Saleh Mohebbi - Brain and Spinal cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Science, Tehran, Iran.
Jakob Lexow - Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany.
Alexander Fuchs - Institute of Mechatronic Systems (IMES), Leibniz Universität Hannover, Hannover, Germany.
Thomas Rau - Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany.

Introduction: Different approaches have been developed to find the position of the internal auditory canal (IAC)in middle cranial fossa approach. A feasibility study was performed to investigate the combination of cone beam computed tomography (CBCT), optical coherence tomography (OCT), and laser ablation to assist a surgeon in a middle cranial fossa approach by outlining the internal auditory canal (IAC).   Materials and Methods: A combined OCT laser setup was used to outline the position of IAC on the surface of the petrous bone in cadaveric semi-heads. The position of the hidden structures, such as IAC, was determined in MATLAB software using an intraoperative CBCT scan. Four titanium spheres attached to the edge of the craniotomy served as reference markers visible in both CBCT and OCT images in order to transfer the plan to the patient. The integrated erbium-doped yttrium aluminum garnet laser was used to mark the surface of the bone by shallow ablation under OCT-based navigation before the surgeon continued the operation.   Result: The technical setup was feasible, and the laser marking of the border of the IAC was performed with an overall accuracy of 300 μm. The depth of each ablation phase was 300 μm. The marks indicating a safe path supported the surgeon in the surgery.   Conclusion: The technique investigated in the present study could decrease the surgical risks for the mentioned structures and improve the pace and precision of operation.

Computer-assisted surgery, Er-YAG laser, Image-guided surgery, Middle cranial fossa, Optical coherence tomography