Validation of a stereo camera system to quantify brain deformation due to breathing and pulsatility

Purpose: A new stereo vision system is presented to quantify brain shift and pulsatility in open-skull neurosurgeries. Methods: The system is endowed with hardware and software synchronous image acquisition with timestamp embedding in the captured images, a brain surface oriented feature detection, and a tracking subroutine robust to occlusions and outliers. A validation experiment for the stereo vision system was conducted against a gold-standard optical tracking system, Optotrak CERTUS. A static and dynamic analysis of the stereo camera tracking error was performed tracking a customized object in different positions, orientations, linear, and angular speeds. Results: The system is able to detect an immobile object position and orientation with a maximum error of 0.5 mm and 1.6. in all depth of field, and tracking a moving object until 3 mm/s with a median error of 0.5 mm. Three stereo video acquisitions were recorded from a patient, immediately after the craniotomy. The cortical pulsatile motion was captured and is represented in the time and frequency domain. The amplitude of motion of the cloud of features' center of mass was inferior to 0.8 mm. Three distinct peaks are identified in the fast Fourier transform analysis related to the sympathovagal balance, breathing, and blood pressure with 0.03-0.05, 0.2, and 1 Hz, respectively. Conclusions: The stereo vision system presented is a precise and robust system to measure brain shift and pulsatility with an accuracy superior to other reported systems.