This workshop was held not only for scientific exchanges but also in the spirit of answering calls of the 7th Framework Programme of the European Union, largely open to non-EU countries. The workshop comprised four scientific sessions, a set of tutorials aimed at introducing students to the use of applied mathematics and engineering science in health problems, and a discussion on defining proposals for research grants.

Presentations
Michael Tzu-Ming Chang (Department of Surgery, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan) gave a presentation on stomach dynamics and surgical design for gastric bypasses used to treat strong obesity with lethal risk. Flow dynamics and coordinated motions between stomach parts must be retained to optimize surgical procedures. Individualized simulations of gastric kinetic patterns will be useful for clinical practice.

André Garon (Département Génie Mécanique de l'Ecole Polytechnique de Montréal) talked about the design and optimization of a ventricular assist device (VAD) for heart failure. The problem to be solved is: which type of cardiac assist pump is best for a given patient, and how should it be implanted? There are two main types of LVAD – pulsatile and continuous pumps. Continuous flow generates wall remodelling and a higher sensitivity to wall defects.

Michel Delfour (Département Mathématiques and Statistiques and CRM, University of Montréal) spoke on optimal design with illustration by coated stents used to treat arterial stenosis. Academic stent models are used for easy stent geometry description. The notion of dose of SMC proliferation inhibitor rather than concentration is introduced for a coated stent. Asymptotic dose is a simple and valid tool for stent design.

Marc Thiriet (REO team, LJLL, University Pierre et Marie Curie, and INRIA, France) gave a tutorial on biofluid mechanics and on image-based (patient-specific) modelling. Although the blood-flow simulations in any explored segment of the vasculature are carried out in a deformable fluid domain, the numerical results remain questionable because: (1) the in vivo material constants are often unknown, and (2) the vessel wall is assumed to be a more or less passive material. The second part of the presentation was then devoted to modelling that integrates mechanotransduction. The latter phenomenon regulates the size of the fluid computational domain by local short-term regulation of the vasomotor tone.

Yin-Yi Han et al. (National Taiwan University, National Taiwan University Hospital, National Cheng-Kung University and Yuan-Ze University) presented their work on 'Application of Fourier cosine spectrum and spectrogram to analyse artery pulse and ECG data'. This study is aimed at developing robust models for monitoring the adaptation of patients to various procedures and after treatments, such as artificial knee joint replacement, and liver and kidney surgery.

Numerical studies in biomedical applications at the National Center for High-performance Computing (NCHC) in collaboration with Chang Gung Memorial Hospital and National Health Research Institute were presented by Ren-Jieh Shih, and included obstructive apnea; dyspnea from vascular rings, which compress airways; cerebral aneurisms; a simple model of a stenosed deformable vessel with bypass graft; stent expansion and implantation; two dental implants with different fixation designs; computer-assisted construction of a cranioplasty implant; and 3DR of the tracheobronchial tree.

I-Liang Chern et al. (Department of Mathematics, Taida Institute for Mathematical Sciences, National Center for Theoretical Science at Taipei, NTU) proposed a coupling interface method (CIM) under a Cartesian grid for solving elliptic complex interface problems in arbitrary dimensions, where the coefficients, the source terms and the solutions can be discontinuous or singular across the interfaces. He gave a proof of the solvability of the coupling equations.

Hurng-Sheng Wu (Department of Surgery, Show-Chwan Memorial Hospital, Chang-Hua) spoke on new developments in minimally invasive surgery. Robotic and traditional mini-invasive (MIS) surgery is carried out in Taiwan in association with IRCAD (Strasbourg, France). Working through fixed entry points has the disadvantage of limiting the manoeuverability of instruments inside the body cavity. Looking at a two-dimensional screen, surgeons are handicapped by the loss of visual depth perception. These limitations are considered to be the major burdens of laparoscopic surgery for surgeons. A new robotic surgical system that has overcome the limitations of conventional laparoscopic technology can provide surgeons with enhanced visual control and dexterity.

A revisit of counter-pulsation circulation support using hybrid circulation model and wave intensity analysis was presented by Pong-Jeu Lu et al. (Department of Aeronautics and Astronautics, Center for Biomaterials and Heart Science Research, National Cheng Kung University, Tainan, and Cardiovascular Research Center, National Cheng Kung University, Tainan). Counter-pulsation perfusion has been fulfilled using either intra-aortic balloon pump (IABP) or para-aortic blood pump (PABP) to treat various acute and/or chronic heart failure.

Pacemaker efficiency and optimal electrode positioning was discussed by L. El Alaoui and L. Dumas (INRIA REO team) using a model of electrochemical impulses. Though current pacemakers give good results, certain questions still arise: how many electrodes should be set? Where should the electrodes be placed? When should the electrodes act? Such problems can be solved with optimization tools like genetic algorithms.

A. Garon and coworkers (Département Génie Mécanique de l'Ecole Polytechnique de Montréal and INRIA REO team) spoke on a computational model of flow in the carotid artery and its validation using PIV. Flow was steady because of the context of a continuous left ventricle assist device. Steady flow has been investigated for various flow distributions in a carotid artery network with two successive embranchments, the carotid bifurcation and a branching of the external carotid artery. Numerical tests have been carried out using the finite element method (P1-P1 stabilized approximation). A phantom has been built from the surface mesh, and the velocity field has been measured using particle image velocimetry. Numerical and experimental results are in good agreement (see Figure 1).

Figure 1: (left) Numerical steady velocity isocontours in selected cross-sections of a carotid artery network; (right) velocity field measured in the same loci using PIV. The phantom was built by rapid prototyping from the surface mesh of the computational model (study carried out at Ecole Polytechnique de Montréal in the framework of INRIA Associated Team 'CFT').
Figure 1: (left) Numerical steady velocity isocontours in selected cross-sections of a carotid artery network; (right) velocity field measured in the same loci using PIV. The phantom was built by rapid prototyping from the surface mesh of the computational model (study carried out at Ecole Polytechnique de Montréal in the framework of INRIA Associated Team 'CFT').

Guan-Yu Chen and collaborators (Department of Electrical Engineering, National Tsing Hua University, Hsinchu) are developing a model-based 3D and 4D cardiac ultrasound system. Ultrasonic imaging is superior for its real-time observation. A patient's heart can be reconstructed from data obtained by conventional 2D ultrasound with controlled probe motion.

The talk of Ruey-Feng Chang (Department of Computer Science and Information Engineering, Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University) targeted computer-aided diagnosis for breast tumours based on ultrasound imaging: the Breast Imaging Recording and Data System (Bi-RADS) provides shape, orientation, margins, boundaries etc. 2D B-mode echography can be combined with elastography to improve results. 3D ultrasound can display tumour spiculation, blood supply (vessel distribution) and so forth. After using a 3D thinning algorithm, the reconstruction of vascular trees allows certain features to be extracted (eg volume ratio, length, curvature and number of branches).

Catalin Fetita et al. (Artemis team, INT, France) presented a 3DR assessment of airway wall thickness with MDCT for therapy planning and evaluation of novel asthma therapies. An axis-based morpho-topologic description allows cross-sections or regions of interest to be defined for parameter quantification. The Lagrangian motion equation controlling the model evolution is parameterized so as to reach equilibrium at the level of the outer bronchus contour, as well as to handle local wall deformations and blood vessel contact zones.
Jun Feng (Northwest University, China) and Horace Ip (AIMtech Centre, and Department of Computer Science, City University of Hong Kong) spoke on the reconstruction and analysis of medical shapes using Statistical Piecewise Assembled Models (SPAM). Statistical deformable models provide an extensible framework with which to segment and reconstruct shapes from medical and biomedical datasets. The research goal of SPAM is a reconstruction methodology that can hierarchically define the shape and texture structures of highly flexible anatomies, automatically select the landmarks, and robustly build the point correspondence among the training samples.

Chien-Cheng Chang and Po-Hsiang Tsui (Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei, and Institute of Applied Mechanics, National Taiwan University) spoke on local scatterer concentration imaging using the Nakagami statistical model. The ultrasonic B-mode image is used to examine the internal structures of the biological tissue. The Nakagami parameter is able to detect the variation of the scatterer concentration, and thus can be used to assist in the B-mode image for tissue characterization. The Nakagami image can be combined with the use of the B-mode image to simultaneously visualize the tissue structures and the scatterer properties for a better medical diagnosis.

3D medical imaging and its clinical applications in surgery assistance were presented by Beender Yang (Yen Tjing Ling Industrial Research Institute, National Taiwan University). 3D medical content always comprises enormous image data. To deal with this problem, most medical facilities equip their centralized radiology departments with advanced 3D software tools to process 3D medical image data into a series of key planar images for their referring physicians and clinicians.

Adel Blouza and coworkers (Laboratoire de mathématiques of University of Rouen and University Haute-Alsace in Mulhouse, and REO team) delivered a talk on stent optimization. An optimization process is built to seek the best three geometric parameters (strut spacing, strut height and strut width) of a simplified bidimensional stent, which reduces blood vorticity in the fluid to minimize eddy formation and elevates blood vorticity at the wall to minimize particle residence time.

Cheng-Maw Ho and collaborators (Department of Surgery and of Medical Imaging, National Taiwan University Hospital, Department of Engineering Science and Ocean Engineering, NTU, and Department of Marine Engineering, National Taiwan Ocean University) presented their work on simulation and validation of hemodynamic changes after live-donor right hepatectomy. The objectives of this study are to reconstruct the portal vein and its intrahepatic branches to simulate the hemodynamic changes after the resection.

Links:
IM2IM Working Group: http://www-rocq.inria.fr/im2im/

Please contact:
Marc Thiriet, INRIA, France
E-mail: Marc.Thiriet@inria.fr

Next issue: October 2018
Special theme:
Digital Twins
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