Bone ablation with Er:YAG and CO2 laser: study of thermal and acoustic effects

A pulsed Er:YAG laser at 2.94 microns and a superpulsed CO2 laser at 10.6 microns are used to investigate bone ablation applications in otolaryngology. Quantitative measurements of mass removal and the ablation depth of cat skull bone and rat femur are presented with the Er:YAG laser at fluences of 9-117 J/cm2. Histological results show that the minimal thermal injury zone from the edge of the lesion is 5-10 microns. Comparison of the photoacoustic and thermal effects during the ablation process indicates that the temperature rise from the 10.6-microns light was higher than that from the 2.94-microns light but that the photoacoustic wave amplitude produced with the Er:YAG laser was higher than that with the CO2 laser. The fluence used for the efficient ablation of bone tissues produces a photoacoustic wave ranging from 100 to 120 dB. The ear can tolerate this level for a short time period. Results of this study suggest that the Er:YAG laser can be an important surgical tool in otolaryngology.