Engineers at the University of Texas
at Austin have
patented a laser microscalpel that allows a surgeon to operate on tissue one
cell at a time, precisely targeting disease while leaving healthy surrounding
cells alive.
The device combines two
technologies–a femtosecond laser and two-photon fluorescence microscopy–into
a single miniaturized, flexible probe. The probe can target single cells in
three-dimensional space, penetrating up to 250 micrometers into tissue.
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The probe could be a significant
advance for endoscopic surgery that requires high precision, such as destroying
cancer cells scattered throughout brain tissue or operating on delicate tissue
like vocal cords without damaging them, says Adela Ben-Yakar, an assistant
professor of mechanical engineering at the University
of Texas at Austin. Ben-Yakar developed the microprobe
along with Stanford
University associate
professor Olav Solgaard and with Chris Hoy, a graduate student in Ben-Yakar’s
lab. The research was published in the June 23 issue of Optics Express.
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Small, flexible laser tools are
often used in endoscopic surgery to vaporize unwanted tissue. But although they
offer greater precision than conventional scalpels, the existing laser tools
tend to generate a lot of heat, causing damage in the areas surrounding the
targeted tissue. “Current technology is really blasting everything around,
causing extensive damage,” says Ben-Yakar.
In contrast, femtosecond lasers use
less energy than conventional laser-surgical tools, and thus generate less heat
in surrounding tissue. Because they are able to destroy targeted cells without
causing damage outside the target area, they are beginning to be used for
surgery that requires great precision: since 2003, ophthalmologists have used
femtosecond laser microscope tools to perform eye surgery.
But the tabletop lasers currently in medical use are bulky, so their use is
restricted to surface areas of the body, such as the skin or eye.
Likewise, two-photon fluorescence
microscopy has also found applications in medicine and biomedical imaging as a
way to get three-dimensional images of small structures. But until now, no one
has combined it with a femtosecond laser in a device small and flexible enough
for endoscopic surgery.
Ben-Yakar and her colleagues were
able to combine the two in a handheld probe by using flexible hollow optical
fibers to transmit the laser light, potentially allowing surgeons to bring the
benefits of femtosecond laser surgery to structures deep inside the body. “You
can do surgery on single cells without harming the surrounding healthy cells,”
she says. “The healing will be much faster, and the removal of tissue will be
more precise.”
Since the same probe is used to
both image cells and destroy them, it is possible to simultaneously identify
and treat diseased tissue. The microprobe is controlled by imaging software,
allowing surgeons to either target individual cells or use algorithms that can
detect diseased cells on the fly and destroy them automatically. Currently, the
laser microprobe is still an experimental tool. Its inventors have used it to
perform surgery on cancer cells grown in bioengineered tissue in the
laboratory, but the device has not yet been used on animals or humans.
A problem that remains to be solved
before the device can be used on patients is shrinking the width of the probe
from 15 to 5 millimeters–the size of the standard tools used in endoscopic
surgery–so that it will be compatible with existing surgical technology. “If
you want to be compatible with the existing systems, you have to reduce the
size,” Ben-Yakar says. “But when you make it smaller, the probe, the optics
will be more difficult. It will be hard to keep the current resolution. That’s
the next step.”