Authors: L. Barbé; B. Bayle; M. de Mathelin; A. Gangi

Abstract: Soft tissues modeling is a very present preoccupation in different scientific fields, from computer simulation to biomechanics or medical robotics. In this article, we consider the interaction of a needle with living tissues, which is a particularly complex modeling problem since it is characterized by inhomogeneity and nonlinearity properties. We propose a robust method to online estimate the interaction between living tissues and a surgical needle. The ability to obtain physically consistent models during in vivo insertions is discussed.

Keywords: soft tissue modeling,online robust estimation,in vivo needle insertion

Identifier: 10.3182/20060920-3-FR-2912.00027

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Terence J. Gilhuly; Alex Bouzane; Stephan K. W. Schwarz; Bernard A. MacLeod; Guy A. Dumont

Abstract: In this paper, preliminary results of the Neuromuscular Blockade Advisory System (NMBAS) clinical trial comparing the safety and efficacy of NMBAS to standard care are presented. The NMBAS offers advice to the anesthesiologist on dosing of rocuronium based on measured patient response. The NMBAS is being compared against standard practice in a randomized, controlled clinical trial. The NMBAS uses a sixth order Laguerre model to approximate neuromuscular response and a extended horizon control scheme to predict future levels and needs for NMB agent. Thirty-six patients were tested, thirteen patients in the NMBAS group, eleven in the standard care group and twelve excluded. Patient health and demographics, procedures, drug use, and ability to maintain surgically useful conditions and with easy reversibility were equivalent between the two groups. The incidence of adverse events in the OR showed a marked improvement with the NMBAS. As well, responses measured at reversal and extubation were higher for the NMBAS indicating less chance of post-operative adverse events.

Keywords: advisory system,automated drug delivery,computer controlled drug therapy,Laguerre model,neuromuscular blockade,pharmacokinetics,rocuronium

Identifier: 10.3182/20060920-3-FR-2912.00075

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: M. Barao; J. M. Lemos

Abstract: Using singular perturbation techniques, a nonlinear state-space model of HIV-1 infection, having as state variables the number of healthy and infected CD4+ T cells and the number of virion particles, is simplified and used to design a control law. The control law comprises an inner block that performs feedback linearizing of the virus dynamics and an outer block implementing an LQ regulator that drives the number of virion particles to a number below the specification. A sensitivity analysis of the resulting law is performed.

Keywords: HIV-1,feedback linearizing control,singular perturbations

Identifier: 10.3182/20060920-3-FR-2912.00061

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Valeriu Vrabie; Régis Huez; Cyril Gobinet; Olivier Piot; Ali Tfayli; Michel Manfait

Abstract: Raman spectroscopy is employed to record spectra which highlight vibrational information of biological structures. These spectra provide useful information about molecular composition of a tissue. However, the tissues are usually embedded into paraffin for a preservation purpose. The Independent Component Analysis (ICA) technique can be used to numerically dewax Raman spectra and to extract the specific information of the tissue. We show in this paper that the paraffin must be modeled by a three-source model in order to succeed. This linear model, confirmed also by analyzing paraffin blocks exclusively, should be preferred instead of commonly used one-source model.

Keywords: Raman spectroscopy,independent Component Analysis,paraffin embedded tissues,three-source linear model of paraffin

Identifier: 10.3182/20060920-3-FR-2912.00039

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Giampaolo Tomasi; Alessandra Bertoldo; Claudio Cobelli

Abstract: C-11-labeled N-methyl-4-piperidin acetate ([11C]MP4A) is used for the quantitative measurement of acetylcholinesterase activity with positron emission tomography (PET). In this study, two new methods, i.e. simplified ridge regression with spatial constraint (SRRSC) and its generalized formulation (GRRSC), are evaluated to quantify, without arterial measurements, [11C]MP4A images at pixel level. Their performance is assessed against state of art quantification methods for [11C]MP4A by Monte Carlo simulations. Although characterized by a little bias, GRRSC emerges as the most reliable and computationally efficient algorithm to generate parametric images of [11C]MP4A when an arterial input function is not available.

Keywords: image analysis,modelling,Monte Carlo simulations,algorithms,mean square error,bias,parameter estimation

Identifier: 10.3182/20060920-3-FR-2912.00055

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Stéphane Bibian; Guy A. Dumont; Mihai Huzmezan; Craig R. Ries

Abstract: The outcome of any surgery is particularly dependent on the adequate delivery of anesthetic drugs. Not surprisingly, clinical researchers have been trying to automatize their delivery in order to provide anesthesiologists with titration tools that can target the exact needs of each individual patient. As compared to today's population-normed drug delivery strategy, closed-loop drug delivery systems would provide patients with customized pharmacological action, thereby improving surgery outcome. While some anesthesia closed-loop designs have already shown promising results within controlled clinical protocols, the pharmacological variability that exists between patients needs to be addressed within a mathematical framework to prove the stability of the control laws, and gain faster and wider acceptance of these systems by the clinical community and regulatory committees. This paper is the first of a series of 2 papers addressing the issue of pharmacological variability, and how this variability translates into quantifiable system uncertainty. In this work, we focus essentially on deriving patient-specific models to assess inter-patient variability. These models will serve as basis for illustrating the uncertainty quantification approach proposed in the accompanying paper.

Keywords: anesthesia closed-loop control,pharmacokinetic modeling,pharmacodynamic modeling,uncertainty,propofol

Identifier: 10.3182/20060920-3-FR-2912.00097

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Stéphane Bibian; Guy A. Dumont; Mihai Huzmezan; Craig R. Ries

Abstract: The outcome of any surgery is particularly dependent on the adequate delivery of anesthetic drugs. Not surprisingly, clinical researchers have been trying to automatize their delivery in order to provide anesthesiologists with titration tools that can target the exact needs of each individual patient. As compared to today's population-normed drug delivery strategy, close loop drug delivery systems would provide patients with customized pharmacological action, thereby improving surgery outcome. While some anesthesia close loop designs have already shown promising results within controlled clinical protocols, the pharmacological variability that exists between patients needs to be addressed within a mathematical framework to prove the stability of the control laws, and gain faster and wider acceptance of these systems by the clinical community and regulatory committees. This paper is the second of a series of 2 papers addressing the issue of pharmacological variability and PKPD uncertainty. In the first paper, we presented our own drug modeling approach, which we applied towards the identification of 44 adult patient models for propofol, a central nervous system depressant drug. The individual patient models have shown a large inter-patient variability. In this paper, we further expand on our previous result in order to derive an uncertainty metrics that can be used in the control design to ensure stability and assess performances.

Keywords: anesthesia closed-loop control,pharmacodynamic modeling,uncertainty,propofol

Identifier: 10.3182/20060920-3-FR-2912.00098

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: M. A. Denaï; M. Mahfouf; O. King; J. J. Ross

Abstract: A physiological model integrating a pulsatile cardiovascular system model with a model of the pulmonary capillary fluid exchange based on the Starling's equations is proposed in order to analyse the micro-circulatory physiological alterations which occur during the evolution of sepsis. Sepsis-induced acute lung injury is typically characterized by an increased microvascular permeability and interstitial edema. Pulmonary edema occurs because the capillary filtration capacity increases and the reflection coefficient to proteins decreases causing fluid leak across the capillary barrier. Patients with severe sepsis may develop respiratory failure and hence requiring ventilatory support. These signs represent the clinical expression of the acute respiratory distress syndrome (ARDS) and are associated with high mortality in medical intensive care units (ICU). The proposed model is used to simulate the cardiovascular hemodynamics under these complex pathophysiological conditions.

Keywords: septic shock,capillary leak,microvascular permeability,pulmonary edema,Starling's force,cardiovascular system

Identifier: 10.3182/20060920-3-FR-2912.00077

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Hassan Amoud; Madhur Agrawal; Uday Bandaru; David Hewson; Michel Doussot; Jacques Duchêne

Abstract: The present paper applies two methods commonly used to calculate entropy to postural time-series data of elderly and control subjects. Approximate entropy provided a biased estimate of regularity for small window lengths. In contrast, sample entropy was able to identify postural differences between elderly and control subjects. Elderly subjects showed less regularity in terms of anteroposterior displacement than did control subjects. However, the observed values of entropy were very small, as were the significant differences observed. Additional work is required to address concerns related to the time series length and the method used to calculate entropy.

Keywords: entropy,nonlinear analysis

Identifier: 10.3182/20060920-3-FR-2912.00041

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: David Dagan Feng; Olivier Dubois; Janan Zaytoon; Ewart Carson

Abstract:

Keywords:

Identifier: 10.3182/20060920-3-FR-2912.00002

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Janusz Mroczka; Adam G. Polak

Abstract: Pathological changes in the lung modify the shape of the flow-volume curve registered during forced expiration. Computational models allowing simulation of the test results are too complex for the estimation of their parameters. In this study a complex model was reduced by introduction of the functions scaling airway properties. Influence of the individual parameters of the reduced model on the flow-volume curve was evaluated by means of the sensitivity analysis. The conclusion is that the parameters of the scaling functions and elastic properties of lung tissue affect the measured data most significantly and that the descending part of the curve should be used to assess them.

Keywords: biomedical systems,modelling,model reduction,sensitivity analysis,inverse problem

Identifier: 10.3182/20060920-3-FR-2912.00032

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Johann Dreo; Jean-Claude Nunes; Pierre Truchetet; Patrick Siarry

Abstract: Retinal fundus photographs are employed as standard diagnostic tools in ophthalmology. We employ optimization techniques for registration of retinal angiograms, using non-linear pre-processing (Wiener filtering and morphological gradient) and computation of a similarity criterion. The present work makes a comparison between different optimization techniques, namely the optical flow minimization method, the Nelder-Mead local search, the CEDA and CHEDA metaheuristics. The impact of the resolution and median filtering of gradient image is studied and the robustness of the approaches is tested through experimental studies, performed on ICG angiographies. Our proposed method has shown interesting results, especially for high resolution registration problems.

Keywords: image registration,optimization,metaheuristic,image processing,biomedical images

Identifier: 10.3182/20060920-3-FR-2912.00010

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Taous-Meriem Laleg; Emmanuelle Crepeau; Michel Sorine

Abstract: A simplified model of arterial blood pressure intended for use in model-based signal processing applications is presented. The main idea is to decompose the pressure into two components: a travelling wave describes the fast propagation phenomena predominating during the systolic phase and a windkessel flow represents the slow phenomena during the diastolic phase. Instead of decomposing the blood pressure pulse into a linear superposition of forward and backward harmonic waves, as in the linear wave theory, a nonlinear superposition of travelling waves matched to a reduced physical model of the pressure, is proposed. Very satisfactory experimental results are obtained by using forward waves, the N-soliton solutions of a Korteweg-de Vries equation in conjunction with a two-element windkessel model. The parameter identifiability in the practically important 3- soliton case is also studied. The proposed approach is briefly compared with the linear one and its possible clinical relevance is discussed.

Keywords: pressure,wave,linear theory,nonlinear theory,identifiability

Identifier: 10.3182/20060920-3-FR-2912.00023

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: C. A. Teixeira; M. Graça Ruano; A. E. Ruano; W. C. A. Pereira; C. Negreira

Abstract: In this paper the performance of a genetically selected radial basis functions neural network is evaluated for non-invasive two-point temperature estimation in a homogeneous medium, irradiated by therapeutic ultrasound at physiotherapeutic levels. In this work a single neural network was assigned to estimate the temperature profile at the two considered points, and more consistent results were obtained than when considering one model for each point. This result was possible by increasing the model complexity. The best model predicts the temperature from two unseen data sequences during approximately 2 hours, with a maximum absolute error less than 0.5°C, as desired for a therapeutic temperature estimator.

Keywords: temperature profiles,temperature control,neural networks-models,radial base function networks,multiobjective optimisations

Identifier: 10.3182/20060920-3-FR-2912.00028

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: J. Geoffrey Chase; Jessica Lin; Dominic S. Lee; Jason Wong; Christopher E. Hann; Geoffrey M. Shaw

Abstract: Hyperglycaemia is prevalent in critical care, and tight control reduces mortality. Targeted glycaemic control can be achieved by frequent fitting and prediction of a modelled insulin sensitivity index, SI. However, this parameter varies significantly in the critically ill as their condition evolves. A 3-D stochastic model of hourly SI variability is constructed using retrospective data from 18 critical care patients. The model provides a blood glucose level probability distribution one hour following an intervention, enabling accurate prediction and more optimal glycaemic control.

Keywords: biomedical control,non-linear models,physiological models,physiology,stochastic modelling,Markov models,medical systems

Identifier: 10.3182/20060920-3-FR-2912.00063

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Berno J. E. Misgeld; Jurgen Werner; Martin Hexamer

Abstract: Three different control strategies for haemodynamic control of extra-corporeal circulation were developed, tested and compared to each other for the total cardiopulmonary bypass case. The controllers were tuned on robust stability and performance with a detailed model of the vascular system and the heart-lung machine. The control strategies were validated in simulation studies and on a haemodynamic vascular system simulator. All controllers were stable during simulations and in-vitro experiments in stationary and pulsatile control. An arterial blood flow controller with arterial pressure boundary control extension shows the best result.

Keywords: robust haemodynamic control,extracorporeal circulation,cardiopulmonary bypass,heart-lung machine

Identifier: 10.3182/20060920-3-FR-2912.00064

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: S. Y. Amy Cheung; James W. T. Yates; Leon Aarons

Abstract: Pharmacokinetic analysis in humans using compartmental models is restricted with respect to the estimation of parameter values. This is because the experimenter usually is only able to apply inputs and observations in a very small number of compartments in the system. This has implications for the structural identifiability of such systems and consequently limits the complexity and mechanistic relevance of the models that may be applied to such experiments. A number of strategies are presented whereby models are rendered globally identifiable by considering a series of experiments in parallel. Examples are taken from the pharmacokinetic literature and analysed using this parallel experiment methodology.

Keywords: algebraic approaches,constrained parameters,controllability,first-order systems,identifiability,parameter identification,parameterization,pharmacokinetic data,state-space models

Identifier: 10.3182/20060920-3-FR-2912.00022

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: T. Bastogne; L. Tirand; M. Barberi-Heyob; A. Richard

Abstract: This study presents the contributions of system identification techniques to the experimental modelling of photosensitiser uptake kinetics in photodynamic therapy. The experimental framework is limited to one cancer cell line (HT29-A4), one photosensitiser (Chlorin e6), one photosensitiser dose (5µg ċ ml-1), four albumin rates in a monolayer culture and eight measurements between 1h and 24h. Issues associated with this experimental modelling study are the deficiency of measurement points, low signal-to-noise ratios and 'poor' excitation signals (step signals). This paper deals with model structure selection, parameter estimation and parameter uncertainty description by probabilistic confidence regions. Moreover, an explicit relationship between the static gain of the estimated model and the albumin rate of the culture medium has been established.

Keywords: system identification,pharmacokinetics,drug delivery,photodynamic therapy

Identifier: 10.3182/20060920-3-FR-2912.00038

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Chi-Ngon Nguyen; Olaf Simanski; Ralf Kähler; Agnes Schubert; Bernhard Lampe

Abstract: In order to improve the applications of intraoperation and internal medicine, this paper presents a method of hypotensive control. The mean arterial pressure (MAP) is decreased and maintained at a low level during anaesthesia by controlling sodium nitroprusside (SNP) infusing rate. In this system, a new dynamical model of MAP response to SNP is modified based on Guyton's model of cardiovascular dynamics. The resulting model is not only useful to design a PID controller, but also for studying the behaviors of patients under anaesthesia condition, such as the perfusion of organs and the reaction of the body at hypotensive state. A fuzzy gain scheduler (FGS) is online updated for tuning the PID gains during control activities to handle the behaviors of the body. Simulation results prove the benefits of using Guyton's model, and indicate the safety and stability of the control system.

Keywords: fuzzy control,fuzzy logic,PID control,scheduling algorithms,medical systems,medical applications,blood pressure

Identifier: 10.3182/20060920-3-FR-2912.00065

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Alessandra Bertoldo; Paolo Vicini; Claudio Cobelli

Abstract: Glucose minimal model parameters are commonly estimated by applying weighted nonlinear least squares separately to each subject's data. Because of the model's nonlinearity. the parameter precision of the single-compartment minimal model is not always satisfactory, especially in presence of a reduced sampling schedule. In the current work, the use of population analysis through nonlinear mixed effects models is evaluated and its performance tested against the parameter estimates obtained by the standard individual approach through weighted nonlinear least squares.

Keywords: modeling,parameter estimation,nonlinear models,physiological models,sampling frequency

Identifier: 10.3182/20060920-3-FR-2912.00044

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Bertrand Simon; Matthieu Debailleul; Vincent Georges; Olivier Haeberle; Vincent Lauer

Abstract: We present a technique to image living transparent specimens in 3-D, based on coherent optical diffraction microscopy. The sample is successively illuminated by a series of plane waves having different directions. Each scattered wave is recorded by phase-shifting interferometry and a Fourier representation of the object is reconstructed. The specimen, first recorded in Fourier space, is then reconstructed in the object space. This technique permits a 3-D reconstruction of the complex index of refraction distribution, with a resolution of the order on a quarter of the wavelength.

Keywords: microscopes,image reconstruction,Fourier optics,tomography,3D-Domain

Identifier: 10.3182/20060920-3-FR-2912.00013

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: David Guiraud; Christine Azevedo; Ken Yoshida; Philippe Poignet; Mohammed Samer; Hassan El Makssoud

Abstract: DEMAR aims at rehabilitation engineering using Functional Electrical Stimulation based on the automatic control theoretical approach but also on the physiology of the system studied, to obtain a useable and useful therapy for disabled people. To simulate, synthesize, and control movements of impaired limbs using Functional Electrical Stimulation, modelling is necessary. Living actuators, i.e. muscles, sensors, i.e. Golgi Tendon Organs and muscle spindles, need to be understood and modelled to perform realistic numerical simulations. The paper describes some results obtained in the DEMAR team.

Keywords: functional electrical stimulation (FES),intra fascicular electroneurograms (ENG),muscle modelling,neuroprostheses

Identifier: 10.3182/20060920-3-FR-2912.00072

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Gael Pages; Nacim Ramdani; Philippe Fraisse; David Guiraud

Abstract: A new approach aiming posture estimation using only forces measurements exerted on handles and geometric constraints is outlined. The behavior of the system is modeled by an ordinary differential equation (ODE) which includes parameters whose value is uncertain. The insufficiency in precision while computation may affect safe decision making. Interval arithmetic is a method for performing computations on measurements that are only known within a fixed error range. The uncertainties are propagated throughout the calculation to obtain safe bounds interval domains. In order to investigate the feasibility of posture estimation by interval methods in this particular case, a simplified model of the human body was developed, in regards to a three degrees of freedom link-segment model.

Keywords: robotics,intervals,integration,differential equation,uncertainty,Paraplegia,rehabilitation,posture estimation

Identifier: 10.3182/20060920-3-FR-2912.00016

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006

Authors: Sonia Khatchadourian; Stéphane Lebonvallet; Michel Herbin; Jean-Claude Liehn; Su Ruan

Abstract: In the framework of detection, diagnostic and treatment planning of tumors, the Positron Emission Tomography (PET) examination coupled with a Computed Tomography (CT) have become recently the most efficient technique. Manual segmentation of regions of interest (ROI) could be time consuming and this is necessary to obtain information about patient pathology. The aim of our study is to propose an automatic solution to this problem. This paper presents an approach of tumor segmentation based on a level set method. One critical step, the algorithm stopping, is automatic. The results obtained by the proposed method dealing with PET-CT images are encouraging.

Keywords: image,partial differential equations,segmentation

Identifier: 10.3182/20060920-3-FR-2912.00048

Conference: 6th IFAC Symposium on Modeling and Control in Biomedical Systems, 2006

Location: Reims Congress Center, France

Start Date: Wed Sep 20 2006 - End Date: Fri Sep 22 2006