Biology subjects

Ialy-Radio, N.

Publications and source records attributed to Ialy-Radio, N..

6 recordsLinked to original sources

bioRxiv2026

Multi-Stage Singular Value Decomposition for Ultrafast Ultrasound Imaging of Microbubbles

Microbubble contrast-enhanced ultrasound (CEUS) relies on discriminating nonlinear bubble signals from linear tissue backscattering. While Singular Value Decomposition (SVD) filtering improves this discrimination, existing techniques often fail to retain the slowly-moving microbubble signals from static clutter. Here, we present a novel multi-stage singular value decomposition (MS-SVD) framework for ultrafast CEUS imaging. Our method employs plane-wave transmissions at multiple angles and acoustic pressure levels (implemented via duty-cycle modulation) and alternating transmit polarity. The beamformed data are then processed by three sequential SVD filters: (1) spatial-angular SVD to extract coherent signals across all transmit angles, (2) spatial-pressure SVD to separate linear fundamental and nonlinear harmonic components, and (3) spatiotemporal SVD to isolate moving microbubble echoes from tissue clutter. In in vitro flow phantoms and in vivo rat brain through a cranial window, MS-SVD dramatically improves microbubble detection compared to conventional SVD filtering, MS-SVD yields much stronger vascular contrast and suppresses tissue clutter to a greater extent. The resulting power-Doppler and super-resolution maps are notably cleaner and more complete: MS-SVD detects substantially more microbubble events in ULM, revealing finer vessel details and more accurate flow speeds. By capturing the full acoustic signature of microbubbles (both fundamental and harmonic), MS-SVD achieves higher contrast-to-noise and sensitivity in CEUS. These gains make it a powerful front-end for super-resolution ultrasound localization microscopy and other high-sensitivity microvascular imaging applications.

bioengineering↗

bioRxiv2026

Temporal Patterns of Brain Network Plasticity During the Onset and Maintenance of Neuropathic Pain in Male Mice

Neuropathic pain arises from complex peripheral and central mechanisms and induces long-lasting maladaptive changes in the brain. To investigate the temporal dynamics of these changes, we examined resting-state functional connectivity (FC) in a mouse model of neuropathic pain across its initiation and maintenance phases. Using functional ultrasound imaging to capture whole-brain FC over disease progression, we conducted two complementary studies: a longitudinal assessment in anesthetized animals and an analysis of awake cohorts at distinct disease stages. Both exploratory and literature-guided analyses revealed that FC across most large-scale networks remained remarkably stable during pain maintenance. In contrast, pain onset was marked by enhanced FC between key regions involved in sensory, emotional, and motivational processing, including the motor cortex and nucleus accumbens, the prelimbic and insular cortices, and the infralimbic cortex and hypothalamus. As pain persisted, we observed reduced FC within the somatomotor network, reflecting functional disconnection. Additionally, postsurgical pain alone produced enduring FC changes within the prefrontal cortex, hippocampus, and insula, indicating long-term central plasticity independent of neuropathic injury. Together, these findings reveal dynamic, network-specific adaptations that distinguish the onset and maintenance phases of neuropathic pain and surgery-related plasticity.

neuroscience↗

bioRxiv2025

Speed Vascular Patterns in the Spatial Navigation System

The hippocampal formation is central to spatial navigation, hosting neurons that encode position, direction, and speed. Yet, the brain-wide vascular dynamics supporting these processes remain poorly understood, especially during naturalistic behaviors. Here, we adapted functional ultrasound (fUS) imaging to examine how cerebral blood volume (CBV) changes relate to behavioral parameters in freely moving rats. High-resolution imaging of hippocampal-parahippocampal regions during open-field exploration reveals strong correlations between CBV dynamics and animal speed, with distinct regional activation patterns and temporal delays. Lagged general linear modeling uncovers information flow from the thalamus to parahippocampal regions, including the medial entorhinal cortex, and to hippocampal subfields (dentate gyrus, CA1-CA3), consistent with a hierarchical processing framework. The analysis also links CBV with angular head speed and the dorsal thalamus. Decoding analyses show that CBV signals not only encode speed precisely but also capture spatial features like proximity to walls and corners, even when univariate analyses do not. This decoding remains robust across animals, underscoring the universality of speed encoding in vascular dynamics. We also identify slow CBV oscillations in the hippocampus aligned with minute-scale speed fluctuations, suggesting a neurovascular signature of exploratory behavior. These findings reveal a hemodynamic signature of speed representation in the navigation system, arising from energy demands in a continuous attractor network model for path integration, where population activity and synaptic currents increase quadratically with animal speed as both peak firing rates and neuronal recruitment scale linearly with animal speed. Moreover, they highlight functional ultrasound imaging as a powerful approach for probing the hemodynamic basis of navigation.

neuroscience↗

bioRxiv2024

Transcranial Brain-Wide Functional Ultrasound and Ultrasound Localization Microscopy in Mice using Multilinear Probes

Functional ultrasound imaging (fUS) and ultrasound localization microscopy (ULM) are advanced ultrasound imaging modalities for assessing both functional and anatomical characteristics of the brain. However, the application of these techniques at a whole-brain scale has been limited by technological challenges. While conventional linear acoustic probes provide a narrow 2D field of view and matrix probes lack sufficient sensitivity for 3D transcranial fUS, multilinear probes have been developed to combine high sensitivity to blood flow with fast 3D acquisitions. In this study, we present a novel approach the combined implementation of transcranial whole-brain fUS and ULM in mice using a motorized multilinear probe. This technique provides high-resolution, non-invasive imaging of neurovascular dynamics across the entire brain. Our findings reveal a significant correlation between absolute cerebral blood volume ({Delta}CBV) increases and microbubble velocity, indicating vessel-level dependency of the evoked response. However, the lack of correlation with relative CBV (rCBV) suggests that fUS cannot distinguish functional responses alterations across different arterial vascular compartments. This methodology holds promise for advancing our understanding of neurovascular coupling and could be applied in brain disease diagnostics and therapeutic monitoring.

neuroscience↗

bioRxiv2024

Development of a novel, non-invasive and whole brain biomarker of demyelination in a mouse model of multiple sclerosis

Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system (CNS), affecting 2.8 million people worldwide, that presents multiple features, one of which is demyelination. Although treatments exist to manage the condition, no cure has been found to stop the progression of neurodegeneration. To develop new treatments and investigate the multiple systems impacted by MS, new imaging technologies are needed at the preclinical stage. Functional ultrasound imaging (fUS) has recently been demonstrated to robustly measure brain cerebral blood volume (CBV) dynamics as an indirect measure of neural activity. This study aimed at proposing a new biomarker of de- and/or re-myelination in a mouse model of MS induced by cuprizone. We demonstrate first that extended demyelination induces an increased hemodynamic response in the primary sensory cortex both spatially and temporally, which is consistent with fMRI data collected on MS patients. Second, using descriptors of the evoked hemodynamic response, we show that 3 of these descriptors allows the prediction of the level of myelin in the primary sensory cortex (p=5. 10-5) and the thalamus (p=6. 10-6). The development of such a non-invasive biomarker is crucial in the MS field as is provides an extremely useful tool for both disease follow-up and drug development. RESEARCH IN CONTEXTO_ST_ABSEvidence before this studyC_ST_ABSMultiple sclerosis (MS) is an autoimmune neurodegenerative disorder of the central nervous system. It is the most common cause of neurological disability in young adults, affecting approximately 2.8 million worldwide. While the field of studies in MS has been very active at identifying the neurobiological cellular and molecular mechanisms underlying MS progression, the number of new treatments has been very limited so far, due to several factors, such as the lack of robust and non-invasive biomarkers of myelin loss in longitudinal studies (measurements during the development of the disease). Unfortunately, quantification of myelin loss, (one of the key neurobiological markers of MS progression) is classically performed post-mortem on fixed tissues, preventing longitudinal studies. Longitudinal follow up of an indirect measure of myelin loss is possible, using magnetic resonance imaging. However, the small size of rodent brains poses a challenge for conventional imaging techniques, requiring the use of high field magnet to achieve the necessary sensitivity and resolution. Added value of this studyIn this study, using a sensitive neuroimaging technique, we developed a simple, non-invasive, predictive biomarker able to quantify the individual amount of myelin content consistently and accurately in brain structures in mice. Implications of all the available evidenceThe development of such a biomarker is extremely important for the MS field as it will accelerate the pre-clinical tests for drug efficacy. The benefits provided by our biomarker encompass: 1) Enhanced sensitivity in individually quantifying myelin content, providing a more comprehensive assessment across diverse brain regions 2) Speeding up the process of the discovery, by reducing the number of animals required per group and 3) It will also likely lead to new scientific outcomes, as many more structures will be studied (most teams and drug compagnies only study the demyelination at the level of the corpus callosum). Finally, from a clinical perspective, given the brain alterations observed in this animal model closely mirror those observed in early stages in patients with MS, we anticipate our biomarker, with minimal additional refinements, to be readily applicable in clinical settings.

neuroscience↗

bioRxiv2023

Backscattering Amplitude in Ultrasound Localization Microscopy

In the last decade, Ultrafast Ultrasound Localisation Microscopy has taken non-invasive deep vascular imaging down to the microscopic level. By imaging diluted suspensions of circulating microbubbles in the blood stream at kHz framerate and localising the center of their individual point spread function with a sub-resolution precision, it enabled to break the unvanquished trade-off between depth of imaging and resolution by microscopically mapping the microbubbles flux and velocities deep into tissue. However, ULM also suffers limitations. Many small vessels are not visible in the ULM images due to the noise level in areas dimly explored by the microbubbles. Moreover, as the vast majority of studies are performed using 2D imaging, quantification is limited to in-plane velocity or flux measurements which hinders the accurate velocity determination and quantification. Here we show that the backscattering amplitude of each individual microbubble can also be exploited to produce backscattering images of the vascularization with a higher sensitivity compared to conventional ULM images. By providing valuable information about the relative distance of the microbubble to the 2D imaging plane in the out-of-plane direction, backscattering ULM images introduces a physically relevant 3D rendering perception in the vascular maps. It also retrieves the missing information about the out-of-plane motion of microbubbles and provides a way to improve 3D flow and velocity quantification using 2D ULM. These results pave the way to improved visualization and quantification for 2D and 3D ULM.

bioengineering↗