Benefits of Side-Firing Optical Fibers in Endoscopic Laser Treatment of the Larynx.

OBJECTIVE: To elucidate potential tissue coverage of side-firing optical fibers in office-based endoscopic laser treatment of larynx, as well as to demonstrate their enhanced ability to address challenging anatomic areas. METHOD: We performed a comparative study of four different fiber designs: a traditional forward-facing fiber, and three side-firing fibers that emit light at an angle of 45°, 70°, and 90°, respectively. The study was conducted in simulation, using eight three-dimensional models of the human larynx generated from microtomography x-ray scans. A computer program simulated the insertion of the endoscope into the larynx, and the Möller-Trumbore algorithm was used to simulate the application of laser light. RESULTS: Side-firing laser fibers increased potential tissue coverage by a mean of 50.2 (standard deviation [SD] 25.8), 73.8 (SD 41.3), and 84.0 (SD 47.6) percent for angles of 45°, 70°, and 90°, respectively, compared to forward-facing fibers. Angled fibers provided access to areas of the larynx considered difficult to address by traditional methods, including the infraglottis, laryngeal ventricle, and right vocal fold. CONCLUSION: Simulation results suggest that side-firing optical fibers have the potential to enhance anatomical access during in-office endoscopic laser procedures in the larynx. Further research is needed to better understand the benefits and any potential risks or contraindications of side-firing optical fibers. LEVEL OF EVIDENCE: NA Laryngoscope, 133:1205-1210, 2023.

Light in the Larynx: a Miniaturized Robotic Optical Fiber for In-office Laser Surgery of the Vocal Folds.

This paper reports the design, construction, and experimental validation of a novel hand-held robot for in-office laser surgery of the vocal folds. In-office endoscopic laser surgery is an emerging trend in Laryngology: It promises to deliver the same patient outcomes of traditional surgical treatment (i.e., in the operating room), at a fraction of the cost. Unfortunately, office procedures can be challenging to perform; the optical fibers used for laser delivery can only emit light forward in a line-of-sight fashion, which severely limits anatomical access. The robot we present in this paper aims to overcome these challenges. The end effector of the robot is a steerable laser fiber, created through the combination of a thin optical fiber (ϕ 0.225 mm) with a tendon-actuated Nickel-Titanium notched sheath that provides bending. This device can be seamlessly used with most commercially available endoscopes, as it is sufficiently small (ϕ 1.1 mm) to pass through a working channel. To control the fiber, we propose a compact actuation unit that can be mounted on top of the endoscope handle, so that, during a procedure, the operating physician can operate both the endoscope and the steerable fiber with a single hand. We report simulation and phantom experiments demonstrating that the proposed device substantially enhances surgical access compared to current clinical fibers.

Optical Fiber Coupling System for Steerable Endoscopic Instruments.

In this paper, we present an optical coupling system that couples light from an Endostat fiber in a commercial laser surgical system into a smaller multimode fiber, in order to enable endoscopic probe steering in a tightly confined space. Unlike the Endostat fibers, which have a minimum bending radius of 12 mm due to the large diameter, our work allows the laser to be delivered by smaller fibers that can be readily bent at a 6-mm bending radius by a distal steerable mechanism. Such a readily achievable sharp bending facilitates the surgical laser to access hard-to-reach anatomies. We experimentally achieved an optical power coupling efficiency of ≈ 50%. Tissue ablation experiments were performed to prove the feasibility and potential of our light coupling system in clinical laser surgeries, as well as other optical fiber-based endoscopic medical devices.Clinical Relevance- Optical fibers are commonly used in laser-based surgical systems. The optical coupling system in this paper enables the laser to be delivered by small fibers, helps realize the fiber bending and steering, and hence allows the laser treatments of previous inaccessible anatomies.

On the Merits of Using Angled Fiber Tips in Office-based Laser Surgery of the Vocal Folds.

Office-based endoscopic laser surgery is an increasingly popular option for the treatment of many benign and pre-malignant tumors of the vocal folds. While these procedures have been shown to be generally safe and effective, recent clinical studies have revealed that there are a number of challenging locations inside the larynx where laser light cannot be easily delivered due to line-of-sight limitations. In this paper, we explore whether these challenges can be overcome through the use of side-firing laser fibers. Our study is conducted in simulation, using three-dimensional models of the human larynx generated from X-ray microtomography scans. Using computer graphics techniques (ray-casting), we simulate the application of laser pulses with different types of laser fibers and compare the total anatomical coverage attained by each fiber. We consider four fiber types: a traditional "forward-looking" fiber - not unlike the ones currently used in clinical practice - and three side-firing fibers that emit light at an angle of 45, 70, and 90 degrees, respectively. Results show that side-firing fibers enable a ~70% increase in accessible anatomy compared to forward-looking fibers.

Computational Optimization of Notch Spacing for a Transnasal Ear Endoscopy Continuum Robot.

This paper presents a computational framework to optimize the visual coverage attainable by a notched-tube continuum robotic endoscope inside the middle ear cavity. Our framework combines anatomically-accurate geometric (mesh) models of the middle ear with a sampling-based motion planning algorithm (RRT) and a ray-casting procedure to quantify what regions of the middle ear can be accessed and visualized by the endoscope. To demonstrate the use of this framework, we run computer simulations to investigate the effect of varying the distance between each pair of consecutive flexure elements (i.e., notches) in our robotic endoscope.