A Non-Contacting 3-D Digitizer For Use in Image-Guided Neurosurgery

H. Sun, H. Farid D. Roberts, K. Rick, A. Kartov, and K. Paulsen

American Society for Stereotactic and Functional Neurosurgery, New York City, 2003

Introduction: We have designed and implemented a non-contacting 3-D digitizer that attaches to the binocular optics of an operating microscope. This system can be used to efficiently and automatically register the surgical scene to the preoperative image volume through cortical feature analysis and then track the 3-D surface topology within the operating field in order to account for motion-induced changes that occur during surgery.

Methods: We have attached two CCD cameras to the binocular optics of an operating microscope. Prior to surgery, this stereo imaging system is calibrated to obtain the extrinsic and intrinsic camera parameters. During surgery the 3-D coordinates of salient image features are automatically estimated from a stereo pair of images and registered to the preoperative image volume to provide navigational guidance. This estimation requires the robust matching of features between the images, which, when combined with the camera calibration, yields the desired 3-D coordinates. A parameterized 3-D surface can then be fit to the estimated 3-D coordinates and, when registered to the preoperative image volume, provides navigational information in the face of tissue motion during surgery.

Results: We are able to estimate the 3-D structure of a surgical scene with an average accuracy of 1.3mm. Executing on a 1.1 GHz Pentium machine, the 3-D estimation from a stereo pair of 1024x768 images requires approximately 8 minutes of computation.

Conclusions: We have demonstrated that an operating microscope is capable of, without inducing brain deformation, digitizing 3-D surfaces with efficient acquisition and image analysis of stereo pairs, which can also be coregistered to the preoperative image volume through related feature analysis.

Learning Objectives: The ability to quickly and automatically estimate 3-D cortical surface topology during neurosurgery has several applications: (1) cortical vasculature can be localized in 3-D and registered with pre-operative imaging data; (2) fiducial markers can be localized in 3-D and used for the intraoperative update of calibration parameters; (3) the 3-D cortical surface can be continuously estimated and tracked for use in FEM-based compensation of brain deformation and shift that occurs in the OR.