Study of the interaction of silica-based Nd: YAG laser optical fibers with tissue

摘要

During laser surgery, light from a Nd:YAG laser can be transmitted through a silica optical fiber. As long as the fiber tip does not contact tissue, it remains in near pristine condition and transmits the laser light to cause a photocoagulative tissue effect. Once the tip contacts tissue; however, degradation of the tip occurs and transmission of the laser energy is decreased. The laser energy is absorbed at the contact tip causing it to heat up. In this condition the tip can only be used for tissue incision or ablation. The process of damaging the tip has been termed as burn-in. The longer the fiber tip is in contact with tissue, the more damage it accumulates such as spalling or melting. Catastrophic damage of the silica fiber tip is an unwanted event during laser surgery. Ideally, a laser optical fiber should remain stable when contacting tissue, that is, never burn-in;The first detailed study has been made of silica laser surgical fibers and their interaction with tissue. Silica optical fibers were lased in chicken and beef tissue using a continuous wave Nd:YAG laser at powers from 5 to 50 Watts and in a pulsed mode. The silica fiber tips were then characterized using surface reflectance infra-red spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. Using the information obtained from the degradation of silica optical fibers, a new laser optical fiber was then developed and its potential as a surgical optical fiber was investigated using the same investigative techniques mentioned above. Also, alternatives to laser fiber optic delivery systems were investigated. These included alternative materials to the sapphire contact probes, and the feasibility of diamond coating existing silica optical fibers.