New steerable optical fiber reaches previously inaccessible larynx tumors

Worcester Polytechnic Institute (WPI) researchers have developed a flexible optical fiber that can be threaded through a medical endoscope and steered into the larynx to destroy hard-to-reach tumors on the vocal folds, an advance that could expand outpatient laser treatment options for patients whose only other choice might be surgery under general anesthesia.

The researchers reported that during tests with a 3D-printed replica of a human larynx, they were able to reach about 81% of 70 targets that otherwise would be impossible to reach during outpatient treatments.

"Some people, such as patients with cardiac conditions, may not be able to undergo general anesthesia and conventional laser surgery for growths in the larynx," says Loris Fichera, associate professor in the Department of Robotics Engineering and leader of the research team that developed the new optical fiber technology. "An improved medical device could address that problem by giving some patients an option to undergo laser treatment while under mild sedation in medical offices instead."

The researchers' device is a flexible optical fiber threaded through a thin-walled nickel-titanium sheath that is 1.6 millimeters in diameter and notched so it can bend. The sheath is thin enough to fit into an endoscope, a tube-like device with a light and camera on the tip. Surgeons insert endoscopes into the body to examine tissues, organs, and structures. 

Once inside an endoscope, the sheath and optical fiber can be steered with hand-held controls to a site in the voice box, tissues that are also known as vocal cords, to destroy growths with pulses of light.

Laser surgery of the vocal folds is typically done to remove tiny benign or precancerous growths such as callus-like nodules and polyps that can leave patients with raspy voices. For professional singers and speakers, the condition can threaten livelihoods. Allergies, underlying illness, smoking, and overuse or misuse of the voice can play a role in the development of growths.

Most procedures are performed in a doctor's office and typically involve snaking an endoscope through the nostril of a patient whose vocal folds have been numbed with a cooling spray. Patients whose growths are harder to reach can be treated in a hospital under general anesthesia.

To test their design, the researchers used 3D printing to build an anatomically correct model of a real human larynx. They plotted 70 points on the model that could not be reached with non-steerable optical fibers, then used their steerable tool to reach 57, or about 81%, of the targets.

Although research results suggest the device created by Fichera's team could expand office-based procedures for laser surgery of the larynx, Fichera says that more research and development of the device is needed. The rigid 3D-printed model could not replicate the movements that occur when a patient is being treated, and the device currently requires two operators working together. Improvements might make it possible for one operator to use the device.

Much of the fundamental research has been completed. We are planning a follow-on project to make improvements that would allow the optical fiber to bend in different directions and curve to reach more places. Ultimately, our goal is to help as many patients as possible by expanding options for office procedures."

Loris Fichera, Associate Professor, Department of Robotics Engineering, Worcester Polytechnic Institute

The research was published in the American Society of Medical Engineers' Journal of Medical Devices. In addition to Fichera, co-authors were Alex Chiluisa, MS '20, PhD '24; undergraduate Kang Zhang; Yao Shen, MS '18, PhD 25; PhD student Lucas Burstein; Yuxiang Liu, associate professor in the Department of Mechanical and Materials Engineering; and Thomas Carroll, associate professor in the Department of Otolaryngology at Harvard Medical School.

Fichera's research focuses on using robotics and computer science to advance technologies used in medicine, especially surgery. He received a prestigious CAREER Award from the National Science Foundation to develop technology for a new class of surgical robots that can treat disease without cutting or touching human tissues. He also is part of a team at WPI that is developing technology for flexible robotic arms that can grasp, lift, and carry objects. He is a co-inventor on a patent protecting the flexible and articulating surgical laser probe for laryngeal surgery.