Charalambos Anastassiou

Use of the photonic band gap fiber assembly CO2 laser system in head and neck surgical oncology

Since its introduction by Jako and Strong in 1972, the benefit of the CO2 laser systems to the head and neck surgeon has been well established in the management of early glottic, supraglottic, oral and oropharyngeal, and hypopharyngeal squamous cell carcinoma. Advantages of the CO2 laser include accuracy, predictability, and limited transmission of energy to adjacent tissues. The beam traditionally has been directed by a micromanipulator affixed to a surgical microscope coupled with a HeNe “guidebeam” to allow the surgeon to appreciate the point of laser contact. Obviously, the CO2 laser is perhaps most limited by the requirement of exposure of the site requiring laser incision. Given the transoral approach to CO2 laser procedures in head and neck surgical oncology, patients with difficult laryngeal exposure as a result of factors such as a short or stiff neck, macroglossia, retrognathia, obesity, or cervical spine immobility can severely limit the use of traditional CO2 laser systems. Traditionally, the Nd:YAG laser has maintained its use in head and neck surgery because of the capability for a flexible fiber system. However, the Nd:YAG laser is significantly more expensive than the CO2 laser and results in less control of energy dispersion to adjacent tissues. OmniGuide, Inc. (Cambridge, MA) has developed a CO2 laser system based on a flexible fiber system to deliver CO2 laser energy. This photonic band gap fiber assembly (PBFA) allows for the direct delivery of CO2 energy to regions of the head and neck in which the direct visualization required for traditional CO2 laser systems cannot be acquired. The OmniGuide Fiber is a hollow-core fiber with a dielectric mirror lining. The mirror, composed of alternating layers of high and low refractive index materials, guides the light through the fiber by reflecting it back into the hollow core. The mirror is surrounded by outer cladding that serves merely as a mechanical support to the mirror. An additional braid-reinforced polyimide jacket provides the final mechanical protection to the fiber device. The distal end of the fiber is fitted with a metal sleeve that protrudes 3 mm beyond the end face of the fiber to protect the fiber end face from tissue debris. Helium is flown through the hollow core of the fiber to allow further protection of the fiber distal tip from tissue debris, cooling of the fiber, cooling of targeted tissue, and clearing of smoke and blood from the field of sight. A gas accessory unit regulates the flow of gas into the fiber such that flow is tied to laser use. Rates of approximately 2 L/minute when the laser is idle and 8 L/minute when laser is fired were used. A Luxar LX-20SP NovaPulse (Lumenis, Yokneam, Israel) is retrofitted with an OmniGuide adapter to allow attachment of the fiber through a standard ST connector to the laser. The OmniGuide adapter couples both the laser radiation and helium flow into the fiber (Fig. 1). Fiber outer diameter of 1.8 mm allows insertion through a variety of standard malleable handpieces (Steiner hand-piece; Karl Storz, Germany; Suction Coagulator, Tyco Health Care Group, Boulder, CO), and length of 1.5 m provides maximum maneuvering ability to the surgeon. The fiber and handpiece were used transorally through a rigid endoscope. The laser was used in both superpulsed and continuous modes. Output powers ranged from 2 W for superficial tissue ablation to 8 W for precise tissue incision. We present three cases illustrating various applications of the OmniGuide flexible fiber CO2 laser system in the management of the patient with head and neck cancer. These cases include examples of diagnostic dilemma From the Department of Head and Neck Surgery (F.C.H., R.S.W.), The University of Texas M.D. Anderson Cancer Center, Houston, Texas, U.S.A.; The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery (C.N.P.), Baylor College of Medicine, Houston, Texas, U.S.A.; OmniGuide, Inc. (G.S., O.W., D.S.T., C.A., E.H.), Cambridge, Massachusetts, U.S.A.; and the Massachusetts Institute of Technology (Y.F.), Cambridge, Massachusetts, U.S.A. Editor’s Note: This Manuscript was accepted for publication February 21, 2006. Send Correspondence to F. Christopher Holsinger, MD, FACS, Department of Head and Neck Surgery, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030-4009, U.S.A. E-mail: holsinger@mdanderson.org.

Photonic bandgap fibers exploiting omnidirectional reflectivity enable flexible delivery of infrared lasers for tissue cutting

Laser cutting of human bone and tissue is one of the oldest and most widespread applications of biophotonics. Due to the unique absorption of different kinds of tissue, choosing an appropriate laser wavelength allows selective ablation of tissue. Consequently, a large variety of laser sources with different emission wavelengths have been successfully applied to an equally large variety of medical indications. However, only a limited set of successful tissue-interaction experiments have translated into standard minimally-invasive procedures. One of the main reasons for this discrepancy between medical research and clinical practice is the lack of a commercially viable, flexible, and easy-to-use fiber optic beam delivery systems for wavelengths longer than 2 μm. In this paper, we will show how OmniGuide fibers, a new type of photonic bandgap fibers, could solve this problem. Recent performance data will be presented for both straight and bent fibers, including losses and power capacity, for delivery of CO2 lasers. We will also highlight medical procedures where these fibers could find first applications.

A New Modality for Minimally Invasive CO2 Laser Surgery: Flexible Hollow-Core Photonic Bandgap Fibers

Carbon dioxide (CO2) lasers have become one of the most common surgical lasers due to excellent tissue interaction properties that offer precise control of cutting and ablation depth, minimal thermal damage to surrounding tissue, and good hemostasis. However, realization of the benefits offered by using surgical CO2 lasers in many endoscopic, minimally invasive surgical procedures has been inhibited by the absence of reliable, flexible fiber laser beam delivery systems. Recently, novel hollow-core photonic bandgap optical fibers for CO2 lasers were developed that offer high flexibility and mechanical robustness with good optical performance under tight bends. These fibers can be used through rigid and flexible endoscopes and various handpieces and will allow surgeons to perform delicate and precise laser surgery procedures in a minimally invasive manner. This paper describes the basic design of laser beam delivery system, different surgical fiber designs and their characteristics, and usage with existing surgical CO2 laser models. A few examples of successful CO2 laser surgeries performed with these fibers are presented.

Quantitative characterization of higher-order mode converters in weakly multimoded fibers

We present a rigorous analysis methodology of fundamental to higher order mode converters in step index few mode optical fibers. We demonstrate experimental conversion from a fundamental LP01 mode to the higher order LP11 mode utilizing a multiple mechanical bend mode converter. We perform a quantitative analysis of the measured light intensity, and demonstrate a modal decomposition algorithm to characterize the modal content excited in the fiber. Theoretical modelling of the current mode converter is then performed and compared with experimental findings.

OmniGuide photonic bandgap fibers for flexible delivery of CO2 laser energy for laryngeal and airway surgery

The CO2 laser is the most widely used laser in laryngology, offering very precise cutting, predictable depth of penetration, and minimal collateral damage due to the efficient absorption of CO2 laser by water. Surgical applications of CO2 laser in microlaryngoscopy include removal of benign lesions and early-stage laryngeal cancer. A Transoral Laser Microsurgery (TLM) approach is routinely employed for treatment of laryngeal cancer; however, the role of TLM in advanced malignant lesions remains controversial. The main limiting factor of TLM is the restrictive exposure of the endoscopes combined with the limited cutting ability offered by the existing micromanipulator, enabling cutting only along the straight line-of-sight axis. A flexible fiber delivery system offering a very high quality output beam can offer tangential cutting and can therefore significantly enhance the existing surgical capabilities. Moreover, a flexible fiber for CO2 laser delivery can be used for treatment of benign conditions through flexible endoscopy in an office setting using local anesthesia. OmniGuide Communications Inc. (OGCI) has fabricated a photonic bandgap fiber capable of flexibly guiding CO2 laser energy. Results of laryngeal in-vivo and in-vitro animal studies will be presented. We will discuss the system setup, fiber performance and clinical outcomes. In addition we will present the results of the first human treatment and highlight additional otolaryngology conditions, which will likely benefit from the new technology herein presented.

Heating of hollow photonic Bragg fibers from field propagation, coupling, and bending

We investigate heating from field propagation, coupling, and bending, which are the potential failure mechanisms for an emerging new type of high-power radiation guides-hollow photonic Bragg fibers. Continuous wave (CW) and pulsed radiation sources are considered, assuming continuous operation of the laser source.