Robot-guided laser craniotome for awake neurosurgery

In certain neurosurgical procedures, patients benefit significantly from awake neurosurgery – particularly in the implantation of electrodes for deep brain stimulation or the resection of brain tumors in eloquent areas. Although these patients receive local anesthesia, they suffer from discomfort, especially psychological stress during the opening of the cranium with mechanical drills and milling cutters. To reduce this stress, a robot-guided laser craniotome has been developed, cutting the bone vibration-free and with low noise. The laser cutting process can be performed by a Q-switched short pulse laser in the mid-infrared (MIR) spectral range whose wavelength is strongly absorbed by bone tissue. Efficient and carbonization free bone cutting with a cutting depth of d = 5.1 mm and an ablation rate of dV/dt = 1.6 mm3/s could be demonstrated with τ = 120 ns short pulses of a CO2 laser at λ = 9.3 µm wavelength and τ = 90 ns short pulses. Because of using nanosecond pulses, thermal damage during laser ablation is reduced, favoring improved bone healing. A sensor based on optical coherence tomography (OCT) measures the cutting depth and the residual bone thickness in a range from 30 µm to 420 µm to ensure safe operation by stopping ablation before the bone is cut through. Laser craniotomy has been demonstrated with a Q-switched CO2 laser on a sheep skull under laboratory conditions.