AIMD design and examples

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Presentation at Sophia Antipolis MicroElectronics conference on October 6th, 2010.

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AIMD design and examples

  1. 1. Theory of operation Architecture Design Active Implantable Medical Device Design : The cochlear implant example Nicolas Veau1 1 Neurelec, MXM group SAME conference, October 6th , 2010 SAME2010 Active Implantable Medical Devices
  2. 2. Theory of operation Architecture Design Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  3. 3. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  4. 4. Theory of operation Overview Architecture The auditory system Design The cochlear implant system What is an Active Implantable Medical Device ? Denition and examples Medical Device: Maintain human physiological functions. Implantable: Inserted into the human body by surgery. Active: Uses energy to power its sensors and actuators. Brain stimulators Heart stimulators SAME2010 Active Implantable Medical Devices
  5. 5. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Economical environment 1 The AIMD is mainly used for : Sensory and functional prosthesis for invalidating disabilities. Automated drug delivery for chronicle diseases therapies. Health monitoring and prevention. Health care outsourcing. 2 The AIMD aims to : Improve the quality of life by reducing disabilities, anxiety. Extend the life time by monitoring vital signs. Decrease the societal cost by improving the patient autonomy. 3 The AIMD market growth is driven by : The rehabilitation of disability considered as a public priority. The population aging. The over weighted people growth. The emergence of new geographic markets. SAME2010 Active Implantable Medical Devices
  6. 6. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Economical environment 1 The AIMD is mainly used for : Sensory and functional prosthesis for invalidating disabilities. Automated drug delivery for chronicle diseases therapies. Health monitoring and prevention. Health care outsourcing. 2 The AIMD aims to : Improve the quality of life by reducing disabilities, anxiety. Extend the life time by monitoring vital signs. Decrease the societal cost by improving the patient autonomy. 3 The AIMD market growth is driven by : The rehabilitation of disability considered as a public priority. The population aging. The over weighted people growth. The emergence of new geographic markets. SAME2010 Active Implantable Medical Devices
  7. 7. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Economical environment 1 The AIMD is mainly used for : Sensory and functional prosthesis for invalidating disabilities. Automated drug delivery for chronicle diseases therapies. Health monitoring and prevention. Health care outsourcing. 2 The AIMD aims to : Improve the quality of life by reducing disabilities, anxiety. Extend the life time by monitoring vital signs. Decrease the societal cost by improving the patient autonomy. 3 The AIMD market growth is driven by : The rehabilitation of disability considered as a public priority. The population aging. The over weighted people growth. The emergence of new geographic markets. SAME2010 Active Implantable Medical Devices
  8. 8. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  9. 9. Theory of operation Overview Architecture The auditory system Design The cochlear implant system The auditory system How does the ear work ? External Ear: Antenna amplier conduction line Middle Ear: Impedance matching Automatic Gain Control Inner Ear: Analog-to-Digital Converter SAME2010 Active Implantable Medical Devices
  10. 10. Theory of operation Overview Architecture The auditory system Design The cochlear implant system The auditory system How does the internal ear work ? Basilar membrane: Transform pressure variation in membrane displacement. Behave as an analog delay line. Corti Organ: Sense the displacement pattern on the basilar membrane. [2] SAME2010 Active Implantable Medical Devices
  11. 11. Theory of operation Overview Architecture The auditory system Design The cochlear implant system The auditory system How does the inner ear work ? Inner Hair Cell: Amplitude time-space sampler. Low frequency detector. Outer Hair Cell: Frequency and phase time-space sampler. Up to 16kHz detector. [2] [3] SAME2010 Active Implantable Medical Devices
  12. 12. Theory of operation Overview Architecture The auditory system Design The cochlear implant system The auditory system Auditory pathway from the inner ear to the brain Auditory pathways: Autocorrelators feedback loops Cortex: Correlators and associative memory [2] SAME2010 Active Implantable Medical Devices
  13. 13. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  14. 14. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Cochlear Implant How does the cochlear implant work ? External ear middle ear = Microphone DSP Inner hair cell Outer hair cells = Electrode array [1] SAME2010 Active Implantable Medical Devices
  15. 15. Theory of operation Overview Architecture The auditory system Design The cochlear implant system Cochlear Implant Clinical needs and their impacts on the electronics requirements 1 Reliability 1 System reliability 2 Data transfer reliability 2 Clinical performance 1 Good signal processing for voice, music, noise environment 2 Better stimulation with higher temporal and spatial resolution 3 User friendly interface 4 Data fusion 3 Low invasiveness 1 Miniaturization 2 Maintenance surgery 3 Active time SAME2010 Active Implantable Medical Devices
  16. 16. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  17. 17. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components AIMD architecture Physical view Subsystems : Constraints : Stimulation Connections Sensors Encapsulation Energy transfer/storage Manufacturing Communications Agreements SAME2010 Active Implantable Medical Devices
  18. 18. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components AIMD architecture Functional view SAME2010 Active Implantable Medical Devices
  19. 19. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components AIMD architecture Data path view SAME2010 Active Implantable Medical Devices
  20. 20. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  21. 21. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Electrode array Characteristics Clinical targets : Preserve neurons Activate neurons on demand Monitor neuron activity Electrode array characteristics : Mechanical control : toxicity, insertion trauma, infection Precise current control : in amplitude, time, in space Tissue impedance measurements Electrode arrays [4] SAME2010 Active Implantable Medical Devices
  22. 22. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Electrode array 3D current control Virtual electrodes : Allow current steering and focusing for higher neuron selectivity. Complex waveforms : Allow better neuron preservation and ecient stimulations. Virtual electrodes concept [4] SAME2010 Active Implantable Medical Devices
  23. 23. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Implantable sensors The interface with the outside world RAIC Acoustic sensor Bio-signal sensor t pic N1 : en et pic P1 : 70 entre 400 fRAIC compri 1 kHz et 1 Amplitude de entre 20 µV et courant de st Low noise, low power Neural response Automatic gain control. Neural synchrony Helium-leak test compliant Stimulation loop back Low prole, small volume Time variability oset SAME2010 Active Implantable Medical Devices
  24. 24. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Radio communication Trans-cutaneous communication interface Usages: Remote control, tting, multimedia accessories Description du canal de propagation: Figures: Below 3mW in 64kbps DL. Below 1µ W in standby. 1Mbps max. Dilemma: Antenna) FA ( Inverted Energy/Data transfer, Magnetic/Electromagnetic Peau Cartilage Graisse Equivalent Epaisseur 1 mm 4 mm 34 mm 39 mm on: Permittivité 38.01 38.77 5.28 9.55 relative r Link budget Antenna réalisé 8.55 13.98 Modèle Conductivité 44.25 52.63 sous HFSS Facteur de 0.0226 0.0190 0.1170 0.07151 perte Caractéristiques des 3 tissues du model équivalent à 2.45 GHz http://niremf.ifac.cnr.it/tissprop/htmlclie Antenne IFA dessinée sous HFSS Loss between external ear and F=2.45GHz, BW=80MHz, implant : - 25dB @ 2.45GHz Z =50Ω L 30.35 mm in l 0.5 mm SAME2010 Active ImplantableHMedical Devices 2 mm
  25. 25. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  26. 26. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Battery Safety : Backup system, safe chemistry, hot swap, EN45502-2-3. Protection : Titanium casing with feed-through, over and under charge, emergency stop. Energy transfer : Capacity vs., charging time, charging time after 10 years. Inductive charging : EN45502-2-3, expected eciency above 70% Energy distribution : 0.9 V. SAME2010 Active Implantable Medical Devices
  27. 27. Theory of operation The AIMD system Architecture The AIMD interfaces Design The AIMD components Processing units 1 Intensive processing routines : Physiological noise ltering, artifact reduction, sensor data fusion, stimulations building, signal features extractions ... 2 Processing units : ASIC, ASP, FPGA, DSP, DMA, MCU 3 Software architecture : Usually no RTOS, no vendors libraries for safety reasons, specic development and test guidelines. Generic datapath SAME2010 Active Implantable Medical Devices
  28. 28. Theory of operation Modeling tools Architecture Simulation tool Design Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  29. 29. Theory of operation Modeling tools Architecture Simulation tool Design Analytical models Multi-physics models 1 Captures tight physics interactions : acoustic, viscosity and thermal combined eects. 2 Ecient for variable sensitivity analysis and optimization under constraints. 3 Supported by simpler and easier to understand lumped elements representations. Subcutaneous microphone !#$%'()$)*+,-. Ossicular chain model % # %% /#01,-+ ! - $ $ %% # 23,- ! $$% 4),-'%*,#',%0 $ $ .% [5] %' # !$0561-$ 4),-'%*,#',%0 201%%(*5$ 201%%718,(9 :!;!20,76)-$= !#$%'()'* +,!'-.-/01230 ( SAME2010 Active Implantable Medical Devices
  30. 30. Theory of operation Modeling tools Architecture Simulation tool Design Analytical models Statistical and biological models 1 The model computes the neurons population recruited by electrical stimulation according to their ring rate. 2 This model is used to identify the virtual electrodes that maximize spatial selectivity and directivity of a stimulation Current focusing and steering Current Focusing − Contour Plot of Number of Neurons Fired Current Focusing − Number of Neurons Fired Current Steering − Contour Plot of Number of Neurons Fired Current Steering − Number of Neurons Fired 2.5 90 100 2.5 90 100 σ=0 α=0 2 80 90 σ = 0.5 2 80 90 α = 0.25 σ = 0.75 α = 0.5 1.5 80 1.5 80 70 σ=1 70 α = 0.75 electrode α=1 1 70 1 70 60 60 electrode Neurons Fired Neurons Fired 0.5 60 0.5 60 Location (x) Location (x) 50 50 0 50 0 50 40 40 −0.5 40 −0.5 40 30 30 −1 30 −1 30 −1.5 20 20 −1.5 20 20 −2 10 10 −2 10 10 −2.5 0 0 −2.5 0 0 0 0.2 0.4 0.6 0.8 1 −2.5 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 −2.5 −2 −1.5 −1 −0.5 0 0.5 1 1.5 2 2.5 σ values Location along Neural Clusters(x) α values Location along Neural Clusters(x) SAME2010 Active Implantable Medical Devices
  31. 31. Theory of operation Modeling tools Architecture Simulation tool Design Numerical models Physics models 1 Useful for complex geometry and numerous interfaces 2 Reduce the number of prototypes and cost 3 Computations intensive, slow optimization convergence 4 Expensive tools, dicult to set them up, lack of interoperability with others tools. Antenna Magnetic systems Piezoelectric systems SAME2010 Active Implantable Medical Devices
  32. 32. Theory of operation Modeling tools Architecture Simulation tool Design Numerical models Statistical and biological models A simplistic 3D model of the cochlea Accompanying electrode array Generated potentials and currents through the cochlea when the electrodes were stimulated. Neural response to electrical stimulation was observed. BEM and HodgkinHuxley model method [6] SAME2010 Active Implantable Medical Devices
  33. 33. Theory of operation Modeling tools Architecture Simulation tool Design Outline 1 How can an AIMD restore lost human sensory functions ? Overview Sensory processing : The auditory system example Sensory prosthesis : The cochlear implant example 2 How can microelectronics benet to AIMD's performances ? The AIMD system The AIMD interfaces The AIMD components 3 How to solve strongly coupled constraints in an AIMD design ? Modeling tools Simulation tool SAME2010 Active Implantable Medical Devices
  34. 34. Theory of operation Modeling tools Architecture Simulation tool Design Cochlear implant simulator SAME2010 Active Implantable Medical Devices
  35. 35. Bibliography I [1] Digisonic SP system http://neurelec.com/ NEURELEC, Vallauris [2] Pujol R. al. Extracts from the website Promenade autour de la cochlée http://www.cochlee.org INSERM U. 254, Montpellier [3] Kiang N., Rho J., Northrop C., Liberman M. Ryugo D. Hair-cell innervation by spiral ganglion cells in adult cats Science, 1982, 217, 175-177 [4] Cu electrodes. http://neurelec.com NEUROMEDICS, Vallauris SAME2010 Active Implantable Medical Devices
  36. 36. Bibliography II [5] O Connor K.N. Puria S. Middle-ear circuit model parameters based on a population of human ears The Journal of the Acoustical Society of America, 2008, 123, 197 [6] Gramfort A., Papadopoulo T., Olivi E., Clerc M. OpenMEEG: opensource software for quasistatic bioelectromagnetics HAL-INRIA. May 2010. SAME2010 Active Implantable Medical Devices

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