The Role of Diameter Variation in Investigation of Coronary Tortuosity

Coronary diameter and tortuosity are two important morphological parameters that both affect the local haemodynamics. However, previous studies on tortuous coronaries neglected any potential associated effects from vascular diameter variations. Here, we investigate the differences in coronary haemodynamics due to diameter variation in tortuous coronaries. 28 models were derived from modifications of four non-bifurcating and bifurcating coronaries each. For the non-bifurcating coronaries, we first generated a uniform cross-sectional diameter model, before scaling it by + and - 1 mm. For the bifurcations, we only scaled the models by + and -1 mm. The computational results showed that the vascular diameter had a great effect on the haemodynamics of torturous arteries. For non-bifurcating models, the modified geometries with constant diameters exhibited a small change in the local velocity field and a smaller percentage vessel area exposed to adverse time - average wall shear stress (TAWSS%), compared to their original coronaries with varying diameters. Moreover, the TAWSS% increased in the modified geometries with constant diameters as the diameter increased. For the bifurcating models with varying diameters, both helicity intensity (ℎ₂) and TAWSS% were 24%, 33% less in -1 mm-smaller models, and 31%, 44% larger in +1 mm larger models, compared to the original equivalents. Overall, the effect of tortuosity on haemodynamics, commonly measured as centreline index, cannot be considered independently of the vessel diameter and potentially other shape characteristics. This may explain contradicting in previous literature to date and thus warrants future studies

Exploring the Interplay of Left Coronary Tree Anatomy and Haemodynamics: Implications for Plaque Formation

The link between atherosclerosis and blood flow-induced haemodynamic luminal shear stresses is well established. However, this understanding has not been translated into clinical practice because of the interdependent effects of the complex coronary anatomy and a multitude of potential haemodynamic metrics, which have been challenging to delineate. Thus, this study aims to identify anatomical and haemodynamic differences in coronary trees at different stages of stenoses. A total of 39 left coronary trees were considered, which are publicly available. Each coronary tree was dissected into bifurcations and non-bifurcating segments for comparisons. We calculated a full set of anatomical metrics and performed transient flow simulations to solve the normalised luminal area exposed to Low Time-Average Endothelial Shear Stress (%LowTAESS), High Oscillatory Shear Index (%HighOSI), and High Relative Residence Time (%HighRRT). We statistically investigated the differences between non-stenosed (n=20, Diameter Stenosis DS=0%), moderately (n=12, 0%=70%) stenosed cases, whereby p<0.05* is considered significant. Only the average curvature and %HighOSI differed between the non-stenosed, and moderately or severely stenosed for the coronary trees (p=0.024* and p<0.001*), and non-bifurcating segments (p=0.027* and p<0.001*). %[email protected] and %[email protected] significantly differed between moderately (0%=70\%) stenosed trees (p=0.009* and p=0.012*). Our findings suggest curvature and potentially %HighOSI being critical factors in coronary plaque onset in non-bifurcating segments, whereas %LowTAESS and %HighRRT affect plaque progression after onset

Sex-Specific Variances in Anatomy and Blood Flow of the Left Main Coronary Bifurcation: Implications for Coronary Artery Disease Risk

Studies have shown marked sex disparities in Coronary Artery Diseases (CAD) epidemiology, yet the underlying mechanisms remain unclear. We explored sex disparities in the coronary anatomy and the resulting haemodynamics in patients with suspected, but no significant CAD. Left Main (LM) bifurcations were reconstructed from CTCA images of 127 cases (42 males and 85 females, aged 38 to 81). Detailed shape parameters were measured for comparison, including bifurcation angles, curvature, and diameters, before solving the haemodynamic metrics using CFD. The severity and location of the normalised vascular area exposed to physiologically adverse haemodynamics were statistically compared between sexes for all branches. We found significant differences between sexes in potentially adverse haemodynamics. Females were more likely than males to exhibit adversely low Time Averaged Endothelial Shear Stress along the inner wall of a bifurcation (16.8% vs. 10.7%). Males had a higher percentage of areas exposed to both adversely high Relative Residence Time (6.1% vs 4.2%, p=0.001) and high Oscillatory Shear Index (4.6% vs 2.3%, p<0.001). However, the OSI values were generally small and should be interpreted cautiously. Males had larger arteries (M vs F, LM: 4.0mm vs 3.3mm, LAD: 3.6mm 3.0mm, LCX:3.5mm vs 2.9mm), and females exhibited higher curvatures in all three branches (M vs F, LM: 0.40 vs 0.46, LAD: 0.45 vs 0.51, LCx: 0.47 vs 0.55, p<0.001) and larger inflow angle of the LM trunk (M: 12.9{\deg} vs F: 18.5{\deg}, p=0.025). Haemodynamic differences were found between male and female patients, which may contribute, at least in part, to differences in CAD risk. This work may facilitate a better understanding of sex differences in the clinical presentation of CAD, contributing to improved sex-specific screening, especially relevant for women with CAD who currently have worse predictive outcomes.Comment: 14 pages, 5 figure

MedShapeNet -- A Large-Scale Dataset of 3D Medical Shapes for Computer Vision

Prior to the deep learning era, shape was commonly used to describe the objects. Nowadays, state-of-the-art (SOTA) algorithms in medical imaging are predominantly diverging from computer vision, where voxel grids, meshes, point clouds, and implicit surface models are used. This is seen from numerous shape-related publications in premier vision conferences as well as the growing popularity of ShapeNet (about 51,300 models) and Princeton ModelNet (127,915 models). For the medical domain, we present a large collection of anatomical shapes (e.g., bones, organs, vessels) and 3D models of surgical instrument, called MedShapeNet, created to facilitate the translation of data-driven vision algorithms to medical applications and to adapt SOTA vision algorithms to medical problems. As a unique feature, we directly model the majority of shapes on the imaging data of real patients. As of today, MedShapeNet includes 23 dataset with more than 100,000 shapes that are paired with annotations (ground truth). Our data is freely accessible via a web interface and a Python application programming interface (API) and can be used for discriminative, reconstructive, and variational benchmarks as well as various applications in virtual, augmented, or mixed reality, and 3D printing. Exemplary, we present use cases in the fields of classification of brain tumors, facial and skull reconstructions, multi-class anatomy completion, education, and 3D printing. In future, we will extend the data and improve the interfaces. The project pages are: https://medshapenet.ikim.nrw/ and https://github.com/Jianningli/medshapenet-feedbackComment: 16 page

Rethinking Authentic Assessment - A Peer-Assessed Virtual conference for Online Collaborative Learning

The COVID-19 pandemic exacerbated the teaching challenges of engaging students, building a learning community, and creating enriching learning experiences. Here, we present an authentic, asynchronous assessment method applied as a peer-assessed virtual conference task. The peer assessment and facilitation effectively generated a strong sense of community and teamwork (95% agreement) and enabled the students to generate a deeper understanding of the course content (73% agreement) by fostering critical self-reflection (87% agreement). Student engagement excelled whereby many choose to engage in additional presentations outside of their allocated peer markings. Consistently positive feedback highlighted the task’s utility as an online learning tool and its efficacy in shaping a collaborative class community besides remote teaching condition. Additionally, the multi-faceted nature of the assessment promoted a broad range of effective teaching qualities, including collaboration, communication, and application of theory in innovative contexts which lends itself to higher education. Overall, the virtual conference tool and its peer-based facilitation can be considered for effective engineering education practice, which may also apply to other scientific disciplines to improve student learning and experiences

Role of secondary flows in coronary artery bifurcations before and after stenting: What is known so far?

Coronary arteries are uniformly exposed to traditional cardiovascular risk factors. However, atherosclerotic lesions occur in preferential regions of the coronary tree, especially in areas with disturbed local blood flow, such as coronary bifurcations. Over the latest years, secondary flows have been linked to the inception and progression of atherosclerosis. Most of these novel findings have been obtained in the field of computational fluid dynamic (CFD) analysis and biomechanics but remain poorly understood by cardiovascular interventionalists, despite the important impact that they may have in clinical practice. We aimed to summarize the current available data regarding the pathophysiological role of secondary flows in coronary artery bifurcation, providing an interpretation of these findings from an interventional perspective