Video Data Acquisition Accuracy for Hand-Held Stereovision in Image Guided Surgery

Hand-held stereovision (HHS) has been implemented as an accurate, affordable, and non-ionizing method for image updating, and marker-less registration. Studies using HHS have collected images via individual snapshots. This study compares the accuracy of data acquisition from snapshots compared to a video stream data acquisition. An HHS system was calibrated via a tracked checkerboard to an accuracy of 0.88 +/- 0.24mm. A cadaver pig was used to measure accuracy of fiducial locations with fiducials placed on each spinous, and transverse process of L2 through L6. The system was then used to collect images of the surgical field. The images were collected 5 times. There was one snapshot image acquisition, and 4 video streams. After, the fiducial locations were localized via a tracked stylus probe. The error was then computed between the stylus fiducial locations and the fiducial locations found on the stereovision depth map. The corresponding mean errors for the snapshots and 4 video acquisitions were as follows: 1.03 +/- 0.24mm, 1.13 +/- 0.34mm, 1.18 +/- 0.59mm,1.19 +/- 0.47mm, and 3.23 +/- 2.27mm respectively. While collecting the video streams the data were collected at what was perceived a constant speed. Each sequential video stream was collected at a higher speed. These speeds were calculated to be 7.22 +/- 1.95mm/s, 12.73 +/- 7.75mm/s, 19.9 +/- 12.74mm/s, and 30.14 +/- 13.33mm/s respectively. These data show that image acquisition via video streams at relatively low speeds have accuracy comparable to that of snapshot image acquisition.