The main purpose of this study is to evaluate the performance of different optical fibers after coupling an Er:YAG laser through them. This allows us to evaluate the feasibility of using them in future for minimally invasive ablation of bone, where a fiber has to be guided inside an endoscopic device. We coupled a high-power Er:YAG laser (λ = 2.94 μm) in different fibers separately. We analyzed the features and benefits of each fiber during the coupling process. The laser was operated at repetition rates of 1, 5, and 10 Hz in the energy range of 10-830 mJ. We used hollow-core, fluoride, sapphire and germanium oxide fibers with core sizes of 500, 450, 425 and 450 μm, respectively. The coupling efficiencies were determined by comparing the measured input and output energies for all the fibers. The resistance of each fiber to the input energy was evaluated by monitoring the stability of the measured output energy over time. From our observations, the coupling efficiencies for all the fibers were in the range 70 to 81 %. Due to the high coupling efficiency, all fibers have the potential to be used in endoscopic applications. However, their use will mostly depend on the individual need of a specific application.
The biological applicability of the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser in surgical processes is so far limited to hard dental tissues. Using the Er:YAG laser for bone ablation is being studied since it has shown good performance for ablating dental hard tissues at the wavelength 2.94 μm, which coincides with the absorption peak of water, one of the main components of hard tissue, like teeth and bone. To obtain a decent performance of the laser in the cutting process, we aim at examining the influence of sequenced water jet irrigation on both, the ablation rate and the prevention of carbonization while performing laser ablation of bone with fixed laser parameters. An Er:YAG laser at 2.94 μm wavelength, 940 mJ energy per pulse, 400 μs pulse width, and 10 Hz repetition rate is used for the ablation of a porcine femur bone under different pulsed water jet irrigation conditions. We used micro-computed tomography (micro-CT) scans to determine the geometry of the ablated areas. In addition, scanning electron microscopy (SEM) is used for qualitative observations for the presence of carbonization and micro-fractures on the ablated surfaces. We evaluate the performance of the laser ablation process for the different water jet conditions in terms of the ablation rate, quantified by the ablated volume per second and the ablation efficiency, calculated as the ablated volume per pulse energy. We provide an optimized system for laser ablation which delivers the appropriate amount of water to the bone and consequently, the bone is ablated in the most efficient way possible without carbonization.
The aim of this paper is to examine the effect of pig bone immersion in different levels of cooling water during laser ablation with a Er:YAG laser. The laser worked at 2940 nm wavelength and 10 Hz repetition rate in microseconds pulse duration regime. The bone was immersed in different levels of cooling water in a sample container for preventing carbonization. The bone samples were ablated with fixed deposited energy to investigate at which water level Er:YAG lasers start ablating bone through a layer of water. Results showed that the maximum level of water that laser can pass through to start the ablation nonlinearly depends on pulse energy.
The aim of the present study is to investigate the effect of laser pulse duration on ablation efficiency of hard bones. The bones were ablated using a microsecond pulsed Er-YAG laser. The laser wavelength was 2.94 μm and the repetition rate was 10Hz. Three samples of porcine femur were used and several areas were ablated with a fixed pulse energy of 280mJ and different pulse durations. The ablation procedure was applied during five seconds for all the experiments, therefore, the same amount of energy (14 J) was deposited in each trial. The ablation efficiency was determined by measuring the ablated volume per second for each experiment.