Model-based design software is playing a behind-the-scenes
role in helping researchers and doctors restore some movement and mobility to
patients suffering from neuromuscular disabilities typically resulting from a
stroke or paralysis.
The Cleveland FES Center
at Case Western Reserve University is a
consortium of the university, the Louis Stokes Cleveland VAMC and MetroHealth
Medical Center, which are working in partnership to advance the clinical
deployment of technologies and treatments dedicated to restoring function in
people that suffer with neuromuscular disorders. The primary focus of the
center's research is functional electrical stimulation (FES), the concept of
applying electrical currents to generate or suppress activity in the nervous
system, which in turn, helps patients produce and control movement of otherwise
paralyzed limbs for such functions as standing or grasping with hands.
At the heart of the center's effort is a physical FES
device, akin to a pacemaker, which is surgically implanted inside a patient
along with lead wires that go to the individual muscles. Both are controlled
through a separate, external device, which consists of a microcontroller along
with a power supply and user interface for administering the unit. While the
physical hardware remains the same with each patient, the software that
controls how and where the electrical stimulation is delivered to produce the
movement varies according to the individual's specific impairment. Once programmed
with a course of action, the external FES control unit sends electrical
impulses to electrodes, which are implanted in the body or worn on the skin.
The electrical impulses restore some mobility to patients allowing them to
stand, in some cases, or to regain some use of their hands for grasping motion,
according to Robert Kirsch, PhD, professor, Biomedial Engineering, at Case
Western Reserve University and associate director of technology for the
Cleveland FES Center.
Traditionally, the research team at the center relied on
electrical engineers to individually program each device to meet the patient's
requirements - a process that could take weeks. Now, using software from The MathWorks, the center's own research
engineers are now able to customize and test prototype FES
devices for a specific patient's course of treatment immediately using
model-based design techniques like graphical block diagramming.
"There's no such thing as a standard spinal cord injury or standard
stroke-people have a variety of impediments and we often have to customize the
application for the particular use," says Kirsch. "It was a very slow process,
from identifying the change to utilizing the change. We were looking for
something to turn it around much faster."
To address the latency issue, the FES Center research
engineers developed the Universal External Control Unit (UECU), a modular
software and hardware architecture so engineers in the clinic can modify FES
controller applications and immediately test the results. Using the Simulink modeling and
simulation software for multidomain systems and the MATLAB technical computing
and programming environment, among other tools, research teams can now develop
algorithms that suit individual patient scenarios, reducing the development
cycle for FES functions to as little as a day.
"The Simulink approach and real-time tools allowed us to
modify our control algorithms and instantaneously try them in a participant,"
Kirsch explains. "All we have to do is adjust the block diagram, build the
model and download it into the external control unit to test in the
participant. Instead of taking three weeks, it now takes a half hour or 20
minutes."
Ultimately, the approach means the FES Center can be more
responsive to its patient's needs - currently close to 50 individuals are
benefiting from the FES technology as part of their research. From a
development perspective, the model-based tools have changed the game in terms
of how the FES Center develops application software. "Software has always been
the bottleneck and that's no longer the case," Kirsch says.
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