J. Beech-Brandt

The University of Edinburgh, Edinburgh, Scotland, United Kingdom

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Publications (13)8.25 Total impact

  • M.X. Li · J.J. Beech-Brandt · L.R. John · P.R. Hoskins · W.J. Easson ·
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    ABSTRACT: Hemodynamics factors and biomechanical forces play key roles in atherogenesis, plaque development and final rupture. In this paper, we investigated the flow field and stress field for different degrees of stenoses under physiological conditions. Disease is modelled as axisymmetric cosine shape stenoses with varying diameter reductions of 30%, 50% and 70%, respectively. A simulation model which incorporates fluid-structure interaction, a turbulence model and realistic boundary conditions has been developed. The results show that wall motion is constrained at the throat by 60% for the 30% stenosis and 85% for the 50% stenosis; while for the 70% stenosis, wall motion at the throat is negligible through the whole cycle. Peak velocity at the throat varies from 1.47 m/s in the 30% stenosis to 3.2m/s in the 70% stenosis against a value of 0.78 m/s in healthy arteries. Peak wall shear stress values greater than 100 Pa were found for > or =50% stenoses, which in vivo could lead to endothelial stripping. Maximum circumferential stress was found at the shoulders of plaques. The results from this investigation suggest that severe stenoses inhibit wall motion, resulting in higher blood velocities and higher peak wall shear stress, and localization of hoop stress. These factors may contribute to further development and rupture of plaques.
    Journal of Biomechanics 01/2007; 40(16):3715-24. DOI:10.1016/j.jbiomech.2007.06.023 · 2.75 Impact Factor
  • M. Li · J. Beech-Brandt · L. R. John · P. R. Hoskins · W. J. Easson ·

    Journal of Biomechanics 12/2006; 39. DOI:10.1016/S0021-9290(06)84791-3 · 2.75 Impact Factor
  • S. J. Hammer · T. J. MacGillivray · W. T. Lee · J. J. Beech-Brandt · W. J. Easson · P. R. Hoskins ·

    Journal of Biomechanics 01/2006; 39. DOI:10.1016/S0021-9290(06)85560-0 · 2.75 Impact Factor
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    ABSTRACT: Background 3D ultrasound (3D US) has been used in imaging research and clinical practice for several years. Wall shear stress (WSS) - the viscous drag of blood on the arterial wall - is implicated in the initiation of arterial disease. This study is concerned with estimation of WSS using an image guided modelling approach. Methods Image guided modelling. This approach uses a computational model of blood flow to estimate the 3D time varying flow field from which WSS may be estimated. This requires the 3D vessel geometry and input flow waveforms as boundary conditions. 3D ultrasound. Stradwin 3D US software developed by Prager et al (Cambridge), along with an optical sensor, a Philips HDI5000 US scanner, and a PC with a video capture card was used to capture freehand 3D US data. The scans were ECG gated near end-diastole. Segmentation. Carotid surface geometries were obtained using registration based segmentation, using software developed by Barber et al (Sheffield). This requires specification of a template 3D carotid surface geometry. Patient or volunteer datasets are registered with the template to produce a 3D displacement vector map. The segmented geometry is found by morphing the template using the displacement map. A single volunteer was scanned 5 times and an average 3D dataset created to create the template. Input and output velocity data. Spectral waveforms were obtained from the common, internal and external carotid arteries. Computational modelling. The segmented artery geometry was imported into Fluent computational fluid dynamics (CFD) software, along with mean velocity input and output boundary conditions. 3D time varying blood flow was estimated from which WSS was estimated. Results Typical results will be presented showing wall shear stress estimates in healthy volunteers. Conclusions This study demonstrates the feasibility of obtaining WSS in healthy volunteers using an image guided modelling approach with 3D ultrasound imaging.
    37th Annual Scientific Meeting of the British Medical Ultrasound Society; 01/2005
  • Source
    C. Chen · T.L. Poepping · J.J. Beech-Brandt · S.J. Hammer · R. Baldock · B. Hill · P. Allan · W.J. Easson · P.R. Hoskins ·
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    ABSTRACT: A method for segmentation of arteries in ultrasound B-mode images using a modified balloon model is presented. The external force which pulls the contour to the arterial boundary is the combination of the gradient and the second order derivative of the image. For 3D segmentation the contour of the first slice is found, and this is used as the initial position for the next slice. As the initial position of the contour may be outside the artery, the pressure term is decided by comparing the feature of texture inside and outside of the contour, allowing the contour to expand or shrink. The model has been tested on 55 images from carotid arteries. The 'gold standard' boundary drawn by a radiologist and the segmented boundary showed an average difference of 0.40±0.30mm. 3D data was obtained using an anatomically correct carotid bifurcation flow phantom and gridded ready for CFD.
    Biomedical Imaging: Nano to Macro, 2004. IEEE International Symposium on; 05/2004
  • S.J. Hammer · J. Beech-Brandt · C. Chen · T.L. Poepping · W.J. Easson · P.R. Hoskins ·
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    ABSTRACT: A 3D Ultrasound (US) phantom scanning device has been developed to provide calibration data for image processing and computational fluid dynamics (CFD) as part of a study into the biomechanical status of diseased arteries in vivo. The cartesian scanning system moves a conventional US probe from a Philips HDI5000 US scanner over the upper surface of the phantom. The device can scan phantoms of up to 150 mm long and 75 mm wide. The transducer can be rotated about two axes and translated in one axis manually. X and Y planar movements are made automatically. Control is provided by a labVIEW based control program and a Parker L25i stepper motor driver system. scalar and rotary positional accuracies are ±50μm and ±0.1° respectively.
    Engineering in Medicine and Biology Society, 2003. Proceedings of the 25th Annual International Conference of the IEEE; 10/2003
  • J. Beech-Brandt · C. Chen · S. J Hammer · T. L Poepping · W. J Easson · P. R Hoskins ·

    Symposium on Modelling of Physiological Flows; 01/2003
  • J. Beech-Brandt · C. Chen · S. J Hammer · T. L Poepping · W. J Easson · P. R Hoskins ·

    Physical, Mathematical, and Numerical Modelling of Blood Flow in Cardiovascular Disease; 01/2003
  • T. L Poepping · S. Meagher · J. Beech-Brandt · C. Chen · S. J Hammer · W. J Easson · P. R Hoskins ·

    The 12th New England Doppler Conference; 01/2003
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    ABSTRACT: Background In order to create 3D artery geometries for computer simulation of artery flow and movement, geometry data must be recorded from flow phantom studies. An accurate and repeatable method of scanning the geometries must therefore be developed. Aim To design and test a 3D ultrasound scanner for use on flow phantoms, in order to record geometry, blood flow, and tissue movement data for use in computer simulations of artery behaviour. Methods A Cartesian scanning system was adopted to move a conventional ultrasound transducer over the upper surface of the test phantom. Two stepper-motor driven linear positioners move the transducer automatically over the phantom in two planes. The transducer can also be rotated manually about its central axis and about the axis of the end where it contacts the top of the phantom. The linear positioners are held above the flow phantom, and the transducer is fixed beneath them. A LabVIEW based control program drives the stepper motors and records positional data. This is linked to US images captured using HDILab software from colour Doppler, tissue Doppler and B-mode scans. These will be taken from a fixed point over a cardiac cycle simulated using the pump controller for the flow phantom and defined using the ECG input of the ultrasound scanner. Multiple scans are taken at different positions along the phantom geometry, and at a range of angles in order to provide sufficient data for a full 3D representation of the flow. Results The design and assembly of the scanner is at an advanced stage. Examples of the data sets created by the device will be presented at the meeting. Conclusions A 3D US scanner for flow phantoms has been developed to provide geometry, blood flow, and tissue movement data for artery simulation. The stepper-driven scanner allows transducer movement in two planes and rotations about two axes. Data sets produced by the scanner will be presented at the meeting.
    IPEM The Physics and Technology of Medical Ultrasound Biennial Meeting; 01/2003
  • C. Chen · P. R Hoskins · W. J Easson · T. L Poepping · S. J Hammer · J. Beech-Brandt ·

    IPEM Physics and Technology of Medical Ultrasound; 01/2003
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    ABSTRACT: Intro: We are developing ultrasound image guided modelling for improved prediction of atherosclerotic plaque and of aneurysmal disease. Initial work involves development of a 3D system for in-vitro flow models to investigate accuracy of estimated quantities. Methods: Two linear positioners hold the ultrasound (HDI5000) transducer above the flow phantom. The transducer holder allows manual rotation of the transducer about two axes, and vertical movement in one axis, giving five degrees of freedom. The ability to adjust probe orientation allows estimation of blood and tissue velocities in different directions, allowing accurate velocity estimation using vector Doppler techniques. The positioners and the ultrasound scanner are automatically controlled using a user-friendly LabVIEW-based control program. Positional data from the control program is linked to US images from colour Doppler, tissue Doppler and B-mode scans captured using HDILab software. 3D ultrasound data has been acquired from anatomical carotid flow models with internal carotid stenosis. Several 3D data sets are collected from each model, with a full 'cardiac' cycle collected at each site, requiring gating to the flow waveform: 1 transverse set for B-mode imaging, 2 transverse and 2 longitudinal colour flow sets for blood velocity estimation, and 2 transverse and 2 longitudinal TDI sets for tissue velocity estimation. This provides all of the input information required by computational modelling. Results: 3D datasets can be collected of size 15 by 5 by 10 cm which is suitable for the carotid flow models. For 0.5 mm spacing the B-mode scan time is 5 minutes. For data collection involving B-mode, colour flow and TDI the collection time is 20 minutes, compared to 15-45 minutes for 3D MRI studies. Discussion: The system is easy to use providing the flexibility needed for 3D data collection in-vitro. The experience gained will be use to design an in-vivo 3D collection system.
    35th Annual Scientific Meeting of the British Medical Ultrasound Society; 01/2003
  • Source
    K H Fraser · P R Hoskins · W J Easson · J J Beech-Brandt · M Li ·

Publication Stats

71 Citations
8.25 Total Impact Points

Top Journals


  • 2003-2007
    • The University of Edinburgh
      • • Department of Medical Physics and Medical Engineering
      • • Institute for Materials and Processes (IMP)
      Edinburgh, Scotland, United Kingdom