Novel Diffusing Optical Fiber: Fabrication and Applications for Photothermal Therapy

Abstract

Photo-thermal therapies has limited efficacy and application due to difficulties in propagating light inside tissue especially in human body. Optical flat fiber recently was used as a feasible tool to deliver laser energy to targeted tissue. In this study, we introduce a novel optical fiber which was micro-machined from a 600 µm flat fiber to achieve the laterally uniform light distribution. Uniform pattern was engraved on the fiber surface using focused CO2 laser beam at 5 W. Spatial emission of the fiber tip was visualized to validate the performance of the fabricated diffuser. For spatial characteristics, polar, azimuthal, and longitudinal emissions were evaluated. The spatial emission characteristics of diffusing fiber presented an almost uniform power distribution along the diffuser tip and around its circumference. Visible light distribution and egg-white test demonstrated a well agreement with the spatial emission characteristics. A computational model was also developed to predict spatio-temporal heat distribution during interstitial laser coagulation. Both simulation and tissue testing demonstrated approximately 1-mm coagulation thickness at 6 W for 10 sec with 1470 nm. A diffuser protected by glass-cap combined with near-infrared wavelength (1470 nm) was used to thermally decompose urethral stricture tissue structure. By providing direct delivery of diffuse light to the target tissue while minimizing undesirable photo-thermal damage in the adjacent tissue, the proposed optical diffuser may be a feasible tool to treat the tubular tissue structures in a uniform and circumferential manner.