E-Book, Englisch, 194 Seiten
Fitzpatrick Implantable Electronic Medical Devices
1. Auflage 2014
ISBN: 978-0-12-416577-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark
E-Book, Englisch, 194 Seiten
ISBN: 978-0-12-416577-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark
Dr Fitzpatrick is a Chartered engineer and lecturer at the University of East Anglia teaching electrical and electronic engineering with a research interest in Biomedical Engineering. His primary research interest is in the use of Functional Electrical Simulation (FES) for the restoration of bladder function and restoration of gait in stroke and spinal cord injured patients. His research focuses on the design and development of custom designed implantable electrodes. His recent book, Analogue Design and Simulation using OrCAD Capture and PSpice, published by Elsevier, has sold worldwide to highly acclaimed reviews in numerous prestigious electronic engineering journals including EDN and Electronic Times, the book being officially endorsed by Cadence Design Systems. Dr Fitzpatrick has published other books in the field of Biomedical Engineering and is the Series editor for the Developments in Biomedical Engineering and Bioelectronics book series by Elsevier.
Autoren/Hrsg.
Weitere Infos & Material
1;Front Cover;1
2;Implantable Electronic Medical Devices;4
3;Copyright Page;5
4;Contents;6
5;Preface;10
6;1 Retinal Implants;12
6.1;1.1 Introduction;12
6.2;1.2 The Retina;13
6.3;1.3 Photoreceptor Cells;14
6.4;1.4 Bipolar and Ganglion Cells;17
6.5;1.5 Retinal Implants;18
6.6;1.6 Microelectrodes;19
6.7;1.7 Microphotodiodes;20
6.8;1.8 Argus II Retinal Prosthesis (Second Sight Medical Products);21
6.9;1.9 Artificial Silicon Retina Implant, Optobionics;23
6.10;1.10 Alpha-IMS Implant by Retina Implant AG;24
6.11;1.11 Bionic Vision Australia;26
6.12;1.12 Boston Retinal Implant Project: Bionic Eye Technologies, Inc. and Visus Technologies, Inc.;28
6.13;Bibliography;29
7;2 Smart Contact Lens;30
7.1;2.1 Introduction;30
7.2;2.2 Measurement of IOP;31
7.3;2.3 Triggerfish from Sensimed;33
7.4;Bibliography;36
8;3 Phrenic Nerve Stimulation;38
8.1;3.1 Introduction;38
8.2;3.2 Atrotech Atrostim Phrenic Nerve Stimulator;40
8.3;3.3 Avery Biomedical Devices Breathing Pacemaker System;41
8.4;3.4 Synapse Biomedical Inc. NeuRx Diaphragm Pacing System;45
8.5;Bibliography;46
9;4 Glucose Biosensors;48
9.1;4.1 Introduction;48
9.2;4.2 Amperometric Glucose Sensor;51
9.2.1;4.2.1 Glucose Detector Based on Measurement of Hydrogen Peroxide;51
9.2.2;4.2.2 Glucose Detector Based on Measurement of Oxygen;54
9.3;4.3 Potentiostat Measurement of Glucose;54
9.4;4.4 Next Generation of Glucose Sensors;56
9.5;4.5 Implantable Glucose Sensor by GlySens;57
9.6;4.6 Implantable Continuous Glucose Monitoring GlySens;58
9.7;4.7 GlucoChip PositiveID Corporation and Receptors LLC;59
9.8;Bibliography;62
10;5 Cochlear Implants;64
10.1;5.1 Introduction;64
10.2;5.2 Types of Hearing Loss;66
10.3;5.3 Cochlear Implants;67
10.4;5.4 Cochlea Electrode Arrays;67
10.5;5.5 Speech Coding;68
10.6;5.6 Cochlear Implant Systems;68
10.7;5.7 Continuous Interleaved Sampling;71
10.8;5.8 HiRes120;72
10.9;5.9 Lifestyle™ Cochlear Implant Systems by Advanced Bionics™;73
10.10;5.10 ClearVoice™;73
10.11;5.11 n-of-m, Spectral Peak Extraction (SPEAK) and Advanced Combinational Encoder (ACE);75
10.12;5.12 Nucleus® 6 System, Cochlear;77
10.13;5.13 Dual-Loop AGC;79
10.14;5.14 Fine Structure Processing;80
10.15;5.15 MAESTRO™ Cochlear Implant System by MED-EL;82
10.16;Bibliography;84
11;6 Pacemakers and Implantable Cardioverter Defibrillators;86
11.1;6.1 Introduction;86
11.2;6.2 Types of Pacemakers;90
11.3;6.3 Revised NASPE/BPEG Generic Code for Antibradycardia Pacing;91
11.4;6.4 Implantable Cardioverter Defibrillators;93
11.5;6.5 NASPE/BPEG Defibrillator Code;95
11.6;6.6 Implantable Cardioverter Design;96
11.7;6.7 Medtronic Micra Transcatheter Pacing System;99
11.8;6.8 Medtronic Viva and Evera;100
11.9;6.9 Sorin Group Kora 100;101
11.10;6.10 Biotronik;103
11.11;6.11 St Jude Medical Nanostim™;104
11.12;6.12 St Jude Unify Quadra™ and Accent™;105
11.13;6.13 Boston Scientific Ingenio™ and Incepta™;106
11.14;6.14 Boston Scientific Subcutaneous ICD;107
11.15;Bibliography;108
12;7 Bladder Implants;110
12.1;7.1 Introduction;110
12.2;7.2 Detrusor Hyperreflexia;111
12.3;7.3 Detrusor Areflexia;112
12.4;7.4 Overactive Bladder Syndrome and Urine Retention;112
12.5;7.5 Sacral Anterior Root Stimulation;112
12.6;7.6 Finetech-Brindley Sacral Anterior Root Stimulators, Finetech Medical Ltd.;113
12.7;7.7 Medtronic InterStim® Therapy;115
12.8;Bibliography;117
13;8 Electrical Stimulation Therapy for Pain Relief and Management;118
13.1;8.1 Occipital Nerve Stimulation;118
13.2;8.2 St Jude Medical Implantable Pulse Generators for ONS of the Occipital Nerves;118
13.3;8.3 Boston Scientific Precision Spectra™ SCS System;119
14;9 Electrical Stimulation Therapy for Parkinson’s Disease and Dystonia;122
14.1;9.1 Introduction;122
14.2;9.2 Vercise™ Deep Brain Stimulator, Boston Scientific;123
14.3;9.3 Medtronic Activa PC+S DBS;124
14.4;9.4 St Jude Medical Brio™ DBS;126
15;10 Electrical Stimulation Therapy for Epilepsy;128
15.1;10.1 Introduction;128
15.2;10.2 Seizure-Detection Methods;129
15.3;10.3 NeuroPace RNS® Stimulator Neurostimulator;131
15.4;10.4 Cyberonics Inc. VNS;133
15.5;Bibliography;134
16;11 Peripheral Nerve Stimulation;136
16.1;11.1 Drop Foot Stimulators;136
16.1.1;11.1.1 Introduction;136
16.1.2;11.1.2 STIMuSTEP® Finetech Medical Ltd.;138
16.1.3;11.1.3 ActiGait®, Ottobock;139
16.2;11.2 Handgrip Stimulators;141
16.2.1;11.2.1 STIMuGRIP® Finetech Medical Ltd.;142
17;12 Lower Esophagus Stimulator;144
17.1;12.1 Introduction;144
17.2;12.2 EndoStim® Lower Esophagus Stimulator;145
18;13 Vagal Blocking Therapy;148
18.1;13.1 Introduction;148
18.2;13.2 EnteroMedics® VBLOC Vagal Blocking Therapy;148
19;14 Implantable Drug Delivery Systems;150
19.1;14.1 Introduction;150
19.2;14.2 Electromagnetic Micropumps;151
19.3;14.3 Osmotic Micropumps;152
19.4;14.4 Electro-osmotic Micropumps;154
19.5;14.5 Electrolysis Micropumps;154
19.6;14.6 Wireless Microchip Drug Delivery System by MicroCHIPS Inc.;155
19.7;14.7 CODMAN® 3000 Constant Flow Infusion System Implantable Pump by Codman & Shurtleff, Inc.;158
19.8;14.8 SynchroMed® II Infusion System by Medtronic;160
19.9;14.9 MIP Implantable from Debiotech™;162
19.9.1;14.9.1 DebioStar™;163
19.10;14.10 Ophthalmic MicroPump™ Replenish, Inc.;164
19.11;14.11 IntelliDrug™ System from IntelliDrug;167
19.12;Bibliography;168
20;15 Wireless Endoscopy Capsules;170
20.1;15.1 Introduction;170
20.2;15.2 PillCam® Capsule Endoscopy by Covidien GI Solutions;172
20.2.1;15.2.1 PillCam® SB 3;173
20.2.2;15.2.2 PillCam® COLON 2;174
20.2.3;15.2.3 PillCam® ESO 2;174
20.2.4;15.2.4 PillCam® patency;175
20.2.5;15.2.5 PillCam® Sensor Belt and Recorder;175
20.3;15.3 Sayaka EndoScope Capsule by RF SYSTEM Lab;177
20.4;15.4 MiroCam® Capsule Endoscope System from IntroMedic Co.;178
20.5;15.5 CapsoCam® Capsule Endoscope SV-2 from CapsoVision;183
20.6;15.6 EndoCapsule System EC-S10 by Olympus, Inc.;185
20.7;15.7 OMOM Capsule Endoscope System by Chongqing Jinshan Science & Technology (Group) Co., Ltd;187
21;Index;190
Retinal Implants
This chapter introduces the main anatomical features of the eye, the processes involved in vision and eye disorders, and diseases such as retinitis pigmentosa and age-related macular degeneration which can affect normal vision. The use of microelectrodes and microphotodiodes in retinal, subretinal, and suprachoroidal implants is introduced with an emphasis on the Argus II Retinal Prosthesis (Second Sight Medical Products); the Artificial Silicon Retina (Optobionics); Alpha-IMS (Retina Implant AG); Wide-View BVA and High-Acuity BVA (Bionic Vision Australia); and Boston Retinal Implant Project (Bionic Eye Technologies, Inc. and Visus Technologies, Inc.).
Keywords
Retina; retinitis pigmentosa; AMD; microphotodiodes; microelectrodes; epiretinal; subretinal; suprachoroidal
1.1 Introduction
Figure 1.1 shows the main anatomical features of the eye. In normal sight, light enters the eye through the pupil and is focused onto the retina at the back of the eye, stimulating photocells that translate the light into electrical signals. These electrical signals travel down the optic nerve to the visual centers in the brain where they are decoded and perceived as images. Progressive diseases of the eye that result in partial or total loss of vision include glaucoma, retinitis pigmentosa, and macular degeneration.
Figure 1.1 Structure of the eye.
Glaucoma results from an increase in the internal pressure of the eye, the effects of which are irreversible, eventually leading to loss of sight. However, if detected early, the onset of the disease can be managed with medical treatment or laser surgery. Measuring the intraocular pressure of the eye can help in detecting the early stages of the disease (see Chapter 2).
Retinitis pigmentosa is a genetic disorder resulting in the degeneration of the photoreceptor cells in the retina, leading to partial or complete loss of sight. Currently there is no cure, although gene therapy in which a virus is used to deliver sight-restoring therapeutic genes to the photoreceptors at the back of the eye may offer an alternative form of treatment in the future.
Age-related macular degeneration (AMD) is another disease of the retina, but it only affects a small area of the retina known as the macula which contains a small population of cone-type photoreceptor cells that are more responsive to bright light levels required for reading and viewing objects close up and in greater detail. The onset of AMD occurs in the later stages of life and only leads to a partial degeneration of sight.
Retinal implants are used to help people with degenerative retinal diseases such as retinitis pigmentosa and AMD where the optic nerve and the visual centers in the brain are still functioning but the patient has lost light or sight perception due to degeneration of the outer layer of the retinal photoreceptor cells. However, the cells in the inner retinal layer are relatively intact compared to the outer cells and it is the inner cells which form a neuronal ganglion interface to the optical nerve. Retinal implants will not benefit people who have been blind from birth because their optical visual neuronal circuits and visual processing centers in the brain have not been developed or conditioned to perceive vision.
1.2 The Retina
Light entering the eye through the lens is focused onto the retina which consists of a thin layer of transparent neural tissue located at the back of the eye. Near the center of the retina is a region known as the macula which has a high concentration of neural cells responsible for seeing detailed colors and represents the center of vision. At the center of the macula is a small depression or dimple known as the fovea which represents the absolute center of vision and highest color resolution attainable, providing the clearest and sharpest images. Subsequently, the eye continuously moves (saccades) such that the lens focuses images of interest onto the fovea for the highest image of color resolution.
The retina is made up of three main functional neural cell layers: photoreceptor cells, bipolar cells, and ganglion cells. Interspersed between the layers are the horizontal and amacrine neural cells as shown in Figure 1.2. The photoreceptor cells at the back of the retina transduce photon light energy into graded neural signals which are transmitted and processed via the bipolar and ganglion cell layers. It is the axons of the ganglion cells which together collectively form the optic nerve which leads to the visual processing centers in the brain.
Figure 1.2 Structure of the retinal layers.
1.3 Photoreceptor Cells
There are two types of photoreceptor cells: rods, which have the ability to detect color but are sensitive to low light levels (scotopic vision), and cones, which in bright light are sensitive to colors (photopic vision) in the visible spectrum. The rods and cones are made up of four segments (Figure 1.3): the outer segment, inner segment, cell body (nucleus), and synaptic terminals.
Figure 1.3 Photoreceptor cone and rod cells.
The outer segment in rods and cones consists of the outer membrane folding in on itself and stacking up to form disks. In the case of rods, the in-folded membranes become detached and the disks float inside the outer segment. Located on the disks are light-sensitive pigment proteins, rhodopsin in rods, and iodopsin in cones. The inner segment contains mitochondria which provide the energy required for chemical reactions and the cell body which contains the cell nucleus and other cell organelles essential to maintain cell functionality. The synaptic terminals provide for the transmission of glutamate neurotransmitters between neural cell synaptic bodies.
In rods, the outer segment is cylindrical, whereas for cones, the outer segment is conical in shape (Figure 1.4). Typical outside diameters for the inner and outer segments are 2 µm for rods and 6 µm for cones. The rods also contain a greater number of light-sensitive disks in the outer segment compared to cones, resulting in a greater sensitivity to light. There are typically 120 million rods compared to 6 million cones in the retina.
Figure 1.4 Structure differences between rods and cones. (http://www.ic.ucsc.edu/~bruceb/psyc123/Vision123.html.pdf.)
In rods, all the disks contain the same light-sensitive pigment, rhodopsin, which exhibits a peak absorption of light energy at a wavelength of 500 nm which lies within the blue-green region of the visual light spectrum. In cones, the light-sensitive iodopsin pigment occurs in three varieties due to differences in their amino acid sequence, each with different peak absorption wavelengths in the red (560 nm), blue (420 nm), and green (530 nm) regions of the visible light spectrum, respectively.
Although each cone contains three different opsin pigment types, there are three different types of defined cones: short-wave (blue light), medium-wave (green light), and long-wave (red light), each with a predominant opsin variety in the cone. The superimposition of the light absorption response of each opsin pigment will result in a peak response around the area of the defined cone color type. For example, the peak response of a long-wave cone will be shifted due to the superimposition of the individual blue and green opsin spectrum absorption responses, toward the yellow-green region of the visible spectrum as shown in Figure 1.5.
Figure 1.5 Electromagnetic spectrum of the human eye.
Figure 1.6 shows a rod photoreceptor cell with sodium- and potassium-specific ion channels in the outer membrane. In the absence of light, there will be a continuous flow of positively charged sodium ions into the cell and potassium ions out of the cell, collectively known as the “dark current.” This dynamic arrangement gives the photoreceptor cell a resting potential of approximately -30 to -40 mV. Neurotransmitters (glutamate) are also released from the synaptic terminals of the photoreceptor cell. When light photons strike the visual pigments in the disks, a series of chemical reactions involving enzyme activity causes the cell to hyperpolarize and reduce the release of synaptic neurotransmitters.
Figure 1.6 Induced ionic currents in photoreceptor cell.
1.4 Bipolar and Ganglion Cells
As shown in Figure 1.2, the bipolar and ganglion cell layers are interlaced with two other cell types, the horizontal and amacrine cells. The neural signals from the photoreceptor cells interface with the bipolar cells directly or indirectly via the horizontal cells, which in turn interface with other bipolar cells or other adjacent horizontal cells. Similarly, the bipolar cells interface with the ganglion cells directly or indirectly via the amacrine cells, which in turn interface with other ganglion cells and other adjacent amacrine cells.
There are two types of bipolar cells, both of which receive the glutamate neurotransmitter, but the ON-center bipolar cells will depolarize, whereas the OFF-center bipolar cells will hyperpolarize. This arrangement helps provide a spatial processing of the visual input derived from the photoreceptor cells. The bipolar cells provide one of many sensory inputs to the ganglion cells which are thought to be involved with temporal aspects of color vision being sensitive to speed of movement. The output synapses of the ganglion...
