Fiber Optics in Medicine
By John C. Colwell, Bishop & Associates Inc.

The earliest known experiments in transmitting light through pipes date back to the mid-19th century, when the Swiss professor Daniel Calladon, and later, the Irish physicist John Tyndall, conducted similar experiments involving light transmission through columns of water. Thus was born what is known today as fiber optics.

Fiber optics remained a scientific curiosity until the 1930s, when German students Heinrich Lamm and Walter Gerlach began experimenting with flexible fiber optic tubes that could be inserted into a patient’s throat. Although they had little success, they were the first researchers to envision fiber optics’ potential to advance medical devices. In 1950, Harold Hopkins and Narander Kapany, while working on thin fibers, were approached by British surgeons to develop a flexible gastroscope. However, it wasn’t until Abraham van Heel of the Netherlands, who had been working on similar technology for submarine periscopes, provided the breakthrough that would make a practical gastroscope possible. Van Heel discovered that coating optical fibers with an outer layer of cladding consisting of different kinds of glass could significantly reduce dispersive losses. At the University of Michigan in the late 1950s, Lawrence Curtiss, Basil Hirschowitz, and Wilbur Peters used van Heel’s discoveries to produce the first fiber-optic gastroscope. This marked the first practical application of fiber optics. Fiber optics moved from a science to a technology with commercial manufacturing in 1960.

It wasn’t until the mid-1960s that fiber optics began to find practical application in telephony. Developments by Charles Kao at ITT’s Standard Telecommunications Laboratories and by researchers at Corning Glass led to today’s state-of-the-art fiber-optic technology.

From these modest beginnings, modern endoscopy evolved. It would be impossible to overstate the transformational role that the endoscope and its derivatives have played in the advancement of quality health care. Derivatives include laparoscopes, sigmoidoscopes, colonoscopes, urethroscopes, arthroscopes, esophagogastroduodenoscopes, and others. With the help of fiber optics, physicians can diagnose ailments and perform surgeries with greater insight and precision than ever before.

Fiber Optics in the Operating Room
Major components of these devices include the basic instrument, a light source, and a charge-coupled device (CCD)-based electronic imaging array and display. The light is delivered from the source to the distal end of the probe, and the image returned by means of optical fiber bundles. Depending on the type of instrument, additional functionality may be employed. These include the following: 

• CO₂ delivery to expand the abdomen

• Delivery of saline solution and suction

• Laser, electrosurgical, or cryogenic ablation capability

• Mechanical manipulators

Because of the functional variations, circular connectors with combination fiber, signal, fluid, and gas connectivity may be employed. Fiber connectors are often of custom design.

In some surgical procedures multiple laparoscopes may be employed. The endoscopic devices are also integrated with robotic systems, as depicted below.

The surgeon sits at a control console and performs the procedure with minimal invasiveness. The robotically controlled end affecter is considerably smaller than a human hand, and has greater stability and flexibility.

 

Another important contribution of fiber optics is found in catheters.

Catheters are used for both diagnostic and therapeutic purposes. Illustrated above is a cardio ablation catheter used to locate and destroy specific tissues within the heart that are responsible for creating arrhythmias. The catheters contain embedded optical fibers and Fiber Bragg Grating sensors (FBGs) that measure pressure and flexure at the catheter tip. This is done to prevent abrasion or puncture of arteries or heart tissue. The ablation tip is connected to an electrosurgical generator located at the other end of the catheter.

A typical catheter connector is illustrated at right. The fiber optic interface is either a separate fiber optic connector, or combined in a hybrid connector.

When electrosurgical procedures are involved, a fluid—usually a saline solution—is brought to the catheter tip for tissue cooling purposes. This requires a separate connector for fluid, or a hybrid connecter insert arrangement to accommodate fluid.

 

Ophthalmology is another area of medicine that fiber optics technology has transformed.

A dynamic light-scattering probe utilizes fiber optics for the early detection of cataracts, illustrated above. Other fiber optic applications in ophthalmology include optical measurement and laser surgery.

Miniature biological sensors are among the more recent developments in medicine, and these innovations flow directly from fiber optics technology. These are implantable, worn directly on the skin, or imbedded in fabric, depending on the application.

According to Scrico, the manufacturer, the new, small lithium niobate photonic electrode, or Photrode™ device, represents a paradigm shift in technology for sensing electrophysiological signals, particularly electroencephalography (EEG) and electrocardiography (EKG) signals.

While current methods for executing EEG and EKG measurements require the attachment of electrical wires to a patient’s scalp or chest, Srico’s Photrode invention manipulates light to measure the electrophysiological signals produced by the body.

IMTEK produces an implantable fiber optic-based sensor, shown below. The sensors are embedded in a biocompatible silicone housing. One sensor type includes fiber-optical components to lead the light to the underlying tissue and collect a part of the backscattered light to a photosensor.



Another sensor consists of a circuit with optoelectronic components mounted on a flexible carrier. The new device enables the physician to estimate the arterial blood pressure and oxygen saturation, without placing a sensor inside the blood vessel.

There are countless examples of optical bio-sensors in medicine. Many of these are under development in national and corporate research and development facilities. They hold the potential to bring about untold cures and remedies.

Bishop and Associates Inc. believe that fiber optic based bio-sensors and fiber optic MEMS devices are among the fastest-growing segments in the medical electronic device arena.

The value of connector shipments to the medical electronic equipment sector was $1.2 billion in 2008. Fiber optic connectors accounted for approximately 6 percent, or $72 million. Clearly, we’re just beginning to see the fruits of those early experiments, and fiber optics will play a major role in medicine’s future.

A new medical study from Bishop & Associates Inc. is available. Email bishop@bishopinc.com to obtain a table of contents.

John Colwell Director, Telecom and Medical, Bishop & Associates Inc. John Colwell’s background includes 10 years at Nortel Networks‑Cable Group, where he directed the U.S. premises’ cable marketing effort. In addition, Colwell directed Nortel's global product development group. Prior to joining Nortel, Colwell held positions in engineering, business planning, and development at Amphenol Corporation.