Review of intraoperative optical coherence tomography: technology and applications [Invited]

Abstract

During microsurgery, en face imaging of the surgical field through the operating microscope limits the surgeon's depth perception and visualization of instruments and sub-surface anatomy. Surgical procedures outside microsurgery, such as breast tumor resections, may also benefit from visualization of the sub-surface tissue structures. The widespread clinical adoption of optical coherence tomography (OCT) in ophthalmology and its growing prominence in other fields, such as cancer imaging, has motivated the development of intraoperative OCT for real-time tomographic visualization of surgical interventions. This article reviews key technological developments in intraoperative OCT and their applications in human surgery. We focus on handheld OCT probes, microscope-integrated OCT systems, and OCT-guided laser treatment platforms designed for intraoperative use. Moreover, we discuss intraoperative OCT adjuncts and processing techniques currently under development to optimize the surgical feedback derivable from OCT data. Lastly, we survey salient clinical studies of intraoperative OCT for human surgery.

Keywords: (110.4500) Optical coherence tomography; (170.0110) Imaging systems.

Fig. 1

External intraoperative handheld OCT (HHOCT) probes. (A) Commercial HHOCT probe used for imaging human ocular surgeries. The probe uses galvanometer scanning mirrors and a 4f optical relay to scan the beam across the sample [79]. (B) Compact research-grade HHOCT probe for intraoperative imaging of anastomoses [91]. A MEMS-based mirror scanner reduced the overall footprint of the probe. (C) Intraoperative research-grade HHOCT probe using a long GRIN lens-based relay for imaging of pediatric vocal fold lesions [96].

Fig. 2

Research-grade needle-based HHOCT probes for intraoperative imaging. (A) 23-gauge side-viewing probe for imaging of breast cancer [103]. Three-dimensional optical scanning was achieved by rotating and retracting the probe during imaging. (B) 25-gauge forward-imaging probe for imaging during vitreoretinal surgery [105]. Transverse optical scanning was enabled by displacing the fiber tip using a customized coil-magnetic system.

Fig. 3

Surgical instruments with integrated OCT imaging. (A) Surgical forceps with a common path OCT system for axial ranging using A-scans only [107]. (B) OCT probe capable of B-scan imaging integrated into surgical forceps for vitreoretinal surgery [112].

Fig. 4

Optical designs of research-grade MIOCT systems for live surgical imaging. (A) MIOCT scanner coupled onto the camera port of a commercial microscope [70]. The OCT beam traversed through the microscope optical zoom module and the OCT lateral resolution and field of view (FOV) were coupled to the microscope zoom level. (B) MIOCT scanner integrated directly prior to the microscope objective [71]. This design required a telescope to magnify the OCT beam prior to the objective, but the OCT resolution and lateral FOV were independent of the microscope zoom level. (C) Alternative MIOCT design integrated directly prior to the objective and employing reflective elements to improve transmission and a tunable focus lens [117].

Fig. 5

Commercial MIOCT systems. (A) Zeiss RESCAN 700, FDA cleared in 2014 [119]. This system houses a permanently-integrated OCT scanner coupled directly prior to the microscope objective. (B) Haag-Streit Surgical iOCT, FDA cleared in 2015 [115]. This system uses a modular OCT scanner attached to the camera port of the microscope. (C) Leica Microsystems Bioptigen EnFocus, FDA cleared in 2015 [120]. This system uses a modular OCT scanner attached prior to the objective. Red arrows denote the location of OCT scanners.

Fig. 6

Surgical imaging with live 2D MIOCT. (A) Retinal surgery imaging protocol using two orthogonal high-resolution B-scans [118]. (B) Anterior eye surgery imaging protocol using five parallel and laterally offset B-scans spanning the area of interest [132]. The B-scan locations are overlaid on the surgical views.

Fig. 7

Surgical imaging with live 3D MIOCT. (A) Real-time enhanced volumetric rendering using GPU-accelerated software. Median filtering and depth-based shading improved visualization of subtle anatomical and pathological structures [137]. Manipulation of the rendering perspective also allowed surgeons to visualize structures from various perspectives. (B) Visualization of commonplace surgical instruments in OCT volumes acquired during porcine eye surgery. ERM: epiretinal membrane, MH: macular hole.

Fig. 8

OCT-guided femtosecond laser surgical module for anterior eye surgery [73]. (A) The two modalities were coupled using a dichroic mirror prior to the scanning mirrors and shared an objective and the contact lens (B) used to deliver light to the surgical site. (C) OCT volumes were used to detect the various tissue surfaces and allowed the surgeon to precisely position the laser cutting pattern and avoid damage to the iris and surrounding structures. (D) Iris camera image denoting the edge of the laser cutting pattern (1) and the pupil boundary determined on OCT (2).

Fig. 9

Heads-up displays (HUD) for intraoperative OCT visualization. (A) Monocular HUD integrated into the commercial Zeiss RESCAN 700 [119]. (B) Binocular HUD integrated into the commercial Haag-Streit Surgical iOCT [115]. Both (A) and (B) are used to project live B-scans into the oculars of the microscope to provide the surgeon with immediate OCT feedback. (C) Custom binocular HUD used to display stereoscopic OCT volumes into the surgical oculars [144]. Volumes rendered from different perspectives were projected into each ocular to provide the surgeon with a stereo presentation of the data in real-time.

Fig. 10

B-scan imaging of mock surgical manipulations with OCT-integrated surgical forceps and robotic assistance [112]. (A) B-scans of manual and (B) robotic-assisted manipulation of gelatin phantom. (C) B-scans of manual and (D) robotic-assisted manipulation of ex vivo goat retina. (E) B-scan imaging during peeling of membrane phantom from gelatin.

Fig. 11

Functional imaging with intraoperative OCT systems. (A) Optical property map derived from attenuation coefficients calculated from OCT volumes in real-time to differentiate cancerous and non-cancerous tissue [164]. (B) Real-time Doppler processing and imaging for intraoperative HHOCT imaging of anastomoses [91].

Fig. 12

Live MIOCT imaging during human retinal surgery. (A-B) Live 2D MIOCT imaging with high-resolution orthogonal B-scans using the commercial Zeiss RESCAN 700 [118] during (A) retinal detachment and (B) proliferative diabetic retinopathy procedures. (C-D) Live 3D MIOCT imaging using real-time volumes [122] during retinal brushing with a (C) diamond dusted scraper and a (D) flex loop. High-speed volumetric imaging enhances visualization of subtle 3D tissue deformations.

Fig. 13

Live MIOCT imaging of human anterior eye surgery. (A) Live 2D MIOCT imaging with high-resolution B-scans using the commercial Haag-Streit Surgical iOCT [188] during Decemet’s membrane endothelial keratoplasty. Real-time direct visualization graft attachment during air filling in B-scans was made possible by MIOCT (B) Live 3D MIOCT imaging using real-time volumes [122] during Decemet’s stripping automated endothelial keratoplasty. Graft unfolding, orientation, and apposition was directly visible in the volumes.

Fig. 14

OCT B-scans acquired with an intraoperative HHOCT probe during breast tumor resection surgery. Diagram on the left denotes tissue areas imaged with OCT B-scan. The blue and red dashed lines in the B-scans correspond to areas of cancerous and noncancerous regions, respectively. (A, C) OCT B-scans of tumor margins acquired in vivo. (B, D) OCT B-scans of tumor margins acquired ex vivo after resection with corresponding histology [94].