Professor Xiao Yun Xu

Torii R, Wood NB, Hadjiloizou N, Wright A, Hughes AD, Thom SAM, Xu XYet al., 2007, Does the difference in realistic waveform before and after stenting affect hemodynamics in stenosed coronary artery?, ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 467-468

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Torii R, Wood NB, Hughes AD, Thom SA, Aguado-Sierra J, Davies JE, Francis DP, Parker KH, Xu XYet al., 2007, A computational study on the influence of catheter-delivered intravascular probes on blood flow in a coronary artery model, JOURNAL OF BIOMECHANICS, Vol: 40, Pages: 2501-2509, ISSN: 0021-9290

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• Citations: 20

Sun N, Torii R, Wood NB, Wright A, Hughes AD, Thom SAM, Xu XYet al., 2007, Numerical simulation of blood-wall albumin transport in a realistic human right coronary artery, ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 107-108

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Borghi A, Wood NB, Mohiaddin RH, Xu XYet al., 2007, Fluid-solid interaction simulation of flow and stress pattern in thoracoabdominal aneurysms: A patient specific study, 6th Symposium on Fluid-Structure Interactions, Aeroelasticity and Flow-Induced Vibration and Noise, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 671-675

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Borghi A, Wood NB, Mohiaddin RH, Xu XYet al., 2006, 3D geometric reconstruction of thoracic aortic aneurysms, BIOMEDICAL ENGINEERING ONLINE, Vol: 5, ISSN: 1475-925X

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• Citations: 15

Wood NB, Zhao SZ, Zambanini A, Jackson M, Gedroyc W, Thom SA, Hughes AD, Xu XYet al., 2006, Curvature and tortuosity of the superficial femoral artery: a possible risk factor for peripheral arterial disease, JOURNAL OF APPLIED PHYSIOLOGY, Vol: 101, Pages: 1412-1418, ISSN: 8750-7587

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• Citations: 104

Ariff B, Zambanini A, Vamadeva S, Barratt D, Xu Y, Sever P, Stanton A, Hughes A, Thom Set al., 2006, Candesartan- and atenolol-based treatments induce different patterns of carotid artery and left ventricular remodeling in hypertension, STROKE, Vol: 37, Pages: 2381-2384, ISSN: 0039-2499

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• Citations: 41

Sun N, Wood NB, Hughes AD, Thom SAM, Xu XYet al., 2006, Fluid-wall modelling of mass transfer in an axisymmetric stenosis: Effects of shear-dependent transport properties, ANNALS OF BIOMEDICAL ENGINEERING, Vol: 34, Pages: 1119-1128, ISSN: 0090-6964

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• Citations: 81

Leung JH, Wright AR, Cheshire N, Crane J, Thom SA, Hughes AD, Xu Yet al., 2006, Fluid structure interaction of patient specific abdominal aortic aneurysms: a comparison with solid stress models, Biomedical Engineering Online, Vol: 5, ISSN: 1475-925X

BackgroundAbdominal aortic aneurysm (AAA) is a dilatation of the aortic wall, which can rupture, if left untreated. Previous work has shown that, maximum diameter is not a reliable determinant of AAA rupture. However, it is currently the most widely accepted indicator. Wall stress may be a better indicator and promising patient specific results from structural models using static pressure, have been published. Since flow and pressure inside AAA are non-uniform, the dynamic interaction between the pulsatile flow and wall may influence the predicted wall stress. The purpose of the present study was to compare static and dynamic wall stress analysis of patient specific AAAs.MethodPatient-specific AAA models were created from CT scans of three patients. Two simulations were performed on each lumen model, fluid structure interaction (FSI) model and static structural (SS) model. The AAA wall was created by dilating the lumen with a uniform 1.5 mm thickness, and was modeled as a non-linear hyperelastic material. Commercial finite element code Adina 8.2 was used for all simulations. The results were compared between the FSI and SS simulations.ResultsResults are presented for the wall stress patterns, wall shear stress patterns, pressure, and velocity fields within the lumen. It is demonstrated that including fluid flow can change local wall stresses slightly. However, as far as the peak wall stress is concerned, this effect is negligible as the difference between SS and FSI models is less than 1%.ConclusionThe results suggest that fully coupled FSI simulation, which requires considerable computational power to run, adds little to rupture risk prediction. This justifies the use of SS models in previous studies.

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Wood N B, Xu X Y, 2006, Modelling of haemodynamics in the cardiovascular system by integrating medical imaging techniques and computer modelling tools., Multidisciplinary Approaches to Theory in Medicine., Editors: Paton, McNamara, Paton, McNamara, Amsterdam, The Netherlands, Publisher: Elsevier B V, Pages: 325-351, ISBN: 9780444518064

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Ma CYJ, Mantalaris A, Xu XY, 2005, Development of a mathematical model for a 3-D perfused bone marrow culture system, AIChE Annual Meeting, Conference Proceedings, Pages: 8808-8818

Bone marrow (BM) is a three-dimensional tissue and the site of blood formation. The successful reconstruction of the BM has enormous potential benefits to the society. Its success depends, partly, on the development of a suitable culture system necessary for its growth. In the present work, we have developed a mathematical model for a 3-D perfused BM culture system that captures the growth characteristics of the BM microenvironment, and as a first approximation, mimics the structural entity of in vivo BM. The model has been used to investigate cellular growth, fluid flow, shear stress and nutrient distribution within a Rotating Wall Perfused Bioreactor - RWPB (Synthecon Inc.). Based on our preliminary results, for a 2 week culture, it was observed that the total cell number increased by 30 and 38 fold for a scaffold with 90% and 80% porosity, respectively. Further analysis showed that, with a 20% oxygen supply, the oxygen tension was sufficiently maintained to avoid hypoxic regions, but with increasing axial distance in the bioreactor some areas experienced low oxygen levels; though this effect varied with porosity of the scaffold.

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• Citations: 1

Leung JH, Wright A, Cheshire N, Thom SA, Hughes AD, Crane J, Xu YXet al., 2005, Fluid-structure interaction in patient specific models of the abdominal aortic aneurysm, Proceedings of the 2005 Summer Bioengineering Conference, Vol: 2005, Pages: 1450-1451

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Wood NB, Exarchou I, Xu XY, Mistry P, Witt N, Thom SA, Hughes ADet al., 2005, Progress with the study of retinal hemodynamics in normotensive and hypertensive patients, Proceedings of the 2005 Summer Bioengineering Conference, Vol: 2005, Pages: 259-260

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• Citations: 1

Nyilas RD, Ng SML, Leung J, Xu XYet al., 2005, Towards a new geometric approach to assess the risk of rupture of abdominal aortic aneurysms using patient specific modelling, Proceedings of the 2005 Summer Bioengineering Conference, Vol: 2005, Pages: 1246-1247

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• Citations: 9

Augst AD, Xu XY, Ariff B, Thom SAMG, Hughes ADet al., 2005, Correlation between haemodynamic wall parameters and intima-media thickness in the carotid arteries, Pages: 411-412

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Borghi A, Wood NB, Mohiaddin RH, Xu XYet al., 2005, Computational modeling of fluid dynamics and stress pattern in thoracic aortic aneurysms, Proceedings of the 2005 Summer Bioengineering Conference, Vol: 2005, Pages: 355-356

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• Citations: 1

Wood NB, Xu XY, 2005, 18 Modelling of haemodynamics in the cardiovascular system by integrating medical imaging techniques and computer modelling tools, Studies in Multidisciplinarity, Vol: 3, Pages: 325-351, ISSN: 1571-0831

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• Citations: 2

Vermeersch SJ, Glor FP, Crowe LA, Ariff B, Bol M, Segers P, Hughes AD, Xu XY, Thom Smcg, Firmin DN, Verdonck PRet al., 2005, Relationship between carotid artery intima-media thickness and wall shear stress derived parameters., Comput Methods Biomech Biomed Engin, Vol: 8, Pages: 279-280, ISSN: 1025-5842

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Ricard F, Brechtelsbauer C, Xu XY, Lawrence CJet al., 2005, Monitoring of multiphase pharmaceutical processes using electrical resistance tomography, 7th World Congress of Chemical Engineering, Publisher: ELSEVIER, Pages: 794-805, ISSN: 0263-8762

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• Citations: 58

Glor FP, Ariff B, Hughes AD, Verdonck PR, McG SA, Barratt DC, Xu XYet al., 2005, Operator dependence of 3-D ultrasound-based computational fluid dynamics for the carotid bifurcation, IEEE TRANSACTIONS ON MEDICAL IMAGING, Vol: 24, Pages: 451-456, ISSN: 0278-0062

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• Citations: 21

Ricard F, Brechtelsbauer C, Xu Y, Lawrence C, Thompson Det al., 2005, Development of an electrical resistance tomography reactor for pharmaceutical processes, 3rd World Congress in Process Tomography, Publisher: WILEY, Pages: 11-18, ISSN: 0008-4034

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• Citations: 12

Augst AD, Ariff B, Barratt DC, Thom SAM, Hughes AD, Xu XYet al., 2005, Application of ultrasound-based computational fluid dynamics to modeling blood flow in the carotid bifurcation, Medical Imaging Systems Technology: Volume 5: Methods in Cardiovascular and Brain Systems, Pages: 109-156, ISBN: 9789812569899

Atherosclerotic plaque formation has been linked to haemodynamic risk factors, such as low and oscillating wall shear stresses (WSS). Experimental and numerical methods have been developed to investigate the mechanisms involved. Computational fluid dynamics (CFD) methods have the advantages of low cost and easily manageable numerical results. In order to obtain physiologically realistic results, CFD can be linked with medical imaging methods, which allow the extraction of in vivo vascular geometry and flow data to be used as input for haemodynamic simulations. Most of the image-based CFD approaches have been based on MRI, which has the disadvantages of relatively high cost and limited availability. Hence, a novel technique based on 3D ultrasound was developed with the advantages of low cost, fast acquisition and high spatial resolution. A methodology was developed to extract geometric information from the ultrasound images, reconstruct the surfaces and generate computational grids for flow simulations of the human carotid artery bifurcation. Additionally, a scheme was devised to utilize Doppler flow information for CFD boundary conditions. Accuracy and reproducibility of the combined imaging and modeling approach were evaluated in vitro and in vivo and the developed protocol was applied to normal subjects. The main conclusion of this work is the feasibility of 3D and Doppler ultrasound based CFD simulations for clinical applications. However, there are several limitations when applying this methodology in carotid bifurcations, i.e. the location of the carotid bulb relative to the jaw bone, which obscures the ultrasound path when the bifurcation is high in the neck. Future work should focus on minimizing the limitations and improve automation and reliability of image processing and reconstruction.

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Glor FP, Ariff B, Hughes AD, Crowe LA, Verdonck PR, Barratt DC, Thom SAM, Firmin DN, Xu XYet al., 2004, Image-based carotid flow reconstruction: a comparison between MRI and ultrasound, PHYSIOLOGICAL MEASUREMENT, Vol: 25, Pages: 1495-1509, ISSN: 0967-3334

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• Citations: 48

Lee KW, Wood NB, Xu XY, 2004, Ultrasound image-based computer model of a common carotid artery with a plaque, MEDICAL ENGINEERING & PHYSICS, Vol: 26, Pages: 823-840, ISSN: 1350-4533

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• Citations: 29

Glor FP, Ariff B, Hughes AD, Verdonck PR, Barratt DC, Augst AD, Thom SAM, Xu XYet al., 2004, Influence of head position on carotid hemodynamics in young adults, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 287, Pages: H1670-H1681, ISSN: 0363-6135

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• Citations: 24

Augst A, Ariff B, Barratt D, Thom SAM, Xu XY, Hughes ADet al., 2004, Blood pressure not shear stress is related to intima-media thickness (IMT) over the entire carotid bifurcation, 9th Annual Meeting of the European Council for Cardiovascular Research, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: 566-566, ISSN: 0194-911X

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Hughes A, Ariff B, Stanton A, Xu Y, Sever P, Thom Set al., 2004, Differential efects of antihypertensive drugs on vascular structure, 14th European Meeting on Hypertension, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: S201-S201, ISSN: 0263-6352

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Ariff B, Zambanini A, Sarita V, Barratt D, Xu Y, Sever P, Chaturvedi N, Stanton A, Thom S, Hughes Aet al., 2004, Hemodynamic determinants of carotid artery structure in essential hypertension, 19th Annual Scientific Meeting of the American-Society-of-Hypertension, Publisher: ELSEVIER SCIENCE INC, Pages: 131A-132A, ISSN: 0895-7061

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Marshall I, Zhao SZ, Papathanasopoulou P, Hoskins P, Xu XYet al., 2004, MRI and CFD studies of pulsatile flow in healthy and stenosed carotid bifurcation models, JOURNAL OF BIOMECHANICS, Vol: 37, Pages: 679-687, ISSN: 0021-9290

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• Citations: 169

Wood NB, Xu XY, 2004, Turbulence in stenoses: Survey and early numerical results, 4th International Conference on Fluid Mechanics, Publisher: TSINGHUA UNIVERSITY PRESS, Pages: 641-644

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• Citations: 1