Laser and wave-guides system for endoscopic/fiberscopic laser surgery

Laser technology in medical applications is a fascinating field for both scientific and non-scientific societies. The main motivation for using lasers in medicine is to attain a contactless procedure, which lowers the risk of viral and bacterial infections, and leads to a less painful, more flexible and, often, faster procedure. Lasers are capable of ablating even the most rigid tissues, such as bone. For this thesis project, a laser system for deep bone ablation was optimized, with the ultimate purpose of implementing the laser system in an endoscopic device for minimally invasive bone surgery.
In the first part of the thesis, an erbium-doped yttrium aluminium garnet (Er:YAG) laser was optimized and paired with a suitable irrigation system to cool down the tissue, and with a feedback system to control the tissue temperature and prevent carbonization. The irrigation system consisted of a novel water jet measuring 50 µm in diameter at 30 bar pressure. The water jet was very fine and its laminar flow regime reached up to 15 cm, making it very useful for irrigation during deep bone ablation. With this optimized laser system, it was possible to reach ablation depths of up to 21 mm in cortical bone.
In the second part of the thesis, the Er:YAG laser was coupled into different fibers: germanium oxide, sapphire, zirconium fluoride, and a hollow-core silica waveguide. Ultimately, a germanium oxide fiber was selected. The beam was refocused using a suitable miniaturized lens system; with this setup, ablation depths of up to 10 mm in cortical bone were achieved.
The results obtained in this thesis open up the possibility of further optimizing laser and fiber systems to achieve greater ablation depths in less time. This thesis was part of the Minimally Invasive Robot-Assisted Computer-guided LaserosteotomE (MIRACLE) project, which aims to develop a robotic endoscope to perform laser-based, contact-free bone surgery.