Medical Design Briefs - November 2023 - 28

tend to have fewer synergies available to
construct
their muscle
activations, "
Fregly says. " You might say they've lost
one or two neural control building
blocks as a result of the stroke, which
means they can't generate the same repertoire
of signals to control their muscles,
and so they can't move as well.
" One of the challenges for stroke rehabilitation
is, can you find ways to train
people's brains so that you can help
them recover lost synergies? We think we
can predict how to do that. We're not
there yet, but we're close. "
Using data from an individual poststroke
walking at their self-selected
speed of 0.5 meters per second, Fregly's
group generated three different predictions
of how the subject would walk at
their fastest-comfortable speed of 0.8
meters per second.
" One prediction assumed we had
torque actuators, like in a robot, controlling
the lower body joints, so no muscles, "
Fregly says. " A second prediction
assumed we had muscle actuators, but all
muscles were controlled independently.
The third prediction also assumed we
had muscle actuators, but now all muscles
were controlled using a small number
of synergies.
" As our model moved from torque
controls to individual muscle controls to
synergy controls, it became more realistic
as well as personalized physiologically.
Interestingly, the approach that was the
most physiological - using synergy controls
- also produced the most accurate
prediction of how the subject walked at
their fastest comfortable speed. It was
like magic. "
Pelvic cancer surgery is another clinical
example where the NMSM Pipeline could
help guide treatment decisions.
" You can't cookie-cutter surgical treatments
for people who get pelvic cancer, "
Fregly says. " Oftentimes, a patient will
lose a hip joint. For some patients, the
best surgical option might be to implant a
custom prosthesis that replaces lost bone
and hip joint function, while other patients
might benefit more from a surgical
option that does not replace the removed
bone and hip joint.
" For both options, we are already collecting
pre-surgery walking data from individual
patients, creating a personalized
computer model of each patient, and predicting
each patient's post-surgery walking
function given knowledge of the implemented
surgical decisions, " he says.
" Once we can closely match each patient's
post-surgery walking data, we will be ready
to inform actual surgical planning with
the goal of maximizing each patient's
post-surgery walking function. "
A computational simulation tool called
HeartFlow is already being used clinically
to determine optimal stent placement for
patients who undergo cardiac procedures.
" HeartFlow combines a scan of a patient's
relevant anatomy with a computational
fluid dynamics model that simulates
blood flow through the arteries in
Digital Power for Medical Applications
Digital communications and
control deliver significant
benefits and flexibility.
Excelsys Technologies
Cork, Ireland
An aging population and a recognition
that early detection of ailments enhances
life expectancy and reduces
costs mean that the number of healthcare
applications is growing rapidly.
While powering medical technology
can be challenging, new digital configurable
power solutions offer a number
of benefits by enabling control and
communication with medical PSUs 'on
the fly.'
28
This article considers advanced power
solutions and how they deliver benefits
during both design and operation.
Medical devices and, in particular large
medical systems, often have complex power
challenges requiring power schemes
with
multiple
rails
and,
sometimes,
non-standard voltages in areas such as specialist
sensors and magnetic control. For
this reason, configurable power supplies
that offer significant design flexibility
have become highly popular in these applications.
These units have a mains-fed
front end and the capability to have multiple
output modules to provide different
voltages. It is also possible to combine the
modules in series or in parallel for the
most challenging of applications.
www.medicaldesignbriefs.com
When deployed for healthcare applications,
the front end of the configurable
power supply will be designed and
certified to meet relevant medical standards
such as EN/IEC 60601. This provides
the necessary safety isolation for
patient, ensures operator safety and limits
parameters such as leakage current
within acceptable ranges. This gives designers
confidence that, once configured,
the power supply will not impede
certification of the entire system.
n Leveraging Digital Power
Technology
Increasingly, configurable power solutions
are leveraging digital technology,
both for control of the power supply and
Medical Design Briefs, November 2023
the heart, " Fregly says. " Doctors can use
it to test different stent sizes and placements
to determine what would work best
for the patient. We hope that the NMSM
Pipeline will eventually be used in a similar
manner to inform treatment design
for movement impairments. "
To encourage the research community
to use the software, Fregly and his
team are running a four-year competition
at the American Society of Biomechanics
annual conference. The competition
will challenge researchers to
develop personalized treatments that
improve walking function for four individuals
who have had a stroke.
" Each year, we're going to provide researchers
with extensive experimental
walking data from a different individual
post-stroke so that they can construct a
personalized model of each individual
and use it to design a personalized treatment
computationally, " Fregly says.
" They could try strengthening specific
muscles, or knocking out specific muscles
with Botox, or modifying neural
control strategy, or training with a splitbelt
treadmill or rehabilitation robot, or
designing an exoskeleton - whatever
treatment they want to explore, they can
simulate it. The goal is to enable the individual
being modeled to walk at a normal
speed with a normal motion. "
This article was written by Silvia Cernea
Clark, Rice University. For more information,
e-mail B.J. Fregly at fregly@
rice.edu or visit www.rice.edu.
http://www.rice.edu http://www.medicaldesignbriefs.com
Medical Design Briefs - November 2023

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