Stereovision registration using a tracked checkerboard calibration object for a breast surgery image guidance system

Abstract

Breast cancer is a leading cause of death among women in the United States, and breast conserving surgery (BCS) is a common treatment option for women with early-stage breast cancer. The goal of BCS is to localize and remove the tumor with negative margins, and incomplete tumor excision can lead to reoperation and recurrence. To aid with intraoperative tumor localization, a BCS image guidance system that features an optical tracking camera (NDI Polaris Vicra) and stereocameras (FLIR Grasshopper stereocamera pair) for tracking surgical tools and surgical scene monitoring, respectively, is being investigated. However, sensor data collected from both stereovision systems are not inherently coregistered. Thus, this paper proposes utilizing a tracked checkerboard calibration object paired with a custom 3DSlicer module for optical tracker and stereo camera co-registration. The module features an easy-to-use user interface to streamline calibration. The calibration process was validated with a tissue-mimicking breast phantom embedded with beads to represent surface fiducials and undergoing deformations (n=5 mock phantom tissue states). Across five independent calibration trials, the average fiducial registration error (FRE) was calculated to be 0.68mm ± 0.11mm while the average target registration error (TRE) was calculated to be 0.35mm ± 0.14mm. With respect to the challenge test conditions using the mock breast phantom under differing deformations, TRE values were on average determined to be 2.58mm ± 0.26mm over all breast phantom states. Thus, a tracked checkerboard tool paired with the custom 3DSlicer module provided the ability to localize and track points of interest for accurate registration of two different optical tracking systems.