Researchers develop steerable catheter for brain surgery

Date:
August 19, 2021
Source:
University of California - San Diego
Summary:
A team of engineers and physicians has developed a steerable
catheter that will give neurosurgeons the ability to steer the
device in any direction they want while navigating the brain's
arteries and blood vessels. The device was inspired by nature,
specifically insect legs and flagella -- tail-like structures that
allow microscopic organisms such as bacteria to swim.



FULL STORY ==========================================================================
A team of engineers and physicians has developed a steerable catheter
that for the first time will give neurosurgeons the ability to steer the
device in any direction they want while navigating the brain's arteries
and blood vessels.

The device was inspired by nature, specifically insect legs and flagella -
- tail-like structures that allow microscopic organisms such as bacteria
to swim.


==========================================================================
The team from the University of California San Diego describes the
breakthrough in the Aug. 18 issue of Science Robotics.

The steerable catheter was successfully tested in pigs at the Center
for the Future of Surgery at UC San Diego.

Approximately one in 50 people in the United States has an unruptured intracranial aneurysm -- a thin-walled, blister-like lesion on a cerebral artery that is prone to rupture. These kinds of lesions affect over 160
million people worldwide, half of them under the age of 50. Of patients
that suffer ruptured aneurysms, more than half die. Half of the survivors experience long- term disabilities. Studies show that a quarter of cases
cannot be operated on because of how difficult the aneurysms are to reach.

"As a neurosurgeon, one of the challenges that we have is directing
catheters to the delicate, deep recesses of the brain," said Dr. Alexander Khalessi, chair of the Department of Neurological Surgery at UC San
Diego Health.

"Today's results demonstrate proof of concept for a soft, easily steerable catheter that would significantly improve our ability to treat brain
aneurysms and many other neurological conditions, and I look forward to advancing this innovation toward patient care." The current state of
the art in aneurysm surgery involves neurosurgeons inserting guidewires
into an artery near the groin to take catheters through the aorta and
all the way up into the brain. Surgeons use curved-tip guidewires to
navigate the brain's arteries and junctions. But these guidewires have
to be removed before the catheter's tip can be used to provide treatment.



========================================================================== "Once the guidewire is retrieved the catheter will return to its native
shape, often straight, resulting in loss of access to the pathology,"
said Dr. Jessica Wen, who was instrumental in serving as a bridge between clinicians and engineers, and coordinated work with the Center for the
Future of Surgery at UC San Diego.

As a result, it is extremely difficult to place and keep it in the right position to release platinum coils that block blood flow to the aneurysm
and prevent a brain bleed.

Steerable catheters are not available for neurosurgery because of how
small the brain's blood vessels are. Specifically, devices need to be
less than one millimeter in diameter -- that's roughly the diameter of
a few human hairs - - and about five feet long (160 cm). Industrial
fabrication methods struggle at this scale. That's partially because
gravity, electrostatics, and the van der Waals force are all similar
at this size. So once you pick something up with tweezers, you cannot
drop it. If you coax it from the tweezers, it may leap into the air from opposing forces and disappear, never to be found again.

"Unfortunately, many of the most important blood vessels we need to treat
are among the most tortuous and fragile in the body," said James Friend,
a professor at the UC San Diego Jacobs School of Engineering and School
of Medicine and the paper's corresponding author. "Although robotics
is rising to the need in addressing many medical problems, deformable
devices at the scales required for these kinds of surgeries simply do
not exist." Bioinspiration To solve this problem, researchers turned
to inspiration both from nature and from soft robotics.



==========================================================================
"We were inspired by flagella and insect legs, as well as beetles mating,
where microscale hydraulics and large aspect deformation are involved,"
said Gopesh Tilvawala, who recently earned a Ph.D. in Friend's research
group and the paper's first author. "This led us to developing [a] hydraulically actuated soft robotic microcatheter." Computer simulations
and new fabrication methods The team had to invent a whole new way of
casting silicone in three dimensions that would work at those scales,
by depositing concentric layers of silicone on top of one another with different stiffnesses. The result is a silicone rubber catheter with four
holes inside its walls, each about one half the diameter of a human hair.

The team also conducted computer simulations to determine the
configuration of the catheter; how many holes it should include; where
these should be placed; and the amount of hydraulic pressure needed to
actuate it. To guide the catheter, the surgeon compresses a handheld
controller to pass saline fluid into the tip to steer it. Saline is used
to protect the patient:; if the device should fail, then saline harmlessly enters the bloodstream. The catheter's steerable tip is visible on X-rays.

A new way of doing neurosurgery "This technology is ideal for situations
when I need to make a 180 degree turn from the catheter position in
the parent artery, and maintaining position and reducing kick-out
is critical," said Dr. David Santiago-Dieppa, neurosurgeon at UC San
Diego Health. "This advance may ultimately allow us to treat aneurysms,
other brain pathologies and even strokes that we haven't been able to
in the past." The work is poised to make a significant difference in
the way aneurysm surgery is conducted, physicians said.

"This type of precision can be realized with steerable tools and the
successful deployment of these tools should move us forward in permitting improved access, decreased procedural time, better capacity utilization, decreased radiation exposure and other related and expected benefits,"
said Dr. Alexander Norbash, chair of the Department of Radiology at UC
San Diego Health.

The next steps include a statistically significant number of animal
trials and first in human trial.

Video is available at https://bit.ly/steerablecathetervideo ========================================================================== Story Source: Materials provided by
University_of_California_-_San_Diego. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Tilvawala Gopesh, Jessica H. Wen, David Santiago-Dieppa, Bernard
Yan, J.

Scott Pannell, Alexander Khalessi, Alexander Norbash, James
Friend. Soft robotic steerable microcatheter for the endovascular
treatment of cerebral disorders. Science Robotics, 2021; 6 (57):
eabf0601 DOI: 10.1126/scirobotics.abf0601 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210819113048.htm

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