3D Vascular Models Research Articles

Accuracy of registration techniques and vascular imaging modalities in fusion imaging for aortic endovascular interventions: a phantom study

BackgroundThis study aimed to assess the error of different registration techniques and imaging modalities for fusion imaging of the aorta in a standardized setting using a anthropomorphic body phantom.Materials and methodsA phantom with the 3D printed vasculature of a patient suffering from an infrarenal aortic aneurysm was constructed. Pulsatile flow was generated via an external pump. CTA/MRA of the phantom was performed, and a virtual 3D vascular model was computed. Subsequently, fusion imaging was performed employing 3D-3D and 2D-3D registration techniques. Accuracy of the registration was evaluated from 7 right/left anterior oblique c-arm angulations using the agreement of centerlines and landmarks between the phantom vessels and the virtual 3D virtual vascular model. Differences between imaging modalities were assessed in a head-to-head comparison based on centerline deviation. Statistics included the comparison of means ± standard deviations, student’s t-test, Bland-Altman analysis, and intraclass correlation coefficient for intra- and inter-reader analysis.Results3D-3D registration was superior to 2D-3D registration, with the highest mean centerline deviation being 1.67 ± 0.24 mm compared to 4.47 ± 0.92 mm. The highest absolute deviation was 3.25 mm for 3D-3D and 6.25 mm for 2D-3D registration. Differences for all angulations between registration techniques reached statistical significance. A decrease in registration accuracy was observed for c-arm angulations beyond 30° right anterior oblique/left anterior oblique. All landmarks (100%) were correctly positioned using 3D-3D registration compared to 81% using 2D-3D registration. Differences in accuracy between CT and MRI were acceptably small. Intra- and inter-reader reliability was excellent.ConclusionIn the realm of registration techniques, the 3D-3D method proved more accurate than did the 2D-3D method. Based on our data, the use of 2D-3D registration for interventions with high registration quality requirements (e.g., fenestrated aortic repair procedures) cannot be fully recommended. Regarding imaging modalities, CTA and MRA can be used equivalently.

Patient-Specific 3-Dimensional Model of Smooth Muscle Cell and Extracellular Matrix Dysfunction for the Study of Aortic Aneurysms

Introduction: Abdominal aortic aneurysms (AAAs) are associated with overall high mortality in case of rupture. Since the pathophysiology is unclear, no adequate pharmacological therapy exists. Smooth muscle cells (SMCs) dysfunction and extracellular matrix (ECM) degradation have been proposed as underlying causes. We investigated SMC spatial organization and SMC-ECM interactions in our novel 3-dimensional (3D) vascular model. We validated our model for future use by comparing it to existing 2-dimensional (2D) cell culture. Our model can be used for translational studies of SMC and their role in AAA pathophysiology. Materials and Methods: SMC isolated from the medial layer of were the aortic wall of controls and AAA patients seeded on electrospun poly-lactide-co-glycolide scaffolds and cultured for 5 weeks, after which endothelial cells (EC) are added. Cell morphology, orientation, mechanical properties and ECM production were quantified for validation and comparison between controls and patients. Results: We show that cultured SMC proliferate into multiple layers after 5 weeks in culture and produce ECM proteins, mimicking their behavior in the medial aortic layer. EC attach to multilayered SMC, mimicking layer interactions. The novel SMC model exhibits viscoelastic properties comparable to biological vessels; cytoskeletal organization increases during the 5 weeks in culture; increased cytoskeletal alignment and decreased ECM production indicate different organization of AAA patients’ cells compared with control. Conclusion: We present a valuable preclinical model of AAA constructed with patient specific cells with applications in both translational research and therapeutic developments. We observed SMC spatial reorganization in a time course of 5 weeks in our robust, patient-specific model of SMC–EC organization and ECM production.

A framework for incorporating 3D hyperelastic vascular wall models in 1D blood flow simulations

We present a novel framework for investigating the role of vascular structure on arterial haemodynamics in large vessels, with a special focus on the human common carotid artery (CCA). The analysis is carried out by adopting a three-dimensional (3D) derived, fibre-reinforced, hyperelastic structural model, which is coupled with an axisymmetric, reduced order model describing blood flow. The vessel transmural pressure and lumen area are related via a Holzapfel–Ogden type of law, and the residual stresses along the thickness and length of the vessel are also accounted for. After a structural characterization of the adopted hyperelastic model, we investigate the link underlying the vascular wall response and blood-flow dynamics by comparing the proposed framework results against a popular tube law. The comparison shows that the behaviour of the model can be captured by the simpler linear surrogate only if a representative value of compliance is applied. Sobol’s multi-variable sensitivity analysis is then carried out in order to identify the extent to which the structural parameters have an impact on the CCA haemodynamics. In this case, the local pulse wave velocity (PWV) is used as index for representing the arterial transmission capacity of blood pressure waveforms. The sensitivity analysis suggests that some geometrical factors, such as the stress-free inner radius and opening angle, play a major role on the system’s haemodynamics. Subsequently, we quantified the differences in haemodynamic variables obtained from different virtual CCAs, tube laws and flow conditions. Although each artery presents a distinct vascular response, the differences obtained across different flow regimes are not significant. As expected, the linear tube law is unable to accurately capture all the haemodynamic features characterizing the current model. The findings from the sensitivity analysis are further confirmed by investigating the axial stretching effect on the CCA fluid dynamics. This factor does not seem to alter the pressure and flow waveforms. On the contrary, it is shown that, for an axially stretched vessel, the vascular wall exhibits an attenuation in absolute distension and an increase in circumferential stress, corroborating the findings of previous studies. This analysis shows that the new model offers a good balance between computational complexity and physics captured, making it an ideal framework for studies aiming to investigate the profound link between vascular mechanobiology and blood flow.

Perceptions of porta-celiac vascular models for hepatic surgery and their use in residency training.

Primary aspect of hepatic navigation surgery is the identification of source vascular details to preserve healthy liver which has a vascular anatomy quite challenging for the young surgeons. The purpose was to determine whether three-dimensional (3D) vascular pattern models of preoperative computed tomography (CT) images will assist resident-level trainees for hepatic surgery. This study was based on the perception of residents who were presented with 5 different hepatic source vascular patterns and required to compare their perception level of CT, and 1:1 models in terms of importance of variability, differential of patterns and preoperative planning. All residents agree that models provided better understanding of vascular source and improved preplanning. Five stations provided qualitative assessment with results showing the usefulness of porta-celiac models when used as anatomical tools in preplanning (p = 0.04), simulation of interventional procedures (p = 0.02), surgical education (p = 0.01). None of the cases had scored less than 8.5. Responses related to understanding variations were significantly higher in the perception of the 3D model in all cases, furthermore 3D models were more useful for seniors in more complex cases 3 and 5. Some open-ended answers: "The 3D model can completely change the operation plan" One of the major factors for anatomical resection of liver transplantation is the positional relationship between the hepatic arteries and the portal veins. The plastic-like material presenting the hepatic vascularity enables the visualization of the origin, pattern, shape, and angle of the branches with appropriate spatial perception thus making it well-structured.

Three-dimensional (3D) vascular cell culture model for disease modeling and screening therapies

Three-dimensional (3D) vascular cell culture model for disease modeling and screening therapies

Accuracy evaluation of patient-specific 3D-printed aortic anatomy

Introduction3D printing has a wide range of applications in medicine. In surgery, this technique can be used for preoperative planning of complex procedures, production of patient specific implants, as well as training. However, accuracy evaluations of 3D vascular models are rare. ObjectivesAim of this study was to investigate the accuracy of patient-specific 3D-printed aortic anatomies. MethodsPatients suffering from aorto-iliac aneurysms and with indication for treatment were selected on the basis of different anatomy and localization of the aneurysm in the period from January 1st 2014 to May 27th 2016. Six patients with aorto-iliac aneurysms were selected out of the database for 3D-printing. Subsequently, computed tomography (CT) images of the printed 3D-models were compared with the original CT data sets. ResultsThe mean deviation of the six 3D-vascular models ranged between −0.73 mm and 0.14 mm compared to the original CT-data. The relative deviation of the measured values showed no significant difference between the 3D-vascular and the original patient CT-data. ConclusionOur results showed that 3D printing has the potential to produce patient-specific 3D vascular models with reliable accuracy. This enables the use of such models for the development of new endovascular procedures and devices.

Taguchi Method for Investigation of Ultrasonication-Assisted Dissolution of Acrylonitrile Butadiene Styrene (ABS) Rod Enclosed Within Polydimethylsiloxane (PDMS) Bulk

A fully transparent and three-dimensional vascular model can be created by using consumer 3D printer to fabricate polymeric molds, casting with Polydimethylsiloxane (PDMS) from printed molds, and dissolution of molds with solvents. Unfortunately, the narrowness of channels makes removal of molds enclosed within the PDMS bulk very challenging. Ultrasonication has been used to accelerate the dissolution of polymeric molds through the effects of cavitation phenomenon, Taguchi method was used to study the most and least influential factor to the overall dissolution process. Experiment results show that: (1) ultrasonication can penetrate the PDMS bulk and improve the dissolution process of ABS rod enclosed in a PDMS bulk; (2) the volume of the PDMS device (E) has the largest influence while the ultrasonication time (B) has the least influence; (3) with those optimized parameters, a 3D and transparent vascular model with two curly channels was successfully demonstrated.

Four-Dimensional Flow Magnetic Resonance Imaging for Assessment of Velocity Magnitudes and Flow Patterns in The Human Carotid Artery Bifurcation: Comparison with Computational Fluid Dynamics.

Purpose: Knowledge of the hemodynamics in the vascular system is important to understand and treat vascular pathology. The present study aimed to evaluate the hemodynamics in the human carotid artery bifurcation measured by four-dimensional (4D) flow magnetic resonance imaging (MRI) as compared to computational fluid dynamics (CFD). Methods: This protocol used MRI data of 12 healthy volunteers for the 3D vascular models and 4D flow MRI measurements for the boundary conditions in CFD simulation. We compared the velocities measured at the carotid bifurcation and the 3D velocity streamlines of the carotid arteries obtained by these two methods. Results: There was a good agreement for both maximum and minimum velocity values between the 2 methods for velocity magnitude at the bifurcation plane. However, on the 3D blood flow visualization, secondary flows, and recirculation regions are of poorer quality when visualized through the 4D flow MRI. Conclusion: 4D flow MRI and CFD show reasonable agreement in demonstrated velocity magnitudes at the carotid artery bifurcation. However, the visualization of blood flow at the recirculation regions and the assessment of secondary flow characteristics should be enhanced for the use of 4D flow MRI in clinical situations.

Automatic Diagnosis Based on Spatial Information Fusion Feature for Intracranial Aneurysm.

Timely and accurate auxiliary diagnosis of intracranial aneurysm can help radiologist make treatment plans quickly, saving lives and cutting costs at the same time. At present, Digital Subtraction Angiography (DSA) is the gold standard for the diagnosis of intracranial aneurysm, but as radiologists interpret those imaging sequences frame by frame, misdiagnosis might occur. The utilization of computer-aided diagnosis (CAD) can ease the burdens of radiologists and improve the detection accuracy of aneurysms. In this article, a deep learning method is applied to detect the intracranial aneurysm in 3D Rotational Angiography (3D-RA) based on a spatial information fusion (SIF) method, and instead of a 3D vascular model, 2D image sequences are used. Given the intracranial aneurysm and vascular overlap having similar feature in the most time, rather than focusing on distinguishing them in one frame, the morphological differences between frames are considered as major feature. In the training data, consecutive frames of every imaging time series are extracted and concatenated in a specific way, so that the spatial contextual information could be embedded into a single two-dimensional image. This method enables the time series with obvious correlation between frames be directly trained on 2D convolutional neural network (CNN), instead of 3D-CNN with huge computational cost. Finally, we got an accuracy of 98.89%, with sensitivity and specificity of 99.38% and 98.19%, respectively, which proves the feasibility and availability of the SIF feature.

Hybrid Three-Dimensional Visualization of Choroidal Vasculature Imaged by Swept-Source Optical Coherence Tomography.

PurposeTo create hybrid three-dimensional (3D) models of the choroidal vasculature from swept-source optical coherence tomography (SS-OCT) angiography images and to evaluate the model's characteristics.MethodsThis study used prospective, noncomparative case series, including 21 eyes of 21 healthy individuals. The 6 × 6-mm macular area was imaged repeatedly to obtain two cube image sets. Images from structural OCT (OCT-S) and OCT angiography (OCT-A) were exported. After vessel-like structures segmentation from the inverted black and white OCT-S images and the OCT-A images, both types of images were reconstructed in a 3D model. The volumes of the outer choroid and the choroidal vessels were measured after thresholding. The similarities of the segmented choroidal vessels (between OCT-S and OCT-A) and between repeatedly acquired images were measured.ResultsMean vessel volume was 2.227 mm3 (29% of the outer choroidal volume) in OCT-S and 0.848 (11%) in OCT-A when measured after removal of the choriocapillaris equivalent volume. Three percent of the vessel volume in OCT-S and 8.4% of that in OCT-A overlapped. The Dice similarity coefficient of vessel volumes in repeated images from the same individual was 0.863 in OCT-S and 0.485 in OCT-A. The ratio of vessel volume to the outer choroidal volume was invariant in OCT-S but increased in OCT-A in the eyes with long axial length.ConclusionsHybrid 3D vascular models of the choroidal vasculature were reconstructed from OCT-S and OCT-A. The new models should prove useful for volumetric analysis of the choroid.Translational RelevanceHybrid 3D models of the choroidal vasculature enable volumetric analysis and facilitate morphologic evaluation.

Integrated electrochemical measurement of endothelial permeability in a 3D hydrogel-based microfluidic vascular model

Mimicking the physiological or pathophysiological barrier function of endothelial and epithelial cells is an essential consideration in organ-on-a-chip models of numerous tissues including the vascular system, lungs, gut and blood-brain barrier. Recent models have furthermore incorporated 3D extracellular matrix hydrogels to recapitulate the composition and cell-matrix interactions found in the native microenvironment. Assessment of barrier function in these 3D organ-on-a-chip models, however, is typically limited to diffusive permeability measurements that are exclusively fluorescence-based. In this work, an on-chip electrochemical method to measure endothelial permeability in a 3D hydrogel-based vascular model was developed that replaces the ubiquitous fluorescent tracer with an electroactive one. Unlike the traditional fluorescent-based method, this electrochemical method eliminates the need for bulky, costly and complex optical instrumentation that require measurements to be performed outside of the incubator. A 3D extracellular matrix gel-based microfluidic model was first developed that incorporates capillary pressure barrier microstructures. Micromilling of thermoplastics was used to fabricate these microstructures in a rapid, moldless fashion. As a proof-of-concept demonstration, the permeability of endothelial cells cultured on hydrogels was electrochemically measured after being subject to perfusion conditions, and following exposure to known permeability mediators. In summary, the electrochemical permeability assay possesses both the benefits of on-chip integration and robustness of the traditional fluorescence-based assay while also enabling the measurement of barrier function in an organ-on-a-chip incorporating 3D culture conditions.

Combining Direct 3D Volume Rendering and Magnetic Particle Imaging to Advance Radiation-Free Real-Time 3D Guidance of Vascular Interventions.

Magnetic particle imaging (MPI) is a novel tomographic radiation-free imaging technique that combines high spatial resolution and real-time capabilities, making it a promising tool to guide vascular interventions. Immediate availability of 3D image data is a major advantage over the presently used digital subtraction angiography (DSA), but new methods for real-time image analysis and visualization are also required to take full advantage of the MPI properties. This laboratory study illustrates respective techniques by means of three different patient-specific 3D vascular flow models. The selected models corresponded to typical anatomical intervention sites. Routine patient cases and image data were selected, relevant vascular territories segmented, 3D models generated and then 3D-printed. Printed models were used to perform case-specific MPI imaging. The resulting MPI images, direct volume rendering (DVR)-based fast 3D visualization options, and their suitability to advance vascular interventions were evaluated and compared to conventional DSA. The experiments illustrated the feasibility and potential to enhance image interpretation during interventions by using MPI real-time volumetric imaging and problem-tailored DVR-based fast (approximately 30 frames/s) 3D visualization options. These options included automated viewpoint selection and cutaway views. The image enhancement potential is especially relevant for complex geometries (e.g., in the presence of superposed vessels). The unique features of the as-yet preclinical imaging modality MPI render it promising for guidance of vascular interventions. Advanced fast DVR could help to fulfill this promise by intuitive visualization of the 3D intervention scene in real time.

Building Three-Dimensional Intracranial Aneurysm Models from 3D-TOF MRA: a Validation Study

To create realistic three-dimensional (3D) vascular models from 3D time-of-flight magnetic resonance angiography (3D-TOF MRA) of an intracranial aneurysm (IA). Thirty-two IAs in 31 patients were printed using 3D-TOF MRA source images from polylactic acid (PLA) raw material. Two observers measured the maximum IA diameter at the longest width twice separately. A total mean of four measurements as well as each observer's individual average MRA lengths were calculated. After printing, 3D-printed anatomic models (PAM) underwent computed tomography (CT) acquisition and each observer measured them using the same algorithm as applied to MRA. Inter- and intra-observer consistency for the MRA and CT measurements were analyzed using the intraclass correlation coefficient (ICC) and a Bland-Altman plot. The mean maximum aneurysm diameter obtained from four MRA evaluations was 8.49mm, whereas it was 8.83mm according to the CT 3D PAM measurement. The Wilcoxon test revealed slightly larger mean CT 3D PAM diameters than the MRA measurements. The Spearman's correlation test yielded a positive correlation between MRA and CT lengths of 3D PAMs. Inter and intra-observer consistency were high in consecutive MRA and CT measurements. According to Bland-Altman analyses, the aneurysmal dimensions obtained from CT were higher for observer 1 and observer 2 (a mean of 0.32mm and 0.35mm, respectively) compared to the MRA measurements. CT dimensions were slightly overestimated compared to MRA measurements of the created models. We believe the discrepancy may be related to the Laplacian algorithm applied for surface smoothing and the high slice thickness selection that was used. However, ICC provided high consistency and reproducibility in our cohort. Therefore, it is technically possible to produce 3D intracranial aneurysm models from 3D-TOF MRA images.

Patient‐Specific Coronary Artery 3D Printing Based on Intravascular Optical Coherence Tomography and Coronary Angiography

Despite the new ideas were inspired in medical treatment by the rapid advancement of three‐dimensional (3D) printing technology, there is still rare research work reported on 3D printing of coronary arteries being documented in the literature. In this work, the application value of 3D printing technology in the treatment of cardiovascular diseases has been explored via comparison study between the 3D printed vascular solid model and the computer aided design (CAD) model. In this paper, a new framework is proposed to achieve a 3D printing vascular model with high simulation. The patient‐specific 3D reconstruction of the coronary arteries is performed by the detailed morphological information abstracted from the contour of the vessel lumen. In the process of reconstruction which has 5 steps, the morphological details of the contour view of the vessel lumen are merged along with the curvature and length information provided by the coronary angiography. After comparing with the diameter of the narrow section and the diameter of the normal section in CAD models and 3D printing model, it can be concluded that there is a high correlation between the diameter of vascular stenosis measured in 3D printing models and computer aided design models. The 3D printing model has high‐modeling ability and high precision, which can represent the original coronary artery appearance accurately. It can be adapted for prevascularization planning to support doctors in determining the surgical procedures.

2D and 3D Vascular Structures Enhancement Via Improved Vesselness Filter and Vessel Enhancing Diffusion

In medical imaging practice, vascular enhancement filtering has been widely performed before vessel segmentation and centerline detection, which provides important pathological information and holds great significance for vessel quantification. In the literature, numerous well known vesselness filtering approaches have been developed. For example, some techniques explore the Hessian matrix of the original images and construct the vessel filter based on the eigenvalues of the Hessian matrix. In this work we develop a hybrid technique for fast and accurate vascular enhancement filter, which contains two main steps: vesselness diffusion and improved vesselness filter based on the eigenvalues ratio. This novel approach is quantitatively and qualitatively tested on the public 2D retinal datasets and 3D synthetic vascular structure models. Experimental results demonstrate that the proposed filter outperforms other existing approaches for curvilinear structure enhancement from noisy images. Moreover, the novel approach is further evaluated on real patient Coronary Computed Tomography Angiography (CCTA) datasets with ground truth regions labelled by professional cardiologist. Our method is proven to produce more accurate coronary artery segmentation results. Given the accuracy and efficiency, the proposed vesselness filter can be further used in medical practice for vascular structures enhancement before vessel segmentation and quantification.

Navigation and visualisation with HoloLens in endovascular aortic repair.

IntroductionEndovascular aortic repair (EVAR) is a minimal-invasive technique that prevents life-threatening rupture in patients with aortic pathologies by implantation of an endoluminal stent graft. During the endovascular procedure, device navigation is currently performed by fluoroscopy in combination with digital subtraction angiography. This study presents the current iterative process of biomedical engineering within the disruptive interdisciplinary project Nav EVAR, which includes advanced navigation, image techniques and augmented reality with the aim of reducing side effects (namely radiation exposure and contrast agent administration) and optimising visualisation during EVAR procedures. This article describes the current prototype developed in this project and the experiments conducted to evaluate it.MethodsThe current approach of the Nav EVAR project is guiding EVAR interventions in real-time with an electromagnetic tracking system after attaching a sensor on the catheter tip and displaying this information on Microsoft HoloLens glasses. This augmented reality technology enables the visualisation of virtual objects superimposed on the real environment. These virtual objects include three-dimensional (3D) objects (namely 3D models of the skin and vascular structures) and two-dimensional (2D) objects [namely orthogonal views of computed tomography (CT) angiograms, 2D images of 3D vascular models, and 2D images of a new virtual angioscopy whose appearance of the vessel wall follows that shown in ex vivo and in vivo angioscopies]. Specific external markers were designed to be used as landmarks in the registration process to map the tracking data and radiological data into a common space. In addition, the use of real-time 3D ultrasound (US) is also under evaluation in the Nav EVAR project for guiding endovascular tools and updating navigation with intraoperative imaging. US volumes are streamed from the US system to HoloLens and visualised at a certain distance from the probe by tracking augmented reality markers. A human model torso that includes a 3D printed patient-specific aortic model was built to provide a realistic test environment for evaluation of technical components in the Nav EVAR project. The solutions presented in this study were tested by using an US training model and the aortic-aneurysm phantom.ResultsDuring the navigation of the catheter tip in the US training model, the 3D models of the phantom surface and vessels were visualised on HoloLens. In addition, a virtual angioscopy was also built from a CT scan of the aortic-aneurysm phantom. The external markers designed for this study were visible in the CT scan and the electromagnetically tracked pointer fitted in each marker hole. US volumes of the US training model were sent from the US system to HoloLens in order to display them, showing a latency of 259±86 ms (mean±standard deviation).ConclusionThe Nav EVAR project tackles the problem of radiation exposure and contrast agent administration during EVAR interventions by using a multidisciplinary approach to guide the endovascular tools. Its current state presents several limitations such as the rigid alignment between preoperative data and the simulated patient. Nevertheless, the techniques shown in this study in combination with fibre Bragg gratings and optical coherence tomography are a promising approach to overcome the problems of EVAR interventions.

An Ex Vivo Vessel Injury Model to Study Remodeling

Objective: Invasive coronary interventions can fail due to intimal hyperplasia and restenosis. Endothelial cell (EC) seeding to the vessel lumen, accelerating re-endothelialization, or local release of mTOR pathway inhibitors have helped reduce intimal hyperplasia after vessel injury. While animal models are powerful tools, they are complex and expensive, and not always reflective of human physiology. Therefore, we developed an in vitro 3D vascular model validating previous in vivo animal models and utilizing isolated human arteries to study vascular remodeling after injury. Approach: We utilized a bioreactor that enables the control of intramural pressure and shear stress in vessel conduits to investigate the vascular response in both rat and human arteries to intraluminal injury. Results: Culturing rat aorta segments in vitro, we show that vigorous removal of luminal ECs results in vessel injury, causing medial proliferation by Day-4 and neointima formation, with the observation of SCA1+ cells (stem cell antigen-1) in the intima by Day-7, in the absence of flow. Conversely, when endothelial-denuded rat aortae and human umbilical arteries were subjected to arterial shear stress, pre-seeding with human umbilical ECs decreased the number and proliferation of smooth muscle cell (SMC) significantly in the media of both rat and human vessels. Conclusion: Our bioreactor system provides a novel platform for correlating ex vivo findings with vascular outcomes in vivo. The present in vitro human arterial injury model can be helpful in the study of EC-SMC interactions and vascular remodeling, by allowing for the separation of mechanical, cellular, and soluble factors.

3D printing of intracranial aneurysm based on intracranial digital subtraction angiography and its clinical application.

The study aimed to develop simulation models including intracranial aneurysmal and parent vessel geometries, as well as vascular branches, through 3D printing technology. The simulation models focused on the benefits of aneurysmal treatments and clinical education. This prospective study included 13 consecutive patients who suffered from intracranial aneurysms confirmed by digital subtraction angiography (DSA) in the Neurosurgery Department of Shaoxing People's Hospital. The original 3D-DSA image data were extracted through the picture archiving and communication system and imported into Mimics. After reconstructing and transforming to Binary STL format, the simulation models of the hollow vascular tree were printed using 3D devices. The intracranial aneurysm 3D printing simulation model was developed based on DSA to assist neurosurgeons in aneurysmal treatments and residency training. Seven neurosurgical residents and 15 standardization training residents received their simulation model training and gave high assessments for the educational course with the follow-up qualitative questionnaire. 3D printed simulation models based on DSA can perfectly reveal target aneurysms and help neurosurgeons select therapeutic strategies precisely. As an educational tool, the 3D aneurysm vascular simulation model is useful for training residents.

Through the HoloLens\u2122 looking glass: augmented reality for extremity reconstruction surgery using 3D vascular models with perforating vessels

Precision and planning are key to reconstructive surgery. Augmented reality (AR) can bring the information within preoperative computed tomography angiography (CTA) imaging to life, allowing the surgeon to ‘see through’ the patient’s skin and appreciate the underlying anatomy without making a single incision. This work has demonstrated that AR can assist the accurate identification, dissection and execution of vascular pedunculated flaps during reconstructive surgery. Separate volumes of osseous, vascular, skin, soft tissue structures and relevant vascular perforators were delineated from preoperative CTA scans to generate three-dimensional images using two complementary segmentation software packages. These were converted to polygonal models and rendered by means of a custom application within the HoloLens™ stereo head-mounted display. Intraoperatively, the models were registered manually to their respective subjects by the operating surgeon using a combination of tracked hand gestures and voice commands; AR was used to aid navigation and accurate dissection. Identification of the subsurface location of vascular perforators through AR overlay was compared to the positions obtained by audible Doppler ultrasound. Through a preliminary HoloLens-assisted case series, the operating surgeon was able to demonstrate precise and efficient localisation of perforating vessels.

Three-dimensional biomimetic vascular model reveals a RhoA, Rac1, and N-cadherin balance in mural cell–endothelial cell-regulated barrier function

The integrity of the endothelial barrier between circulating blood and tissue is important for blood vessel function and, ultimately, for organ homeostasis. Here, we developed a vessel-on-a-chip with perfused endothelialized channels lined with human bone marrow stromal cells, which adopt a mural cell-like phenotype that recapitulates barrier function of the vasculature. In this model, barrier function is compromised upon exposure to inflammatory factors such as LPS, thrombin, and TNFα, as has been observed in vivo. Interestingly, we observed a rapid physical withdrawal of mural cells from the endothelium that was accompanied by an inhibition of endogenous Rac1 activity and increase in RhoA activity in the mural cells themselves upon inflammation. Using a system to chemically induce activity in exogenously expressed Rac1 or RhoA within minutes of stimulation, we demonstrated RhoA activation induced loss of mural cell coverage on the endothelium and reduced endothelial barrier function, and this effect was abrogated when Rac1 was simultaneously activated. We further showed that N-cadherin expression in mural cells plays a key role in barrier function, as CRISPR-mediated knockout of N-cadherin in the mural cells led to loss of barrier function, and overexpression of N-cadherin in CHO cells promoted barrier function. In summary, this bicellular model demonstrates the continuous and rapid modulation of adhesive interactions between endothelial and mural cells and its impact on vascular barrier function and highlights an in vitro platform to study the biology of perivascular-endothelial interactions.