Off-axis holographic laser speckle contrast imaging of blood vessels in tissues

Laser speckle contrast imaging (LSCI) has become one of the most common tools for functional imaging in tissues. Incomplete theoretical description and sophisticated interpretation of measurement results are completely sidelined by a low-cost and simple hardware, fastness, consistent results, and repeatability. In addition to the relatively low measuring volume with around 700   μ m of the probing depth for the visible spectral range of illumination, there is no depth selectivity in conventional LSCI configuration; furthermore, in a case of high NA objective, the actual penetration depth of light in tissues is greater than depth of field (DOF) of an imaging system. Thus, the information about these out-of-focus regions persists in the recorded frames but cannot be retrieved due to intensity-based registration method. We propose a simple modification of LSCI system based on the off-axis holography to introduce after-registration refocusing ability to overcome both depth-selectivity and DOF problems as well as to get the potential possibility of producing a cross-section view of the specimen

Off-axis holographic laser speckle contrast imaging of blood vessels in tissues

Laser speckle contrast imaging (LSCI) has become one of the most common tools for functional imaging in tissues. Incomplete theoretical description and sophisticated interpretation of measurement results are completely sidelined by a low-cost and simple hardware, fastness, consistent results, and repeatability. In addition to the relatively low measuring volume with around 700   μ m of the probing depth for the visible spectral range of illumination, there is no depth selectivity in conventional LSCI configuration; furthermore, in a case of high NA objective, the actual penetration depth of light in tissues is greater than depth of field (DOF) of an imaging system. Thus, the information about these out-of-focus regions persists in the recorded frames but cannot be retrieved due to intensity-based registration method. We propose a simple modification of LSCI system based on the off-axis holography to introduce after-registration refocusing ability to overcome both depth-selectivity and DOF problems as well as to get the potential possibility of producing a cross-section view of the specimen

Recueil des actes administratifs de la Délégation générale du Gouvernement en Algérie : Lois et décrets...

28 octobre 19581958/10/28 (A1,N27)-1958/10/28

Blood-brain barrier and cerebral blood flow: Age differences in hemorrhagic stroke

Neonatal stroke is similar to the stroke that occurs in adults and produces a significant morbidity and long-term neurologic and cognitive deficits. There are important differences in the factors, clinical events and outcomes associated with the stroke in infants and adults. However, mechanisms underlying age differences in the stroke development remain largely unknown. Therefore, treatment guidelines for neonatal stroke must extrapolate from the adult data that is often not suitable for children. The new information about differences between neonatal and adult stroke is essential for identification of significant areas for future treatment and effective prevention of neonatal stroke. Here, we studied the development of stress-induced hemorrhagic stroke and possible mechanisms underlying these processes in newborn and adult rats. Using histological methods and magnetic resonance imaging, we found age differences in the type of intracranial hemorrhages. Newborn rats demonstrated small superficial bleedings in the cortex while adult rats had more severe deep bleedings in the cerebellum. Using Doppler optical coherent tomography, we found higher stress-reactivity of the sagittal sinus to deleterious effects of stress in newborn vs. adult rats suggesting that the cerebral veins are more vulnerable to negative stress factors in neonatal vs. adult brain in rats. However, adult but not newborn rats demonstrated the stroke-induced breakdown of blood brain barrier (BBB) permeability. The one of possible mechanisms underlying the higher resistance to stress-related stroke injures of cerebral vessels in newborn rats compared with adult animals is the greater expression of two main tight junction proteins of BBB (occludin and claudin-5) in neonatal vs. mature brain in rats

Hidden stage of intracranial hemorrhage in newborn rats studied with laser speckle contrast imaging and wavelets

Using the laser speckle contrast imaging and wavelet-based analyses, we investigate a latent (a "hidden") stage of the development of intracranial hemorrhages (ICHs) in newborn rats. We apply two measures based on the continuous wavelet-transform of blood flow velocity in the sagittal sinus, namely, the spectral energy in distinct frequency ranges and a multiscality degree characterizing complexity of experimental data. We show that the wavelet-based multifractal formalism reveals changes in the cerebrovascular blood flow at the development of ICH

Distribution of normalized wall shear stress after flow-diverter placement.

<p>a)—B01; b)—B02; c)—A01.</p

Pre-operative distribution of normalized wall shear stress in aneurysm models.

<p>a)—B01; b)—B02; c)—A01.</p

Velocity distribution for central cross-section of A01 aneurysm after flow-diverter placement.

<p>a) CFD simulation; b) MRI measurement.</p