Flexible optical fibers would provide access to hard-to-reach areas of the body

Laser technology has proved to be an invaluable surgical tool, be it to improve eyesight, repair torn retinas, zap kidney stones, or to delicately remove spinal tumors. Still, despite more than four decades of use in the operating room, laser surgery has been limited by the fact that its energy travels in straight lines. This means that a laser works best on areas that can be reached with a straight shot. Maneuvering the beam so that it can reach out-of-the-way areas—without damaging healthy tissue—is sometimes done, using a series of mirrors to guide the laser beam, but this typically dilutes the laser's strength.

An approach to laser surgery on the market for barely more than a year, however, seeks to add a new level of flexibility to optical scalpels by directing the infrared energy of a high-intensity carbon dioxide (CO2) laser through a flexible fiber tube lined with reflective material. This gives the surgeon the ability to snake the laser safely through the body to wherever it is needed without losing any of the beam's strength.

The BeamPath CO2 laser energy system (manufactured by OmniGuide, an optics company in Cambridge, Mass.) marks a significant improvement over optical scalpels used over the past three decades to perform precision microsurgery, says Yair Schindel, OmniGuide's vice president of clinical affairs and business development.

"Going deeper into the body, to places where you couldn't see, was impossible" with the old lasers, delivered through a large articulating arm, he says. "If you couldn't see it, you couldn't get to it."

OmniGuide chose the CO2 laser—produced by exciting carbon dioxide gas within a sealed tube—because it was already commonly used in operating rooms, given its ability to effectively ablate, cut and cauterize tissue. It is the most precise optical scalpel available, Schindel says, adding, other laser-light wavelengths, such as those created using argon or krypton lasers, are not absorbed as quickly by certain human tissues, "so they do more cooking than cutting."

Still, conventional CO2 lasers have difficulty with incisions that must be made at awkward angles. "If you think of a large tumor in the throat, you would have to shoot the laser from [16 inches (40 centimeters)] away, manipulating both the light and the patient to reach the tumor," Schindel says. The alternative: a laryngectomy, a less precise procedure in which all or some the vocal cords are removed. OmniGuide's laser can also be used with a flexible fiber–tipped endoscope. "The surgeon can go through the nose, mouth, ear or other small openings," Schindel says, "and [laser] and view at the same time."

Inside each BeamPath fiber, fewer than 20 microscopic layers of alternating, custom-designed infrared glass and polymer form a reflective system known as a "photonic band-gap structure." (pdf) The design stemmed from research conducted by OmniGuide co-founder and CEO Yoel Fink in 1998 when he was a graduate student at the Massachusetts Institute of Technology's (M.I.T.) Plasma Science and Fusion Center. Fink and his colleagues studied ways to devise the "perfect mirror," a surface that reflects light of all wavelengths and from all angles, for the Defense Advanced Research Projects Agency (DARPA), the U.S. Defense Department's the research arm. Since its 2000 start up, OmniGuide has invested $70 million into researching and developing the materials and technology needed to produce this superthin silicon fiber.

Water, which constitutes more than 60 percent of human tissue, absorbs CO2 laser energy well, enabling such devices to make a more precise cut than a normal scalpel with minimal thermal damage to surrounding healthy tissue, says Lee Nelson, a neurosurgeon with Boulder Neurosurgical Associates in Colorado. BeamPath technology allows CO2 laser energy to be transmitted down a hollow-core fiber and used as a handheld laser scalpel, which Nelson says he used in 30 brain and spinal cord surgeries that he has performed since October. "We knew about the advantages of the CO2 laser," he says, "but it had never been practical to use."

The BeamPath allows surgeons to do some procedures that a normal scalpel cannot do. For example, when a surgeon presses a regular metal scalpel into an organ, it depresses the tissue around it, potentially causing damage to healthy cells surrounding targeted tumors. Unlike a normal scalpel, the BeamPath fiber does not require tissue manipulation, Nelson says, adding, it also controls bleeding better than a metal scalpel by cauterizing, or searing and sealing, nearby blood vessels.

The flexible CO2 laser scalpel has special appeal for lower-back surgery, an area where diseased tissue is often difficult to remove. "When you remove this tissue with standard tools, you are sometimes left with arthritic tissue in the spinal canal causing patients to continue to feel pain even after the surgery," Nelson says. "With the CO2 laser, you can dissolve that [damaged] tissue. Instead of pulling or tearing that tissue, we're now simply ablating it." Nelson says that so far, the patients he has treated this way have experienced less pain than those who have undergone traditional surgery, but he adds that he needs a few more years to expand his sample size enough to prove that the laser is the reason for the reduction in pain.

The cost of the technology—from $500 to $1,800 a fiber—has been the major reason it is not used more widely yet. Nelson says he needs to prove that the BeamPath improves patient outcomes to justify opening his wallet for more of these devices. There are two potential limitations on the fibers: their stability when energized and their inability to be sterilized, which means they must be discarded after each use, Nelson notes.