clustering to define innovation driven Co-Activation Patterns (iCAPs), which are building blocks that allow us to study how distributed brain regions overlay and interact in time. Finally, I will explain how iCAPs can be yet used to capture complex temporal dynamics in terms of network-to-network modulatory influences. dynamic interactions between brain region. First, I will present a framework that combines temporal and spatial regularization to deconvolve the fMRI blood oxygen-level dependent (BOLD) signals; i.e., undo them from the influence of the hemodynamic response and thus reveal exact moments of sustained activity in the brain. Second, I will show how these recovered signals can be further exploited by temporal clustering to define innovation driven Co-Activation Patterns (iCAPs), which are building blocks that allow us to study how distributed brain regions overlay and interact in time. Finally, I will explain how iCAPs can be yet used to capture complex temporal dynamics in terms of network-to-network modulatory influences.
2018/05/25: "Beyond Fiber Orientations: Microstructure Informed Tractography" by Gabriel Girard
Time and Place: 10 am at CHUV, BH-08 Salle séminaire 2, Add to my calendar
Abstract: Diffusion tractography has become the tool of choice to probe the human brain’s white matter in vivo. Recent results have shown that, albeit tractography can extract large white matter pathways, there is a high incidence of erroneous pathways. In this talk, I will present recent improvements to tractography reconstructions using anatomical information from a high-resolution T1-weighted image and using microstructural information from densely sampled diffusion-weighted images. This paves the way for a new generation of tractography algorithms able to deal with intricate configurations of white matter fibers and providing more quantitative connectivity analysis.