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F Lauwers - One of the best experts on this subject based on the ideXlab platform.
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simulation study of brain blood flow regulation by intra cortical arterioles in an anatomically accurate large human Vascular Network part ii flow variations induced by global or localized modifications of arteriolar diameters
NeuroImage, 2011Co-Authors: Sylvie Lorthois, Francis Cassot, F LauwersAbstract:In a companion paper (Lorthois et al., Neuroimage, in press), we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical Vascular Network (~10000 segments), using a 1D non-linear model taking into account the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, volumes of functional Vascular territories, regional flow at voxel and Network scales, etc. Using the same approach, we study flow reorganizations induced by global arteriolar vasodilations (an isometabolic global increase in cerebral blood flow). For small to moderate global vasodilations, the relationship between changes in volume and changes in flow is in close agreement with Grubb's law, providing a quantitative tool for studying the variations of its exponent with underlying Vascular architecture. A significant correlation between blood flow and Vascular structure at the voxel scale, practically unchanged with respect to baseline, is demonstrated. Furthermore, the effects of localized arteriolar vasodilations, representative of a local increase in metabolic demand, are analyzed. In particular, localized vasodilations induce flow changes, including Vascular steal, in the neighboring arteriolar trunks at small distances (<300 μm), while their influence in the neighboring veins is much larger (about 1 mm), which provides an estimate of the Vascular point spread function. More generally, for the first time, the hemodynamic component of various functional neuroimaging techniques has been isolated from metabolic and neuronal components, and a direct relationship with several known characteristics of the BOLD signal has been demonstrated.
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simulation study of brain blood flow regulation by intra cortical arterioles in an anatomically accurate large human Vascular Network part i methodology and baseline flow
NeuroImage, 2011Co-Authors: Sylvie Lorthois, Francis Cassot, F LauwersAbstract:Hemodynamically based functional neuroimaging techniques, such as BOLD fMRI and PET, provide indirect measures of neuronal activity. The quantitative relationship between neuronal activity and the measured signals is not yet precisely known, with uncertainties remaining about the relative contribution by their metabolic and hemodynamic components. Empirical observations have demonstrated the importance of the latter component and suggested that micro-Vascular anatomy has a potential influence. The recent development of a 3D computer-assisted method for micro-Vascular cerebral Network analysis has produced a large quantitative library on the microcirculation of the human cerebral cortex (Cassot et al., 2006), which can be used to investigate the hemodynamic component of brain activation through fluid dynamic modeling. For this purpose, we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical Vascular Network (~10000 segments), using a 1D non-linear model taking account of the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, as well as volumes of functional Vascular territories, and regional flow at voxel and Network scales. First, the influence of the prescribed boundary conditions (BCs) on the baseline flow structure is investigated, highlighting relevant lower- and upper-bound BCs. Independent of these BCs, large heterogeneities of baseline flow from vessel to vessel and from voxel to voxel, are demonstrated. These heterogeneities are controlled by the architecture of the intra-cortical Vascular Network. In particular, a correlation between the blood flow and the proportion of Vascular volume occupied by arterioles or venules, at voxel scale, is highlighted. Then, the extent of venous contamination downstream to the sites of neuronal activation is investigated, demonstrating a linear relationship between the catchment surface of the activated area and the diameter of the intra-cortical draining vein.
Joseph P Vacanti - One of the best experts on this subject based on the ideXlab platform.
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influence of Vascular Network design on gas transfer in lung assist device technology
Asaio Journal, 2011Co-Authors: Erik K Bassett, David M Hoganson, Elliot J N Penson, Joseph P VacantiAbstract:Blood oxygenators are vital for the critically ill, but their use is limited to the hospital setting. A portable blood oxygenator or a lung assist device for ambulatory or long-term use would greatly benefit patients with chronic lung disease. In this work, a biomimetic blood oxygenator system was developed which consisted of a microfluidic Vascular Network covered by a gas permeable silicone membrane. This system was used to determine the influence of key microfluidic parameters-channel size, oxygen exposure length, and blood shear rate-on blood oxygenation and carbon dioxide removal. Total gas transfer increased linearly with flow rate, independent of channel size and oxygen exposure length. On average, CO(2) transfer was 4.3 times higher than oxygen transfer. Blood oxygen saturation was also found to depend on the flow rate per channel but in an inverse manner; oxygenation decreased and approached an asymptote as the flow rate per channel increased. These relationships can be used to optimize future biomimetic Vascular Networks for specific lung applications: gas transfer for carbon dioxide removal in patients with chronic obstructive pulmonary disease or oxygenation for premature infants requiring complete lung replacement therapy.
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branched Vascular Network architecture a new approach to lung assist device technology
The Journal of Thoracic and Cardiovascular Surgery, 2010Co-Authors: David M Hoganson, Eli F Weinberg, Eric J Swart, Brian K Orrick, Jeffrey T Borenstein, Jennifer L. Anderson, Joseph P VacantiAbstract:Objective A lung assist device would serve an important clinical need as a bridge to transplant or destination therapy for patients with end-stage lung disease. A new lung assist device has been developed that incorporates a branched Network of Vascular channels adjacent to a gas chamber, separated by a thin, gas-permeable membrane. This study investigated 2 potential gas exchange membranes within this new architecture. Methods Oxygen and carbon dioxide exchange within the device was tested in vitro using 3 gas-permeable membranes. Two of the membranes, silicone only and silicone-coated microporous polymer, were plasma impermeable. The third, a microporous polymer, was used as a control. Gas exchange testing was done using anticoagulated porcine blood over a range of flow rates. Results Oxygen and carbon dioxide transfer was demonstrated in the device and increased nearly linearly from 0.6 to 8.0 mL/min blood flow for all of the membranes. There was no significant difference in the gas transfer between the silicone and the silicone-coated microporous polymer membranes. The transfer of oxygen and carbon dioxide in the device was similar to existing hollow fiber oxygenators controlling for surface area. Conclusions The silicone and silicone-coated microporous polymer membranes both show promise as gas-permeable membranes in a new lung assist device design. Further optimization of the device by improving the membranes and reducing the channel diameter in the Vascular Network will improve gas transfer. The current device may be scaled up to function as an adult lung assist device.
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Principles of Biomimetic Vascular Network Design Applied to a Tissue-Engineered Liver Scaffold
Tissue engineering. Part A, 2010Co-Authors: David M Hoganson, Howard I. Pryor, Ira Spool, Owen Burns, J. Randall Gilmore, Joseph P VacantiAbstract:Branched Vascular Networks are a central component of scaffold architecture for solid organ tissue engineering. In this work, seven biomimetic principles were established as the major guiding technical design considerations of a branched Vascular Network for a tissue-engineered scaffold. These biomimetic design principles were applied to a branched radial architecture to develop a liver-specific Vascular Network. Iterative design changes and computational fluid dynamic analysis were used to optimize the Network before mold manufacturing. The Vascular Network mold was created using a new mold technique that achieves a 1:1 aspect ratio for all channels. In vitro blood flow testing confirmed the physiologic hemodynamics of the Network as predicted by computational fluid dynamic analysis. These results indicate that this biomimetic liver Vascular Network design will provide a foundation for developing complex Vascular Networks for solid organ tissue engineering that achieve physiologic blood flow.
Jiang Liu - One of the best experts on this subject based on the ideXlab platform.
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retinal Vascular Network topology reconstruction and artery vein classification via dominant set clustering
IEEE Transactions on Medical Imaging, 2020Co-Authors: Yitian Zhao, Yonghuai Liu, Jianyang Xie, Huaizhong Zhang, Yalin Zheng, Yifan Zhao, Yangchun Zhao, Jiang LiuAbstract:The estimation of Vascular Network topology in complex Networks is important in understanding the relationship between Vascular changes and a wide spectrum of diseases. Automatic classification of the retinal Vascular trees into arteries and veins is of direct assistance to the ophthalmologist in terms of diagnosis and treatment of eye disease. However, it is challenging due to their projective ambiguity and subtle changes in appearance, contrast, and geometry in the imaging process. In this paper, we propose a novel method that is capable of making the artery/vein (A/V) distinction in retinal color fundus images based on Vascular Network topological properties. To this end, we adapt the concept of dominant set clustering and formalize the retinal blood vessel topology estimation and the A/V classification as a pairwise clustering problem. The graph is constructed through image segmentation, skeletonization, and identification of significant nodes. The edge weight is defined as the inverse Euclidean distance between its two end points in the feature space of intensity, orientation, curvature, diameter, and entropy. The reconstructed Vascular Network is classified into arteries and veins based on their intensity and morphology. The proposed approach has been applied to five public databases, namely INSPIRE, IOSTAR, VICAVR, DRIVE, and WIDE, and achieved high accuracies of 95.1%, 94.2%, 93.8%, 91.1%, and 91.0%, respectively. Furthermore, we have made manual annotations of the blood vessel topologies for INSPIRE, IOSTAR, VICAVR, and DRIVE datasets, and these annotations are released for public access so as to facilitate researchers in the community.
Sylvie Lorthois - One of the best experts on this subject based on the ideXlab platform.
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simulation study of brain blood flow regulation by intra cortical arterioles in an anatomically accurate large human Vascular Network part ii flow variations induced by global or localized modifications of arteriolar diameters
NeuroImage, 2011Co-Authors: Sylvie Lorthois, Francis Cassot, F LauwersAbstract:In a companion paper (Lorthois et al., Neuroimage, in press), we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical Vascular Network (~10000 segments), using a 1D non-linear model taking into account the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, volumes of functional Vascular territories, regional flow at voxel and Network scales, etc. Using the same approach, we study flow reorganizations induced by global arteriolar vasodilations (an isometabolic global increase in cerebral blood flow). For small to moderate global vasodilations, the relationship between changes in volume and changes in flow is in close agreement with Grubb's law, providing a quantitative tool for studying the variations of its exponent with underlying Vascular architecture. A significant correlation between blood flow and Vascular structure at the voxel scale, practically unchanged with respect to baseline, is demonstrated. Furthermore, the effects of localized arteriolar vasodilations, representative of a local increase in metabolic demand, are analyzed. In particular, localized vasodilations induce flow changes, including Vascular steal, in the neighboring arteriolar trunks at small distances (<300 μm), while their influence in the neighboring veins is much larger (about 1 mm), which provides an estimate of the Vascular point spread function. More generally, for the first time, the hemodynamic component of various functional neuroimaging techniques has been isolated from metabolic and neuronal components, and a direct relationship with several known characteristics of the BOLD signal has been demonstrated.
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simulation study of brain blood flow regulation by intra cortical arterioles in an anatomically accurate large human Vascular Network part i methodology and baseline flow
NeuroImage, 2011Co-Authors: Sylvie Lorthois, Francis Cassot, F LauwersAbstract:Hemodynamically based functional neuroimaging techniques, such as BOLD fMRI and PET, provide indirect measures of neuronal activity. The quantitative relationship between neuronal activity and the measured signals is not yet precisely known, with uncertainties remaining about the relative contribution by their metabolic and hemodynamic components. Empirical observations have demonstrated the importance of the latter component and suggested that micro-Vascular anatomy has a potential influence. The recent development of a 3D computer-assisted method for micro-Vascular cerebral Network analysis has produced a large quantitative library on the microcirculation of the human cerebral cortex (Cassot et al., 2006), which can be used to investigate the hemodynamic component of brain activation through fluid dynamic modeling. For this purpose, we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical Vascular Network (~10000 segments), using a 1D non-linear model taking account of the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, as well as volumes of functional Vascular territories, and regional flow at voxel and Network scales. First, the influence of the prescribed boundary conditions (BCs) on the baseline flow structure is investigated, highlighting relevant lower- and upper-bound BCs. Independent of these BCs, large heterogeneities of baseline flow from vessel to vessel and from voxel to voxel, are demonstrated. These heterogeneities are controlled by the architecture of the intra-cortical Vascular Network. In particular, a correlation between the blood flow and the proportion of Vascular volume occupied by arterioles or venules, at voxel scale, is highlighted. Then, the extent of venous contamination downstream to the sites of neuronal activation is investigated, demonstrating a linear relationship between the catchment surface of the activated area and the diameter of the intra-cortical draining vein.
Pierre Chambon - One of the best experts on this subject based on the ideXlab platform.
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prevention of skin flap necrosis by estradiol involves reperfusion of a protected Vascular Network
Circulation Research, 2009Co-Authors: Celine E Toutain, Laurent Brouchet, Isabelle Raymondletron, Patricia Vicendo, Hortense Berges, Julie Favre, Mariejose Fouque, Andree Krust, Annemarie Schmitt, Pierre ChambonAbstract:Although 17beta-estradiol (E2) is protective in experimental models of myocardial and brain ischemia, its effect on skin ischemia remains unknown. Here, we assessed the protective effect of E2 in a mouse model of skin ischemia, mimicking the surgery of skin flaps. Whereas necrosis appeared in the half portion of the skin flap within 1 week after surgery in ovariectomized mice, it was reduced up to 10-fold when mice were pretreated with E2, at least 3 days before the surgery. The beneficial effect of E2 appeared to be attributable to an increase in skin survival, revealed by measuring viability of ex vivo explants and enhancement of the antiapoptotic Bcl-2 protein expression in vivo. This protective effect on the skin contributed to the protection of the Vascular Network and facilitated reperfusion, which was found to be accelerated in ovariectomized E2-treated mice, whereas hemorrhages were observed in untreated mice. E2 also increased expression of fibroblast growth factor-2 isoforms in the skin and circulating Vascular endothelial growth factor in the serum. Finally, this protective effect of E2 was abolished in estrogen receptor-deficient mice (ERalpha(-/-)) but maintained in chimeric mice reconstituted with ERalpha-deficient bone marrow, indicating dispensable action of E2 in bone marrow-derived cells. This protective effect of E2 was mimicked by treatment with tamoxifen, a selective estrogen receptor modulator. In conclusion, we have demonstrated for the first time that E2 exerts a major preventive effect of skin flap necrosis through a prevention of ischemic-induced skin lesions, including those of the Vascular Network, which contributes to accelerate the reperfusion of the skin flap.
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prevention of skin flap necrosis by estradiol involves reperfusion of a protected Vascular Network
Circulation Research, 2009Co-Authors: Celine E Toutain, Laurent Brouchet, Isabelle Raymondletron, Patricia Vicendo, Hortense Berges, Julie Favre, Mariejose Fouque, Andree Krust, Annemarie Schmitt, Pierre ChambonAbstract:Although 17β-estradiol (E2) is protective in experimental models of myocardial and brain ischemia, its effect on skin ischemia remains unknown. Here, we assessed the protective effect of E2 in a mouse model of skin ischemia, mimicking the surgery of skin flaps. Whereas necrosis appeared in the half portion of the skin flap within 1 week after surgery in ovariectomized mice, it was reduced up to 10-fold when mice were pretreated with E2, at least 3 days before the surgery. The beneficial effect of E2 appeared to be attributable to an increase in skin survival, revealed by measuring viability of ex vivo explants and enhancement of the antiapoptotic Bcl-2 protein expression in vivo. This protective effect on the skin contributed to the protection of the Vascular Network and facilitated reperfusion, which was found to be accelerated in ovariectomized E2-treated mice, whereas hemorrhages were observed in untreated mice. E2 also increased expression of fibroblast growth factor-2 isoforms in the skin and circula...
