Advanced cutting strategy for navigated, robot-driven laser craniotomy for stereoelectroencephalography: An in Vivo non-recovery animal study

Abstract

Objectives: In this study we aimed to present an updated cutting strategy and updated hardware for a new camera system that can increase cut-through detection using a cold ablation robot-guided laser osteotome.Methods: We performed a preoperative computed tomography scan of each animal. The laser was mounted on a robotic arm and guided by a navigation system based on a tracking camera. Surgery was performed with animals in the prone position. A new cutting strategy was implemented consisting of two circular paths involving inner (full cylindric) and outer (hollow cylindric) sections, with three different ablation phases. The depth electrodes were inserted after cut-through detection was confirmed on either the coaxial camera system or optical coherence tomography signal.Results: A total of 71 precision bone channels were cut in four pig specimens using a robot-guided laser. No signs of hemodynamic or respiratory irregularities were observed during anesthesia. All bone channels were created using the advanced cutting strategy. The new cutting strategy showed no irregularities in either cylindrical (parallel walled; n = 38, 45° = 10, 60° = 14, 90° = 14) or anticonical (walls widening by 2 degrees; n = 33, 45° = 11, 60° = 13, 90° = 9) bone channels. The entrance hole diameters ranged from 2.25–3.7 mm and the exit hole diameters ranged from 1.25 to 2.82 mm. Anchor bolts were successfully inserted in all bone channels. No unintended damage to the cortex was detected after laser guided craniotomy.Conclusion: The new cutting strategy showed promising results in more than 70 precision angulated cylindrical and anti-conical bone channels in this large, in vivo non-recovery animal study. Our findings indicate that the coaxial camera system is feasible for cut-through detection.

A navigated, robot-driven laser craniotomy tool for frameless depth electrode implantation. An in-vivo recovery animal study

“…In four burr holes, monopolar coagulation was performed to stop minor bleeding through the anchor bolts before inserting the depth electrode. This technique has been previously described ( Winter et al, 2022 ).…”

“…Notably, numerous reports exist on implementing lasers in medicine, especially in cutting bone ( Baek et al, 2015 ; Augello et al, 2018 ). The benefits of laser osteotomies are high precision and freedom of geometry ( Winter et al, 2022 ). So far, combining a laser osteotome with a reliable navigation system has been a challenge without losing the geometry within the operating room.…”

“…A registration accuracy of <1.0 mm root mean square was considered acceptable. The registration procedure has already been described in our previous works ( Winter et al, 2021 ; Winter et al, 2022 ).…”

“…As previously described, the laser osteotome uses a 2.94 μm erbium-doped yttrium aluminum garnet (Er:YAG) laser ( Baek et al, 2015 ; Roessler et al, 2021 ; Winter et al, 2021 ). The cutting strategy was previously updated to facilitate cut-through detection ( Winter et al, 2022 ). Once cut-through detection was confirmed on either the coaxial camera system or OCT signal, the anchor bolts were placed, and the depth electrodes were inserted.…”

“…However, in the first in vivo trials, cut-through detection through its coaxial camera and optical coherence tomography (OCT) signals was obscured through inflowing liquids ( Winter et al, 2021 ). Therefore, the cutting strategy was updated, and a new camera system was implemented to enhance cut-through detection ( Winter et al, 2022 ). Previous trials were limited due to the non-recovery setting, and no postoperative imaging or histopathological analysis was conducted.…”