Imperial College London

Professor Xiao Yun Xu

Faculty of EngineeringDepartment of Chemical Engineering

Professor, Biofluid Mechanics & Director of Graduate School
 
 
 
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Contact

 

yun.xu Website

 
 
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Location

 

407ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

242 results found

Liu D, Wood NB, Witt N, Hughes AD, Thom SA, Xu XYet al., 2012, Assessment of Energy Requirement for the Retinal Arterial Network in Normal and Hypertensive Subjects, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 134, ISSN: 0148-0731

Journal article

Foin N, Toni R, Mortier P, De Beule M, Viceconte N, Chan PH, Davies JE, Xu XY, Krams R, Di Mario Cet al., 2012, Kissing Balloon or Sequential Dilation of the Side Branch and Main Vessel for Provisional Stenting of Bifurcations Lessons From Micro-Computed Tomography and Computational Simulations, JACC-CARDIOVASCULAR INTERVENTIONS, Vol: 5, Pages: 47-56, ISSN: 1936-8798

Journal article

Borghi A, Wood NB, Mohiaddin RH, Xu XYet al., 2012, Computational analysis of flow and stress patterns in patient specific thoracic aortic aneurysm models, Lecture Notes in Computational Vision and Biomechanics, Pages: 133-159

© 2012, Springer Science+Business Media Dordrecht. Thoracic Aortic Aneurysms (TAAs) are associated with low frequency in a given population but high mortality rate. No reliable surgical criterion is available at present but internal wall stress has proved to be more reliable as a predictor of rupture than the maximum diameter in case of Abdominal Aortic Aneurysms (AAAs). However, few studies have been reported on the role of biomechanical factors in the development and rupture of TAAs. This chapter describes a computational mechanics model of TAA based on patient-specific anatomical and flow conditions, acquired from Magnetic Resonance Imaging (MRI). The model has been applied to five patients with TAAs at different locations of the aorta. The results showed no correlation between peak stress and aneurysm size such as the maximum diameter. The effects of intra-luminal thrombus (ILT) and its mechanical properties on wall stress patterns were investigated. It has been found that the shape, size and location of ILT have a significant effect on wall stress patterns. Peak stress calculated using a fully coupled fluid-structure interaction simulation was similar to that predicted by a static solid simulation, in agreement with previous studies of AAA. The work presented here serves as a first step towards developing a reliable predictive tool to allow improved prognosis and surgical decision making for TAA patients.

Book chapter

Xu XY, Sun N, Liu D, Wood NBet al., 2012, Patient-Specific Analysis of Blood Flow and Mass Transport in Small and Large Arteries, Studies in Mechanobiology, Tissue Engineering and Biomaterials, Pages: 189-215

© 2011, Springer-Verlag Berlin Heidelberg. Recent advances in medical image-based computational modelling have made it possible for patient-specific analysis of blood flow and mass transport in the circulation. In this chapter, we describe mathematical models for (1) flow and transport of macromolecules in large arteries, and (2) flow and oxygen delivery in an arteriolar network. Detailed examples are given of mass transport in specific cases, including applications to atherosclerotic arteries and microvascular network. The first example shows transport of a large molecule, low-density lipoprotein, in a human right coronary artery with a mild stenosis, whilst the second is about a small dissolved molecule, oxygen, in an abdominal aortic aneurysm illustrating the effect of intraluminal thrombus. Finally, the additional effects of non-Newtonian properties of blood and haemoglobin-bound oxygen on oxygen transport in the retinal arteriolar network of normal and hypertensive subjects are described. Patient-specific geometries obtained by means of a variety of imaging techniques are used in these examples.

Book chapter

Liu C, Krishnan J, Xu X-Y, 2012, An investigation of effects of drugs on solid tunmours within a systems-based mathematical modelling framework, Innovative simulation methods in healthcare

Conference paper

Tan FPP, Xu XY, Torii R, Wood NB, Delahunty N, Mullen M, Moat N, Mohiaddin Ret al., 2012, Comparison of Aortic Flow Patterns Before and After Transcatheter Aortic Valve Implantation, Cardiovascular Engineering and Technology, Vol: 3, Pages: 123-135

Abstract—Little is known of the likely changes in blood flowvelocity profiles and aortic wall shear stress (WSS) followingtranscatheter aortic valve implantation (TAVI). The objectiveof this study was to investigate the effects of TAVI onflow patterns in the thoracic aorta by using cardiovascularmagnetic resonance imaging (CMR) and computational fluiddynamics (CFD). An elderly patient with aortic stenosis wasexamined using MRI pre- and post-TAVI, and CFDsimulations were carried out incorporating MRI-derivedpatient-specific anatomy and upstream flow conditions. Pre-TAVI velocity profiles demonstrated the highly disturbedturbulent flow and jet impacting the wall of the arch owing tothe partial opening of the stenosed aortic valve, with likelypathological effects. In the Post-TAVI aorta, velocity profileswere similar to those of healthy aortas with spatially moreuniform WSS and lower turbulence levels, demonstrating thefavourable effects of the TAVI procedure in restoring normalaortic flow. This study has shown both the effectiveness ofTAVI on an individual patient and the advantage of thecombined CMR and CFD method for a comprehensivepatient-specific assessment of pre- and post-TAVI aortic flowpatterns and WSS over CMR alone.

Journal article

Pierce IT, Gatehouse PD, Kalodiki E, Lattimer C, Geroulakos G, Xu XY, Firmin DNet al., 2012, Magnetic resonance venous velocity mapping during intermittent pneumatic compression of the calf and foot, Phlebology, Vol: 27, Pages: 352-359

Journal article

Zhang X, Luckham PF, Hughes AD, Thom S, Xu XYet al., 2011, Development of lysolipid-based thermosensitive liposomes for delivery of high molecular weight proteins, INTERNATIONAL JOURNAL OF PHARMACEUTICS, Vol: 421, Pages: 291-292, ISSN: 0378-5173

Journal article

Liu C, Krishnan J, Xu XY, 2011, A systems-based mathematical modelling framework for investigating the effect of drugs on solid tumours, THEORETICAL BIOLOGY AND MEDICAL MODELLING, Vol: 8, ISSN: 1742-4682

Journal article

Su J, Gu Z, Xu XY, 2011, Discrete element simulation of particle flow in arbitrarily complex geometries, CHEMICAL ENGINEERING SCIENCE, Vol: 66, Pages: 6069-6088, ISSN: 0009-2509

Journal article

Foin N, Torii R, Mortier P, De Beule M, Viceconte N, Davies JE, Xu XY, Krams R, Di Mario Cet al., 2011, Sequential Side Branch and Main Vessel Dilatation instead of Kissing Balloon after Provisional Bifurcation Stenting: Lessons from Micro-CT and Computational Simulations, 23rd Annual Transcatheter Cardiovascular Therapeutics (TCT) Symposium, Publisher: ELSEVIER SCIENCE INC, Pages: B82-B82, ISSN: 0735-1097

Conference paper

Pierce IT, Gatehouse PD, Xu XY, Firmin DNet al., 2011, MR Phase-Contrast Velocity Mapping Methods for Measuring Venous Blood Velocity in the Deep Veins of the Calf, JOURNAL OF MAGNETIC RESONANCE IMAGING, Vol: 34, Pages: 634-644, ISSN: 1053-1807

Journal article

Liu C, Krishnan J, Stebbing J, Xu XYet al., 2011, Use of mathematical models to understand anticancer drug delivery and its effect on solid tumors, PHARMACOGENOMICS, Vol: 12, Pages: 1337-1348, ISSN: 1462-2416

Journal article

Tan FPP, Wood NB, Tabor G, Xu XYet al., 2011, Comparison of LES of Steady Transitional Flow in an Idealized Stenosed Axisymmetric Artery Model With a RANS Transitional Model, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 133, ISSN: 0148-0731

Journal article

Malkawi AH, Hinchliffe RJ, Xu XY, Pirianov G, Tornsey E, Loftus IM, Cockerill G, Thompson MMet al., 2011, Lamin A/C over- expression at regions exposed to high wall stress; A novel, mechano-sensitive pathway in abdominal aortic aneurysm (AAA) pathogenesis, Annual Meeting of the Society-of-Academic-and-Research-Surgery, Publisher: WILEY-BLACKWELL, Pages: 35-36, ISSN: 0007-1323

Conference paper

Starmans-Kool MJ, Stanton AV, Xu YY, Thom SAM, Parker KH, Hughes ADet al., 2011, High dietary salt intake increases carotid blood pressure and wave reflection in normotensive healthy young men, JOURNAL OF APPLIED PHYSIOLOGY, Vol: 110, Pages: 468-471, ISSN: 8750-7587

Journal article

Ariff BB, Glor FP, Crowe L, Xu XY, Vennart W, Firmin DN, Thom SM, Hughes ADet al., 2010, Carotid Artery Hemodynamics: Observing Patient-specific Changes with Amlodipine and Lisinopril by Using MR Imaging Computation Fluid Dynamics, RADIOLOGY, Vol: 257, Pages: 662-669, ISSN: 0033-8419

Journal article

Malkawi AH, Hinchliffe RJ, Xu XY, Pirianov G, Torsney E, Loftus IM, Cockerill GW, Thompson MMet al., 2010, Lamin A/C Overexpression at Regions Exposed to High Wall Stress: A Novel, Mechanosensitive Pathway in Abdominal Aortic Aneurysm (AAA) Pathogenesis, Scientific Sessions on Arteriosclerosis, Thrombosis and Vascular Biology, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: E233-E233, ISSN: 1079-5642

Conference paper

Makris GC, Nicolaides AN, Xu XY, Geroulakos Get al., 2010, Introduction to the biomechanics of carotid plaque pathogenesis and rupture: review of the clinical evidence, BRITISH JOURNAL OF RADIOLOGY, Vol: 83, Pages: 729-735, ISSN: 0007-1285

Journal article

Malkawi AH, Hinchliffe RJ, Xu Y, Holt PJ, Loftus IM, Thompson MMet al., 2010, Patient-specific biomechanical profiling in abdominal aortic aneurysm development and rupture, JOURNAL OF VASCULAR SURGERY, Vol: 52, Pages: 480-488, ISSN: 0741-5214

Journal article

Rosell DR, Thompson JL, Slifstein M, Xu X, Frankle WG, New AS, Goodman M, Weinstein SR, Laruelle M, Abi-Dargham A, Siever LJet al., 2010, Increased Serotonin 2A Receptor Availability in the Orbitofrontal Cortex of Physically Aggressive Personality Disordered Patients, BIOLOGICAL PSYCHIATRY, Vol: 67, Pages: 1154-1162, ISSN: 0006-3223

Journal article

Sakalihasan N, Defraigne JO, Xu XY, 2010, Response to Comment on "High Levels of 18F-FG Uptake in Aortic Aneurysm Wall are Associated with High Wall Stress", EUROPEAN JOURNAL OF VASCULAR AND ENDOVASCULAR SURGERY, Vol: 39, Pages: 795-796, ISSN: 1078-5884

Journal article

Cheng Z, Tan FPP, Riga CV, Bicknell CD, Hamady MS, Gibbs RGJ, Wood NB, Xu XYet al., 2010, Analysis of Flow Patterns in a Patient-Specific Aortic Dissection Model, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 132, ISSN: 0148-0731

Journal article

Xu XY, Borghi A, Nchimi A, Leung J, Gomez P, Cheng Z, Defraigne JO, Sakalihasan Net al., 2010, High Levels of 18F-FDG Uptake in Aortic Aneurysm Wall are Associated with High Wall Stress, EUROPEAN JOURNAL OF VASCULAR AND ENDOVASCULAR SURGERY, Vol: 39, Pages: 295-301, ISSN: 1078-5884

Journal article

Malkawi A, Cheng Z, Hinchliffe R, Loftus I, Xu Y, Thompson Met al., 2010, Abdominal aortic aneurysm (AAA) wall thickness at regions of high and low wall stress: implications for aortic wall stress computation and rupture prediction, 44th Annual Scientific Meeting of the Vascular-Society-of-Great-Britain-and-Ireland, Publisher: WILEY-BLACKWELL, Pages: 15-15, ISSN: 0007-1323

Conference paper

Xu Y, McCormack A, Chester A, Hariri B, Sarathchandra P, Rose MLet al., 2010, The Indirect Alloimmune Response Causes Endothelial Dysfunction without Endothelial Replacement after Cardiac Transplantation, 30th Annual Meeting and Scientific Sessions of the International-Society-for-Heart-and-Lung-Transplantation, Publisher: ELSEVIER SCIENCE INC, Pages: S129-S129, ISSN: 1053-2498

Conference paper

Su JW, Gu ZL, Jiao JY, Xu XYet al., 2010, Local fixed pivot quadratue method of moment for bubble population balance equation including coalescence and breakage, 6TH INTERNATIONAL SYMPOSIUM ON MULTIPHASE FLOW, HEAT MASS TRANSFER AND ENERGY CONVERSION, Vol: 1207, Pages: 610-+, ISSN: 0094-243X

Journal article

Torii R, Keegan J, Wood NB, Dowsey AW, Hughes AD, Yang G-Z, Firmin DN, Thom SA, Xu Yet al., 2010, MR image-based geometric and hemodynamic investigation of the right coronary artery withdynamic vessel motion, Annals of Biomedical Engineering, Vol: in press

The aim of this study was to develop a fully subject-specific model of the right coronaryartery (RCA), including dynamic vessel motion, for computational analysis to assess the effects ofcardiac-induced motion on hemodynamics and resulting wall shear stress (WSS). Vascular geometrieswere acquired in the right coronary artery (RCA) of a healthy volunteer using a navigator-gatedinterleaved spiral sequence at 14 time points during the cardiac cycle. A high temporal resolutionvelocity waveform was also acquired in the proximal region. Cardiac-induced dynamic vessel motionwas calculated by interpolating the geometries with an active contour model and a CFD simulationwith fully subject-specific information was carried out using this model. The results showed theexpected variation of vessel radius and curvature throughout the cardiac cycle, and also revealed thatdynamic motion of the right coronary artery consequent to cardiac motion had significant effects oninstantaneous WSS and oscillatory shear index (OSI). Subject specific MRI-based CFD is feasible and, ifscan duration could be shortened, this method may have potential as a non-invasive tool to investigatethe physiological and pathological role of hemodynamics in human coronary arteries.

Journal article

Soloperto G, Keenan NG, Sheppard MN, Ohayon J, Wood NB, Pennell DJ, Mohiaddin RH, XY Xet al., 2010, Combined imaging, computational and histological analysis of a ruptured carotid plaque: A patient-specific analysis., Artery Research, Vol: 4, Pages: 59-65

Background: Rupture of carotid plaques is an important cause of cerebrovascularevents. Several factors, including wall shear stress (WSS), plaque morphology and peak capstress, have been associated with plaque vulnerability. The aim of this study was to investigatethe relationship between these factors in an in vivo human ruptured carotid plaque.Methods: A 74-year-old male presenting with a transient ischemic attack underwent carotidmagnetic resonance imaging (MRI), which indicated a ruptured plaque, followed by carotidendarterectomy, from which plaque histology was assessed. The carotid bifurcation was reconstructedfrom the MRI data, and three-dimensional flow simulations were performed usingcomputational fluid dynamics to determine WSS and related parameters. Plaque vulnerabilitywas assessed using a biomechanical method based on modified Glagov criteria.Results: The plaque rupture was just distal to the site of maximum stenosis in a region of lowWSS, where MRI and histology both demonstrated fibrous cap thinning, a large lipid pool andcalcification in the shoulder region. Plaque vulnerability analysis indicated critically vulnerableplaque at the rupture site by a wide margin.Conclusions: Both low and high WSS have been associated with plaque vulnerability, and highmechanical stress in the cap has been linked to plaque rupture, but these parameters are notroutinely assessed clinically. This study demonstrates a complete analysis by combiningimaging, histology and bio-fluid and biomechanical modelling.

Journal article

Soloperto G, Keenan N, Sheppard M, Wood N, Pennell DJ, Mohiaddin R, Xu XYet al., 2009, A COMBINED IMAGING, COMPUTATIONAL AND HISTOLOGICAL ANALYSIS OF A RUPTURED CAROTID ARTERY, Spring Meeting of the British-Society-for-Cardiovascular-Research, Publisher: B M J PUBLISHING GROUP, ISSN: 1355-6037

Conference paper

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