Single Fiber Optical Coherence Tomography Microsurgical Instruments for Computer and Robot-Assisted Retinal Surgery

Unsupervised out-of-distribution detection for safer robotically guided retinal microsurgery

PURPOSE

A fundamental problem in designing safe machine learning systems is identifying when samples presented to a deployed model differ from those observed at training time. Detecting so-called out-of-distribution (OoD) samples is crucial in safety-critical applications such as robotically guided retinal microsurgery, where distances between the instrument and the retina are derived from sequences of 1D images that are acquired by an instrument-integrated optical coherence tomography (iiOCT) probe.

METHODS

This work investigates the feasibility of using an OoD detector to identify when images from the iiOCT probe are inappropriate for subsequent machine learning-based distance estimation. We show how a simple OoD detector based on the Mahalanobis distance can successfully reject corrupted samples coming from real-world ex vivo porcine eyes.

RESULTS

Our results demonstrate that the proposed approach can successfully detect OoD samples and help maintain the performance of the downstream task within reasonable levels. MahaAD outperformed a supervised approach trained on the same kind of corruptions and achieved the best performance in detecting OoD cases from a collection of iiOCT samples with real-world corruptions.

CONCLUSION

The results indicate that detecting corrupted iiOCT data through OoD detection is feasible and does not need prior knowledge of possible corruptions. Consequently, MahaAD could aid in ensuring patient safety during robotically guided microsurgery by preventing deployed prediction models from estimating distances that put the patient at risk.

Investigation of Micro-motion Kinematics of Continuum Robots for Volumetric OCT and OCT-guided Visual Servoing

Continuum robots (CR) have been recently shown capable of micron-scale motion resolutions. Such motions are achieved through equilibrium modulation using indirect actuation for altering either internal preload forces or changing the cross-sectional stiffness along the length of a continuum robot. Previously reported, but unexplained, turning point behavior is modeled using two approaches. An energy minimization approach is first used to explain the source of this behavior. Subsequently, a kinematic model using internal constraints in multi-backbone CRs is used to replicate this turning point behavior. An approach for modeling the micro-motion differential kinematics is presented using experimental data based on the solution of a system of linear matrix equations. This approach provides a closed-form approximation of the empirical micro-motion kinematics and could be easily used for real-time control. A motivating application of image-based biopsy using 3D optical coherence tomography (OCT) is envisioned and demonstrated in this paper. A system integration for generating OCT volumes by sweeping a custom B-mode OCT probe is presented. Results showing high accuracy in obtaining 3D OCT measurements are shown using a commercial OCT probe. Qualitative results using a miniature probe integrated within the robot are also shown. Finally, closed-loop visual servoing using OCT data is demonstrated for guiding a needle into an agar channel. Results of this paper present what we believe is the first embodiment of a continuum robot capable of micro and macro motion control for 3D OCT imaging. This approach can support the development of new technologies for CRs capable of surgical intervention and micro-motion for ultra-precision tasks.

A Review of Robotic and OCT-Aided Systems for Vitreoretinal Surgery

The introduction of the intraocular vitrectomy instrument by Machemer et al. has led to remarkable advancements in vitreoretinal surgery enabling the limitations of human physiologic capabilities to be reached. To overcome the barriers of perception, tremor, and dexterity, robotic technologies have been investigated with current advancements nearing the feasibility for clinical use. There are four categories of robotic systems that have emerged through the research: (1) handheld instruments with intrinsic robotic assistance, (2) hand-on-hand robotic systems, (3) teleoperated robotic systems, and (4) magnetic guidance robots. This review covers the improvements and the remaining needs for safe, cost-effective clinical deployment of robotic systems in vitreoretinal surgery.

Eye Explorer: A robotic endoscope holder for eye surgery

Background

Holding endoscopes by hand when performing eye surgery reduces the dexterity of the surgeon.

Methods

A robotic endoscope holder called “Eye Explorer” is proposed to hold the endoscope and free the surgeon's hand.

Results

This device satisfies the engineering and clinical requirements of eye surgery. The force for manual operation is less than 0.5 N. The observable ranges inside the patient's eye considering horizontal and vertical perspectives are 118° and 97°, and the motion of the holder does not interfere with the surgeon's hand and other surgical devices. The self‐weight compensation can prevent the endoscope from falling when extra supporting force is released. When comparing the external force exerted on the eye by the Eye Explorer with that in case of manual operation, a decrease of more than 15% can be observed. Moreover, the consumption time of endoscope view adjustment using the Eye Explorer and manual operation does not significantly differ.

Conclusion

The Eye Explorer allows dual‐hand operation, facilitating a successful endoscopic eye surgery.

Towards Bimanual Robot-Assisted Retinal Surgery: Tool-to-Sclera Force Evaluation

The performance of retinal microsurgery often requires the coordinated use of both hands. During bimanual retinal surgery, dominant hand performance may be negatively impacted by poor non-dominant hand assistance. Therefore understanding bimanual latent determinants, and establishing safety criteria for bimanual manipulation is relevant to robotic development and to eventual patient care. In this paper, we present a preliminary study to quantitatively evaluate one aspect of bimanual tool use in retinal surgery. Two force sensing tools were designed and fabricated using fiber Bragg grating sensors. Tool-to-sclera contact force is measured using the developed tools and analyzed. The tool forces were recorded during five basic surgical maneuvers typical of retinal surgery. Two subjects are involved in experiments, including one clinician and one engineer. For comparison, all manipulations were replicated under robot-assisted conditions. The results indicate that the average tool-to-sclera force recorded from the dominant hand tool is significantly higher than that from the non-dominant hand tool (p = 0.004). Moreover, the average forces under robot-assisted conditions with the present steady hand robot is notably higher than freehand conditions(p = 0.01). The forces obtained from the dominant and not-dominant hand instruments indicate a weak correlation.

User Behavior Evaluation in Robot-Assisted Retinal Surgery

Retinal microsurgery is technically demanding and requires high surgical skill with very little room for manipulation error. The introduction of robotic assistance has the potential to enhance and expand a surgeon's manipulation capabilities during retinal surgery, i.e., improve precision, cancel physiological hand tremor, and provide sensing information. However, surgeon performance may also be negatively impacted by robotic assistance due to robot structural stiffness and nonintuitive controls. In complying with robotic constraints, the surgeon loses the dexterity of the human hand. In this paper, we present a preliminary experimental study to evaluate user behavior when affected by robotic assistance during mock retinal surgery. In these experiments user behavior is characterized by measuring the forces applied by the user to the sclera, the tool insertion/retraction speed, the tool insertion depth relative to the scleral entry point, and the duration of surgery. The users' behavior data is collected during three mock retinal surgery tasks with four users. Each task is conducted using both freehand and robot-assisted techniques. The univariate user behavior and the correlations of multiple parameters of user behavior are analyzed. The results show that robot assistance prolongs the duration of the surgery and increases the manipulation forces applied to sclera, but refines the insertion velocity and eliminates hand tremor.

Combined OCT distance and FBG force sensing cannulation needle for retinal vein cannulation: in vivo animal validation

PURPOSE

Retinal vein cannulation is an experimental procedure during which a clot-dissolving drug is injected into an obstructed retinal vein. However, due to the fragility and minute size of retinal veins, such procedure is considered too risky to perform manually. With the aid of surgical robots, key limiting factors such as: unwanted eye rotations, hand tremor and instrument immobilization can be tackled. However, local instrument anatomy distance and force estimation remain unresolved issues. A reliable, real-time local interaction estimation between instrument tip and the retina could be a solution. This paper reports on the development of a combined force and distance sensing cannulation needle, and its experimental validation during in vivo animal trials.

METHODS

Two prototypes are reported, relying on force and distance measurements based on FBG and OCT A-scan fibres, respectively. Both instruments provide an 80 [Formula: see text] needle tip and have outer shaft diameters of 0.6 and 2.3 mm, respectively.

RESULTS

Both prototypes were characterized and experimentally validated ex vivo. Then, paired with a previously developed surgical robot, in vivo experimental validation was performed. The first prototype successfully demonstrated the feasibility of using a combined force and distance sensing instrument in an in vivo setting.

CONCLUSION

The results demonstrate the feasibility of deploying a combined sensing instrument in an in vivo setting. The performed study provides a foundation for further work on real-time local modelling of the surgical scene. This paper provides initial insights; however, additional processing remains necessary.

Robot-assisted vitreoretinal surgery: current perspectives

Vitreoretinal microsurgery is among the most technically challenging of the minimally invasive surgical techniques. Exceptional precision is required to operate on micron scale targets presented by the retina while also maneuvering in a tightly constrained and fragile workspace. These challenges are compounded by inherent limitations of the unassisted human hand with regard to dexterity, tremor and precision in positioning instruments. The limited human ability to visually resolve targets on the single-digit micron scale is a further limitation. The inherent attributes of robotic approaches therefore, provide logical, strategic and promising solutions to the numerous challenges associated with retinal microsurgery. Robotic retinal surgery is a rapidly emerging technology that has witnessed an exponential growth in capabilities and applications over the last decade. There is now a worldwide movement toward evaluating robotic systems in an expanding number of clinical applications. Coincident with this expanding application is growth in the number of laboratories committed to "robotic medicine". Recent technological advances in conventional retina surgery have also led to tremendous progress in the surgeon's capabilities, enhanced outcomes, a reduction of patient discomfort, limited hospitalization and improved safety. The emergence of robotic technology into this rapidly advancing domain is expected to further enhance important aspects of the retinal surgery experience for the patients, surgeons and society.

Robotic Vitreoretinal Surgery

PURPOSE

To review the current literature on robotic assistance for ophthalmic surgery, especially vitreoretinal procedures.

METHODS

MEDLINE, Embase, and Web of Science databases were searched from inception to August, 2016, for articles relevant to the review topic. Queries included combinations of the terms: robotic eye surgery, ophthalmology, and vitreoretinal.

RESULTS

In ophthalmology, proof-of-concept papers have shown the feasibility of performing many delicate anterior segment and vitreoretinal surgical procedures accurately with robotic assistance. Multiple surgical platforms have been designed and tested in animal eyes and phantom models. These platforms have the capability to measure forces generated and velocities of different surgical movements. "Smart" instruments have been designed to improve certain tasks such as membrane peeling and retinal vessel cannulations.

CONCLUSION

Ophthalmic surgery, particularly vitreoretinal surgery, might have reached the limits of human physiologic performance. Robotic assistance can help overcome biologic limitations and improve our surgical performance. Clinical studies of robotic-assisted surgeries are needed to determine safety and feasibility of using this technology in patients.

Motorized Micro-Forceps with Active Motion Guidance based on Common-Path SSOCT for Epiretinal Membranectomy

In this study, we built and tested a handheld motion-guided micro-forceps system using common-path swept source optical coherence tomography (CP-SSOCT) for highly accurate depth controlled epiretinal membranectomy. A touch sensor and two motors were used in the forceps design to minimize the inherent motion artifact while squeezing the tool handle to actuate the tool and grasp, and to independently control the depth of the tool-tip. A smart motion monitoring and a guiding algorithm were devised to provide precise and intuitive freehand control. We compared the involuntary tool-tip motion occurring while grasping with a standard manual micro-forceps and our touch sensor activated micro-forceps. The results showed that our touch-sensor-based and motor-actuated tool can significantly attenuate the motion artifact during grasping (119.81 μm with our device versus 330.73 μm with the standard micro-forceps). By activating the CP-SSOCT based depth locking feature, the erroneous tool-tip motion can be further reduced down to 5.11μm. We evaluated the performance of our device in comparison to the standard instrument in terms of the elapsed time, the number of grasping attempts, and the maximum depth of damage created on the substrate surface while trying to pick up small pieces of fibers (Ø 125 μm) from a soft polymer surface. The results indicate that all metrics were significantly improved when using our device; of note, the average elapsed time, the number of grasping attempts, and the maximum depth of damage were reduced by 25%, 31%, and 75%, respectively.

Microscope-integrated optical coherence tomography: A new surgical tool in vitreoretinal surgery

Optical coherence tomography (OCT) has revolutionized imaging of ocular structures and various disease conditions. Though it has been used in the clinic for some decades, the OCT has only recently found its way into the operating theater. Early attempts at intraoperative OCT, hand-held and microscope mounted, have already improved our understanding of the surgical pathology and the role it might play in surgical decision-making. The microscope-integrated OCT now allows seamless, high-resolution, real-time imaging of surgical maneuvers from the incision to wound closure. Visualization of instruments and intraoperative tissue manipulation are possible with this in vivo modality and, therefore, help improve the outcome of surgery. In this article, we describe the advantages it offers during various vitreoretinal procedures.

Automated stereo vision instrument tracking for intraoperative OCT guided anterior segment ophthalmic surgical maneuvers

Microscope-integrated intraoperative OCT (iOCT) enables imaging of tissue cross-sections concurrent with ophthalmic surgical maneuvers. However, limited acquisition rates and complex three-dimensional visualization methods preclude real-time surgical guidance using iOCT. We present an automated stereo vision surgical instrument tracking system integrated with a prototype iOCT system. We demonstrate, for the first time, automatically tracked video-rate cross-sectional iOCT imaging of instrument-tissue interactions during ophthalmic surgical maneuvers. The iOCT scan-field is automatically centered on the surgical instrument tip, ensuring continuous visualization of instrument positions relative to the underlying tissue over a 2500 mm(2) field with sub-millimeter positional resolution and <1° angular resolution. Automated instrument tracking has the added advantage of providing feedback on surgical dynamics during precision tissue manipulations because it makes it possible to use only two cross-sectional iOCT images, aligned parallel and perpendicular to the surgical instrument, which also reduces both system complexity and data throughput requirements. Our current implementation is suitable for anterior segment surgery. Further system modifications are proposed for applications in posterior segment surgery. Finally, the instrument tracking system described is modular and system agnostic, making it compatible with different commercial and research OCT and surgical microscopy systems and surgical instrumentations. These advances address critical barriers to the development of iOCT-guided surgical maneuvers and may also be translatable to applications in microsurgery outside of ophthalmology.

Evaluation of microsurgical tasks with OCT-guided and/or robot-assisted ophthalmic forceps

Real-time intraocular optical coherence tomography (OCT) visualization of tissues with surgical feedback can enhance retinal surgery. An intraocular 23-gauge B-mode forward-imaging co-planar OCT-forceps, coupling connectors and algorithms were developed to form a unique ophthalmic surgical robotic system. Approach to the surface of a phantom or goat retina by a manual or robotic-controlled forceps, with and without real-time OCT guidance, was performed. Efficiency of lifting phantom membranes was examined. Placing the co-planar OCT imaging probe internal to the surgical tool reduced instrument shadowing and permitted constant tracking. Robotic assistance together with real-time OCT feedback improved depth perception accuracy. The first-generation integrated OCT-forceps was capable of peeling membrane phantoms despite smooth tips.

Integrative advances for OCT-guided ophthalmic surgery and intraoperative OCT: microscope integration, surgical instrumentation, and heads-up display surgeon feedback

Purpose

To demonstrate key integrative advances in microscope-integrated intraoperative optical coherence tomography (iOCT) technology that will facilitate adoption and utilization during ophthalmic surgery.

Methods

We developed a second-generation prototype microscope-integrated iOCT system that interfaces directly with a standard ophthalmic surgical microscope. Novel features for improved design and functionality included improved profile and ergonomics, as well as a tunable lens system for optimized image quality and heads-up display (HUD) system for surgeon feedback. Novel material testing was performed for potential suitability for OCT-compatible instrumentation based on light scattering and transmission characteristics. Prototype surgical instruments were developed based on material testing and tested using the microscope-integrated iOCT system. Several surgical maneuvers were performed and imaged, and surgical motion visualization was evaluated with a unique scanning and image processing protocol.

Results

High-resolution images were successfully obtained with the microscope-integrated iOCT system with HUD feedback. Six semi-transparent materials were characterized to determine their attenuation coefficients and scatter density with an 830 nm OCT light source. Based on these optical properties, polycarbonate was selected as a material substrate for prototype instrument construction. A surgical pick, retinal forceps, and corneal needle were constructed with semi-transparent materials. Excellent visualization of both the underlying tissues and surgical instrument were achieved on OCT cross-section. Using model eyes, various surgical maneuvers were visualized, including membrane peeling, vessel manipulation, cannulation of the subretinal space, subretinal intraocular foreign body removal, and corneal penetration.

Conclusions

Significant iterative improvements in integrative technology related to iOCT and ophthalmic surgery are demonstrated.

The value of intraoperative optical coherence tomography imaging in vitreoretinal surgery

PURPOSE OF REVIEW

To evaluate the role of intraoperative optical coherence tomography (iOCT) in vitreoretinal surgery, assess the current state-of-the art, and to examine possible future directions in the field.

RECENT FINDINGS

Numerous vitreoretinal surgical conditions and procedures have been described utilizing iOCT. These conditions include macular holes, epiretinal membranes, retinal detachments, and retinopathy of prematurity. Significant alterations appear to occur during surgical manipulations in many of these conditions that can be identified with iOCT. The most common current systems used are portable OCT probes that are either mounted to a microscope or used in a handheld fashion. Prototypes are also being utilized that are integrated into the microscope to allow for true 'real-time' imaging of instrument-tissue interactions. Current generation surgical instrument materials (e.g., metal) limit optimal visualization with integrated OCT systems because of shadowing and light scattering properties.

SUMMARY

The role of iOCT in vitreoretinal surgery continues to be defined by active research and enhancements to integrative technologies. Further research is needed to better define the specific applications of iOCT that impact patient outcomes and surgical decision-making. Future advancements in integrative systems, OCT-friendly instrumentation, and software algorithms will further expand the horizon of iOCT in the vitreoretinal surgical theater. As OCT transformed the clinical management of the vitreoretinal conditions, iOCT has the potential to be a paradigm-shifting technology in the operating room.

Microscope-integrated intraoperative OCT with electrically tunable focus and heads-up display for imaging of ophthalmic surgical maneuvers

We present novel optical and mechanical designs for a microscope-integrated intraoperative optical coherence tomography (iOCT) system with enhanced function and ergonomics for visualization of ophthalmic surgical maneuvers. Integration of an electrically tunable lens allows rapid focal plane adjustment and iOCT imaging of both anterior and posterior segment tissue microstructures while maintaining parfocality with the ophthalmic surgical microscope. We demonstrate novel visualization of instrument positions relative to tissue layers of interest as colormap overlays onto en face OCT data, which may provide integrative display of volumetric information during surgical maneuvers. Finally, we implement a heads-up display system to provide real-time feedback as proof-of-principle for iOCT-guided ophthalmic surgery.

Preclinical evaluation and intraoperative human retinal imaging with a high-resolution microscope-integrated spectral domain optical coherence tomography device

PURPOSE

The authors have recently developed a high-resolution microscope-integrated spectral domain optical coherence tomography (MIOCT) device designed to enable OCT acquisition simultaneous with surgical maneuvers. The purpose of this report is to describe translation of this device from preclinical testing into human intraoperative imaging.

METHODS

Before human imaging, surgical conditions were fully simulated for extensive preclinical MIOCT evaluation in a custom model eye system. Microscope-integrated spectral domain OCT images were then acquired in normal human volunteers and during vitreoretinal surgery in patients who consented to participate in a prospective institutional review board-approved study. Microscope-integrated spectral domain OCT images were obtained before and at pauses in surgical maneuvers and were compared based on predetermined diagnostic criteria to images obtained with a high-resolution spectral domain research handheld OCT system (HHOCT; Bioptigen, Inc) at the same time point. Cohorts of five consecutive patients were imaged. Successful end points were predefined, including ≥80% correlation in identification of pathology between MIOCT and HHOCT in ≥80% of the patients.

RESULTS

Microscope-integrated spectral domain OCT was favorably evaluated by study surgeons and scrub nurses, all of whom responded that they would consider participating in human intraoperative imaging trials. The preclinical evaluation identified significant improvements that were made before MIOCT use during human surgery. The MIOCT transition into clinical human research was smooth. Microscope-integrated spectral domain OCT imaging in normal human volunteers demonstrated high resolution comparable to tabletop scanners. In the operating room, after an initial learning curve, surgeons successfully acquired human macular MIOCT images before and after surgical maneuvers. Microscope-integrated spectral domain OCT imaging confirmed preoperative diagnoses, such as full-thickness macular hole and vitreomacular traction, and demonstrated postsurgical changes in retinal morphology. Two cohorts of five patients were imaged. In the second cohort, the predefined end points were exceeded with ≥80% correlation between microscope-mounted OCT and HHOCT imaging in 100% of the patients.

CONCLUSION

This report describes high-resolution MIOCT imaging using the prototype device in human eyes during vitreoretinal surgery, with successful achievement of predefined end points for imaging. Further refinements and investigations will be directed toward fully integrating MIOCT with vitreoretinal and other ocular surgery to image surgical maneuvers in real time.

Optical coherence tomography scanning with a handheld vitreoretinal micromanipulator

An active handheld micromanipulator has been developed that is capable of automated intraocular acquisition of B-mode and C-mode optical coherence tomography scans that are up to 4 mm wide. The manipulator is a handheld Gough-Stewart platform actuated by ultrasonic linear motors. The manipulator has been equipped with a Fourier-domain common-path intraocular OCT probe that fits within a 25-gauge needle. The paper describes the systems and techniques involved, and presents preliminary results of B-mode and C-mode scans.

Robot-assisted intraocular surgery: development of the IRISS and feasibility studies in an animal model

PURPOSE

The aim of this study is to develop a novel robotic surgical platform, the IRISS (Intraocular Robotic Interventional and Surgical System), capable of performing both anterior and posterior segment intraocular surgery, and assess its performance in terms of range of motion, speed of motion, accuracy, and overall capacities.

PATIENTS AND METHODS

To test the feasibility of performing 'bimanual' intraocular surgical tasks using the IRISS, we defined four steps out of typical anterior (phacoemulsification) and posterior (pars plana vitrectomy (PPV)) segment surgery. Selected phacoemulsification steps included construction of a continuous curvilinear capsulorhexis and cortex removal in infusion-aspiration (I/A) mode. Vitrectomy steps consisted of performing a core PPV, followed by aspiration of the posterior hyaloid with the vitreous cutter to induce a posterior vitreous detachment (PVD) assisted with triamcinolone, and simulation of the microcannulation of a temporal retinal vein. For each evaluation, the duration and the successful completion of the task with or without complications or involuntary events was assessed.

RESULTS

Intraocular procedures were successfully performed on 16 porcine eyes. Four eyes underwent creation of a round, curvilinear anterior capsulorhexis without radialization. Four eyes had I/A of lens cortical material completed without posterior capsular tear. Four eyes completed 23-gauge PPV followed by successful PVD induction without any complications. Finally, simulation of microcannulation of a temporal retinal vein was successfully achieved in four eyes without any retinal tears/perforations noted.

CONCLUSION

Robotic-assisted intraocular surgery with the IRISS may be technically feasible in humans. Further studies are pending to improve this particular surgical platform.

Validating retinal fundus image analysis algorithms: issues and a proposal

This paper concerns the validation of automatic retinal image analysis (ARIA) algorithms. For reasons of space and consistency, we concentrate on the validation of algorithms processing color fundus camera images, currently the largest section of the ARIA literature. We sketch the context (imaging instruments and target tasks) of ARIA validation, summarizing the main image analysis and validation techniques. We then present a list of recommendations focusing on the creation of large repositories of test data created by international consortia, easily accessible via moderated Web sites, including multicenter annotations by multiple experts, specific to clinical tasks, and capable of running submitted software automatically on the data stored, with clear and widely agreed-on performance criteria, to provide a fair comparison.

Hybrid tracking and mosaicking for information augmentation in retinal surgery

Current technical limitations in retinal surgery hinder the ability of surgeons to identify and localize surgical targets, increasing operating times and risks of surgical error. In this paper we present a hybrid tracking and mosaicking method for augmented reality in retinal surgery. The system is a combination of direct and feature-based tracking methods. A novel extension for direct visual tracking using a robust image similarity measure in color images is also proposed. Several experiments conducted on phantom, in vivo rabbit and human images attest the ability of the method to cope with the challenging retinal surgery scenario. Applications of the proposed method for tele-mentoring and intra-operative guidance are demonstrated.

Vision-based proximity detection in retinal surgery

In retinal surgery, surgeons face difficulties such as indirect visualization of surgical targets, physiological tremor, and lack of tactile feedback, which increase the risk of retinal damage caused by incorrect surgical gestures. In this context, intraocular proximity sensing has the potential to overcome current technical limitations and increase surgical safety. In this paper, we present a system for detecting unintentional collisions between surgical tools and the retina using the visual feedback provided by the opthalmic stereo microscope. Using stereo images, proximity between surgical tools and the retinal surface can be detected when their relative stereo disparity is small. For this purpose, we developed a system comprised of two modules. The first is a module for tracking the surgical tool position on both stereo images. The second is a disparity tracking module for estimating a stereo disparity map of the retinal surface. Both modules were specially tailored for coping with the challenging visualization conditions in retinal surgery. The potential clinical value of the proposed method is demonstrated by extensive testing using a silicon phantom eye and recorded rabbit in vivo data.

Unprocessed real-time imaging of vitreoretinal surgical maneuvers using a microscope-integrated spectral-domain optical coherence tomography system

BACKGROUND

We have recently developed a microscope-integrated spectral-domain optical coherence tomography (MIOCT) device towards intrasurgical cross-sectional imaging of surgical maneuvers. In this report, we explore the capability of MIOCT to acquire real-time video imaging of vitreoretinal surgical maneuvers without post-processing modifications.

METHODS

Standard 3-port vitrectomy was performed in human during scheduled surgery as well as in cadaveric porcine eyes. MIOCT imaging of human subjects was performed in healthy normal volunteers and intraoperatively at a normal pause immediately following surgical manipulations, under an Institutional Review Board-approved protocol, with informed consent from all subjects. Video MIOCT imaging of live surgical manipulations was performed in cadaveric porcine eyes by carefully aligning B-scans with instrument orientation and movement. Inverted imaging was performed by lengthening of the reference arm to a position beyond the choroid.

RESULTS

Unprocessed MIOCT imaging was successfully obtained in healthy human volunteers and in human patients undergoing surgery, with visualization of post-surgical changes in unprocessed single B-scans. Real-time, unprocessed MIOCT video imaging was successfully obtained in cadaveric porcine eyes during brushing of the retina with the Tano scraper, peeling of superficial retinal tissue with intraocular forceps, and separation of the posterior hyaloid face. Real-time inverted imaging enabled imaging without complex conjugate artifacts.

CONCLUSIONS

MIOCT is capable of unprocessed imaging of the macula in human patients undergoing surgery and of unprocessed, real-time, video imaging of surgical maneuvers in model eyes. These capabilities represent an important step towards development of MIOCT for efficient, real-time imaging of manipulations during human surgery.

The use of optical coherence tomography in intraoperative ophthalmic imaging

Optical coherence tomography (OCT) has transformed diagnostic ophthalmic imaging but until recently has been limited to the clinic setting. The development of spectral-domain OCT (SD-OCT), with its improved speed and resolution, along with the development of a handheld OCT scanner, enabled portable imaging of patients unable to sit in a conventional tabletop scanner. This handheld SD-OCT unit has proven useful in examinations under anesthesia and, more recently, in intraoperative imaging of preoperative and postoperative manipulations. Recently, several groups have pioneered the development of novel OCT modalities, such as microscope-mounted OCT systems. Although still immature, the development of these systems is directed toward real-time imaging of surgical maneuvers in the intraoperative setting. This article reviews intraoperative imaging of the posterior and anterior segment using the handheld SD-OCT and recent advances toward real-time microscope-mounted intrasurgical imaging.

Data-driven visual tracking in retinal microsurgery

In the context of retinal microsurgery, visual tracking of instruments is a key component of robotics assistance. The difficulty of the task and major reason why most existing strategies fail on in-vivo image sequences lies in the fact that complex and severe changes in instrument appearance are challenging to model. This paper introduces a novel approach, that is both data-driven and complementary to existing tracking techniques. In particular, we show how to learn and integrate an accurate detector with a simple gradient-based tracker within a robust pipeline which runs at framerate. In addition, we present a fully annotated dataset of retinal instruments in in-vivo surgeries, which we use to quantitatively validate our approach. We also demonstrate an application of our method in a laparascopy image sequence.

Surgical vision

The emergence of Minimal Access Surgery (MAS) as a paradigm in modern healthcare treatment has created new challenges and opportunities for automated image understanding and computer vision. In MAS, images recovered from inside the body using specialized devices are used to visualize and operate on the surgical site but they can also be used to computationally infer in vivo 3D tissue surface shape, soft-tissue morphology, and surgical instrument motion. This information is important for facilitating in vivo biophotonic imaging modalities where the interaction between light and tissue is used to infer the structural and functional properties of the tissue. This article provides a review of the literature for computer vision and image understanding techniques applied to MAS images. The focus of this article is to elucidate a perspective on how computer vision techniques can be used to support and enhance the capabilities of biophotonic imaging modalities during surgery. Note that while MAS encompasses a variety of surgical specializations this review does not involve procedures performed in the interventional suite. The review has been carried out based on searches in the PubMed and IEEE databases using the article's keywords.

Integration of a spectral domain optical coherence tomography system into a surgical microscope for intraoperative imaging

PURPOSE

To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging.

METHODS

A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board-approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting.

RESULTS

High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes).

CONCLUSIONS

High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon.

Common-Path Optical Coherence Tomography for Biomedical Imaging and Sensing

This paper describes a development of a fiber optic common-path optical coherence tomography (OCT) based imaging and guided system that possess ability to reliably identify optically transparent targets that are on the micron scale; ability to maintain a precise and safe position from the target; ability to provide spectroscopic imaging; ability to imaging biological target in 3-D. The system is based on a high resolution fiber optic Common-Path OCT (CP-OCT) that can be integrated into various mini-probes and tools. The system is capable of obtaining >70K A-scan per second with a resolution better than 3 μm. We have demonstrated that the system is capable of one-dimensional real-time depth tracking, tool motion limiting and motion compensation, oxygen-saturation level imaging, and high resolution 3-D images for various biomedical applications.