Vascular Bifurcations Research Articles

Predictors of distal embolization during thrombectomy for anterior circulation large vessel bifurcation occlusion stroke.

Distal embolization is a frequent complication of mechanical thrombectomy (MT) for acute ischemic stroke, often leading to poor clinical outcomes. The vascular bifurcations represent a specialized anatomical location, thereby augmenting the complexity of MT. The specific factors contributing to distal embolization in this context have not been thoroughly explored. This study seeks to identify the factors associated with distal embolization during MT in patients with anterior circulation large vessel bifurcation occlusion stroke. A retrospective analysis was conducted on patients who underwent MT for acute anterior circulation bifurcation occlusion stroke between January 2015 and December 2023. Baseline characteristics, procedural details, and clinical outcomes were assessed. Univariate and multivariable analyses were performed to identify predictors of distal embolization during MT. The study included 119 patients. Univariate analysis revealed significant associations between distal embolization and occlusion location, internal carotid artery (ICA) tortuosity, first-line thrombectomy strategy, and the number of device passes. Multivariate analysis identified ICA bifurcation occlusions (odds ratio (OR) 3.21, 95% confidence interval (CI) 1.188 to 8.672, P=0.021), stent retriever thrombectomy (SRT) (OR 6.177, 95% CI 1.77 to 21.555, P=0.004), and a higher number of device passes (OR 1.778, 95% CI 1.132 to 2.792, P=0.013) as independent predictors of distal embolization. ICA bifurcation occlusion, the use of SRT, and an increased number of device passes are significant predictors of distal embolization during MT in patients with anterior circulation large vessel bifurcation occlusion strokes.

Assessment of Interrater Reliability and Accuracy of Cerebral Aneurysm Morphometry Using 3D Virtual Reality, 2D Digital Subtraction Angiography, and 3D Reconstruction: A Randomized Comparative Study.

Detailed morphometric analysis of an aneurysm and the related vascular bifurcation are critical factors when determining rupture risk and planning treatment for unruptured intracranial aneurysms (UIAs). The standard visualization of digital subtraction angiography (DSA) and its 3D reconstruction on a 2D monitor provide precise measurements but are subject to variability based on the rater. Visualization using virtual (VR) and augmented reality platforms can overcome those limitations. It is, however, unclear whether accurate measurements of the aneurysm and adjacent arterial branches can be obtained on VR models. This study aimed to assess interrater reliability and compare measurements between 3D VR, standard 2D DSA, and 3D DSA reconstructions, evaluating the reliability and accuracy of 3D VR as a measurement tool. A pool of five neurosurgeons performed three individual analyses on each of the ten UIA cases, measuring them in completely immersed 3D VR and the standard on-screen format (2D DSA and 3D reconstruction). This resulted in three independent measurements per modality for each case. Interrater reliability of measurements and morphology characterization, comparative differences, measurement duration, and VR user experience were assessed. Interrater reliability for 3D VR measurements was significantly higher than for 3D DSA measurements (3D VR mean intraclass correlation coefficient [ICC]: 0.69 ± 0.22 vs. 3D DSA mean ICC: 0.36 ± 0.37, p = 0.042). No significant difference was observed between 3D VR and 2D DSA (3D VR mean ICC: 0.69 ± 0.22 vs. 2D DSA mean ICC: 0.43 ± 0.31, p = 0.12). A linear mixed-effects model showed no effect of 3D VR and 3D DSA (95% CI = -0.26-0.28, p = 0.96) or 3D VR and 2D DSA (95% CI = -0.02-0.53, p = 0.066) on absolute measurements of the aneurysm in the anteroposterior, mediolateral, and craniocaudal dimensions. 3D VR technology allows for reproducible, accurate, and reliable measurements comparable to measurements performed on a 2D screen. It may also potentially improve precision for measurements of non-planar aneurysm dimensions.

Topographic analysis of retinal and choroidal vascular displacements after macular hole surgery

It has been reported that the retinal vessel and macular region of the retina are displaced after macular hole (MH) surgery. However, there is no detailed information for correlations between retinal and choroidal displacements. We obtained optical coherence tomography angiography (OCTA) and en-face optical coherence tomography (OCT) images from 24 eyes to measure the retinal and choroidal vascular displacement before and after surgery. These images were merged into infrared images using blood vessel patterns. The same vascular bifurcation points were automatically selected for each follow-up image, and the displacements of the bifurcation points were analyzed as a vector unit for prespecified grid regions in a semi-automated fashion. The results showed displacements of the choroidal intermediate vessels and retinal vessels following MH surgery (p = 0.002, p < 0.001). The topographic changes showed inferior, nasal, and centripetal displacement of the retina and inferiorly displaced choroid. The ILM peeling size and basal MH size were significantly associated with the retinal displacement (p < 0.001 and p = 0.010). Additionally, changes in the amount of the choroidal displacement were significantly correlated with that of the retinal displacements (p = 0.002). Clinicians should keep in mind that there might be topographic discrepancies of the displacement between retina and choroid when analyzing them following surgery.

Enhanced Vascular Bifurcations Mapping: Refining Fundus Image Registration

Enhanced Vascular Bifurcations Mapping: Refining Fundus Image Registration

A case of MCA arising from ICA: a case report.

Complete mesocolic excision (CME) and central vascular detachment are very important procedures in surgery for colorectal cancer. Preoperative and intraoperative assessments of the anatomy of major colorectal vessels are necessary to avoid massive bleeding, especially in endoscopic surgery. A case with a rare anomaly in which the middle colic artery (MCA) and ileocolic artery (ICA) had a common trunk is reported. The patient was a 73-year-old woman diagnosed with ascending colon cancer on colonoscopy. Preoperative abdominal contrast-enhanced computed tomography confirmed that the MCA and ICA had a common trunk. She underwent laparoscopic ileocecal resection for the ascending colon cancer with D3 lymph node dissection. Intraoperative indocyanine green fluorescence imaging was conducted. After confirming vessel bifurcation, the ICA was dissected at the distal end of the MCA bifurcation. The patient has been followed as an outpatient, with no signs of recurrence as of 2 years postoperatively. A case of an ascending colon cancer with a unique vascular bifurcation pattern was presented. Preoperative and intraoperative evaluations of the major colorectal vessels are very important for preventing perioperative and postoperative complications.

Superior Vena Cava Thrombosis in A Young Hemodialysis Patient After 1 year of Central Venous Catheter Removal: A Case Report

Introduction:&#x0D; Superior vena cava (SVC) syndrome is a rare but serious condition resulting from obstruction of the superior vena cava or its tributaries. Although often associated with malignancy, it can also occur due to central venous catheterization(1). Acute SVC syndrome following catheter removal is uncommon. &#x0D; Case Report: &#x0D; We present a 35-year-old hemodialysis patient with a history of central venous catheterization for hemodialysis one year prior. During a routine hemodialysis session, the patient developed symptoms of shortness of breath, neck swelling, and cyanosis of the lips. Physical examination revealed neck edema and prominent superficial vascular bifurcations. Without imaging studies, it was confused with cellulitis, but CT angiography later confirmed SVC thrombosis. The patient was started on anticoagulation and transferred to a tertiary hospital for further management. &#x0D; Conclusion: &#x0D; Emergency physicians should be aware of SVC syndrome, especially in hemodialysis patients with a history of central venous catheterization. Although it is often associated with malignancy, this case highlights the importance of considering SVC thrombosis even after catheter removal. Prompt diagnosis and appropriate management are essential to prevent life-threatening complications. Therefore, recognition and inclusion of SVC syndrome in the differential diagnosis is essential for timely intervention and improved patient outcomes.

Towards effects from stent implantation into coronary bifurcation stenosis: experiment and simulation

Coronary artery disease is a widespread cause of death and disability in the population. Angioplasty of the coronary arteries is one of the most common methods of eliminating the cause of ischemia – stenosis of the coronary arteries. As a result of stent installation, a change in the angle of vascular bifurcation occurs usually, as well as a redistribution of volumetric blood flow in the coronary artery system. Considering the high variability of the branching angioarchitecture of these arteries, as well as the structure of their environment, the problem of predicting the specific redistribution of blood flow in these arteries remains unsolved; the main ways of its implementation are computational and experimental hemodynamics. Material and methods. This paper uses an experimental approach to explore the effect of stent placement in a model of coronary artery stenosis, and also provides an analysis of the current level of awareness of the scientific community on this issue. Results and discussion. The experiment showed that the throughput of the model increases by 14 % compared to the model with stenosis, and the redistribution of flows in the model depends not on diameters but on the anatomy of a particular vascular network. The data of the performed mathematical modeling are generally consistent with the results of the experiment before stent installation, when the coronary tree consists of several load-bearing branches, but have quantitative differences for the distal branches of the coronary artery model in the presence of an installed stent. Conclusions. The results of the work can be used to accumulate an experimental data array on the restructuring of blood flow during angioplasty, and can also be used to verify the numerical hemodynamics of the coronary arteries during the virtual installation of a stent in them to resolve stenosis.

Human-scale navigation of magnetic microrobots in hepatic arteries.

Using external actuation sources to navigate untethered drug-eluting microrobots in the bloodstream offers great promise in improving the selectivity of drug delivery, especially in oncology, but the current field forces are difficult to maintain with enough strength inside the human body (>70-centimeter-diameter range) to achieve this operation. Here, we present an algorithm to predict the optimal patient position with respect to gravity during endovascular microrobot navigation. Magnetic resonance navigation, using magnetic field gradients in clinical magnetic resonance imaging (MRI), is combined with the algorithm to improve the targeting efficiency of magnetic microrobots (MMRs). Using a dedicated microparticle injector, a high-precision MRI-compatible balloon inflation system, and a clinical MRI, MMRs were successfully steered into targeted lobes via the hepatic arteries of living pigs. The distribution ratio of the microrobots (roughly 2000 MMRs per pig) in the right liver lobe increased from 47.7 to 86.4% and increased in the left lobe from 52.2 to 84.1%. After passing through multiple vascular bifurcations, the number of MMRs reaching four different target liver lobes had a 1.7- to 2.6-fold increase in the navigation groups compared with the control group. Performing simulations on 19 patients with hepatocellular carcinoma (HCC) demonstrated that the proposed technique can meet the need for hepatic embolization in patients with HCC. Our technology offers selectable direction for actuator-based navigation of microrobots at the human scale.

Effect of vessel compression on blood flow in microvascular networks and its implications for tumour tissue hypoxia

The tumour microenvironment is abnormal and one of its consequences is that blood vessels are compressed. Vessel compression correlates with reduced survival rates, while decompression of vessels improves tissue oxygenation as well as increases survival rates. Vessel compression contributes, at a single vascular bifurcation, to the increase of heterogeneity of red blood cell (RBC) transport. However, the effect that vessel compression has at a network level is unknown. This work numerically investigates the effect of vessel compression on RBC transport in microvascular networks. The key findings are that vessel compression both reduces the average haematocrit, and increases haematocrit heterogeneity, in vessels in the network. The mechanisms for these changes in haematocrit distribution are unravelled, and a parameter sweep shows that networks with lower inlet haematocrits are more susceptible to haemodilution from vessel compression over a wide range of compressed fraction of a network. These findings provide a theoretical underpinning for the link between vessel compression and tumour tissue hypoxia.

A 4D printed nanoengineered super bioactive hydrogel scaffold with programmable deformation for potential bifurcated vascular channel construction.

Four-dimensional (4D) printing of hydrogels enabled the fabrication of complex scaffold geometries out of static parts. Although current 4D fabrication strategies are promising for creating vascular parts such as tubes, developing branched networks or tubular junctions is still challenging. Here, for the first time, a 4D printing approach is employed to fabricate T-shaped perfusable bifurcation using an extrusion-based multi-material 3D printing process. An alginate/methylcellulose-based dual-component hydrogel system (with defined swelling behavior) is nanoengineered with carbonized alginate (∼100 nm) to introduce anti-oxidative, anti-inflammatory, and anti-thrombotic properties and shape-shifting properties. A computational model to predict shape deformations in the printed hydrogels with defined infill angles was designed and further validated experimentally. Shape deformations of the 3D-printed flat sheets were achieved by ionic cross-linking. An undisrupted perfusion of a dye solution through a T-junction with minimal leakage mimicking blood flow through vessels is also demonstrated. Moreover, human umbilical vein endothelial and fibroblast cells seeded with printed constructs show intact morphology and excellent cell viability. Overall, the developed strategy paves the way for manufacturing self-actuated vascular bifurcations with remarkable anti-thrombotic properties to potentially treat coronary artery diseases.

A cross-sectional study of macular displacement after macular hole surgery with ILM peeling in patients with idiopathic macular hole.

To examine the retinal displacement and change in mean superficial foveal avascular zone (FAZ) after successful closure of macular hole (MH) with vitrectomy with internal limiting membrane peeling (ILM) and gas tamponade. A total of 45 patients with idiopathic MH who underwent 23G pars plana vitrectomy with ILM peeling and tamponade with 20% SF6/14% C3F8 were included. Follow-up visits were performed at 2, 4, and 8 weeks. OCT and OCT-A scans were performed along with detailed ocular examination. Distance between optic disc and an easily identifiable vascular bifurcation nasal and temporal to fovea, FAZ, was noted. Chi-square test (categorical data) and Mann-Whitney U test and t tests for other parameters were performed for statistical analysis. The mean displacement (µm) of an easily identifiable vascular bifurcation in the nasal quadrant was 96.58 ± 36.55 at 8 weeks and in the temporal quadrant was 273.07 ± 85.51 at 8 weeks. The change was statistically significant in the temporal quadrant (P = <0.001). The mean BCVA changed from a minimum of 0.08 at the preoperative timepoint to a maximum of 0.23 at 8 weeks (P = <0.001). The mean FAZ area (mm²) decreased from a maximum of 0.37 at the preoperative timepoint to a minimum of 0.19 at 8 weeks (p = <0.001). The retina in the temporal quadrant is displaced significantly more than nasal quadrant after successful closure of macular hole. The mean superficial FAZ also decreases suggesting a centripetal movement of the foveal tissue postoperatively.

MPI/FLI/CTA multi-modality imaging of atherosclerotic plaque with plexind1-targeted nanoparticles

Abstract M1 macrophage is one of important components which contribute to the progression of atherosclerotic plaques.[1]Previous research of our team showed that plexind1 was expressed more in atherosclerotic plaques at vascular bifurcation than those at straight site and co-localized with M1 macrophages. This study aims to develop a novel multimodal imaging platform by designing a nanoprobe targeting plexind1 to detect and monitor bifurcation lesion and provide detecting method for animal research. Methods A novel multimodal imaging agent,A12-Fe3O4-Cy7, was constructed by coupling superparamagnetic iron oxide nanoparticle (SPIONs) with cyanine 7 N-hydroxysuccin imide ester（Cy7）and nanobody A12 which could target plexind1 specifically. The physical and biological properties were evaluated. To assess the A12-Fe3O4-Cy7 recognition and monitoring for plaque,high-fat-fed 10-week and 20-week Apoe-/- atherosclerosis mouse models were imaged using MPI and FLI,and both 3D images were fused with CTA. HE,Prussian blue and plexind1 immunohistochemical staining were performed on mouse carotid tissue sections. Results The A12-Fe3O4-Cy7 was of favorable stability, biocompatibility（concentration&amp;lt; 200ug/ml) and targeting effect.It could detect, locate, and monitor atherosclerotic plaques at bifurcation of carotid artery in ApoE-/- mice accurately and sensitively, showing significantly higher MPI and FLI signals both in vivo and ex vivo compared with both themselves before nanoprobe injection and two control groups(n=3,p&amp;lt;0.05). FLI is more sensitive than MPI to detect high-fat-fed 10-week mouse plaques.The results were confirmed histologically. Conclusion A12-Fe3O4-Cy7 might serve as a method to detect plaques at the bifurcation by targeting plexind1 in vivo. Limitations MPI is tested only in mouse models presently and it requires combination with CT to provide anatomical information. Besides，there was no intervention on plexind1,so the mechanism of plexind1 in bifurcation plaque occurrence and progression is not illustrated clearly,which is worth exploring in the future.In vitro and vivo assessmentIn vivo and ex vivo imaging

Using deep learning for an automatic detection and classification of the vascular bifurcations along the Circle of Willis.

Most of the intracranial aneurysms (ICA) occur on a specific portion of the cerebral vascular tree named the Circle of Willis (CoW). More particularly, they mainly arise onto fifteen of the major arterial bifurcations constituting this circular structure. Hence, for an efficient and timely diagnosis it is critical to develop some methods being able to accurately recognize each Bifurcation of Interest (BoI). Indeed, an automatic extraction of the bifurcations presenting the higher risk of developing an ICA would offer the neuroradiologists a quick glance at the most alarming areas. Due to the recent efforts on Artificial Intelligence, Deep Learning turned out to be the best performing technology for many pattern recognition tasks. Moreover, various methods have been particularly designed for medical image analysis purposes. This study intends to assist the neuroradiologists to promptly locate any bifurcation presenting a high risk of ICA occurrence. It can be seen as a Computer Aided Diagnosis scheme, where the Artificial Intelligence facilitates the access to the regions of interest within the MRI. In this work, we propose a method for a fully automatic detection and recognition of the bifurcations of interest forming the Circle of Willis. Several neural networks architectures have been tested, and we thoroughly evaluate the bifurcation recognition rate.

Different stimuli induce endothelial dysfunction and promote atherosclerosis through the Piezo1/YAP signaling axis

Vascular endothelial dysfunction is the initial step in atherosclerosis (AS). AS tends to occur at vascular bifurcations and curves, and endothelial cells(ECs) are highly susceptible to injury due to mechanical forces induced by disturbed flow (DF) with inconsistent blood flow directions. However, the pathogenesis of endothelial cell dysfunction in AS remains unclear and needs further study. Here, we found that Piezo1 expression was significantly increased in DF- and oxidized low-density lipoprotein(ox-LDL)-treated HUVECs in vitro and a model of atherosclerotic plaque growth in ApoE−/− mice fed a Western diet. Furthermore, Piezo1 upregulated autophagy levels in the HUVECs model, which was reversed by Piezo1 knockdown with a lentivirus-mediated shRNA system. Mechanistically, the level of Yes-associated protein (YAP), a transcriptional coactivator in the Hippo pathway, was significantly elevated in the DF- and ox-LDL-induced HUVECs model, and this effect was further inhibited by Piezo1 knockdown. Moreover, the Piezo1 agonist Yoda1 inhibited the protein level of microtubule-associated protein 1 light chain 3-II(LC3-II) and increased the protein level of sequestosome1(p62/SQSTM1) in a dose-dependent manner, while significantly promoting the protein expression and nuclear translocation of YAP. The YAP inhibitor CA3 weakened Yoda1-mediated inhibition of autophagy. Our results suggest that Piezo1 may regulate endothelial autophagy by promoting YAP activation and nuclear translocation, thereby contributing to vascular endothelial dysfunction.

Validation of boundary conditions for coronary circulation model based on a lumped parameter approach

Abstract In the present work, we construct a model of coronary flow, which utilizes both CT scans of large coronary arteries and coronary CT perfusion. The model describes pulsatile flow in the patient’s network of coronary vessels and takes into account a number of physiological effects: myocardium contractions, stenoses, impairment of microvascular perfusion. The main novelty of this model is the new smooth boundary conditions that have not been used before in patient-specific simulations of coronary circulation. New boundary conditions use 0D lumped model approach and provide asymptotic convergence of the solution for the cases of one-to-one vascular connection and bifurcation with a very thin child vessel. The new boundary conditions make it possible to estimate the fractional flow margin more accurately. We also studied sensitivity of haemodynamic indices (fractional flow reserve, coronary flow reserve, instantaneous wave-free ratio) to the variations of microcirculation impairment. No substantial difference in sensitivity was observed between new model and original approach. The advantage of the presented approach is the availability of the required data in everyday clinical practice and, thus, improved personalization of the model.

Impact of CT scan parameters on deformable image registration accuracy using deformable thorax phantom.

The purpose of this study was to evaluate the deformable image registration (DIR) accuracy using various CT scan parameters with deformable thorax phantom. Our developed deformable thorax phantom (Dephan, Chiyoda Technol Corp, Tokyo, Japan) was used. The phantom consists of a base phantom, an inner phantom, and a motor-derived piston. The base phantom is an acrylic cylinder phantom with a diameter of 180mm, which simulates the chest wall. The inner phantom consists of deformable, 20mm thick disk-shaped sponges with 48 Lucite beads and 48 nylon cross-wires which simulate the vascular and bronchial bifurcations of the lung. Peak-exhale and peak-inhale images of the deformable phantom were acquired using a CT scanner (Aquilion LB, TOSHIBA). To evaluate the impact of CT scan parameters on DIR accuracy, we used the four tube voltages (80, 100, 120, and 135kV) and six reconstruction algorithms (FC11, FC13, FC15, FC41, FC44, and FC52). Intensity-based DIR was performed between the two images using MIM Maestro (MIM software, Cleveland, USA). Fiducial markers (beads and cross-wires) based target registration error (TRE) was used for quantitative evaluation of DIR. In case with different tube voltages, the range of average TRE were 4.44-5.69mm (reconstruction algorithm: FC13). In case with different reconstruction algorithms, the range of average TRE were 4.26-4.59mm (tube voltage: 120kV). The TRE were differed by up to 3.0mm (3.96-6.96mm) depending on the combination of tube voltage and reconstruction algorithm. Our result indicated that CT scan parameters had moderate impact of TRE, especially for reconstruction algorithms for the deformable thorax phantom.

Quantification of shunt fraction using contrast ultrasound and indicator dilution in an in vitro model

Transthoracic saline contrast echocardiography is commonly used to assess intrathoracic shunt flow in vivo. Though the technique has many advantages (safe, simple, repeatable), the measurement technique lacks specificity, and the contrast agent has limited stability. This study sought to determine if the indicator dilution modeling technique could be applied to ultrasound contrast data to quantify shunt fraction and to determine if buoyant force has a significant effect on microbubble pathway determination at a “vascular” bifurcation. A model of the pulmonary circuit was perfused with blood at three distinct flow rates (low, medium and high) over shunt fractions ranging from ∼2–10 %. The buoyancy effect on contrast was quantified using a simplified in vitro model of a vascular bifurcation that had an upper and lower outflow tract where saline contrast formed from carbon monoxide (CO) gas passed through the bifurcation, was collected and quantified. The indicator dilution model was found to have a mean bias of − 3.2 % for the low flow stage, − 2.6 % for the medium flow stage and − 1.4 % for the high flow stage compared to volumetric measurements, suggesting agreement increases with increasing flow rate. Investigations of the buoyant effects revealed that at lower flow rates, contrast bubbles that encounter a bifurcation will favor the upper outflow tract over the lower. However, this effect is reduced by increasing the flow rate two-fold. These data identify that application of indicator dilution theory to contrast ultrasound data and the pathway ultrasound contrast travels in a network of tubules is flow dependent.

Deep segmentation of OCTA for evaluation and association of changes of retinal microvasculature with Alzheimer’s disease and mild cognitive impairment

BackgroundOptical coherence tomography angiography (OCTA) enables fast and non-invasive high-resolution imaging of retinal microvasculature and is suggested as a potential tool in the early detection of retinal microvascular changes in...

Changes in retinal vascular bifurcation in eyes with myopia

ObjectiveTo evaluate the effect of myopia on retinal vascular bifurcation.MethodsA cross-sectional study that retrospectively analyzed the fundus photographs and clinical data of 493 people who participated in routine physical examinations in Huadong Sanatorium. One eye of each subject was included in the analysis. Retinal vascular bifurcation measurements were extracted by using a validated computer program. One-way ANOVA and analysis of covariance were performed to compare the measurements across high myopia, low to moderate myopia, and non-myopia groups.ResultsThe mean age was 41.83 ± 10.43 years and 63.49% were women. The mean spherical equivalent refraction (SER) was − 4.59 ± 3.07 D. Ninety-nine (20.08%) eyes met the definition of high myopia (SER ≤ -6.0 D), along with 234 (47.46%) low to moderate myopia (-6.0 D < SER <-0.5 D), and 160 (32.45%) non-myopia (SER ≥ -0.5 D). The differences in the arteriolar branching angle, venular branching coefficient, venular asymmetry ratio, venular angular asymmetry, and venular junctional exponent among the three groups remained significant (p < 0.05) after multivariate adjustment. Pairwise comparisons showed arteriolar branching angle and venular angular asymmetry in high myopia were significantly lower than low to moderate myopia (p < 0.001, p = 0.014 respectively) and non-myopia (p = 0.007, p = 0.048 respectively). Venular asymmetry ratio and venular branching coefficient in high myopia were significantly higher than low to moderate myopia (p = 0.029, p = 0.001 respectively) and non-myopia (p = 0.041, p = 0.043 respectively). There was a significant difference in venular junctional exponent between high myopia and low to moderate myopia (p = 0.031).ConclusionThe vascular bifurcation differs in dependence on the myopic refractive error and a significant increase in the difference can be observed in high myopic eyes.

4D Biofabrication of T‐Shaped Vascular Bifurcation

Abstract4D Biofabrication – a pioneering biofabrication technique – involves the automated fabrication of 3D constructs that are dynamic and show shape‐transformation capability. Although current 4D biofabrication methods are highly promising for the fabrication of vascular elements such as tubes, the fabrication of tubular junctions is still highly challenging. Here, for the first time, a 4D biofabrication‐based concept for the fabrication of a T‐shaped vascular bifurcation using 3D printed shape‐changing layers based on a mathematical model is reported. The formation of tubular structures with various diameters is achieved by precisely controlling the parameters (e.g. crosslinking time). Consequently, the 3D printed films show self‐transformation into a T‐junction upon immersion in water with a diameter of a few millimeters. Perfusion of the tubular T‐junction with an aqueous medium simulating blood flow through vessels shows minimal leakages with a maximum flow velocity of 0.11 m s–1. Furthermore, human umbilical vein endothelial cells seeded on the inner surface of the plain T‐junction show outstanding growth properties and excellent cell viability. The achieved diameters are comparable to the native blood vessels, which is still a challenge in 3D biofabrication. This approach paves the way for the fabrication of fully automatic self‐actuated vascular bifurcations as vascular grafts.