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  • Journal article
    Moraldo M, Bergamini C, Malaweera ASN, Dhutia NM, Pabari PA, Willson K, Baruah R, Manisty C, Davies JE, Xu XY, Hughes AD, Francis DPet al., 2013,

    A novel fully automated method for mitral regurgitant orifice area quantification

    , International Journal of Cardiology, Vol: 166, Pages: 688-695, ISSN: 1874-1754

    Background: Effective regurgitant orifice area (EROA) in mitral regurgitation (MR) is difficult to quantify.Clinically it is measured using the proximal isovelocity surface area (PISA) method, which is intrinsicallynot automatable, because it requires the operator to manually identify the mitral valve orifice. We introducea new fully automated algorithm, (“AQURO”), which calculates EROA directly from echocardiographic colourM-mode data, without requiring operator input.Methods: Multiple PISA measurements were compared to multiple AQURO measurements in twenty patientswith MR. For PISA analysis, three mutually blinded observers measured EROA from the four stored videoloops. For AQURO analysis, the software automatically processed the colour M-mode datasets and analysedthe velocity field in the flow-convergence zone to extract EROA directly without any requirement for manualradius measurement.Results: Reproducibility, measured by intraclass correlation (ICC), for PISA was 0.80, 0.83 and 0.83 (for 3 observersrespectively). Reproducibility for AQURO was 0.97. Agreement between replicate measurements calculatedusing Bland-Altman standard deviation of difference (SDD) was 21,17 and 17mm2for the threerespective observers viewing independent video loops using PISA. Agreement between replicate measurementsfor AQURO was 6, 5 and 7mm2for automated analysis of the three pairs of datasets.Conclusions: By eliminating the need to identify the orifice location, AQURO avoids an important source ofmeasurement variability. Compared with PISA, it also reduces the analysis time allowing analysis and averagingof data from significantly more beats, improving the consistency of EROA quantification.AQURO, being fully automated, is a simple, effective enhancement for EROA quantification using standardechocardiographic equipment.

  • Conference paper
    Zhan W, Gedroyc W, Xu X, 2013,

    Computational Study of Drug Transport in Realistic Models of Solid Tumour

    , Mathways into Cancer II
  • Journal article
    Wang Y, Downie S, Wood N, Firmin D, Xu XYet al., 2013,

    Finite element analysis of the deformation of deep veins in the lower limb under external compression

    , MEDICAL ENGINEERING & PHYSICS, Vol: 35, Pages: 515-523, ISSN: 1350-4533
  • Journal article
    Cheng Z, Riga C, Chan J, Hamady M, Wood NB, Cheshire NJW, Xu Y, Gibbs RGJet al., 2013,

    Initial findings and potential applicability of computational simulation of the aorta in acute type B dissection

    , JOURNAL OF VASCULAR SURGERY, Vol: 57, Pages: 35S-43S, ISSN: 0741-5214
  • Journal article
    Kousera CA, Wood NB, Seed WA, Torii R, O'Regan D, Xu XYet al., 2013,

    A Numerical Study of Aortic Flow Stability and Comparison With In Vivo Flow Measurements

  • Journal article
    Liu C, Krishnan J, Xu X-Y, 2013,

    Investigating the effects of ABC-transporter mediated acquired drug resistance mechanisms at the cell and tissue scale

    , Integrative Biology
  • Journal article
    Zhan W, Xu XY, 2013,

    A mathematical model for thermosensitive liposomal delivery of Doxorubicin to solid tumour.

    , J Drug Deliv, Vol: 2013, ISSN: 2090-3014

    The effectiveness of anticancer treatments is often hampered by the serious side effects owing to toxicity of anticancer drugs and their undesirable uptake by healthy cells in vivo. Thermosensitive liposome-mediated drug delivery has been developed as part of research efforts aimed at improving therapeutic efficacy while reducing the associated side effect. Since multiple steps are involved in the transport of drug-loaded liposomes, drug release, and its uptake, mathematical models become an indispensible tool to analyse the transport processes and predict the outcome of anticancer treatment. In this study, a computational model is developed which incorporates the key physical and biochemical processes involved in drug delivery and cellular uptake. The model has been applied to idealized tumour geometry, and comparisons are made between continuous infusion of doxorubicin and thermosensitive liposome-mediated delivery. Results show that thermosensitive liposome-mediated delivery performs better in reducing drug concentration in normal tissues, which may help lower the risk of associated side effects. Compared with direct infusion over a 2-hour period, thermosensitive liposome delivery leads to a much higher peak intracellular concentration of doxorubicin, which may increase cell killing in tumour thereby enhancing the therapeutic effect of the drug.

  • Journal article
    Moraldo M, Cecaro F, Shun-Shin M, Pabari P, Davies JE, Xu XY, Hughes AD, Manisty C, Francis DPet al., 2012,

    Evidence-based recommendations for PISA measurements in mitral regurgitation: systematic review, clinical and in-vitro study

    , Iinternational Journal of Cardiology

    BackgroundGuidelines for quantifying mitral regurgitation (MR) using “proximal isovelocity surface area” (PISA) instruct operators to measure the PISA radius from valve orifice to Doppler flow convergence “hemisphere”. Using clinical data and a physically-constructed MR model we (A) analyse the actually-observed colour Doppler PISA shape and (B) test whether instructions to measure a “hemisphere” are helpful.Methods and resultsIn part A, the true shape of PISA shells was investigated using three separate approaches. First, a systematic review of published examples consistently showed non-hemispherical, “urchinoid” shapes. Second, our clinical data confirmed that the Doppler-visualized surface is non-hemispherical. Third, in-vitro experiments showed that round orifices never produce a colour Doppler hemisphere.In part B, six observers were instructed to measure hemisphere radius rh and (on a second viewing) urchinoid distance (du) in 11 clinical PISA datasets; 6 established experts also measured PISA distance as the gold standard. rh measurements, generated using the hemisphere instruction significantly underestimated expert values (−28%, p<0.0005), meaning rh2 was underestimated by approximately 2-fold. du measurements, generated using the non-hemisphere instruction were less biased (+7%, p=0.03).Finally, frame-to-frame variability in PISA distance was found to have a coefficient of variation (CV) of 25% in patients and 9% in in-vitro data. Beat-to-beat variability had a CV of 15% in patients.ConclusionsDoppler-visualized PISA shells are not hemispherical: we should avoid advising observers to measure a hemispherical radius because it encourages underestimation of orifice area by approximately two-fold. If precision is needed (e.g. to detect changes reliably) multi-frame averaging is essential.

  • Conference paper
    Zhan W, Gedroyc W, Xu X, 2012,

    Computational Study of Drug Transport in Realistic Models of Solid Tumour

    , AIChE Annual Conference
  • Journal article
    Liu X, Fan Y, Xu XY, Deng Xet al., 2012,

    Nitric oxide transport in an axisymmetric stenosis

    , JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 9, Pages: 2468-2478, ISSN: 1742-5689
  • Journal article
    Paopo I, Xu XY, Mantalaris A, 2012,

    Differentiation of murine embryonic stem cells (mESCs) into type II pneumocytes in a 3D sparged bioreactor

  • Journal article
    Massai D, Soloperto G, Gallo D, Xu XY, Morbiducci Uet al., 2012,

    Shear-induced platelet activation and its relationship with blood flow topology in a numerical model of stenosed carotid bifurcation

    , EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 35, Pages: 92-101, ISSN: 0997-7546
  • Journal article
    Torii R, El-Hamamsy I, Donya M, Babu-Narayan SV, Ibrahim M, Kilner PJ, Mohiaddin RH, Xu XY, Yacoub MHet al., 2012,

    Integrated morphologic and functional assessment of the aortic root after different tissue valve root replacement procedures

    , JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY, Vol: 143, Pages: 1422-+, ISSN: 0022-5223
  • Conference paper
    Foin N, Torii R, Mortier P, De Beule M, Xu Y, Davies J, Di Mario Cet al., 2012,


    , 61st Annual Scientific Session and Expo of the American-College-of-Cardiology (ACC), Publisher: ELSEVIER SCIENCE INC, Pages: E87-E87, ISSN: 0735-1097
  • Conference paper
    Prapa S, Mccarthy KP, Kilner PJ, Xu XY, Johnson MR, Ho SY, Gatzoulis MAet al., 2012,

    Biomechanical perspectives of thoracic aortic aneurysm formation in patients with a bicuspid aortic valve: an integrated analysis

    , 2nd Congress of the European-Society-of-Cardiology Council on Basic Cardiovascular Science - Frontiers in Cardiovascular Biology, Publisher: OXFORD UNIV PRESS, Pages: S86-S86, ISSN: 0008-6363
  • Journal article
    Ma CYJ, Panoskaltsis N, Kumar R, Xu XY, Mantalaris Aet al., 2012,

    Simulation of ex vivo bone marrow culture: Application to chronic myeloid leukaemia growth model

    , BIOCHEMICAL ENGINEERING JOURNAL, Vol: 61, Pages: 66-77, ISSN: 1369-703X
  • Journal article
    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 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
    Wang Y, Pierce I, Gatehouse P, Wood N, Firmin D, Xu XYet al., 2012,

    Analysis of flow and wall shear stress in the peroneal veins under external compression based on real-time MR images

    , MEDICAL ENGINEERING & PHYSICS, Vol: 34, Pages: 17-27, ISSN: 1350-4533
  • Conference paper
    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

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