Influence of Respiration of Spinal CSF Pulsation

The cardiac related intracranial pulsations are the main influence on the spinal CSF movement. There is agreement about the additional influence of respiration which has not been imaged so far. The dynamic echo planar sequence (EPI) presented here delineates the influence of pulse and respiration on the spinal CSf pulsation. The physiological variation of the pulsation from the upper cervical to the lumbar region can be delineated. The influence of respiration is present on any spinal level with a maximum in the upper cervical and thoracolumbar region. We could not confirm a pronounced respiratory influence below an absolute stenosis

Scatter-based magnetic resonance elastography

Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 ± 0.1 and 1.7 ± 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations

MR-elastography reveals degradation of tissue integrity in multiple sclerosis

In multiple sclerosis (MS), diffuse brain parenchymal damage exceeding focal inflammation is increasingly recognized to be present from the very onset of the disease, and, although occult to conventional imaging techniques, may present a major cause of permanent neurological disability. Subtle tissue alterations significantly influence biomechanical properties given by stiffness and internal friction, that - in more accessible organs than the brain - are traditionally assessed by manual palpation during the clinical exam. The brain, however, is protected from our sense of touch, and thus our current knowledge on cerebral viscoelasticity is very limited. We developed a clinically feasible magnetic resonance elastography setup sensitive to subtle alterations of brain parenchymal biomechanical properties. Investigating 45 MS patients revealed a significant decrease (13%, P<0.001) of cerebral viscoelasticity compared to matched healthy volunteers, indicating a widespread tissue integrity degradation, while structure-geometry defining parameters remained unchanged. Cerebral viscoelasticity may represent a novel in vivo marker of neuroinflammatory and neurodegenerative pathology

Motion tracking and strain map computation for quasi-static magnetic resonance elastography

10.1007/978-3-642-23623-5_54Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)6891 LNCSPART 1428-43

Weak synchronization and large-scale collective oscillation in dense bacterial suspensions

International audienceCollective oscillatory behaviour is ubiquitous in nature1, having a vital role in many biological processes from embryogenesis2 and organ development3 to pace-making in neuron networks4. Elucidating the mechanisms that give rise to synchronization is essential to the understanding of biological self-organization. Collective oscillations in biological multicellular systems often arise from long-range coupling mediated by diffusive chemicals2, 5, 6, 7, 8, 9, by electrochemical mechanisms4, 10, or by biomechanical interaction between cells and their physical environment11. In these examples, the phase of some oscillatory intracellular degree of freedom is synchronized. Here, in contrast, we report the discovery of a weak synchronization mechanism that does not require long-range coupling or inherent oscillation of individual cells. We find that millions of motile cells in dense bacterial suspensions can self-organize into highly robust collective oscillatory motion, while individual cells move in an erratic manner, without obvious periodic motion but with frequent, abrupt and random directional changes. So erratic are individual trajectories that uncovering the collective oscillations of our micrometre-sized cells requires individual velocities to be averaged over tens or hundreds of micrometres. On such large scales, the oscillations appear to be in phase and the mean position of cells typically describes a regular elliptic trajectory. We found that the phase of the oscillations is organized into a centimetre-scale travelling wave. We present a model of noisy self-propelled particles with strictly local interactions that accounts faithfully for our observations, suggesting that self-organized collective oscillatory motion results from spontaneous chiral and rotational symmetry breaking. These findings reveal a previously unseen type of long-range order in active matter systems (those in which energy is spent locally to produce non-random motion)12, 13. This mechanism of collective oscillation may inspire new strategies to control the self-organization of active matter14, 15, 16, 17, 18 and swarming robot