Analysis of fibre tip damage risk during pulsed holmium laser application under water

Breaking of optical fibre tips during medical holmium laser applications involving endoscopic irradiation in a liquid environment, such as arthroscopy, has been reported. This represents a risk of complications due to foreign body reactions induced by quartz fragments remaining at the operation site. Fibre breakage has been analysed under controlled conditions at clinically used laser energies of 20-1000 mJ. The generation of pressure transients at the collapse of laser-induced vapour bubbles is identified as the mechanism of fibre tip destruction. Fibre damage is observed only in a confining liquid envivronment. The highest fibre damage occurrence is observed for laser fluences of 70-250 J cm-25 at the bare fibre tip, at pulse durations of 200-350 Μs. The fibre damage occurrence and extent increase with the fibre diameter. Avoiding the identified dangerous fluence range or use of fibres smaller than 400Μm diameter is recommended to perform endoscopic holmium laser application with minimal fibre damage ris

Laser induced mechanical effects in biomaterials

Mechanical effects induced by lasers with nanoseconds to hundreds of microseconds pulse duration on biomaterials are discussed. Strong shock waves are generally observed during laser irradiation due to very rapid heating and phase change in the interaction zone. Moreover even stronger shock waves can be generated some hundreds of microseconds later in response to the collapse of the induced cavitation bubble in confined environment. The impact of the laser induced cavitation processes on the observed damage on selected biotargets (bone, cartilage and urinary stones) will be discussed. The effect of the laser pulse characteristics on both acoustical transients will be discussed as well