Large Vascular Network Research Articles

Modeling and hexahedral meshing of cerebral arterial networks from centerlines.

Computational fluid dynamics (CFD) simulation provides valuable information on blood flow from the vascular geometry. However, it requires extracting precise models of arteries from low-resolution medical images, which remains challenging. Centerline-based representation is widely used to model large vascular networks with small vessels, as it encodes both the geometric and topological information and facilitates manual editing. In this work, we propose an automatic method to generate a structured hexahedral mesh suitable for CFD directly from centerlines. We addressed both the modeling and meshing tasks. We proposed a vessel model based on penalized splines to overcome the limitations inherent to the centerline representation, such as noise and sparsity. The bifurcations are reconstructed using a parametric model based on the anatomy that we extended to planar n-furcations. Finally, we developed a method to produce a volume mesh with structured, hexahedral, and flow-oriented cells from the proposed vascular network model. The proposed method offers better robustness to the common defects of centerlines and increases the mesh quality compared to state-of-the-art methods. As it relies on centerlines alone, it can be applied to edit the vascular model effortlessly to study the impact of vascular geometry and topology on hemodynamics. We demonstrate the efficiency of our method by entirely meshing a dataset of 60 cerebral vascular networks. 92% of the vessels and 83% of the bifurcations were meshed without defects needing manual intervention, despite the challenging aspect of the input data. The source code is released publicly.

Application of machine learning in predicting blood flow and red cell distribution in capillary vessel networks.

Capillary blood vessels in the body partake in the exchange of gas and nutrients with tissues. They are interconnected via multiple vascular junctions forming the microvascular network. Distributions of blood flow and red cells (RBCs) in such networks are spatially uneven and vary in time. Since they dictate the pathophysiology of tissues, their knowledge is important. Theoretical models used to obtain flow and RBC distribution in large networks have limitations as they treat each vessel as a one-dimensional segment and do not explicitly consider cell-cell and cell-vessel interactions. High-fidelity computational models that accurately model each individual RBC are computationally too expensive to predict haemodynamics in large vascular networks and over a long time. Here we investigate the applicability of machine learning (ML) techniques to predict blood flow and RBC distributions in physiologically realistic vascular networks. We acquire data from high-fidelity simulations of deformable RBC suspension flowing in the networks. With the flow and haematocrit specified at an inlet of vasculature, the ML models predict the time-averaged flow rate and RBC distributions in the entire network, time-dependent flow rate and haematocrit in each vessel and vascular bifurcation in isolation over a long time, and finally, simultaneous spatially and temporally evolving quantities through the vessel hierarchy in the networks.

Bacillary Layer Detachment (BALAD) in Macular Choroidal Metastasis of a Low-grade Rectal Adenocarcinoma

Choroidal metastases are the most common intraocular malignant tumors in adults [1]. Because of its large vascular network, the choroid is the most frequently involved ocular layer. The majority of patients with choroidal metastasis have been previously diagnosed with systemic cancer. In one-third of the patients, the choroidal metastasis is found before the primary tumor [1]. Breast (45%) and lung cancer (25%) are the most common primary neoplasms [1]. The gastrointestinal tract (4%), in particular, the rectum (< 0.5%), is an unusual site of origin [1], [2].

Diabetes mellitus and the lungs

Diabetes mellitus is a chronic disease characterized by hyperglycemia causing damage to the vascular system. The lungs with a large vascular network are also predisposed to diabetes’ vascular damage. Diabetes may lead to pulmonary parenchymal damage besides alterations in the vascular system and the alveolar-capillary membrane. Symptoms and damage caused by diabetes are usually underdiagnosed because of the large pulmonary reserves. Pulmonary involvement in diabetes is an area that draws attention in recent years. This attention increases especially with the new Coronavirus disease-2019 (COVID-19) pandemic when the worse prognosis is detected in diabetics. In this review, possible mechanisms leading to pulmonary involvement and pulmonary function abnormalities in diabetes, the interaction between COVID-19 and diabetes concerning lungs, and the basic effects of antidiabetic drugs on the lungs are discussed in the view of the literature.

MicroRNAs in the Lymphatic Endothelium: Master Regulators of Lineage Plasticity and Inflammation.

microRNAs (miRNAs) are highly conserved, small non-coding RNAs that regulate gene expression at the posttranscriptional level. They have crucial roles in organismal development, homeostasis, and cellular responses to pathological stress. The lymphatic system is a large vascular network that actively regulates the immune response through antigen trafficking, cytokine secretion, and inducing peripheral tolerance. Here, we review the role of miRNAs in the lymphatic endothelium with a particular focus on their role in lymphatic endothelial cell (LEC) plasticity, inflammation, and regulatory function. We highlight the lineage plasticity of LECs during inflammation and the importance of understanding the regulatory role of miRNAs in these processes. We propose that targeting miRNA expression in lymphatic endothelium can be a novel strategy in treating human pathologies associated with lymphatic dysfunction.

A multi-scale FE model for convective–diffusive drug transport within tumor and large vascular networks

Abstract Mass transport within an organ occurs through networks of blood vessels and surrounding tissue. This convective–diffusive transport is a very complex process which spans several different scales, from nano- to micro- to macro-scale. The blood vessel network is usually very intricate and irregular with respect to size and geometry, with mass transport being directly coupled to the neighboring tissue. Due to such complexity, development of a comprehensive transport model remains a challenge. The primary focus of this study is on solid tumors which are extremely complex autonomous systems with regard to mass transport. Additionally, tumors develop various biological barriers which hinder effective delivery of drug molecules into cancer tissue. We introduce a multi-scale tumor transport model where larger tumor vessels are modeled by simple 1D finite elements, whereas the capillary bed is replaced by equivalent 3D continuum finite elements. The model couples convective–diffusive transport within capillaries (fluid domain) and tissue (solid domain). These fluid and solid domains are connected by fictitious 1D elements. The proposed tumor model incorporates the imaged inhomogeneous tumor tissue and blood vessel network—from larger vessels to the smallest capillary bed. The tumor model is also applicable to transport within organs, such as the mouse brain, which is presented here as an example.

In silico modeling of magnetic resonance flow imaging in complex vascular networks.

The paper presents a computational model of magnetic resonance (MR) flow imaging. The model consists of three components. The first component is used to generate complex vascular structures, while the second one provides blood flow characteristics in the generated vascular structures by the lattice Boltzmann method. The third component makes use of the generated vascular structures and flow characteristics to simulate MR flow imaging. To meet computational demands, parallel algorithms are applied in all the components. The proposed approach is verified in three stages. In the first stage, experimental validation is performed by an in vitro phantom. Then, the simulation possibilities of the model are shown. Flow and MR flow imaging in complex vascular structures are presented and evaluated. Finally, the computational performance is tested. Results show that the model is able to reproduce flow behavior in large vascular networks in a relatively short time. Moreover, simulated MR flow images are in accordance with the theoretical considerations and experimental images. The proposed approach is the first such an integrative solution in literature. Moreover, compared to previous works on flow and MR flow imaging, this approach distinguishes itself by its computational efficiency. Such a connection of anatomy, physiology and image formation in a single computer tool could provide an in silico solution to improving our understanding of the processes involved, either considered together or separately.

Morphological characteristics of the cervix in domestic sows

Artificial insemination is commonly practiced in several domestic animals, including sows. Postcervical insemination is used to increase the fertility index, given that the volume of semen is optimized. Knowledge of the anatomical and physiological characteristics of the genital tract can be used to improve our understanding of the fertilization process that occurs during artificial insemination, and possibly to improve the technique. The aim of our study was to examine the gross morphology and histological properties of the cervix of recently slaughtered multiparous sows, using different stains. The results indicate that the porcine cervix has two regions: a uterine region characterized by the presence of glandular acini, and a vaginal region with a large vascular network. Both regions showed a mixed secretory activity by epithelial cells, which produced sulfated mucins (mucous secretion), intermingled with abundant glycogen-rich cells (serous secretion). This study contributes to the understanding of the morphologic features of the porcine cervix.

Collateral Artery Blood Flow Measurements Made in the Mouse Ischemic Hindlimb Model Using Deep Laser Speckle Imaging

Laser speckle imaging (LSI) is a technique that measures relative blood flow in large vascular networks through the motion of scattered coherent light. Conventionally, LSI uses epi‐illumination, which collects the light scattering information from the surface and limits the depth of imaging to the most superficial tissues. We hypothesized that the use of transmitted coherent light could (1) project the dominant scattering signals from structures deeper in the tissue and (2) allow for in vivo measurements of blood flow in the superficial muscles of the mouse hindlimb during femoral arterial ligation (FAL). (1) In vitro testing in a muscle tissue phantom showed an ~3.4±0.3 fold increase in the flow signal at various depths from 0.6mm to 1.6mm and extension of the minimum signal depth by ~200%. (2) In vivo, we measured changes in blood flow through the two collateral arteries (CA) of the gracilis muscle in C57Bl6 mice. Hindlimbs were trans‐illuminated with a 658nm wavelength laser, and images were acquired before FAL, and 10, 20, and 30 minutes after FAL. Before FAL, flow in the CA was a function of longitudinal position: flow was high where CA entered the muscle and ~0 at the convergence point in the center of the muscle. After FAL, CA flows increased substantially and equilibrated along the vessel length. The concept of transmitted LSI allows for deep tissue imaging, and these data represent the first quantitative measurements of flow change throughout a CA network during mouse FAL, the standard model of revascularization research. NIH HL74082 and AHA 10GRNT3490001.

Obstructive cardiac tumour perfused by large vascular network from right coronary artery

Obstructive cardiac tumour perfused by large vascular network from right coronary artery

Hierarchical microimaging for multiscale analysis of large vascular networks

There is a wide range of diseases and normal physiological processes that are associated with alterations of the vascular system in organs. Ex vivo imaging of large vascular networks became feasible with recent developments in microcomputed tomography (μCT). Current methods permit to visualize only limited numbers of physically excised regions of interests (ROIs) from larger samples. We developed a method based on modified vascular corrosion casting (VCC), scanning electron microscopy (SEM), and desktop and synchrotron radiation μCT (SRμCT) technologies to image vasculature at increasing levels of resolution, also referred to as hierarchical imaging. This novel approach allows nondestructive 3D visualization and quantification of large microvascular networks, while retaining a precise anatomical context for ROIs scanned at very high resolution. Scans of entire mouse brain VCCs were performed at 16-μm resolution with a desktop μCT system. Custom-made navigation software with a ROI selection tool enabled the identification of anatomical brain structures and precise placement of multiple ROIs. These were then scanned at 1.4-μm voxel size using SRμCT and a local tomography setup. A framework was developed for fast sample positioning, precise selection of ROIs, and sequential high-throughput scanning of a large numbers of brain VCCs. Despite the use of local tomography, exceptional image quality was achieved with SRμCT. This method enables qualitative and quantitative assessment of vasculature at unprecedented resolution and volume with relatively high throughput, opening new possibilities to study vessel architecture and vascular alterations in models of disease.

405 広範囲にわたる血管網を対象とした血管モデリング手法の開発(GS-02 : イメージベーストモデリング)

405 広範囲にわたる血管網を対象とした血管モデリング手法の開発(GS-02 : イメージベーストモデリング)

Polypoidal choroidal vasculopathy with large vascular network.

To report characteristics of polypoidal choroidal vasculopathy (PCV) of large vascular networks that expand across the retinal vascular arcade. Among 60 consecutive eyes diagnosed as having PCV by fluorescein and indocyanine green (ICG) angiography, 12 eyes (9 patients) showed large lesions. The clinical and angiographic features of these 12 eyes were studied retrospectively. Cases of large PCV typically showed dilated network vessels, which spread radially, and multiple polypoidal dilations at the end of the network vessels. Most of the polypoidal dilations formed clusters resembling bunches of grapes and caused large serous and/or hemorrhagic pigment epithelial detachments (PEDs). Among the 12 eyes, 5 showed rapid expansion of the lesions and became large PCVs within 3-24 months. In these eyes, ICG angiography revealed mesh-like choroidal vessels beneath the retinal pigment epithelium. PCV with a large vascular network that expands across the vascular arcade is not uncommon. Some of these cases seems to have characteristics of choroidal neovascularization rather than choroidal vasculopathy. It is not easy to distinguish such cases from exudative age-related macular degeneration even though they showed typical findings of PCV on ICG angiography.

Neovascularization of the intestinal graft transplanted in subcutaneous pocket in rats

Clinically, the intestinal graft can survive without blood supply through its vascular pedicle for a certain period after transplantation, which is generally considered to be due to newly formed vessels from the surrounding tissue to the graft. Vascular synthesis from the surrounding tissue to the pedicled intestinal graft, transplanted subcutaneously was studied in rat model. Both the carbon dye infusion technique and hematoxylin-eosin stain were employed. After transplantation of the intestine, the number and diameter of carbon stained vessels were scored on days 2, 5, 7, 10, 14, 28, and 56, when the pedicle was ligated. All the histological specimens of the intestinal grafts were analyzed and then classified into three phases depending on the extent of surviving mucosa: ‘necrosis’, no live mucosa were observed; ‘incomplete take’, some islands of mucosa were alive; and ‘complete take’, all mucosa were alive. We characterized the relationship between the changes of the newly formed (carbon-dyed) vessels and the three histological phases. At ‘necrosis’, the newly formed vessels were rare and did not reach the intestinal graft. At ‘incomplete take’, random thin vascular networks were observed and some of them reached the graft. Some specimens were in the ‘incomplete take’ phase. At ‘complete take’, regular large vascular networks were observed. This transformation of the vascular networks seemed to reduce the the resistance of the vascular flow and to finally lead to the ‘complete take’ of the graft.