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  • Hollow-core optical fiber enables laser-assisted robotic surgery

BioPhotonics
Apr 2006
Gary Boas, News Editor, gary.boas@photonics.com

CO2 lasers have become a common cutting tool in laryngology. They offer submillimeter cutting precision, which is especially important because many lesions sit on the vocal cords. An error in cutting can potentially cause scarring and irreversible damage to the patient’s vocal function. The lasers also keep to a minimum thermal damage during cutting and the closing up of blood vessels. Thus, surgeons can both cut and coagulate at the same time, allowing resection of lesions in a bloodless, easily viewable field.

Until recently, though, these lasers had no fiber delivery system. Surgeons had to insert a rigid instrument, known as a laryngoscope, into patients’ mouths to create a line of sight between the laser and the lesions. This did not work well in all settings. Sometimes surgeons had trouble exposing the larynx in patients who were obese or who had short necks.

The problem of delivering CO2 laser light through the mouth was especially vexing to Dr. Marshall M. Strome, chairman of the Cleveland Clinic Head and Neck Institute. He wanted to use a robot developed for other medical applications for head and neck surgeries. The robot could provide vastly improved precision and flexibility, but he needed articulated arms with mirrors and prisms to transmit CO2 lasers. These were incompatible with the robot.

Then someone suggested that he take a look at a new technology from Cambridge, Mass.-based OmniGuide Inc. — a hollow-core optical fiber that can flexibly guide a CO2 laser beam. Attaching the fiber to the robotic arm could enable laser-assisted robotic surgery for head and neck applications.


A hollow-core optical fiber that can guide a CO2 laser beam improves flexibility and precision of surgery of the throat. However, because of the combinations of materials used, the developers of the technology had to devise a way to pull the fiber over long lengths while maintaining uniform submicron-thick layers.


The technology grew out of work conducted by Yoel Fink, now associate professor of materials science at MIT, also in Cambridge. For his doctoral dissertation, Fink designed a “perfect” mirror based on a dielectric stack of alternating high- and low-refractive-index materials. The original idea was reported in Science in 1998. Fink and others formed OmniGuide in 2000, and in 2002, they published a letter in Nature describing use of the technology to deliver CO2 lasers through hollow-core fibers.

Confinement of light is achieved by alternating submicron-thick layers of high-refractive-index glass and low-refractive-index polymer, they explained, creating large photonic bandgaps and leading to ultralow losses. Still, they needed to develop a manufacturing method.

At first, they employed the technique commonly used to make telecommunications fibers — pulling fiber from a preform. However, this can be challenging when the fiber contains a combination of materials in its core. The high- and low-refractive-index materials used in the mirror have different optical properties and, consequently, may have different mechanical and thermal properties, which can cause difficulties when pulling the fibers. Ultimately, the research group at MIT and at OmniGuide devised proprietary scalable ways to draw the fibers over very long lengths while maintaining a uniform layer thickness on the submicron scale.

The company worked with Strome to attach the hollow-core fibers to a robotic system made by Intuitive Surgical Inc. of Sunnyvale, Calif., enabling delivery of CO2 laser light through the mouth without the laryngoscope. The system consists of a surgeon’s console, a cart with four interactive robotic arms, a three-dimensional vision system that is based on two cameras situated near the mouth, and instruments designed with 7° of motion to mimic the movements of the surgeon’s hand and wrist. The instruments are assigned specific surgical tasks, including clamping, suturing and tissue manipulation.

The robot allows more flexibility and precision than is possible when performing procedures manually. For example, it enables the surgeon to make circumferential cuts. “You can get to the bottom of the tumor and take it out much more readily,” Strome said.

He recently used the setup to perform laser-assisted robotic surgery at the clinic on a patient with a massive cancerous tumor involving the larynx and pharynx. He removed the tumor in about four hours, avoiding an invasive open procedure and saving more than two hours of operating-room time. The patient reported less pain than prior to the surgery just two days later and could swallow again within a week.

The combination of the robot and CO2 laser light delivered via the hollow-core optical fiber provides much higher precision than could be achieved otherwise, Strome said, enabling tremendous potential for head and neck surgeries. Indeed, he plans to use it for resection of a tongue-based tumor. It could contribute to even more significant advances in the next five years, as the robots become smaller and more manageable. Moreover, the ability to control the robot remotely means that, in the future, a surgeon could sit at a console and operate on someone in another country, Strome added. This could open up a number of markets in areas that lack adequately trained doctors.


The fiber technology incorporates a “perfect” mirror that is based on a dielectric stack of alternating high- and low-refractive-index materials to create large photonic bandgaps, enabling ultralow losses.


Ultimately, he would like the manufacturer of the robot to integrate the fiber technology into the instrumentation. Currently, he attaches the fiber to the robot via a sheath with a hook. “It would be very nice to develop an arm with a channel in it that the laser could go through,” he said.

Contact: Dr. Marshall M. Strome, Cleveland Clinic Head and Neck Institute, Cleveland; +1 (216) 444-6686. Gil Shapira, OmniGuide Inc.; e-mail: gils@omni-guide.com.


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