Surgical Instrument Tracking Image Guidance for Intraoperative OCT

Abstract

Purpose: : Intra-operative OCT has considerable promise for visualization of retinal morphology and surgical manipulation of tissues during vitreo-retinal surgery. We have previously reported on a microscope-mounted OCT (MMOCT) system which is fully integrated with a surgical microscope to enable real-time intrasurgical OCT without disrupting surgery. This system is currently undergoing clinical trials in human patients. The utility of intraoperative OCT could be much improved if the OCT imaging location could be made to track the location of highest interest of the surgeon, such as the location of intersection of the surgical instrument with the tissue. In this study, we report on a novel system for automatically tracking the OCT imaging location to the position of the surgical tool tip.

Methods: : We utilized a custom MMOCT scanner integrated with a standard surgical microscope (Leica), with OCT image acquisition and processing from a commercial OCT console (Bioptigen) operating at 17 images/second. We modified this system to track surgical tool movements utilizing a color CCD camera on an accessory port of the surgical microscope. Custom software was written (Labview) to automatically locate the surgical tool tip in the fundus image as the position feedback signal, and to lock the OCT imaging position to that location. The update rate of the feedback loop in this initial trial was 15 Hz.

Results: : We evaluated feedback system performance on hemi-sectioned cadaveric porcine eyes. Following optimization of acquisition and fundus imaging parameters such as image brightness and contrast, and correction for image distortion and scanner calibration, accurate tracking of the tool tip was obtained as evidenced by consistent visibility of the surgical tool tip within each OCT image frame.

Conclusions: : Intraoperative OCT during vitreoretinal surgery has the potential to provide valuable information to the surgeon, which could be further enhanced if the OCT imaging location could be updated in real time. We have demonstrated that OCT image location based on real-time tracking of the surgical tool tip is a potential solution to this problem.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • vitreoretinal surgery • retina