Optical properties of sol-gel fiber optic applicators for laser interstitial therapy

A new type of applicator for interstitial laser coagulation is proposed in this paper. The new fiber optic applicator is made by removing the original fiber cladding and replacing it with a sol-gel coating. The sol-gel coating was prepared from the silicate precursor TEOS (tetraethylorthosilicate), mixed with ethanol in acid, which catalyzes hydrolysis. The material is produced with the factor R = 20, where R denotes the number of solvent moles to the number of TEOS moles. In these studies, optical fibers were used from Laser Components (core diameter 400 µm, HCS, low OH). The external jacket was mechanically removed, leaving a remaining 2-cm length of bare fiber. The modified dip-coating method was used to cover the bare fibers with sol-gel material. Two types of applicators were produced: pure sol-gel coated devices and applicators with sol-gel coating doped with photosensitive dyes. The photodynamic activity of chlorophyll-based Photolon and Protoporphyrin IX (PPIX) incorporated within the sol-gels was studied spectrophotometrically. It was demonstrated that sol-gel applicators are capable of performing laser interstitial coagulation using a semiconductor cw laser at 980 nm. It was also demonstrated that the incorporated photosensibilizers retain their photochemical activity.