Weiland_bme 410 fall 2011

Weiland_bme 410 fall 2011 - Biomaterials Issues for Neural...

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Biomaterials Issues for Neural Implants BME 410 10/6/2011 Jim Weiland jweiland@usc.edu http://bmes-erc.usc.edu/brl/home/
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Key Concepts Basis for neural stimulation Basis for neural recording Clinical and experimental systems Common system components Material requirements for neural implants Hermetic packaging (Jiang) Leads Neural stimulation material issues (Cogan) Electrode material (Cogan) Tissue (Shah, McCreery) Neural recording material issues (Polikov) Electrode array designs Tissue response (Polikov)
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Electric fields applied by microelectrode can activate nerve cells Biphasic Current Pulse Electrodes are made of • flexible or rigid substrate • conducting material (noble metal, conducting polymer, carbon nanotubes)
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Circuit models of Nerve recording Zin •Input impedance of amplifier must be high to accurately record voltage •Larger electrodes with lower impedance help, but less selective •Decrease impedance while maintaining size
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Cochlear Implants Today’s implants stimulate the cochlea at up to 32 locations, but usually use fewer (4-8) Best subjects can talk on the telephone (i.e. no lip reading)
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Deep Brain Stimulation Indications: Parkinsons Tremor Traumatic Brain Injury Others? www.sfn.com Illustration by Lydia Kibiuk Lead Lead Extension
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Implanted Stimulator DBS Electrode Deep Brain Stimulation System Clinician Programmer Implanted Electrode 1.27 mm
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Spinal Cord Stimulation Indications: Chronic Pain www.mayfieldclinic.com
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Cortical Stimulation Indications: Depression www.northstarneuro.com www.cyberonics.com Vagus Nerve Stimulation Indications: Epilepsy
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Retinal Prosthesis Argus I feasibility IDE 16 electrodes 6 Subjects implanted between 2002-2004 Argus II feasibility IDE 60 electrodes 17 subjects implanted to date (reported) Indication: Retinitis Pigmentosa – Bare Light Perception or worse www.clinicaltrials.gov , search “Argus II” for inclusion and exclusion criteria Other efforts: IMI, Retina Implant, Epi-Ret, MIT-Harvard, UNSW, Korea, others
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ARGUS I & II Clinical Trial Results Most electrode thresholds below published chronic safety limits for Pt Simple visual tasks can be performed (object identification) Improved mobility Letter Reading
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Brain Machine Interfaces Direct recording of brain activity to obtain a control signal for motor prosthesis or robotic limb Trigger neuromodulation to prevent seizure Hochberg, Nature, 2006
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Key Concepts Basis for neural stimulation Basis for neural recording Clinical and experimental systems Common system components Material requirements for neural implants Hermetic packaging (Jiang) Leads Neural stimulation material issues (Cogan) Electrode material (Cogan) Tissue (Shah, McCreery) Neural recording material issues (Polikov) Electrode array designs Tissue response (Polikov)
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Weiland_bme 410 fall 2011 - Biomaterials Issues for Neural...

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