Microscope-integrated Optical Coherence Tomography System Research Articles

Microscope-integrated optical coherence tomography for in vivo human brain tumor detection with artificial intelligence.

It has been shown that optical coherence tomography (OCT) can identify brain tumor tissue and potentially be used for intraoperative margin diagnostics. However, there is limited evidence on its use in human in vivo settings, particularly in terms of its applicability and accuracy of residual brain tumor detection (RTD). For this reason, a microscope-integrated OCT system was examined to determine in vivo feasibility of RTD after resection with automated scan analysis. Healthy and diseased brain was 3D scanned at the resection edge in 18 brain tumor patients and investigated for its informative value in regard to intraoperative tissue classification. Biopsies were taken at these locations and labeled by a neuropathologist for further analysis as ground truth. Optical OCT properties were obtained, compared, and used for separation with machine learning. In addition, two artificial intelligence-assisted methods were utilized for scan classification, and all approaches were examined for RTD accuracy and compared to standard techniques. In vivo OCT tissue scanning was feasible and easily integrable into the surgical workflow. Measured backscattered light signal intensity, signal attenuation, and signal homogeneity were significantly distinctive in the comparison of scanned white matter to increasing levels of scanned tumor infiltration (p < 0.001) and achieved high values of accuracy (85%) for the detection of diseased brain in the tumor margin with support vector machine separation. A neuronal network approach achieved 82% accuracy and an autoencoder approach 85% accuracy in the detection of diseased brain in the tumor margin. Differentiating cortical gray matter from tumor tissue was not technically feasible in vivo. In vivo OCT scanning of the human brain has been shown to contain significant value for intraoperative RTD, supporting what has previously been discussed for ex vivo OCT brain tumor scanning, with the perspective of complementing current intraoperative methods for this purpose, especially when deciding to withdraw from further resection toward the end of the surgery.

NOVEL METHOD FOR VISUALIZING PERIPHERAL RETINAL STRUCTURES WITH MICROSCOPE-INTEGRATED OPTICAL COHERENCE TOMOGRAPHY.

Visualization of peripheral retinal structures with optical coherence tomography (OCT) can be challenging but can offer valuable clinical information. We describe a method for intraoperative OCT of the peripheral retina. An investigational microscope-integrated OCT system with real-time 4D volumetric imaging was used in conjunction with a Goldmann style mirrored contact lens intraoperatively to capture peripheral images in three patients. We identified retinoschisis, a retinal break, and areas of focal retinal detachment using our peripheral OCT method. Use of a Goldmann lens in conjunction with intraoperative OCT offers surgeons the ability to resolve peripheral pathology that cannot be easily evaluated with OCT otherwise.

Application of Intraoperative Optical Coherence Tomography Technology in Anterior Segment Surgery.

The use of optical coherence tomography (OCT) technology in anterior segment diseases allows for precise assessment of the changes following anterior segment surgery. Advances in microscope-integrated OCT systems have allowed the utilization of intraoperative OCT (iOCT) in anterior segment surgeries, i.e., cornea, cataract, and refractive surgery. iOCT has enabled real-time precise visualization of anterior segment tissues as well as interactions between surgical instruments and ocular tissue; thus, the device can facilitate surgical procedures and provide valuable information for decision-making during anterior segment surgeries. In this review, the authors will introduce studies regarding the development of iOCT technology and its application in various anterior segment surgeries. Multiple studies have shown the efficacy of the iOCT for intraoperative assistance and guidance, suggesting the potential of the device for optimizing the surgical outcomes after cornea, cataract, and refractive surgery.

Optical Coherence Tomography for Diagnosis and Treatment of Corneal Diseases

Optical coherence tomography (OCT) is a modern non-contact real-time imaging of anterior and posterior eye’s segments. Based on the principle of low-coherence interferometry, it provides the analysis of tissue structures. In this review, we discuss technical aspects of two different OCT platforms: Time-Domain OCT (TD-OCT), and Spectral-Domain (SD-OCT) with the use of Fourier transformation — Fourier-Domain (FD-OCT). Over the last several years, the development of OCT has increased the resolution of images by different ways of optical filtering. The usage of tunable swept laser instead of superluminescent diode in modern Swept-Source OCT (SS-OCT) provides the sufficient quality of image. Anterior segment OCT can detect the pathological changes in different ocular structures and may be a key tool for monitoring of their progression. In pterygium OCT shows the true extent of fibrovascular granulation tissue in stromal layers, whereas in keratitis it provides imaging of corneal infiltration. Frequently, OCT-pachymetry can be advantageous in the detection of subclinical keratectasias. In patients with bullous keratopathy OCT can help to distinguish corneal edema and fibrosis. The new era of OCT is characterized by application of this method in keratorefractive surgery. Microscope-mounted (portable) and microscopeintegrated OCT systems have been developed. During LASIK surgery intraoperative OCT (iOCT) helps to assess flap interface, measure flap and residual bed thickness. It is a useful tool to reveal the structural changes during corneal collagen crosslinking. At the beginning of keratoplasty, iOCT helps to determine the corneal thickness, extent and depth of opacity, Descemet membrane perforation. iOCT guides decision-making regarding keratoplasty modification, depth and diameter of trephination. Furthermore, a real-time visualization of ocular structures during keratoplasty decreases the frequency of intra- and postsurgical complications.

Microscope integrated optical coherence tomography system combined with augmented reality.

One of the disadvantages in microscope-integrated optical coherence tomography (MI-OCT) systems is that medical images acquired via different modalities are usually displayed independently. Hence, surgeons have to match two-dimensional and three-dimensional images of the same operative region subjectively. In this paper, we propose a simple registration method to overcome this problem by using guided laser points. This method combines augmented reality with an existing MI-OCT system. The basis of our idea is to introduce a guiding laser into the system, which allows us to identify fiducials in microscopic images. At first, the applied voltages of the scanning galvanometer mirror are used to calculate the fiducials' coordinates in an OCT model. After gathering data at the corresponding points' coordinates, the homography matrix and camera parameters are used to superimpose a reconstructed model on microscopic images. After performing experiments with artificial and animal eyes, we successfully obtain two-dimensional microscopic images of scanning regions with depth information. Moreover, the registration error is 0.04 mm, which is within the limits of medical and surgical errors. Our proposed method could have many potential applications in ophthalmic procedures.

Feasibility of microscope-integrated swept-source optical coherence tomography in canaloplasty.

BackgroundSeveral researchers have used commercial microscope-integrated optical coherence tomography (OCT) systems in glaucoma surgery, including ab interno trabeculectomy and canaloplasty. However, the 840 nm wavelength light source of the OCT systems is not ideal for imaging the anterior chamber angle structures because of its limited penetration. We evaluated the potential value of a microscope-integrated swept-source OCT system with a 1,310 nm center-wavelength light in canaloplasty for glaucoma.MethodsSixteen porcine eyes were used to simulate canaloplasty. The critical surgical steps were monitored using a prototype microscope-integrated OCT system with a 1,310 nm light source and a high axial scan rate of 100 kHz. The images from swept-source OCT and three-dimensional images from the microscope were projected simultaneously onto a liquid crystal display three-dimensional monitor (LMD-4251TD, Sony, Japan). The changes in the collector vessel (aqueous drainage structure in the porcine eye, similar to Schlemm’s canal in humans) were measured using Image J software. Histological sections stained with hematoxylin and eosin were used to assess surgical efficacy.ResultsHigh-resolution real-time images of the anterior segment were acquired during canaloplasty using the microscope-integrated OCT system. With the real-time OCT images, the position of the collector vessel was identified and the scleral flap could be created at the ideal location. The expansion of the collector vessel after viscoelastic injection was also visualized in real time. Compared with baseline, there was a significant increase in the cross-sectional area (from 14,502.98±9,242.55 to 59,499.04±20,506.41 µm2, P<0.001) of the collector vessel.ConclusionsUsing the microscope-integrated OCT system, real-time images of the anterior segment were successfully acquired during the operation. The microscope-integrated OCT system might be useful in future anti-glaucoma surgery.

What Is the Impact of Intraoperative Microscope-Integrated OCT in Ophthalmic Surgery? Relevant Applications and Outcomes. A Systematic Review.

Background: Optical coherence tomography (OCT) has recently been introduced in the operating theatre. The aim of this review is to present the actual role of microscope-integrated optical coherence tomography (MI-OCT) in ophthalmology. Method: A total of 314 studies were identified, following a literature search adhering to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. After full-text evaluation, 81 studies discussing MI-OCT applications in ophthalmology were included. Results: At present, three microscope-integrated optical coherence tomography systems are commercially available. MI-OCT can help anterior and posterior segment surgeons in the decision-making process, providing direct visualization of anatomic planes before and after surgical manoeuvres, assisting in complex cases, and detecting or confirming intraoperative complications. Applications range from corneal transplant to macular surgery, including cataract surgery, glaucoma surgery, paediatric examination, proliferative diabetic retinopathy surgery, and retinal detachment surgery. Conclusion: The use of MI-OCT in ophthalmic surgery is becoming increasingly prevalent and has been applied in almost all procedures. However, there are still limitations to be overcome and the technology involved remains difficult to access and use.

Intraoperative OCT for surgical microscope with sensitivity drop and depth of focus correction based on variable focus and dynamic reference.

We have developed a surgical microscope-integrated optical coherence tomography (MI-OCT) system based on an active feedback method to obtain uniform optimal OCT image contrast along the depth of focus (DOF) of a surgical microscope. Conventional MI-OCT systems use a shorter DOF objective lens than those of surgical microscopes for OCT imaging. The existing MI-OCT system was developed to overcome sensitivity roll-off by using an electrically tunable lens (ETL). However, active change in the focus position through the ETL cannot cope with the sensitivity decrease due to optical path length difference (OPD) mismatch. The proposed active feedback method was able to maintain high sensitivity by actively performing OPD matching using a linear motor in the reference arm while tuning the focal position in the sample arm using the ETL. The optical system designed to maintain the OCT resolution and a retroreflector used for ensuring regular reflection intensity in the reference arm during OPD compensation contributed to the uniform sensitivity and stable OCT imaging performance. The simultaneous and automatic actuation of the ETL and linear motor provided sensitivity variation of 3 dB from 17 dB for 10-mm sample displacement corresponding to the DOF of the surgical microscope used in the MI-OCT system. By using an infrared detection card and a mouse brain tumor model, it was demonstrated that the proposed MI-OCT system could acquire OCT images with optimal sensitivity without the limitations due to short OCT DOF.

VISUALIZATION FROM INTRAOPERATIVE SWEPT-SOURCE MICROSCOPE-INTEGRATED OPTICAL COHERENCE TOMOGRAPHY IN VITRECTOMY FOR COMPLICATIONS OF PROLIFERATIVE DIABETIC RETINOPATHY

To evaluate the use of live volumetric (4D) intraoperative swept-source microscope-integrated optical coherence tomography in vitrectomy for proliferative diabetic retinopathy complications. In this prospective study, we analyzed a subgroup of patients with proliferative diabetic retinopathy complications who required vitrectomy and who were imaged by the research swept-source microscope-integrated optical coherence tomography system. In near real time, images were displayed in stereo heads-up display facilitating intraoperative surgeon feedback. Postoperative review included scoring image quality, identifying different diabetic retinopathy-associated pathologies and reviewing the intraoperatively documented surgeon feedback. Twenty eyes were included. Indications for vitrectomy were tractional retinal detachment (16 eyes), combined tractional-rhegmatogenous retinal detachment (2 eyes), and vitreous hemorrhage (2 eyes). Useful, good-quality 2D (B-scans) and 4D images were obtained in 16/20 eyes (80%). In these eyes, multiple diabetic retinopathy complications could be imaged. Swept-source microscope-integrated optical coherence tomography provided surgical guidance, e.g., in identifying dissection planes under fibrovascular membranes, and in determining residual membranes and traction that would benefit from additional peeling. In 4/20 eyes (20%), acceptable images were captured, but they were not useful due to high tractional retinal detachment elevation which was challenging for imaging. Swept-source microscope-integrated optical coherence tomography can provide important guidance during surgery for proliferative diabetic retinopathy complications through intraoperative identification of different complications and facilitation of intraoperative decision making.

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

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.

Intrasurgical Human Retinal Imaging With Manual Instrument Tracking Using a Microscope-Integrated Spectral-Domain Optical Coherence Tomography Device.

To characterize the first in-human intraoperative imaging using a custom prototype spectral-domain microscope-integrated optical coherence tomography (MIOCT) device during vitreoretinal surgery with instruments in the eye. Under institutional review board approval for a prospective intraoperative study, MIOCT images were obtained at surgical pauses with instruments held static in the vitreous cavity and then concurrently with surgical maneuvers. Postoperatively, MIOCT images obtained at surgical pauses were compared with images obtained with a high-resolution handheld spectral-domain OCT (HHOCT) system with objective endpoints, including acquisition of images acceptable for analysis and identification of predefined macular morphologic or pathologic features. Human MIOCT images were successfully obtained before incision and during pauses in surgical maneuvers. MIOCT imaging confirmed preoperative diagnoses, such as epiretinal membrane, full-thickness macular hole, and vitreomacular traction and demonstrated successful achievement of surgical goals. MIOCT and HHOCT images obtained at surgical pauses in two cohorts of five patients were comparable with greater than or equal to 80% correlation in 80% of patients. Real-time video-imaging concurrent with surgical manipulations enabled, for the first time using this device, visualization of dynamic instrument-retina interaction with targeted OCT tracking. MIOCT is successful for imaging at surgical pauses and for real-time image guidance with implementation of targeted OCT tracking. Even faster acquisition speeds are currently being developed with incorporation of a swept-source MIOCT engine. Further refinements and investigations will be directed toward continued integration for real-time volumetric imaging of surgical maneuvers. Ongoing development of seamless MIOCT systems will likely transform surgical visualization, approaches, and decision-making.

Quantification of cardiac fiber orientation using optical coherence tomography

Heterogeneity in cardiac tissue microstructure is a potential mechanism for the generation and maintenance of arrhythmias. Abnormal changes in fiber orientation increase the likelihood of arrhythmia. We present optical coherence tomography (OCT) as a method to image myofibers in excised intact heart preparations. Three-dimensional (3-D) image sets were gathered from the rabbit right ventricular free wall (RVFW) using a microscope-integrated OCT system. An automated algorithm for fiber orientation quantification in the plane parallel to the wall surface was developed. The algorithm was validated by comparison with manual measurements. Quantifying fiber orientation in the plane parallel to the wall surface from OCT images can be used to help understand the conduction system of the specific sample being imaged.