Selective photothermal ablation of tissue with a fiber-delivered Er:YAG laser

The feasibility of using laser-induced photoemission signals to distinguish between hard and soft biological tissues during photothermal ablation with a pulsed Er:YAG laser has been investigated. Time-resolved emission spectroscopy indicated a threshold fluence of approximately 35 J/cm 2 to regularly initiate photoemission from dental enamel, while no emission was detected from porcine muscle tissue with incident laser fluences of up to approximately 140 J/cm 2 . The delay time of an emission signal with respect to the incident, ablative Er:YAG laser pulse was found to decrease from approximately 150 microseconds near the emission threshold fluence to approximately 60 microseconds at the highest fluence level used. Optical multichannel analyzer spectroscopy of Er:YAG irradiated enamel demonstrated that photoemissions typically consisted of a broad, continuous background in the visible region, with superimposed peaks arising from the presence of elements including calcium, characteristic of plasma emission either from the sample surface or emission plume.