Transcript No Slide Title

Lecture 17
Dimitar Stefanov
Functional Neural Stimulation for
Movement Restoration (FNS)
•FNS activates paralyzed skeletal muscles by using an
electronic stimulator, which delivers trains of pulses to
neuromuscular structures.
•The basic phenomenon of the stimulation is a contraction
of muscle due to the controlled delivery of electric charge
to neuromuscular structures.
FES systems is applied to restoration of:
1. Goal-oriented movements (movements at hand or arm);
2. Cyclic movements (walking and standing movements).
Block diagram of FNS model
The time delay between muscle stimulation and muscle activation is called the
neural dynamics.
Non-linear relationship between input activation and generated joint torque
(depends on the joint angle, the joint velocity and acceleration).
Limb dynamics – depends on the mass and inertia characteristics of the limb,
damping, elasticity, stiffness.
Upper extremity FES
A./ Classification, regarding the part of the upper limb, which will be
stimulated:
a./ FES of hand motions;
b./ FES of elbow motions;
c./ FES of shoulder motions.
B./ Classification, regarding the source of control signals to
trigger or regulate the FES patterns:
1. Shoulder control (Buckett et al., 1988);
2. Voice control (Handa at al., 1982; Nathan&Ohry, 1990);
3. Respiratory control (Hoshimiya et al., 1989);
4. Joystick control (Peckham&Keith, 1992)
5. Position transducers (Prochazka, 1993;
Rebersek&Vodovnik, 1973).
C./ Classification, regarding the number of the channels for FES patterns:
1. Systems with one- or two channels;
2. Multi channels systems.
D./ Classification of the systems, regarding the type of the
electrodes:
1. FES systems based on surface electrodes (transcutaneous
electrodes);
2. FES systems based on implanted electrodes (percutaneous
electrodes);
3.
FES systems based on implantable stimulators.
Review of some systems for FES:
1963 (Long&Mascirelli) – the first grasping system (prehension and
release); a spring for hand closure and electrical stimulation for
of the the thumb extensor for release.
1984 (Rudel at al.) simple two-channel stimulation system and a
shoulder activated position transducer (sliding potentiometer); at
the neutral position of the potentiometer –stimulation pulses
stop;
First FES clinic - in Sendai (Japan) – many persons are implanted
with up to 30 intramuscular electrodes – mainly for therapy, not
to assist in grasping.
Review of some systems for FES (continue):
Japanese FES systems for functional grasping, activated by
voice or suck&puff interface; use of pre-programmed EMGbased stimulation patterns; applied to subjects with lack of
natural grasping and elbow movements.
1989 – Ben Gurion University, Israel (Nathan) – voice
controlled multichannel surface electrode system; 12 bipolar
stimulation channels; control of elbow, wrist and hand
function; surface stimulation (doesn’t allow dexterity while
grasping); problem – need of everyday mounting and fitting
of the system.
Institut fuer Biokibernetic, Karlsruhe, Germany –recording of
the EMG of weak muscle; amplifying the EMG and
stimulation the same muscle; special means to prevent the
positive feedback (Hollaender at al., 1987);
Review of some systems for FES (continue):
The Case Western Reserve University (CWRU) – fully
implantable system; hand opening/closing, selection of the
grasp, proportional control of palmar and lateral grip; joystick
for control of the stimulation signals; preprogrammed control;
joystick, activated by the contralateral shoulder. The
movement of the joystick activates preprogrammed sequence
of stimulation (the palmar grip starts from the extended
fingers and thumb, followed by movement of the thumb and
after that by fingers flexion); 1992 – (Peckham&Keith),
surgically modification of the grasp (pining some joints and
fixation of some tendons); two modes: grasp and hold,
potentiometer for control of the grip and additional EMG
signal for to hold the hand closed; application at home for
daily living tasks.
The Cleveland FES Center includes: Cleveland VA Medical Center, MetroHealth
Medical Center, Case Western Reserve University, and Edison BioTechnology Center.
Some projects of the Cleveland FES Center
http://feswww.fes.cwru.edu/projects/index.htm#briefs
Implantable Stimulation, Telemetry, and Transducer System for Neural Control
The transducer, implanted in the wrist, allows the individual to control
grasp opening and closing through voluntary movement of the wrist.
Under development – new version of stimulator; up to sixteen channels of
stimulation, one implanted joint angle transducer and two channels of myoelectric
signal transduction.
Myoelectric signal obtained from arm or neck muscles will be used to control
various features of the grasp and/or arm movements.
EEG-based Controller for FNS Hand Grasp Systems (P. Hunter Peckham); Persons with
C5 - C6 level spinal cord injury.
http://feswww.fes.cwru.edu/projects/phprsf.htm
Bionic glove (University of Alberta, CA, Arthur Prochazka), 1997; Neuromotion
Inc.,
http://www.ualberta.ca/~aprochaz/hpage.html
Hand opening and closing stimulator for C5-C6 quadriplegic people
Self-adhesive electrodes over certain muscles; elastic glove over the electrodes;
tightening the glove causes electrical contact with the electrodes; user's wrist
movements are sensed by a transducer control a microprocessor based stimulator.
Tremor suppression system, based on FES (A. Prochazka).
Restoration of standing and walking
Ljubljana, Slovenija (Bajd, 1982, Gracanin, 1967)
Single-channel stimulation system – applicable to special group of
patients with incomplete spinal cord injury who can perform limited
walking without FES system.
Multichannel system (1989) –FES system with at least four channels;
oriented to patients with complete spinal cord injury, who have preserved
upper-body control; stimulation of the quadriceps locks the knee. Swing
phase – by movement of the upper part of the body and using of rolling
walker; hand- or foot switches are used for flexion-extension alternation.
The Parastep Functional Electrical Stimulation System
Invented by Daniel Graupe (University of Illinois at Chicago, EECS
Dept.), produced by Sigmedics, Inc. of Northfield, IL.
The user controls the stimulation through switches on the handgrips of the
walker or through a keypad on the stimulator unit; standing and sitting,
taking right steps, taking left steps, and increasing and decreasing the
electrical current.
Implantable standing FES systems
http://feswww.fes.cwru.edu/standingsystem/index.html
Cleveland FES
center
Studies that include investigational devices for human use are registered with the Food and
Drug Administration (FDA).
Eight channel fully implantable system.
Remotely controlled wireless microstimulators
BION
Advanced Bionics Corporation
http://www.advancedbionics.com/products_frame.asp
Gerald Loeb, a biomedical engineer
at the University of Southern
California
The muscle wasting that afflicts many
stroke patients can lead to serious
complications such as thrombosis in
bedridden patients.
http://www.newscientist.com/ns/19991211/newsstory1.html
2 millimetres in diameter; can be injected directly into a
muscle using a 12-gauge needle; once in place they are
activated by a radio signal from a coil worn by the patient;
deliver a pulse of 30 milliamps for about 0.5 milliseconds.
•Devised in a cylindrical shape with a stimulation electrode on each end, the
microelectrodes contain their electronics in a hermetic glass capsule.
•Their physical dimensions are 2 mm in diameter and 16 mm in length.
•The electrodes are made of an activated iridium disk and an oxidized sintered
tantalum slug which also serves as a power storage capacitor.
•The challenge of making the micro-stimulator consists of building a
miniature, temperature sensitive electronic assembly and enclosing it into a
slightly larger hermetic capsule made of high temperature glass.
• A custom CMOS chip, a rectifying diode and a chip resistor are mounted on a
miniature two-sided printed circuit board, 0.18 mm thick.
•The components are connected by gold wire bonds and 0.15 mm wide goldplated copper traces.
CUSTOM SILICON CHIP TECHNOLOGY FOR IMPLANTABLE FES MICROSTIMULATORS
Primoþ Strojnik, Joseph Schulman, Philip Troyk,Gerald Loeb, and Paul Meadows
http://www.bme.med.ualberta.ca/~fes/ifess/page/p21.htm
http://www.dinf.org/resna96/page116.htm
•The chip-PC board assembly is sandwiched between two ferrite
half-cylinders.
•Two layers (200 turns) of 25 mm insulated copper wire wound on
the ferrite represent a self-resonating receiving coil.
• The ends are attached to the PC board.
• A layer of a glob-top epoxy secures the components and the bond
wires.
•Building the hermetic package involves making hermetic glass
bead to metal seals to make electrode feed-throughs, creating
contacts on the inside of the feed-through, and making a glass bead
to glass capsule final seal.
•A miniature spring coil maintains a reliable connection between the
inside feed-through contacts and the electronic assembly.
•Hermeticity better than 1x10^-10 atm-cc/s was achieved in sealing
the microstimulators.
CUSTOM SILICON CHIP TECHNOLOGY FOR IMPLANTABLE FES MICROSTIMULATORS
Primoþ Strojnik, Joseph Schulman, Philip Troyk,Gerald Loeb, and Paul Meadows
http://www.bme.med.ualberta.ca/~fes/ifess/page/p21.htm
http://www.dinf.org/resna96/page116.htm
•The BION produces asymmetric biphasic constantcurrent pulses.
•The BION receives power as well as stimulation
commands via magnetic link from an external coil
that is worn by the patient.
•An amplitude modulated 2 MHz carrier powers and
transfers stimulation data to the micro-stimulator
and provides the basic clock for the digital part of
the micro-stimulator circuitry.
•The microstimulators are addressable. One coil can
control up to 255 uniquely addressable BIONs.
http://www.biontech.org/about/what_is_a_bion_01.html
Problems, which limit the effectiveness of the FES systems:
•Fast fatigue
•Reduced torques generated through FES in comparison with
central nervous system control
•Osteoporosis and stress fractures.
Hybrid Assistive systems (HAS)
Integration of two assistive systems: FES system and external
mechanical orthosis.
Advantages:
1. Partial mechanical support
2. Parallel operation of the biological and mechanical system
3. Sequential operation of the biological and the mechanical system.