Exacting precision

MU researchers have
high hopes for new laser that reduces damage
to surrounding tissue
Sunday, October 8, 2006 | 12:00 a.m. CDT; updated 5:49 p.m. CDT, Monday, July 21, 2008

Imagine a world where doctors could perform precise surgery without scarring or pain, destroy cancer cells like in the video game Space Invaders and where the terrifying whine of the dentist’s drill would be little more than a distant memory. According to MU engineers, that world is just around the corner.

First, let us talk a little about lasers.

The word laser is an acronym for the phrase “light amplified by the stimulated emission of radiation.” A laser is a device in which atoms are energized, or pumped, until their electrons reach an excited state. Although the electrons are excited, they want to return to a low-energy state. When they do, the electrons release their excess energy in the form of a photon, a particle of light. As the electrons release photons, those photons interact with other electrons and cause them to lose their energy and release even more photons. A gain, or lasing, medium collects and concentrates these photons until they reach a critical intensity. Once this happens, the photons burst from the lasing medium as a focused stream of photons, a laser beam.

Since its birth 50 years ago, the laser has become nearly ubiquitous. Its applications include medicine, manufacturing, communications and guidance systems. Lasers light stereo displays, decode the information embedded on the surfaces of CDs and DVDs, read bar codes at supermarkets and reshape the cornea of the human eye. Lasers have revolutionized our lives, but lasers are undergoing a revolution of their own.

The next generation of lasers employ some of the same basic principles as their predecessors, but use new techniques that are able to produce a pulse of light every quadrillionth of a second, otherwise known as a femtosecond, which is a million times faster than a typical laser.

The high speed allows scientists to pack more energy into a single burst, creating a beam that unleashes the equivalent of all the energy of all the world’s power plants on a single small area for a very short period. Femtosecond, or UUL for ultra-fast, ultra-intense, lasers were so powerful in fact that they destroyed the devices that generated them when they were first developed.

Researchers at the University of Rochester’s Laboratory for Laser Energetics initially solved this problem in 1985 by using a technique called chirped pulse amplification. Chirped pulse amplification is a process by which scientists tear apart the laser beam, amplify it and then reassemble it with the desired pulse width. While chirped pulse amplification allowed scientists to determine that UUL lasers were feasible, the technique had some drawbacks.

In August, Jinn Chen, MU mechanical and aerospace engineering professor, was given the green light from the MU Office of Research to submit a major research instrumentation proposal to the National Science Foundation for a $750,000 grant. If they win, the grant would be used to build an UUL research laboratory on the MU campus.

The laboratory would be open to researchers in the chemistry, physics, engineering and medical fields. Robert Tzou, MU mechanical and aerospace engineering professor, said that the addition of a UUL facility to the MU campus and the focus on interdisciplinary research access would catapult the university to the forefront of laser research for medical applications and draw new talent to Columbia. The proposal is due in January and the winner will be announced in August 2007.

“Other lasers use pulse compression devices that are complicated, expensive and diffuse the power of the beam,” said Vitaly Gruzdev, a post-doctoral fellow at the MU College of Engineering. “We are trying to simplify the process by which the pulse is amplified so that we can increase the density of the beam more efficiently and make it better suited for practical applications.”

Gruzdev would not give specifics as to how the MU team is seeking to accomplish this, but he is confident that they would prevail within the next five to 10 years.

The UUL laser is unique because it enables scientists to vaporize individual atoms using a novel physical process called ablation. When a material is ablated, its atoms are heated so quickly that its electrons are converted instantaneously to an ionized gas, a kind of energy soup that exists within stars. The practical upshot of this is that the blast’s heat does not have the opportunity to affect the surrounding area. This results in cuts that are very precise and smooth. This promises vast potential applications in the life science and medical fields and are what most excite Tzou.

“The extremely short contact time is the key,” said Tzou. “Surgeons still use chisels, saws and scalpels, which create heat that seeps into the surrounding tissues and kills them. The UUL laser will not only be more precise than these tools, but will cause negligible damage to the surrounding tissue.”

Tzou and Chen are creating computer simulations that model the interactions of the beam with a variety of materials such as silicon, skin and bone. These simulations will pave the way for the development of new applications for medical and surgical procedures.

Although the laser is at least five to 10 years from being perfected for clinical use, Tzou has some ideas about how it could be used that are reminiscent of a science-fiction story.

“Doctors already use fiber optic cables to look inside the body and view individuals cells, and it has been observed that cancer cells are darker in color than healthy cells. When I heard that, I thought that it would be possible to use the cable as a waveguide for the laser so that we could shoot the individual cancer cells as we find them in the body,” he said.

“This would allow doctors and patients to bypass traditional cancer therapies like chemotherapy and radiation treatment that kill both healthy and cancerous cells. People that undergo these conventional therapies take years to recover from them. The laser will be able to pinpoint and destroy just the cancer cells leaving the healthy cells intact.”

The possibilities for nerve surgery are also profound. In experiments done with mice, the UUL is able to slice through neurons causing so little damage that the neurons grow back in 24 hours. According to Chen, this could mean that doctors will one day be able to correct spinal cord injuries using the laser to cut off dead and damaged nerve cells without harming the undamaged cells. This would allow the undamaged cells to reconnect eventually resulting in minimal or no loss of bodily control for persons who would otherwise have been paralyzed for life.

While many hurdles still remain before the UUL will be ready for medical use, Tzou said that the opportunity to be a part of this type of research that could help so many people is inspiring.

“It is this kind of dream that motivates engineers to do better,” Tzou said. “But when doing this kind of research we have to be much more conservative because we are dealing with living tissue. We have to make sure that we know what we are doing so that we can use the UUL safely and effectively.”

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