BIOMATERIALS AND COCHLEAR IMPLANTS
Transcript of BIOMATERIALS AND COCHLEAR IMPLANTS
11
BIOMATERIALSBIOMATERIALSANDAND
COCHLEARCOCHLEAR IMPLANTSIMPLANTS
AttiaAttia QamarQamar & Paolo & Paolo SabatiniSabatini
22
CochleaCochlea
Middle Ear
Tympanic
MembraneVibrationVibrationVibration
External Ear
Inner Ear
CN VIIIBony LabyrinthBony LabyrinthBony LabyrinthCoclear DuctCoclearCoclear DuctDuct
To round windowTo round window
From oval windowFrom oval windowFrom oval window
PerilymphPerilymphPerilymph
Vibrations transmitted through the Vibrations transmitted through the perilymphperilymph in thein thebony labyrinth will be transmitted to the bony labyrinth will be transmitted to the endolymphendolymph in in
the cochlear ductthe cochlear duct
vestibule
EAR ANATOMY & MECHANICSEAR ANATOMY & MECHANICS
33
Perilymph inscala vestibuli
Perilymph inscala tympani
Endolymph inCochlear Duct /scala media
Organ of Organ of CortiCorti
Vibrations ofTectorial Membrane Stimulation of
cilia on hair cells
Transmission of stimulus along CN VIIITransmission of stimulus along CN VIII
TectorialTectorial Membrane
Membrane
Basilar membrane
Vestib
ular m
embran
e
Vibrations conveyed toVibrations conveyed toOrgan of Organ of CortiCorti
Tension of Basilar membranedampens vibration
From oval windowFrom oval window
To round windowTo round window
44
Low Frequency
High Frequency
The Basilar Membrane in ActionThe Basilar Membrane in Action::http://www.hhmi.org/biointeractive/animations/cochlea/coc_mov2.hhttp://www.hhmi.org/biointeractive/animations/cochlea/coc_mov2.htmtm
55
Hearing ImpairmentHearing ImpairmentTwo types of hearing impairment:Two types of hearing impairment:
•• Conductive hearing lossConductive hearing loss: Damaged apparatus that : Damaged apparatus that transmits sound energy to cochlea. (transmits sound energy to cochlea. (EgEg/ Damaged / Damaged eardrum, bone tissue encrusted ossicles)eardrum, bone tissue encrusted ossicles)
Treatment:Treatment: Hearing Aid or SurgeryHearing Aid or Surgery
•• Sensorineural hearing lossSensorineural hearing loss: Damaged/destroyed hair : Damaged/destroyed hair cells within organ of cells within organ of CortiCorti or destroyed auditory nerve or destroyed auditory nerve (can be caused by a tumor).(can be caused by a tumor).
Treatment:Treatment: Cochlear implant in case of viable auditory Cochlear implant in case of viable auditory nerve, direct stimulation of sound centre in brain nerve, direct stimulation of sound centre in brain required otherwise.required otherwise.
66
Main Causes of Hearing LossMain Causes of Hearing Loss
•• HeredityHeredity•• Infections:Infections: egeg. rubella, bacterial meningitis. rubella, bacterial meningitis
•• Acoustic TraumaAcoustic Trauma: : due to acute or chronic exposure due to acute or chronic exposure to loud soundsto loud sounds
•• Prescription drugsPrescription drugs (streptomycin. (streptomycin. tobramycintobramycin, , cisplatincisplatin –– a chemotherapy agent)a chemotherapy agent)
•• PresbycusisPresbycusis: : due to old age, acoustic trauma and due to old age, acoustic trauma and age hardening of microscopic blood vessels in inner ear. age hardening of microscopic blood vessels in inner ear.
77
Candidate CriteriaCandidate Criteria
•• Profound sensorineural hearing loss of cochlea Profound sensorineural hearing loss of cochlea site. site.
•• Extremely poor word recognition in openExtremely poor word recognition in open--set set paradigms.paradigms.
•• A patent cochlea and viable auditory nerve.A patent cochlea and viable auditory nerve.
•• Good health to withstand anesthesia and Good health to withstand anesthesia and surgery.surgery.
88
Cochlear Implant MechanicsCochlear Implant Mechanics
BRIEF OVERVIEW OF THE IMPLANT:BRIEF OVERVIEW OF THE IMPLANT:http://www.cochlearimplant.com/mov/coch_anim.htmlhttp://www.cochlearimplant.com/mov/coch_anim.html
99
Cochlear Implant Processing StrategiesCochlear Implant Processing Strategies
Processing Strategy Electrode Type
Max. # of Channels
Feature extraction Longitudinal bipolar 21
Bipolar 15Compressed analog(Simultaneous
Stimulation) Monopolar 4
Interleaved pulsatile Radial bipolar 8
(Digital) Longitudinal bipolar 21
1010
Multichannel vs. Single ChannelMultichannel vs. Single Channel(Prosthesis Audio Samples)(Prosthesis Audio Samples)
•• Speech: increasing channels 1, 2, 4, 8, 16Speech: increasing channels 1, 2, 4, 8, 16(more tolerant of degradation)(more tolerant of degradation)
http://www.hei.org/research/depts/aip/increase_channels.mp3http://www.hei.org/research/depts/aip/increase_channels.mp3
•• Music (instrumental, complex): increasing Music (instrumental, complex): increasing channels 4, 8, 16, 32channels 4, 8, 16, 32
(requires fine processing to achieve melody (requires fine processing to achieve melody recognition)recognition)
http://www.hei.org/research/depts/aip/rhapsodydemo.mp3http://www.hei.org/research/depts/aip/rhapsodydemo.mp3
1111
Goals•• Transmit coded frequency intensities through electrode Transmit coded frequency intensities through electrode
array to CNS (Central Nervous System) via multiarray to CNS (Central Nervous System) via multi--channel electrical stimulation of hearing nerves.channel electrical stimulation of hearing nerves.
•• Insert electrode array into correct location in cochlea, to Insert electrode array into correct location in cochlea, to minimize tissue and auditory nerve damage.minimize tissue and auditory nerve damage.
•• Non toxic and biocompatible materials to prevent injury Non toxic and biocompatible materials to prevent injury to cochlea and auditory nerve.to cochlea and auditory nerve.
•• Minimize current and charge density build up to prevent Minimize current and charge density build up to prevent damage to surrounding tissue.damage to surrounding tissue.
•• Proper electrode geometry for localizing current to Proper electrode geometry for localizing current to separate nerve fibers.separate nerve fibers.
•• Proper implant procedure to prevent infections from Proper implant procedure to prevent infections from spreading to inner ear from middle ear (spreading to inner ear from middle ear (egeg. meningitis). meningitis)
•• Sealed electronics to prevent corrosive body fluids from Sealed electronics to prevent corrosive body fluids from entering and causing device failureentering and causing device failure
•• Durable enough to not result in damage due to head Durable enough to not result in damage due to head impact or result in fatigue or fracture due to acute impact or result in fatigue or fracture due to acute movements.movements.
1212
BiomaterialsBiomaterials
External ComponentsExternal Components Internal ComponentsInternal Components
••Microphone Microphone -- directionaldirectional••Speech Processor Speech Processor ––Platinum Platinum (strong, light, one (strong, light, one quartzquartz--crystal oscillator)crystal oscillator)
••TransmitterTransmitter
••ReceiverReceiver••StimulatorStimulator••Electrode Array Electrode Array ••ElectrodesElectrodes
1313
1414
Receiver/ Stimulator PackageReceiver/ Stimulator Package(side by side placement, cylindrical)(side by side placement, cylindrical)
RequirementRequirement MaterialMaterial•• Impervious to body Impervious to body fluidsfluids•• RobustRobust•• No corrosion No corrosion •• No leaks No leaks
•• Sintered Ceramics SealSintered Ceramics Seal(AlO(AlO22, SiO, SiO22, , MgOMgO))••Titanium case (bonds Titanium case (bonds with ceramic material)with ceramic material)•• Seal container halves Seal container halves by welding (Ti to Ti)by welding (Ti to Ti)•• Helium Helium
1515
Receiver specificallyReceiver specifically
RequirementRequirement MaterialMaterial•• Efficient Signal Efficient Signal TransmissionTransmission•• RobustRobust•• No Migration No Migration
•• coil wrapped around coil wrapped around rare earth magnetrare earth magnet••Titanium capsuleTitanium capsule•• Seal container halves Seal container halves by welding (Ti to Ti)by welding (Ti to Ti)
1616
Electrode ArrayElectrode Array
RequirementRequirement MaterialMaterial•• No Migration No Migration ••Easy insertion/ limited Easy insertion/ limited traumatrauma••Not an infection carrierNot an infection carrier••OsseointegrationOsseointegration••InsulativeInsulative
•• SilasticSilastic MDXMDX--44--42104210(Graded stiffness)(Graded stiffness)
••Fascia homograft, Fascia homograft, titanium collar, with titanium collar, with hydroxyapatitiehydroxyapatitie coatcoat••SilasticSilastic type A type A (biocompatible glue)(biocompatible glue)
Simulation of contour insertion
1717
Electrode ContactsElectrode ContactsRequirementRequirement MaterialMaterial•• ConductiveConductive•• No electrolysisNo electrolysis••Minimum toxic Minimum toxic electrochemical electrochemical reactionsreactions
•• PlatinumPlatinum•• IridiumIridium
A. Deaf, Stimulated B. Deaf, Unstimulated
1818
BiocompatibiltyBiocompatibiltyIssueIssue SolutionSolution
Channel Interaction Channel Interaction (conductive fluid in (conductive fluid in cochlea)cochlea)
Sequential Stimulation Sequential Stimulation (Interleaving)(Interleaving)
Charge density buildup Charge density buildup (tissue and implant (tissue and implant damage)damage)
Increase contact surface Increase contact surface area (mushroom shape)area (mushroom shape)
Spread of infections Spread of infections (meningitis and (meningitis and streptococousstreptococouspneumonia)pneumonia)
GraftinGraftin fascia about fascia about electrode entry point,electrode entry point,Prevent seeding bacteria Prevent seeding bacteria at time of surgeryat time of surgery
1919
MigrationMigration Fixation and Fixation and retrospective magnetretrospective magnet
Head growth and Head growth and electrode extractionelectrode extraction
Additional 20Additional 20--25 mm 25 mm loop in lead wire and loop in lead wire and fixing array to floor of fixing array to floor of mastoid mastoid atrumatrum
Electrode junction weekElectrode junction week Stress relief via spiral Stress relief via spiral electrodeselectrodes
MRI (implant damage)MRI (implant damage) Non magnetic versionNon magnetic version
2020
SurgerySurgeryPrecautions: Precautions: •• micromicro--clawclaw•• protocol to prevent seeding bacteriaprotocol to prevent seeding bacteria•• Flap < 6mm Flap < 6mm •• Bed depth approxBed depth approx
5mm, round5mm, round
Complications:Complications:•• Hemorrhage : mastoid emissary vein; control with diamond burr, Hemorrhage : mastoid emissary vein; control with diamond burr,
bone wax, crushed muscle, bone wax, crushed muscle, GelfoamGelfoam•• Facial Nerve and Facial Nerve and ChordaChorda Tympani InjuryTympani Injury•• Perilymph GusherPerilymph Gusher
Emplantedelectrode array
2121
Postoperative ComplicationsPostoperative Complications
•• Wound BreakdownWound Breakdown•• Pain: infection, Pain: infection, extracochlearextracochlear spread of spread of
current, excessively strong magnetscurrent, excessively strong magnets•• InfectionInfection•• LabyrinthitisLabyrinthitis and Meningitisand Meningitis
2222
The ManufacturesThe Manufactures
•• Advanced BionicsAdvanced Bionics -- ClarionClarionwww.cochlearimplant.comwww.cochlearimplant.com
•• Cochlear CorporationCochlear Corporation -- NucleusNucleuswww.cochlear.comwww.cochlear.com
•• MEDMED--ELEL -- CombiCombi 40+40+www.medel.comwww.medel.com
2323
The FutureThe Future
For those with destroyed auditory nervesFor those with destroyed auditory nerves-- Implantation of electrodes into cochlear Implantation of electrodes into cochlear
nucleusnucleus-- Implantation of Electrodes into auditory Implantation of Electrodes into auditory
cortexcortex
2424
RefrencesRefrences
•• www.cochlearimplant.comwww.cochlearimplant.com•• www.cochlear.comwww.cochlear.com•• www.medel.comwww.medel.com•• http://forms.gradsch.psu.edu/equity/sroppapers/2004/SeshadriSudhhttp://forms.gradsch.psu.edu/equity/sroppapers/2004/SeshadriSudh
arshana.pdfarshana.pdf•• http://http://www.phm.gov.au/hsc/cochlear/commercial.htmwww.phm.gov.au/hsc/cochlear/commercial.htm•• “Cochlear Implants”; Fundamentals and Applications, Graeme Clar“Cochlear Implants”; Fundamentals and Applications, Graeme Clarkk•• “Cochlear Implants”, Schindler & M. “Cochlear Implants”, Schindler & M. MerzenichMerzenich•• “Cochlear Implants”, Roger F. Gray“Cochlear Implants”, Roger F. Gray•• “Cochlear Implants in Adults and Children”, NIH Consensus “Cochlear Implants in Adults and Children”, NIH Consensus
Development Conference, May 15Development Conference, May 15--17, 199517, 1995•• “Practical Hearing Aid Selection and Fitting”, Henry Tobin“Practical Hearing Aid Selection and Fitting”, Henry Tobin
2525
The ENDThe END