In vivo MRI assessment of permanent middle cerebral artery occlusion by electrocoagulation: pitfalls of procedure

Permanent middle cerebral artery (MCA) occlusion (pMCAO) by electrocoagulation is a commonly used model but with potential traumatic lesions. Early MRI monitoring may assess pMCAO for non-specific brain damage. The surgical steps of pMCAO were evaluated for traumatic cerebral injury in 22 Swiss mice using diffusion and T2-weighted MRI (7T) performed within 1 h and 24 h after surgery. Temporal muscle cauterization without MCA occlusion produced an early T2 hyperintensity mimicking an infarct. No lesion was visible after temporal muscle incision or craniotomy. Early MRI monitoring is useful to identify non-specific brain injury that could hamper neuroprotective drugs assessment

Clinical Imaging of Choroid Plexus in Health and in Brain Disorders: A Mini-Review

The choroid plexuses (ChPs) perform indispensable functions for the development, maintenance and functioning of the brain. Although they have gained considerable interest in the last years, their involvement in brain disorders is still largely unknown, notably because their deep location inside the brain hampers non-invasive investigations. Imaging tools have become instrumental to the diagnosis and pathophysiological study of neurological and neuropsychiatric diseases. This review summarizes the knowledge that has been gathered from the clinical imaging of ChPs in health and brain disorders not related to ChP pathologies. Results are discussed in the light of pre-clinical imaging studies. As seen in this review, to date, most clinical imaging studies of ChPs have used disease-free human subjects to demonstrate the value of different imaging biomarkers (ChP size, perfusion/permeability, glucose metabolism, inflammation), sometimes combined with the study of normal aging. Although very few studies have actually tested the value of ChP imaging biomarkers in patients with brain disorders, these pioneer studies identified ChP changes that are promising data for a better understanding and follow-up of diseases such as schizophrenia, epilepsy and Alzheimer’s disease. Imaging of immune cell trafficking at the ChPs has remained limited to pre-clinical studies so far but has the potential to be translated in patients for example using MRI coupled with the injection of iron oxide nanoparticles. Future investigations should aim at confirming and extending these findings and at developing translational molecular imaging tools for bridging the gap between basic molecular and cellular neuroscience and clinical research

IMAGERIE PAR RESONANCE MAGNETIQUE (IRM) DE LA PERFUSION CEREBRALE (MODELISATION DE LA CINETIQUE D'UN PRODUIT DE CONTRASTE POUR LA QUANTIFICATION DE LA PERFUSION (DOCTORAT : BIOL. HUM.))

LYON1-BU Santé (693882101) / SudocTOURS-Polytech'Informat.Product. (372612209) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

In vivo evaluation of the potential neurotoxicity of aerosols released from mechanical stress of nano-TiO2 additived paints in mice chronically exposed by inhalation

Engineered Nanomaterials (ENM) provide technical and specific benefits due to theirphysical-chemical properties at the nanometer scale. For instance, many ENM are used to improveproducts in the building industry. Nanoscaled titanium dioxide (TiO2) is one of the most used ENM inthis industry. Incorporated in different matrix, cement, glass, paints… TiO2 nanoparticles (NPs) providethe final product with anti-UV, air purification and self-cleaning properties, thanks to theirphotocatalytic activity. However, ageing processes of such products, as photocatalytic paints, during amechanical stress have been shown to release TiO2 NPs from this matrix associated with sanding dust.Thus, workers who sand painted walls could be exposed to TiO2 NPs through inhalation. As inhalationmay lead to a translocation of particulate matter to the brain via olfactory or trigeminal nerves, there isan urgent need for evaluating a potential neurotoxicity. In order to provide new knowledge on this topic,we developed a dedicated experimental set-up using a rodent model exposed via inhalation. The aerosolreleased from a mechanical stress of photocatalytic paints containing TiO2 NPs was characterized andcoupled to an exposition chamber containing group of mice free to move and chronically exposed(2 hours per day for 5 days a week during 8 weeks)

Influence of perfusion on high-intensity focused ultrasound prostate ablation: a first-pass MRI study.

International audienceOur aim was to evaluate the influence of regional prostate blood flow (rPBF) on high-intensity focused ultrasound (HIFU) treatment outcome. A total of 48 patients with clinically localized prostate cancer were examined by dynamic contrast-enhanced (DCE)-MRI prior to HIFU therapy. A prostate-specific antigen (PSA) nadir threshold of 0.2 ng/ml was used to define the populations of responders and nonresponders. A dedicated tracer kinetic model, namely "monoexponential plus constant" (MPC) deconvolution, was implemented to provide quantitative estimates of rPBF. The results were compared with those obtained by semiquantitative (steepest slope, mean gradient) and quantitative (Fermi deconvolution) approaches. Of the four methods studied, quantitative rPBF obtained by MPC deconvolution proved the most sensitive to the perfusion changes encountered in this study. Furthermore, blood-flow values obtained with MPC deconvolution in the prostate and muscle (12 +/- 8 and 5 +/- 3 ml/min/100 g, respectively) were in good agreement with literature data. The mean pretreatment rPBF obtained with MPC deconvolution was significantly higher in nonresponders compared to responders (16 +/- 9 vs. 10 +/- 6 ml/min/100 g), suggesting a correlation between baseline perfusion and treatment outcome. The present work describes and validates the use of dynamic MRI to estimate rPBF in patients, which in the future may help to refine the conduct of HIFU therapy

Tracking cells in the brain of small animals using synchrotron multi-spectral phase contrast imaging

International audienceSynchrotron X-ray multi-spectral imaging is a novel imaging modality that may allow tracking cells at high resolution in small animal models. The data volume generated by such technique can be of hundreds of Gigabytes for one animal Automatic, robust and rapid pipeline is therefore of paramount importance for large-scale studies. The goal of this article is to present a full image analysis pipeline ranging from the CT reconstruction up to the segmentation of nanoparticles - labeled-cells. Experimentally, rats that had received an intracerebral transplantation of gold nanoparticles-labeled cells were imaged in vivo in phase contrast mode (propagation based-imaging technique) at two different energies strategically chosen around the k-edge of gold. We apply a dedicated phase retrieval technique on each projection (out of 2000 for complete 2 pi rotation) before CT reconstruction. Then, a rigid registration is performed between the images below and above k-edge for accurate subtraction of the two data sets, leading to gold concentration maps. Due to the large number of specimens, the registration is based on the automatic segmentation of the cranial skull. Finally, an automatic segmentation of gold-labeled cells within the brain is performed based on high spots of gold concentrations. An example of an in-vivo data set for stroke cell therapy is presented

MRI coupled with clinically-applicable iron oxide nanoparticles reveals choroid plexus involvement in a murine model of neuroinflammation

International audienceChoroid plexus (ChPs) are involved in the early inflammatory response that occurs in many brain disorders. However, the activation of immune cells within the ChPs in response to neuroinflammation is still largely unexplored in-vivo. There is therefore a crucial need for developing imaging tool that would allow the non-invasive monitoring of ChP involvement in these diseases. Magnetic resonance imaging (MRI) coupled with superparamagnetic particles of iron oxide (SPIO) is a minimally invasive technique allowing to track phagocytic cells in inflammatory diseases. Our aim was to investigate the potential of ultrasmall SPIO (USPIO)-enhanced MRI to monitor ChP involvement in-vivo in a mouse model of neuroinflammation obtained by intraperitoneal administration of lipopolysaccharide. Using high resolution MRI, we identified marked USPIO-related signal drops in the ChPs of animals with neuroinflammation compared to controls. We confirmed these results quantitatively using a 4-points grading system. Ex-vivo analysis confirmed USPIO accumulation within the ChP stroma and their uptake by immune cells. We validated the translational potential of our approach using the clinically-applicable USPIO Ferumoxytol. MR imaging of USPIO accumulation within the ChPs may serve as an imaging biomarker to study ChP involvement in neuroinflammatory disorders that could be applied in a straightforward way in clinical practice

Segmentation of amyloid-β plaques in three mouse models of Alzheimer’s disease using X-ray phase contrast-computed tomography

International audienc

INFLAM - INFLAMmation in Brain and Vessels with Iron Nanoparticles and Cell Trafficking: A Multiscale Approach of Tissue Microenvironment, Iron Nanostructure and Iron Biotransformation

International audienceBackground: Inflammation is a share process in atherosclerosis and stroke and is thought to be a key player in the evolution of these diseases. Ten years ago, inflammation imaging with magnetic resonance imaging (MRI) was considered very promising for both pre-clinical and clinical studies of atherosclerosis and stroke. Contribution: We report here contributions to the field of inflammation imaging with USPIO-enhanced MRI. The goal was to investigate the life cycle of USPIOs in the body, and how the MRI signal has been impacted during their bio-interactions and bioprocessing. Those mechanisms were applied to pre-clinical longitudinal studies of inflammation in atherosclerosis and at the acute stage of ischemic stroke thus allowing the monitoring of treatment effects. Conclusion: This review presents the contribution of the collaborative research project under the "TecSan" grant from the French Research Agency (ANR) as well as pre-clinical and clinical perspectives of USPIO's inflammation MRI in atherosclerosis and stroke. (C) 2018 Published by Elsevier Masson SAS on behalf of AGBM