220 research outputs found
Network-Based Approach for Modeling and Analyzing Coronary Angiography
Significant intra-observer and inter-observer variability in the
interpretation of coronary angiograms are reported. This variability is in part
due to the common practices that rely on performing visual inspections by
specialists (e.g., the thickness of coronaries). Quantitative Coronary
Angiography (QCA) approaches are emerging to minimize observer's error and
furthermore perform predictions and analysis on angiography images. However,
QCA approaches suffer from the same problem as they mainly rely on performing
visual inspections by utilizing image processing techniques.
In this work, we propose an approach to model and analyze the entire
cardiovascular tree as a complex network derived from coronary angiography
images. This approach enables to analyze the graph structure of coronary
arteries. We conduct the assessments of network integration, degree
distribution, and controllability on a healthy and a diseased coronary
angiogram. Through our discussion and assessments, we propose modeling the
cardiovascular system as a complex network is an essential phase to fully
automate the interpretation of coronary angiographic images. We show how
network science can provide a new perspective to look at coronary angiograms
The Evolution of Data Fusion Methodologies Developed to Reconstruct Coronary Artery Geometry From Intravascular Imaging and Coronary Angiography Data: A Comprehensive Review
Understanding the mechanisms that regulate atherosclerotic plaque formation and
evolution is a crucial step for developing treatment strategies that will prevent plaque
progression and reduce cardiovascular events. Advances in signal processing and the
miniaturization of medical devices have enabled the design of multimodality intravascular
imaging catheters that allow complete and detailed assessment of plaque morphology
and biology. However, a significant limitation of these novel imaging catheters is that they
provide two-dimensional (2D) visualization of the lumen and vessel wall and thus they
cannot portray vessel geometry and 3D lesion architecture. To address this limitation
computer-based methodologies and user-friendly software have been developed. These
are able to off-line process and fuse intravascular imaging data with X-ray or computed
tomography coronary angiography (CTCA) to reconstruct coronary artery anatomy. The
aim of this review article is to summarize the evolution in the field of coronary artery
modeling; we thus present the first methodologies that were developed to model vessel
geometry, highlight the modifications introduced in revised methods to overcome the
limitations of the first approaches and discuss the challenges that need to be addressed,
so these techniques can have broad application in clinical practice and research
Optimal Site for Proximal Optimization Technique in Complex Coronary Bifurcation Stenting: A Computational Fluid Dynamics Study
Background/purpose: The optimal position of the balloon distal radio-opaque marker during the post optimization technique (POT) remains debated. We analyzed three potential different balloon positions for the final POT in two different two-stenting techniques, to compare the hemodynamic effects in terms of wall shear stress (WSS) in patients with complex left main (LM) coronary bifurcation. Methods/materials: We reconstructed the patient-specific coronary bifurcation anatomy using the coronary computed tomography angiography (CCTA) data of 8 consecutive patients (6 males, mean age 68.2± 18.6 years) affected by complex LM bifurcation disease. Subsequently a virtual bench test was performed in each patient using two different double stenting techniques represented by the DK and Nano crush using the reconstruction of Orsiro stents (Biotronik IC, Bulack, Switzerland). Results: A significant reduction in the mean WSS values in all the lesion's sites was observed when the final POT was performed 1 mm distally the carina cut plane in both techniques. Moreover, a significant improvement in the mean WSS values of the entire SB (e.g. LCX) was obtained performing the POT 1 mm distally to the carina cut plane. The proximal POT resulted in larger area of lower WSS values at the carina using both the Nano crush and the DK crush techniques. Conclusions: In patients with complex LM bifurcation disease the use of a final POT performed 1 mm distally to the carina cut plane might results in more favorable WSS patterns (i.e. higher WSS values) along all stented segments and, especially, along the entire LCX lesions
Advances in IVUS/OCT and Future Clinical Perspective of Novel Hybrid Catheter System in Coronary Imaging
Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have been
developed and improved as both diagnostic and guidance tools for interventional
procedures over the past three decades. IVUS has a resolution of 100”m with a
high tissue penetration and capability of assessing the entire structure of a coronary
artery including the external elastic membrane, whereas OCT has a higher resolution of
10â20”m to assess endoluminal structures with a limited tissue penetration compared
to IVUS. Recently, two companies, CONAVI and TERUMO, integrated IVUS and OCT into
a single catheter system. With their inherent strength and limitations, the combined IVUS
and OCT probes are complementary and work synergistically to enable a comprehensive
depiction of coronary artery. In this review, we summarize the performance of the two
intracoronary imaging modalit
Pressure drop and recovery in cases of cardiovascular disease: a computational study
The presence of disease in the cardiovascular system results in changes in flow and pressure patterns. Increased resistance to the flow observed in cases of aortic valve and coronary artery disease can have as a consequence abnormally high pressure gradients, which may lead to overexertion of the heart muscle, limited tissue perfusion and tissue damage.
In the past, computational fluid dynamics (CFD) methods have been used coupled with medical imaging data to study haemodynamics, and it has been shown that CFD has great potential as a way to study patient-specific cases of cardiovascular disease in vivo, non-invasively, in great detail and at low cost. CFD can be particularly useful in evaluating the effectiveness of new diagnostic and treatment techniques, especially at early âconceptâ stages.
The main aim of this thesis is to use CFD to investigate the relationship between pressure and flow in cases of disease in the coronary arteries and the aortic valve, with the purpose of helping improve diagnosis and treatment, respectively.
A transitional flow CFD model is used to investigate the phenomenon of pressure recovery in idealised models of aortic valve stenosis. Energy lost as turbulence in the wake of a diseased valve hinders pressure recovery, which occurs naturally when no energy losses are observed. A âconceptâ study testing the potential of a device that could maximise pressure recovery to reduce the pressure load on the heart muscle was conducted. The results indicate that, under certain conditions, such a device could prove useful.
Fully patient-specific CFD studies of the coronary arteries are fewer than studies in larger vessels, mostly due to past limitations in the imaging and velocity data quality. A new method to reconstruct coronary anatomy from optical coherence tomography (OCT) data is presented in the thesis. The resulting models were combined with invasively acquired pressure and flow velocity data in transient CFD simulations, in order to test the ability of CFD to match the invasively measured pressure drop. A positive correlation and no bias were found between the calculated and measured results. The use of lower resolution reconstruction methods resulted in no correlation between the calculated and measured results, highlighting the importance of anatomical accuracy in the effectiveness of the CFD model. However, it was considered imperative that the limitations of CFD in predicting pressure gradients be further explored. It was found that the CFD-derived pressure drop is sensitive to changes in the volumetric flow rate, while bench-top experiments showed that the estimation of volumetric flow rate from invasively measured velocity data is subject to errors and uncertainties that may have a random effect on the CFD pressure result.
This study demonstrated that the relationship between geometry, pressure and flow can be used to evaluate new diagnostic and treatment methods. In the case of aortic stenosis, further experimental work is required to turn the concept of a pressure recovery device into a potential clinical tool. In the coronary study it was shown that, though CFD has great power as a study tool, its limitations, especially those pertaining to the volumetric flow rate boundary condition, must be further studied and become fully understood before CFD can be reliably used to aid diagnosis in clinical practice.Open Acces
Three-dimensional quantitative coronary angiography and the registration with intravascular ultrasound and optical coherence tomography
This thesis proposes several new algorithms including X-ray angiographic image enhancement, three-dimensional (3D) angiographic reconstruction, angiographic overlap prediction, and the co-registration of X-ray angiography with intracoronary imaging devices, such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The algorithms were integrated into prototype software packages that were validated at a number of clinical centers. The feasibility of using such software packages in typical clinical population was verified, while the advantages and accuracy of the proposed algorithms were demonstrated by phantoms and in-vivo clinical studies. In addition, based on the proposed approaches and the conducted studies, this thesis reports a number of findings including the impact of acquisition angle difference on 3D quantitative coronary angiography (QCA), the clinical characteristics of bifurcation optimal viewing angles and bifurcation angles, and the discrepancy of lumen dimensions as assessed by 3D QCA and by IVUS or OCT.UBL - phd migration 201
Expert recommendations on the assessment of wall shear stress in human coronary arteries : existing methodologies, technical considerations, and clinical applications
The aim of this manuscript is to provide guidelines for appropriate use of CFD to obtain reproducible and reliable wall shear stress maps in native and instrumented human coronary arteries. The outcome of CFD heavily depends on the quality of the input data, which include vessel geometrical data, proper boundary conditions, and material models. Available methodologies to reconstruct coronary artery anatomy are discussed in âImaging coronary arteries: a brief reviewâ section. Computational procedures implemented to simulate blood flow in native coronary arteries are presented in âWall shear stress in native arteriesâ section. The effect of including different geometrical scales due to the presence of stent struts in instrumented arteries is highlighted in âWall shear stress in stentsâ section. The clinical implications are discussed in âClinical applicationsâ section, and concluding remarks are presented in âConcluding remarksâ section
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