Implantable Neural Prostheses 1 (eBook)

Preface 6
Contents 7
Contributors 9
List of Acronyms 12
Microelectronic Visual Prostheses 16
1 Introduction 16
2 Biomedical Engineering Approaches for Restoring Vision to the Blind 17
2.1 Visual Pathway 17
2.2 Eye and the Retina 18
2.3 Candidate Retina Diseases for the Retinal Implants 20
2.4 Biomedical Engineering Approaches for Visual Implants 21
3 Microelectronic Visual Implant Technologies 21
3.1 Retinal Stimulation and Retinal Implants 22
3.2 Epiretinal Implant 23
3.3 Subretinal Implant 27
3.4 Extraocular Implant 30
3.5 Visual Stimulation in the Brain 32
3.5.1 Cortical Stimulation 32
3.5.2 Visual Stimulation in LGN of the Thalamus 34
3.6 Optic Nerve Stimulation 35
4 Engineering Challenges in the Development of Visual Prostheses 35
4.1 Implant Packaging and Biocompatibility of Materials 36
4.2 Thermal Effects of Stimulator on Tissues and Heat Damage 39
4.3 Stimulation Microelectrode Arrays 41
4.3.1 Planar Electrodes 42
4.3.2 Flexible Thin-Film Electrode Arrays 43
4.4 Electrode Materials 45
4.4.1 Capacitive Electrodes 45
4.4.2 Titanium Nitride 46
4.4.3 Iridium Oxide 47
4.4.4 Platinum Gray 47
4.5 Surgical Attachment of Stimulation Microelectrode Arrays 49
5 Conclusion 51
References 51
Visual Prosthesis for Optic Nerve Stimulation 58
1 Introduction 58
2 Penetrating Microelectrode Arrays 61
2.1 Noise and Impedance Analyses 61
2.2 The Tungsten Shafts 63
2.3 The Pt/Ir Alloy Shafts 64
2.4 Silicon-Based Microelectrode Arrays 65
3 Neural Electrical Stimulator 67
3.1 Communication Unit 67
3.2 Processing and Control Unit 68
3.3 Electrode Driver Unit 69
4 Image Acquisition and Processing 71
4.1 Image Acquisition 71
4.2 DSP-Based Image Processing System 72
4.2.1 Hardware of Image Processing System 72
4.2.2 Image Processing Strategies 73
Image Classification 74
Different Image Processing Strategies According to Various Complexities 75
(A) Strategy 1: Simple Image 75
(B) Strategy 2: Middle-Complexity Image 75
(C) Strategy 3: Complex Image 76
5 Psychophysical Study for Visual Prosthesis 77
5.1 Recognition of Chinese Characters with a Limited Number of Pixels 78
5.1.1 Recognition Accuracy of Pixelized Chinese Characters Using Simulated Prosthetic Vision 78
5.1.2 Recognition of Chinese Characters with a Limited Number of Pixels Based on Complexity Analysis 79
5.2 Image Processing Based Recognition of Images with a Limited Number of Pixels 80
5.3 Dispersion and Accuracy of Simulated Phosphene Positioning 83
5.3.1 Tactile Perception Based on Phosphene Positioning Using Simulated Prosthetic Vision 84
5.3.2 Dispersion and Accuracy of Simulated Phosphene Positioning Using Tactile Board 86
6 Surgical Approach to Expose the Optic Nerve 87
6.1 Surgical Technique 87
6.2 Efficiency and Safety 88
7 In Vivo Electrophysiological Study 89
7.1 Subjects 89
7.2 Temporal Properties 89
7.2.1 Stimulations 89
7.2.2 Recordings 90
7.2.3 Temporal Properties of EEP 91
7.3 Spatial Properties 93
7.3.1 Stimulations 93
7.3.2 Recordings 94
7.3.3 The Spatial Responses to the Optic Nerve Stimulation 94
7.4 Assessment of the Damage to the Optic Nerve 96
8 Conclusion 96
References 96
Cochlear Implants 99
1 Introduction 99
2 System Review 101
3 External Unit 104
4 Radio Frequency Transmission Link 106
5 Internal Unit 108
5.1 Receiver and Decoder 108
5.2 Stimulator 110
5.3 Electrodes 111
5.3.1 Current Electrodes, Efficiency, and Intracochlear Trauma 111
5.3.2 Insertion Depth 114
5.3.3 Future Cochlear Implant Electrode Design 115
5.3.4 Summary 116
5.4 Back Telemetry 117
6 Safety Considerations 118
6.1 Biocompatibility 118
6.2 Sterilization 119
6.3 Mechanical Safety 120
6.4 Energy Exposure 120
7 Evaluation 121
8 Future Direction 121
References 123
A New Auditory Prosthesis Using Deep Brain Stimulation: Development and Implementation 131
1 Introduction 132
1.1 Rationale 132
1.2 Design Considerations 136
2 Device Development and Testing 141
2.1 Human Prototype Array 141
2.2 Feasibility and Safety Studies 144
3 Implementation in Humans 149
3.1 Surgical Approach 149
3.2 Patient Fitting 154
3.3 Hearing Performance 158
4 Future Directions 160
4.1 Electrode Technologies 161
4.2 Stimulation Strategies 163
References 164
Spinal Cord Stimulation: Engineering Approaches to Clinical and Physiological Challenges 168
1 Introduction to Spinal Cord Stimulation Therapy 168
1.1 Brief History of Spinal Cord Stimulation 168
1.2 Paresthesia: A Serendipitous ‘Side Effect’ 172
1.3 Introduction to Clinical and Physiological Challenges 174
2 Optimization of the Electric Field 175
2.1 Number of Implanted Contacts 175
2.2 Contact Size and Spacing 176
2.3 Electrical Sources for Stimulation 180
2.3.1 Voltage and Current Regulation 182
2.3.2 Single- and Multiple-Source Systems 183
2.3.3 Examples of Multiple-Source Systems 185
2.4 Electrical Management of Lead Migration 186
3 Clinical Programming Time 189
3.1 Historical Programming Approach 189
3.2 Device Programming in the Operating Room and Post-implant 190
3.3 Device Reprogramming 191
3.4 Real-Time Programming Strategies 192
4 Stimulation Parameters 194
4.1 Effects of Pulse Width 194
4.2 Effects of Stimulation Rate 195
5 Computational Models as an Engineering Tool 196
5.1 University of Twente Computational Model: Insight and Clinical Impact 196
5.1.1 Sensitivity Analysis of Transverse Tripolar Stimulation with Percutaneous Leads 197
5.1.2 Field Steering Between Contacts of Parallel Leads 199
5.1.3 Effect of Pulse Width 200
6 Summary 202
References 202
Microelectrode Technologies for Deep Brain Stimulation 208
1 Introduction 208
2 Implant Sites and Emerging Applications 210
3 Design Considerations and Challenges for Microelectrode Technologies in DBS 211
3.1 Summary of Key Requirements 211
3.2 Fabrication Technology and Materials 213
3.2.1 Substrates 213
3.2.2 Electrode Materials 217
3.3 Stimulation Parameters and Requirements of a Clinical System 219
3.4 Stimulation Safety and Tissue Response 220
3.5 Closed-Loop Control of DBS 222
3.6 Recording Capability and Long-Term Stability 223
4 Conclusions 225
References 225
Implantable Cardiac Electrostimulation Devices 233
1 Introduction 233
2 Pacemaker, ICD, and Lead Codes 234
3 Pacemakers and ICDs 234
3.1 External Pacemakers 234
3.2 Artificial Implantable Ventricular Pacemakers 236
3.3 Artificial Implantable Atrial Pacemakers 242
3.4 Dual-Chamber Pacemakers 243
3.5 Cardiac Resynchronization Therapy (CRT) Devices (Pacing Both the Right and the Left Heart) 244
3.6 Implantable Cardioverter Defibrillators 248
4 Modern Pacemaker and ICD Components 248
4.1 Pacemaker Power Sources 248
4.2 ICD Power Sources 249
4.3 Pacemaker Circuitry Design Requirements 249
4.4 ICD Circuitry Design Elements 250
4.5 Pacemaker and ICD Mechanical Components 250
4.6 Leads 251
4.7 Programmability and Automaticity 253
5 Summary of Indications for Pacemaker Implant 253
5.1 The Cardiac Conduction System 254
5.2 Acquired AV Block 255
5.3 Sinus Node Dysfunction (Sick Sinus Syndrome or SSS) 255
5.4 Prevention and Termination of Tachyarrhythmias 255
5.5 Hypersensitive Carotid Sinus and Neurocardiogenic Syncope 256
5.6 Cardiac Transplantation 256
5.7 Atrial Fibrillation (AF) and Flutter 256
5.8 Heart Failure 256
6 Summary of Indications for ICD Implant 257
7 Clinical Management of Complications, and Related Improvements Over Time 258
7.1 Medical Complications 258
7.2 Hardware Complications 259
8 Conclusions 259
References 260
The Bion Microstimulator and its Clinical Applications 264
1 Introduction 264
2 Development of Bion Microstimulator 265
2.1 First-Generation RF-Powered Bion Microstimulator 266
2.2 Second-Generation RF-Powered BionMicrostimulator 267
2.3 First-Generation Battery-Powered Bion Microstimulator 271
2.4 Second-Generation Battery-Powered Bion Microstimulator 272
3 Clinical Applications of Bion Microstimulator 272
3.1 RFB1 Applications 272
3.1.1 RFB1 for Shoulder Subluxation in Post-Stroke Patients 273
3.1.2 RFB1 for Knee Osteoarthritis 274
3.1.3 RFB1 for Post-Stroke Hand Contractures 274
3.1.4 RFB1 for Foot Drop 275
3.1.5 RFB1 for Pressure Ulcer Prevention 275
3.2 RFB2 Applications 276
3.2.1 RFB2 for Post-Stroke Shoulder Subluxation 276
3.2.2 RFB2 for Post-Stroke Hand and Arm Rehabilitation 276
3.3 BPB1 Applications 277
3.3.1 BPB1 for Overactive Bladder 277
3.3.2 BPB1 for Refractory Headaches 279
3.3.3 BPB1 for GERD (Preclinical) 281
4 Summary 281
References 282
Brain Control and Sensing of Artificial Limbs 285
1 Introduction 285
2 Limb Loss and Electrical Neural Stimulation 286
2.1 Limb Loss in the United States 286
2.2 Stimulation on Peripheral Nerves, Neurons, and Neuroma 287
3 Experiments on Humans and Animals 288
3.1 Development of the Utah Bed of Nails Electrode Array 288
3.2 First Human Implant to Control Robotic Devices 288
3.3 Testing of the Concept in Amputees 291
4 Implants: Designing the Ultimate Peripheral Nerve Interface 292
4.1 The Implant Design 292
4.2 Challenges and Problems in the Development of Implantable Miniature Peripheral Nerve Interface 294
4.2.1 Packaging Hermeticity 294
4.2.2 Implant Size 296
4.2.3 Internal Construction of the Implant 296
4.2.4 Components on the Hybrid Circuit 297
4.2.5 Coil and Antenna 298
4.2.6 Chip and Crystal Oscillator 298
4.2.7 Indifferent Electrodes 298
4.2.8 Wireless Power 298
4.2.9 Wireless Communication 298
4.2.10 Prosthetic Master Control Unit (PMCU) 299
4.2.11 Clinicians Fitting Unit 300
5 Conclusion 300
References 300
Magnetic Stimulation of Neural Tissue: Techniques and System Design 302
1 Introduction 302
2 Field-Based Comparison of Electrical and Magnetic Stimulation 304
3 Magnetic Modeling 310
4 Core 317
5 Systems for Magnetic Stimulation 321
6 Pulsed System 322
6.1 Scaling 326
7 Current Source System 327
7.1 Overview 327
7.2 Circuit Design 328
7.3 Rate of Closure Stability Analysis 330
7.4 Output Stage Design Details 332
7.4.1 Scaling 334
7.5 Circuit Testing 334
7.5.1 Verification of the Current Waveforms 334
7.5.2 Verification of the Electric Field 336
8 Neural Preparations 336
9 Selection 340
10 Methods 341
10.1 Data Acquisition and Control 341
10.1.1 Electrophysiological Recording and Stimulation 342
10.1.2 Tissue Culture 344
11 Results 345
12 Conclusion 347
Appendix: Modeling Magnetic Stimulation with Solenoid Coil 347
Current Slew Rate and Power Consumption 350
14.1 Slew Rate 350
14.2 Power Consumption 352
15 Scaling with Planar Coil 352
References 353
Regulatory Approval of Implantable Medical Devices in the United States and Europe 361
1 Introduction 361
2 Regulatory Affairs Approval Process in the United States 361
2.1 Classification Panels 362
2.1.1 Class I Devices 362
2.1.2 Class II Devices 363
2.1.3 Class III Devices 364
2.2 Clinical Phase 365
2.2.1 Pilot Trial 365
2.2.2 Pivotal Trial 365
2.3 Clinical Trials 366
2.4 Types of Domestic Applications 367
2.4.1 Premarket Notifications or 510(k)s 367
2.4.2 Expedited PMAs 368
2.4.3 Premarket Reports 368
2.4.4 Panel-Track Supplements 368
2.4.5 180-Day PMA Supplements 368
2.4.6 Real-Time PMA Supplements 368
2.4.7 Original Premarket Approval (PMA) 368
2.5 The 510(k) Review Process 368
2.6 The PMA Process 369
2.7 Humanitarian Device Exemptions (HDEs) 372
3 European Regulatory Approval Process 375
3.1 European Union (EU) Regulatory Approval 375
3.1.1 Competent Authority 375
3.1.2 Notified Bodies 376
3.2 European Device Classification 376
3.2.1 Class I 376
3.2.2 Class IIa 377
3.2.3 Class IIb 377
3.2.4 Class III 377
4 Conclusion 377
References 378
Index 379