영상 기반 대동맥-장골 기하학 및 혈관 내 동맥류 수술 후 비폐쇄성 혈전증 위험의 혈역학적 평가 = Imaging-based aorto-iliac geometry and hemodynamic evaluation of non-occlusive thrombosis risk following endovascular aneurysm repair

다국어 초록 (Multilingual Abstract)

Background: Thrombotic complications following endovascular aneurysm repair (EVAR) remain a significant concern, often leading to limb occlusion or distal embolism. While clinical and procedural factors have been investigated, the combined influence of post-EVAR vessel geometry and local hemodynamics on thrombosis formation is not well understood.
Objectives: This thesis aimed to evaluate the relationship between thrombosis formation and aorto-iliac geometric parameters, hemodynamic parameters derived from patient-specific vessel 3D model and computational fluid dynamics (CFD) simulations, to identify predictors of non-occlusive thrombus formation following EVAR.
Methods: A retrospective single-center analysis was performed on 101 EVAR patients treated between 2015-2022. Three-dimensional aorto-iliac models were reconstructed from post-EVAR CTA. Geometric parameters - including diameter, area, circumference, bifurcation and iliac angles, and tortuosity - were quantified. CFD simulations using COMSOL Multiphysics calculated time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and wall shear stress (WSS) under pulsatile flow conditions. Statistical correlations between geometry, hemodynamic variables, and thrombus presence were analyzed using t-tests and Spearman’s rho.
Results: Aortic thrombotic segments exhibited significantly larger maximal circumference (79.98 ± 6.78 mm vs 70.94 ± 10.57 mm, p=0.011) and maximal cross-sectional area (495.69 ± 87.20 mm² vs 398.89 ± 123.34 mm², p=0.021). In iliac segments, thrombotic limbs showed larger diameters (17.48 ± 0.95 mm vs 14.14 ± 0.62 mm, p=0.006), smaller graft limb angle (117.5° ± 5.6° vs 148.5° ± 4.3°, p<0.001) and aorto-iliac angles (123.5° ± 4.7° vs 142.0° ± 4.8°, p=0.009), and higher tortuosity (p=0.021). CFD results revealed that thrombotic iliac limbs had markedly lower TAWSS (0.16 Pa vs 0.79 Pa, p<0.001) and maximum WSS, and higher OSI (0.047 vs 0.0001, p<0.001). These parameters correlated strongly with thrombus status (ρ = −0.626 for TAWSS; ρ = 0.415 for OSI).
Conclusions: Enlarged vessel caliber, increased tortuosity, and reduced outflow angles significantly alter post-EVAR hemodynamics, promoting regions of low shear and oscillatory flow leading to thrombus formation. CFD-based analysis of patient-specific aorto-iliac geometry provides valuable insight into thrombosis risk and may enhance individualized surveillance and stent-graft design strategies.

목차 (Table of Contents)

• I. INTRODUCTION 1
• 1. Aorto-iliac artery anatomy 1
• 2. CTA of the aorto-iliac artery 1
• 3. Endovascular aneurysm repair and thrombotic complications 3
• 4. Geometry and thrombosis 6
• 5. CFD of artery and thrombosis 6
• 6. Motivation and objectives 9
• II. MATERIALS AND METHODS 10
• 1. Study population and design 10
• 2. Outline of workflow 11
• 3. Imaging acquisition and interpretation 13
• 4. Post-EVAR 3D aorta and iliac artery model reconstruction and stent graft removal 15
• 5. Geometry measurement 15
• 6. CFD analysis 18
• 7. Statistical analysis 20
• 1. Geometry analysis of post-EVAR thrombotic risk in the aortic segments 24
• 2. Geometry analysis of post-EVAR thrombotic risk in the iliac segments 28
• 3. Hemodynamic analysis of post-EVAR thrombotic risk in the aorta stent component 33
• 4. Hemodynamic analysis of post-EVAR thrombotic risk in the iliac stent component 36
• IV. DISCUSSION 44
• V. CONCLUSION 48
• VI. REFERENCES 49
• VII. 국문초록 56
• VIII. ACKNOWLEDGMENTS 59
• List of publications 60