CC BY
22LM-I-39
Fs laser ablation of bone tissue for high resolution bone surgery
Laura Gemini1 , Samy Al Bourgol1 , Guillaume Machinet1, Marc Fauçon1 , Rainer Kling1
1- ALPhANOV, Rue François Mitterrand, 33400 Talence, France laura.gemini@alphanov. com
Thanks to the current readiness of the technology, lasers have become the tool of choice for surgeries where high precision and lack of unwanted tissue damage are essential [1]. Indeed several unique advantages with respect to conventional mechanical cutting can be found such as no direct contact with the tissue and the possibility to process any geometry with unique precision [2]. Nowadays CW/QCW Er:YAG lasers are mainly employed in bone surgery because of their optimized emission wavelengths of 2.94^m. Nevertheless, strong thermal effects followed by high degrees of tissue carbonization are often associated to the use of these sources, preventing the process of tissue regeneration and a fast post-surgery healing. In this frame, the use of pulsed laser sources has shown to be an interesting option to obtain the minimization the thermal damage in the treated bone tissue and its surrounding [3,4]. It has been shown that an optimization of the ablation rate through an upscaling approach is possible by employing industrial femtosecond laser sources and parameters can be found to achieve an optimal quality of ablation without tissue carbonization [5]. Nevertheless, during the ablation process temperatures high enough to induce tissue denaturation can be reached also when no evident calcination is observable on the bone tissue. In this work, a comprehensive study of the thermal behavior of bone tissue during ultra-fast laser ablation is presented in order to define the best processing environment to avoid tissue denaturation. Three different processing environments were considered for the ablation of bone tissue: water, pressured-air flow and pressured-water flow. Temperatures were recorded during the laser interaction by two different methods to demonstrate the reliability of the measurements. A IR camera FLIR was employed to observe the temperature distribution; measurements at varying angles of view were also initially carried on a reference control sample to demonstrate the negligible dependance of the results from the angle of view between the camera and the sample. Temperature measurements by thermo-couple were also done to be able to compare the results from the two methods and obtain a more complete overview of the temperature behavior of bone tissue during ultra-fast laser processing. The best results were obtained in pressured-water flow where the temperature of the tissue stays always below the temperature for protein denaturation. The dynamics of heat dispersion shows that the maximum temperature in the tissue is reached after the laser processing ends, highlighting the need for efficient cooling of the tissue also after the process ends.
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