Patient Registration Using Intraoperative Stereovision in Image-guided Open Spinal Surgery

Abstract

Despite its widespread availability and success in open cranial neurosurgery, image-guidance technology remains more limited in use in open spinal procedures, in large part because of patient registration challenges. In this study, we evaluated the feasibility of using intraoperative stereovision (iSV) for accurate, efficient and robust patient registration in open spinal fusion surgery. Geometrical surfaces of exposed vertebrae were first reconstructed from iSV. A classical multi-start registration was then executed between point clouds generated from iSV and preoperative CT (pCT) images of the spine. With two pairs of feature points manually identified to facilitate the registration, an average registration accuracy of 1.43 mm in terms of surface-to-surface distance error was achieved in 8 patient cases using a single iSV image pair sampling 2–3 vertebral segments. The iSV registration error was consistently smaller than the conventional landmark approach for every case (average of 2.02 mm with the same error metric). The large capture ranges (average of 23.8 mm in translation and 46.0 deg in rotation) found in the iSV patient registration suggest the technique may offer sufficient robustness for practical application in the operating room. Although some manual effort was still necessary, the manually-derived inputs for iSV registration only needed to be approximate as opposed to be precise and accurate for the manual efforts required in landmark registration. The total computational cost of the iSV registration was 1.5 min on average, significantly less than the typical ~30 min required for the landmark approach. These findings support the clinical feasibility of iSV to offer accurate, efficient and robust patient registration in open spinal surgery, and therefore, its potential to further increase the adoption of image-guidance in this surgical specialty.

Intraoperative CT as a registration benchmark for intervertebral motion compensation in image-guided open spinal surgery

“…Patient registration in spine surgery can be directly established by registering tracked iSV and pCT, as reported elsewhere [14]. For simplicity, here we employed the ground-truth registrations obtained from the bone-implanted screws via the Medtronic StealthStation to transform iSV reconstructed surfaces into the pCT or iCT image space, respectively, at the two imaging stages.…”

“…Our research team is investigating low-cost, radiation-free intraoperative stereovision (iSV [14]) and three-dimensional (3D) ultrasound (iUS) to perform initial patient registration and intraoperative re-registration to compensate for intervertebral motion in spinal surgery (analogously to brain shift compensation in neurosurgery [15,16]). To this end, it is important to identify a reliable means to assess the registration accuracy in order to establish their clinical utility in human patients.…”

Stereovision Co-Registration in Image-Guided Spinal Surgery: Accuracy Assessment Using Explanted Porcine Spines

“…The details of calibration, correspondence matching, and image preprocessing of iSV and CT images have been previously published and are not repeated here. 10…”

Perspective review on applications of optics in spinal surgery

“…48 Prototype systems based on stereovision alone have been trialled in the context of spinal anatomy. 49,50 Our group is the first to develop an optical active projection technique for patient-to-image registration based on structured-light illumination; the technology is now available as a commercial device from 7D Surgical Inc.™. In this technique, termed optical topographic imaging (OTI), the exposed surgical cavity is illuminated with a two-dimensional (2-D) spatially varying pattern of known periodicity and intensity, captured subsequently by grayscale visible-band cameras.…”