After making some basic measurements using a conventional spectrometer
at the FEL Center, Edwards sent a message by fax to ophthalmologist Denis
O'Day, chairman of the department, and to neurosurgeon Robert Maciunas,
suggesting an alternative solution to Logan's problem.
Within 30 minutes of receiving the fax, the Department of Ophthalmology
had scheduled a meeting. By early January the following year, the resulting
research team had indications that a wavelength of 6.45 microns resulted
in improved ablation of corneal tissue and far less damage to adjacent tissue.
"The back-of-the-envelope calculation worked. The first time it worked,"
says Edwards, still incredulous about the results. "Regan and I drilled
a perfect hole in corneal tissue. We looked at it in disbelief. I have never
had an experiment work the first time."
At wavelengths of about 6.4 microns, vibrations occur in both proteins
and water. Energy at that wavelength essentially melts the proteins that
make up tissue. Water molecules still absorb radiation but not as explosively
as at 3 microns. It's as if the shell of a bomb melts on impact, leaving
no shrapnel.
"Neurosurgeon Michael Copeland quickly became involved. We conducted
months of control experiments. We invited others in," Edwards says.
Their study moved from corneal tissue to neural tissue to dermal tissue
and the team-10 other Vanderbilt researchers had joined Edwards and Logan-
concluded that wavelengths near 6.45 microns are optimal for ablation of
all soft tissues.
By September 1994, their results were acclaimed in the prestigious journal
Nature. "We changed the way people think about tissue ablation,"
Edwards says. "It has been this interaction between the physicists
and the physicians that made it possible."
Edwards' own work on the internal motions of DNA contributed to solving
the vexing tissue ablation problem. "DNA is like a very complicated
slinky. It has all sorts of internal motions. I was investigating how to
melt its hydrogen bonds with FEL radiation," Edwards says.
"What I had learned about how DNA comes apart applies to the way that
collagen falls apart or how any soft tissue falls apart. Rather than concentrating
on the water peak-vaporizing the water in tissue or cells-why not concentrate
on melting proteins non-explosively?"
Last year, when Edwards was named director of the FEL Center, his role
changed. His duties now include making the FEL more reliable and delivering
the FEL beam to the new surgical suites that were added to the facility
during the recently completed expansion of the center.
"The race now is to do the engineering that will give us the reliability
necessary for medical applications," he says.
At the same time, researchers in a variety of fields are lining up to apply
the new technology. "We are also looking toward the next set of multidisciplinary
breakthroughs - monochromatic x-rays and tissue welding look very promising,"
Edwards says.
-Brenda Ellis