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Accurate identification of genetic alterations in tumors, such as Fibroblast Growth Factor Receptor, is crucial for treating with targeted therapies; however, molecular testing can delay patient care due to the time and tissue required. Successful development, validation, and deployment of an AI-based, biomarker-detection algorithm could reduce screening cost and accelerate patient recruitment. Here, we develop a deep-learning algorithm using >3000 H&E-stained whole slide images from patients with advanced urothelial cancers, optimized for high sensitivity to avoid ruling out trial-eligible patients. The algorithm is validated on a dataset of 350 patients, achieving an area under the curve of 0.75, specificity of 31.8% at 88.7% sensitivity, and projected 28.7% reduction in molecular testing. We successfully deploy the system in a non-interventional study comprising 89 global study clinical sites and demonstrate its potential to prioritize/deprioritize molecular testing resources and provide substantial cost savings in the drug development and clinical settings., (© 2024. The Author(s).)

Nonalcoholic steatohepatitis (NASH) is the most common chronic liver disease globally and a leading cause for liver transplantation in the US. Its pathogenesis remains imprecisely defined. We combined two high-resolution modalities to tissue samples from NASH clinical trials, machine learning (ML)-based quantification of histological features and transcriptomics, to identify genes that are associated with disease progression and clinical events. A histopathology-driven 5-gene expression signature predicted disease progression and clinical events in patients with NASH with F3 (pre-cirrhotic) and F4 (cirrhotic) fibrosis. Notably, the Notch signaling pathway and genes implicated in liver-related diseases were enriched in this expression signature. In a validation cohort where pharmacologic intervention improved disease histology, multiple Notch signaling components were suppressed., Competing Interests: Declaration of interests J.C. is an employee and shareholder of PathAI, Inc. M.P. is a shareholder of PathAI, Inc. Y.G. is a shareholder of Gilead Sciences, Inc. D.Z.P. is an employee of and shareholder of Gilead Sciences, Inc. O.M.C.-Z. is a shareholder of PathAI, Inc. V.M. is an employee and shareholder of PathAI, Inc. G.M.S. is an employee and shareholder of OrsoBio, Inc., and a shareholder of Gilead Sciences, Inc. M.C.M. is an employee and shareholder of PathAI, Inc. M.R. is an employee and shareholder of PathAI, Inc. A.H.B. is a co-founder, employee, and shareholder of PathAI, Inc. R.S.H. is an employee and shareholder of OrsoBio, Inc., and a shareholder of Gilead Sciences, Inc. R.P.M. is an employee and shareholder of OrsoBio, Inc., and a shareholder of Gilead Sciences, Inc. A.T.-W. is an employee and shareholder of PathAI, Inc. I.W. is an employee and shareholder of PathAI, Inc. C.C. is an employee and shareholder of Inipharm, Inc., and shareholder of Gilead Sciences, Inc., (Copyright © 2023. Published by Elsevier Inc.)

To discover distinct immune responses promoting or inhibiting hepatocellular carcinoma (HCC), we perform a three-dimensional analysis of the immune cells, correlating immune cell types, interactions, and changes over time in an animal model displaying gender disparity in nonalcoholic fatty liver disease (NAFLD)-associated HCC. In response to a Western diet (WD), animals mount acute and chronic patterns of inflammatory cytokines, respectively. Tumor progression in males and females is associated with a predominant CD8 + > CD4 + , Th1 > Th17 > Th2, NKT > NK, M1 > M2 pattern in the liver. A complete rescue of females from HCC is associated with an equilibrium Th1 = Th17 = Th2, NKT = NK, M1 = M2 pattern, while a partial rescue of males from HCC is associated with an equilibrium CD8 +  = CD4 + , NKT = NK and a semi-equilibrium Th1 = Th17 > Th2 but a sustained M1 > M2 pattern in the liver. Our data suggest that immunological pattern-recognition can explain immunobiology of HCC and guide immune modulatory interventions for the treatment of HCC in a gender-specific manner., Competing Interests: Declaration of interests A.J.S. is the President of Sanyal Biotechnology. A.J.S. and F.M. are shareholders in Sanyal Biotechnology and hold a patent on DIAMOND mouse model, PCT/US2016/056506., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background and Aims: The hepatic venous pressure gradient (HVPG) is the standard for estimating portal pressure but requires expertise for interpretation. We hypothesized that HVPG could be extrapolated from liver histology using a machine learning (ML) algorithm., Approach and Results: Patients with NASH with compensated cirrhosis from a phase 2b trial were included. HVPG and biopsies from baseline and weeks 48 and 96 were reviewed centrally, and biopsies evaluated with a convolutional neural network (PathAI, Boston, MA). Using trichrome-stained biopsies in the training set (n = 130), an ML model was developed to recognize fibrosis patterns associated with HVPG, and the resultant ML HVPG score was validated in a held-out test set (n = 88). Associations between the ML HVPG score with measured HVPG and liver-related events, and performance of the ML HVPG score for clinically significant portal hypertension (CSPH) (HVPG ≥ 10 mm Hg), were determined. The ML-HVPG score was more strongly correlated with HVPG than hepatic collagen by morphometry (ρ = 0.47 vs. ρ = 0.28; P < 0.001). The ML HVPG score differentiated patients with normal (0-5 mm Hg) and elevated (5.5-9.5 mm Hg) HVPG and CSPH (median: 1.51 vs. 1.93 vs. 2.60; all P < 0.05). The areas under receiver operating characteristic curve (AUROCs) (95% CI) of the ML-HVPG score for CSPH were 0.85 (0.80, 0.90) and 0.76 (0.68, 0.85) in the training and test sets, respectively. Discrimination of the ML-HVPG score for CSPH improved with the addition of a ML parameter for nodularity, Enhanced Liver Fibrosis, platelets, aspartate aminotransferase (AST), and bilirubin (AUROC in test set: 0.85; 95% CI: 0.78, 0.92). Although baseline ML-HVPG score was not prognostic, changes were predictive of clinical events (HR: 2.13; 95% CI: 1.26, 3.59) and associated with hemodynamic response and fibrosis improvement., Conclusions: An ML model based on trichrome-stained liver biopsy slides can predict CSPH in patients with NASH with cirrhosis., (© 2021 by the American Association for the Study of Liver Diseases.)

Rapid histological assessment of large areas of prostate tissue is required for many intraoperative consultation scenarios such as margin evaluation. Nonlinear microscopy (NLM) enables imaging of large (whole mount) specimens without freezing or cryotoming. This study demonstrates rapid histological imaging of unsectioned prostate cancer surgical specimens using nonlinear microscopy and compares features of prostate pathology to standard paraffin embedded H&E histology. Fresh or formalin fixed specimens were stained in 2.5 min with fluorescent nuclear and stromal dyes. Nonlinear microscopy images of unsectioned tissues were generated by nonlinear (two-photon) excitation of the fluorophores, where fluorescence is only emitted from tissue at the microscope focus, avoiding the need for physical sectioning. The images were displayed in real time using a color scale similar to H&E, then tissues were processed for standard paraffin embedded H&E histology. Seventy nonlinear microscopy and corresponding paraffin H&E images of fresh and fixed prostate specimens (15 cancer, 55 benign) from 24 patients were read by genitourinary pathologists to assess if nonlinear microscopy could achieve an equivalent evaluation to paraffin embedded H&E histology. Differences between nonlinear microscopy images and paraffin H&E slides, including cytoplasmic color and stromal density, were observed, however nonlinear microscopy images could be interpreted with minimal training. Nonlinear microscopy enabled visualization of benign, atrophic and hyperplastic glands and stroma, ejaculatory ducts, vasculature and inflammatory changes. Nonlinear microscopy enabled identification of typical and variants of adenocarcinoma, as well as Gleason patterns. Perineural invasion and extraprostatic extension could also be assessed. Nonlinear microscopy images closely resemble paraffin H&E slides and enable rapid assessment of normal prostate architecture, benign conditions, and carcinoma in freshly excised and fixed specimens. Nonlinear microscopy can image large regions of tissue, equivalent to multiple frozen section tissue blocks, within minutes because cryotoming/microtoming are not required, making it a promising technique for intraoperative consultation.

The recent clinical adoption of optical coherence tomography (OCT) angiography (OCTA) has enabled non-invasive, volumetric visualization of ocular vasculature at micron-scale resolutions. Initially limited to 3 mm × 3 mm and 6 mm × 6 mm fields-of-view (FOV), commercial OCTA systems now offer 12 mm × 12 mm, or larger, imaging fields. While larger FOVs promise a more complete visualization of retinal disease, they also introduce new challenges to the accurate and reliable interpretation of OCTA data. In particular, because of vignetting, wide-field imaging increases occurrence of low-OCT-signal artifacts, which leads to thresholding and/or segmentation artifacts, complicating OCTA analysis. This study presents theoretical and case-based descriptions of the causes and effects of low-OCT-signal artifacts. Through these descriptions, we demonstrate that OCTA data interpretation can be ambiguous if performed without consulting corresponding OCT data. Furthermore, using wide-field non-perfusion analysis in diabetic retinopathy as a model widefield OCTA usage-case, we show how qualitative and quantitative analysis can be confounded by low-OCT-signal artifacts. Based on these results, we suggest methods and best-practices for preventing and managing low-OCT-signal artifacts, thereby reducing errors in OCTA quantitative analysis of non-perfusion and improving reproducibility. These methods promise to be especially important for longitudinal studies detecting progression and response to therapy.

Ultrahigh speed optical coherence tomography (OCT) systems with >100 kHz A-scan rates can generate volumes rapidly with minimal motion artifacts and are well suited for 4D imaging (volumes through time) applications such as intra-operative imaging. In such systems, high OCT data acquisition efficiency (defined as the fraction of usable A-scans generated during the total acquisition time) is desired to maximize the volumetric frame rate and sampling pitch. However, current methods for beam scanning using non-resonant and resonant mirror scanners can result in severe scan distortion and transverse oversampling as well as require acquisition dead times, which limit the acquisition efficiency and performance of ultrahigh speed 4D OCT. We introduce constant linear velocity spiral scanning (CLV-SC) as a novel beam scanning method to maximize the data acquisition efficiency of ultrahigh speed 4D OCT systems. We demonstrate that CLV-SC does not require acquisition dead times and achieves more uniform transverse sampling compared to raster scanning. To assess its clinical utility, we implement CLV-SC with a 400 kHz OCT system and image the anterior eye and retina of healthy adults at up to 10 volumes per second with isotropic transverse sampling, allowing B-scans with equal sampling pitch to be extracted from arbitrary locations within a single volume. The feasibility of CLV-SC for intra-operative imaging is also demonstrated using a 800 kHz OCT system to image simulated retinal surgery at 15 volumes per second with isotropic transverse sampling, resulting in high quality volume renders that enable clear visualization of surgical instruments and manipulation of tissue., Competing Interests: JAI: Leica Microsystems (P, R).

Virtual reality (VR) head-mounted displays are an attractive technology for viewing intrasurgical optical coherence tomography (OCT) volumes because they liberate surgeons from microscope oculars. We demonstrate real-time, interactive viewing of OCT volumes in a commercial HTC Vive immersive VR system using previously reported ray casting techniques. Furthermore, we show interactive manipulation and sectioning of volumes using handheld controllers and guidance of mock surgical procedures in porcine eyes exclusively within VR. To the best of our knowledge, we report the first immersive VR-OCT viewer with stereo ray casting volumetric renders, arbitrary sectioning planes, and live acquisition support. We believe VR-OCT volume displays will advance ophthalmic surgery towards VR-integrated surgery., Competing Interests: AK: Leica Microsystems (P), ClarVista (C). JI: Leica Microsystems (P, R), Carl Zeiss Meditec (P, R).

Purpose: To evaluate the images produced in an initial surgical series of intraoperative near-real-time volumetric swept-source (SS) OCT imaging., Design: Prospective translational study., Participants: Forty-one consecutive adult patients undergoing vitreoretinal surgery between July 22, 2014, and July 1, 2015, at the Duke University Eye Center who agreed to participate., Methods: A novel microscope-integrated SS-OCT prototype captured volumetric renderings of imaging of macular surgery in near-real-time and showed them to the surgeon via a heads-up display through the microscope oculars. Then the images were analyzed formally after surgery., Main Outcome Measures: Image quality, successful capture of surgical instruments, maneuvers and associated retinal deformation volumetrically over time, and qualitative image analysis., Results: Volumetric SS-OCT images were graded as acceptable in 92% of patients. Volumetric imaging of scraping and peeling procedures was achieved in 75% and 78% of patients in whom it was performed, respectively. Imaging provided the surgeon with near-real-time volumetric visualization of the position of the instrument relative to the retinal surface, flap initiation, flap removal, and retinal deformation during instrumentation via a heads-up display., Conclusions: This volumetric, microscope-integrated SS-OCT prototype seems to provide high-detail, near-real-time volumetric imaging of delicate maneuvers during macular surgery., (Copyright © 2017. Published by Elsevier Inc.)

Purpose: We advance studies of subretinal treatments by developing a microscope-integrated optical coherence tomography (MIOCT) image-based method for measuring the volume of therapeutics delivered into the subretinal space., Methods: A MIOCT image-based volume measurement method was developed and assessed for accuracy and reproducibility by imaging an object of known size in model eyes. This method then was applied to subretinal blebs created by injection of diluted triamcinolone. Bleb volumes obtained from MIOCT were compared to the intended injection volume and the surgeon's estimation of leakage., Results: Validation of the image-based volume measurement method showed accuracy to ±1.0 μL (6.0% of measured volume) with no statistically significant variation under different imaging settings. When this method was applied to subretinal blebs, four of 11 blebs without surgeon-observed leakage yielded a mean volume of 32 ± 12.5 μL, in contrast to the intended 50 μL volume injected from the delivery device. This constituted a mean difference of -18 μL (mean percent error, 36 ± 25%). For all 11 blebs, the surgeon's estimations of leakage were significantly different from and showed no correlation with the volume loss based on image-based volume measurements ( P < 0.001, paired t -test; intraclass correlation = 0)., Conclusions: We validated an accurate and reproducible method for measuring subretinal volumes using MIOCT. Use of this method revealed that the intended volume might not be delivered into the subretinal space. MIOCT can allow for accurate assessment of subretinal dose delivered, which may have therapeutic implications in evaluating the efficacy and toxicity of subretinal therapies., Translational Relevance: Use of MIOCT can provide feedback on the accuracy of subretinal injection volumes delivered.

Purpose: We determined the feasibility of fovea and optic nerve head imaging with a long working distance (LWD) swept source optical coherence tomography (OCT) prototype in adults, teenagers, and young children., Methods: A prototype swept source OCT system with a LWD (defined as distance from the last optical element of the imaging system to the eye) of 350 mm with custom fixation targets was developed to facilitate imaging of children. Imaging was performed in 49 participants from three age groups: 26 adults, 16 children 13 to 18 years old (teenagers), and seven children under 6 years old (young children) under an approved institutional review board protocol. The imaging goal was to acquire high quality scans of the fovea and optic nerve in each eye in the shortest time possible. OCT B-scans and volumes of the fovea and optic nerve head of each eligible eye were captured and graded based on four categories (lateral and axial centration, contrast, and resolution) and on ability to determine presence or absence of pathology., Results: LWD-OCT imaging was successful in 88 of 94 eligible eyes, including seven of 10 eyes of young children. Of the successfully acquired OCT images, 83% of B-scan and volumetric images, including 86% from young children, were graded as high-quality scans. Pathology was observed in high-quality OCT images., Conclusions: The prototype LWD-OCT system achieved high quality retinal imaging of adults, teenagers, and some young children with and without pathology with reasonable alignment time., Translational Relevance: The LWD-OCT system can facilitate imaging in children.

Purpose: To investigate the relationship between intraocular pressure (IOP) and big bubble (BB) formation in a model of deep anterior lamellar keratoplasty (DALK)., Design: Ex-vivo., Methods: Corneoscleral buttons from human donors were loaded onto an artificial anterior chamber connected to a column of balanced salt solution. A surgeon-in-training learned to perform DALK via the BB technique using swept-source microscope-integrated optical coherence tomography (SS-MIOCT) with heads-up display (HUD). DALK procedures were performed at 6 different IOPs (5, 10, 15, 20, 30, or 40 mm Hg; n = 6 per group) in a randomized fashion, with the surgeon-in-training masked to the pressure and guided by SS-MIOCT with HUD. For a subset of corneas within each pressure group, DALK was performed on matching donor tissue at a control IOP. BB diameter was recorded, and a diameter exceeding the trephine diameter was considered optimal., Results: Wilcoxon rank sum test showed a difference in BB diameter among the different pressure groups (mean ± SD of 7.75 ± 1.60, 8.33 ± 1.99, 10.9 ± 0.92, 9.08 ± 1.07, 6.67 ± 3.33, and 3.42 ± 3.77 mm in the 5, 10, 15, 20, 30, and 40 mm Hg groups, respectively; P = 0.0014). Per Tukey test, this difference was attributable to comparisons between the 40 mm Hg group and the 5, 10, 15, or 20 mm Hg groups (P = 0.04, 0.02, 0.0001, 0.004, respectively)., Conclusions: In this ex-vivo model of DALK, the BB technique guided by SS-MIOCT with HUD yielded bubbles of optimal diameters only at physiologic pressures (10‒20 mm Hg). Extremely high IOP (40 mm Hg) resulted in BBs of significantly smaller diameter than BBs obtained at physiologic and low (5 mm Hg) IOPs., (Copyright 2017 Asia-Pacific Academy of Ophthalmology.)

Importance: Intraoperative optical coherence tomography (OCT) has gained traction as an important adjunct for clinical decision making during vitreoretinal surgery, and OCT angiography (OCTA) has provided novel insights in clinical evaluation of retinal diseases. To date, these two technologies have not been applied in combination to evaluate retinal vascular disease in the operating suite., Objective: To conduct microscope-integrated, swept-source OCTA (MIOCTA) in children with retinal vascular disease., Design, Setting, and Participants: In this case report analysis, OCT imaging in pediatric patients, MIOCTA images were obtained during examination under anesthesia from a young boy with a history of idiopathic vitreous hemorrhage and a female infant with familial exudative vitreoretinopathy., Main Outcomes and Measures: Side-by-side comparison of research MIOCT angiograms and clinically indicated fluorescein angiograms., Results: In 2 young children with retinal vascular disease, the MIOCTA images showed more detailed vascular patterns than were visible on the fluorescein angiograms although within a more posterior field of view. The MIOCTA system allowed visualization of small pathological retinal vessels in the retinal periphery that were obscured in the fluorescein angiograms by fluorescein staining from underlying, preexisting laser scars., Conclusions and Relevance: This is the first report to date of the use of MIOCTA in the operating room for young children with retinal vascular disease. Further optimization of this system may allow noninvasive detailed evaluation of retinal vasculature during surgical procedures and in patients who could not cooperate with in-office examinations.

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.

The authors report the use of swept-source microscope-integrated optical coherence tomography (SS-MIOCT), capable of live four-dimensional (three-dimensional across time) intraoperative imaging, to directly visualize suture depth during lateral rectus resection. Key surgical steps visualized in this report included needle depth during partial and full-thickness muscle passes along with scleral passes. [J Pediatr Ophthalmol Strabismus. 2017;54:e1-e5.]., (Copyright 2017, SLACK Incorporated.)

We report the first use of swept-source microscope-integrated optical coherence tomography (SS-MIOCT) capable of live four-dimensional (4D) (three-dimensional across time) imaging intraoperatively to directly visualize tube shunt placement and trabeculectomy surgeries in two patients with severe open-angle glaucoma and elevated intraocular pressure (IOP) that was not adequately managed by medical intervention or prior surgery. We performed tube shunt placement and trabeculectomy surgery and used SS-MIOCT to visualize and record surgical steps that benefitted from the enhanced visualization. In the case of tube shunt placement, SS-MIOCT successfully visualized the scleral tunneling, tube shunt positioning in the anterior chamber, and tube shunt suturing. For the trabeculectomy, SS-MIOCT successfully visualized the scleral flap creation, sclerotomy, and iridectomy. Postoperatively, both patients did well, with IOPs decreasing to the target goal. We found the benefit of SS-MIOCT was greatest in surgical steps requiring depth-based assessments. This technology has the potential to improve clinical outcomes.

The peripheral retina of the human eye offers a unique opportunity for assessment and monitoring of ocular diseases. We have developed a novel wide-field (>70°) optical coherence tomography system (WF-OCT) equipped with wavefront sensorless adaptive optics (WSAO) for enhancing the visualization of smaller (<25°) targeted regions in the peripheral retina. We iterated the WSAO algorithm at the speed of individual OCT B-scans (~20 ms) by using raw spectral interferograms to calculate the optimization metric. Our WSAO approach with a 3 mm beam diameter permitted primarily low- but also high- order peripheral wavefront correction in less than 10 seconds. In preliminary imaging studies in five normal human subjects, we quantified statistically significant changes with WSAO correction, corresponding to a 10.4% improvement in average pixel brightness (signal) and 7.0% improvement in high frequency content (resolution) when visualizing 1 mm (~3.5°) B-scans of the peripheral (>23°) retina. We demonstrated the ability of our WF-OCT system to acquire non wavefront-corrected wide-field images rapidly, which could then be used to locate regions of interest, zoom into targeted features, and visualize the same region at different time points. A pilot clinical study was conducted on seven healthy volunteers and two subjects with prodromal Alzheimer's disease which illustrated the capability to image Drusen-like pathologies as far as 32.5° from the fovea in un-averaged volume scans. This work suggests that the proposed combination of WF-OCT and WSAO may find applications in the diagnosis and treatment of ocular, and potentially neurodegenerative, diseases of the peripheral retina, including diabetes and Alzheimer's disease.

Purpose: To examine big-bubble (BB) formation success rates in deep anterior lamellar keratoplasty (DALK) at various corneal depths using real-time guidance from swept-source, microscope-integrated optical coherence tomography (SS-MIOCT)., Methods: The DALK procedure was performed ex vivo with 34 human donor corneoscleral buttons on pressurized artificial anterior chambers using the BB technique employed by Anwar and Teichmann. We inserted a needle under controlled ex vivo conditions to corneal depths ranging from 40% to ≥90% using real-time guidance from SS-MIOCT and injected air. BB success was then determined for each injection., Results: The average needle depth for successful full BB formation was 79.9% ± 3.0% compared with 66.9% ± 2.6% for partial BB formation and 49.9% ± 3.4% for no BB formation (P < 0.0001). Expressed as stroma below the needle tip, this corresponded to 123.9 ± 20.0 μm for successful full BB formation compared with 233.7 ± 23.8 μm for partial BB formation and 316.7 ± 17.3 μm for no BB formation (P < 0.0001). All other variables tested (sex, race, age, endothelial cell density, air injected, needle angle, and central corneal thickness) did not significantly affect BB formation success rates., Conclusions: BB formation in DALK is more successful if needle insertion and air injection occur at deeper corneal depth. However, ≥90% corneal depth was not necessary in this ex vivo model of DALK. SS-MIOCT can be used to accurately guide the needle in real time., Competing Interests: For the remaining authors no conflicts of interest were declared.

Young and/or autistic children cannot be imaged with tabletop or handheld optical coherence tomography (OCT) because of their lack of attention and fear of large objects close to their face. We demonstrate a prototype retinal swept-source OCT system with a long working distance (from the last optical element to the subject's eye) to facilitate pediatric imaging. To reduce the number of optical elements and axial length compared to the traditional 4f telescope, we employ a compact 2f retinal scanning configuration and achieve a working distance of 350 mm with a 16° OCT field of view. We test our prototype system on pediatric and adult subjects.

Volumetric acquisition with anterior segment optical coherence tomography (ASOCT) is necessary to obtain accurate representations of the tissue structure and to account for asymmetries of the anterior eye anatomy. Additionally, recent interest in imaging of anterior segment vasculature and aqueous humor flow resulted in application of OCT angiography techniques to generate en face and 3D micro-vasculature maps of the anterior segment. Unfortunately, ASOCT structural and vasculature imaging systems do not capture volumes instantaneously and are subject to motion artifacts due to involuntary eye motion that may hinder their accuracy and repeatability. Several groups have demonstrated real-time tracking for motion-compensated in vivo OCT retinal imaging, but these techniques are not applicable in the anterior segment. In this work, we demonstrate a simple and low-cost pupil tracking system integrated into a custom swept-source OCT system for real-time motion-compensated anterior segment volumetric imaging. Pupil oculography hardware coaxial with the swept-source OCT system enabled fast detection and tracking of the pupil centroid. The pupil tracking ASOCT system with a field of view of 15 x 15 mm achieved diffraction-limited imaging over a lateral tracking range of +/- 2.5 mm and was able to correct eye motion at up to 22 Hz. Pupil tracking ASOCT offers a novel real-time motion compensation approach that may facilitate accurate and reproducible anterior segment imaging., Competing Interests: At the time this study was conducted, Dr. Izatt was Chairman and Chief Scientific Advisor for Bioptigen, Inc. (since acquired by Leica Microsystems) and had corporate, equity, and intellectual property interests (including royalties) in this company. OMCZ, BK, CV, and JAI are inventors on pending patents pertaining to the technology described in this paper. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons. Additionally, 4D MIOCT imaging was performed in 48 human eye surgeries and was demonstrated to successfully visualize the pathology of interest in concordance with preoperative diagnosis in 93% of retinal surgeries and the surgical site of interest in 100% of anterior segment surgeries. In vivo 4D MIOCT imaging revealed sub-surface pathologic structures and instrument-induced lesions that were invisible through the operating microscope during standard surgical maneuvers. In select cases, 4D MIOCT guidance was necessary to resolve such lesions and prevent post-operative complications. Our novel surgical visualization platform achieves surgeon-interactive 4D visualization of live surgery which could expand the surgeon's capabilities.

Purpose: The integration of swept-source optical coherence tomography (SS-OCT) into the operating microscope enables real-time, tissue-level three-dimensional (3D) imaging to aid in ophthalmic microsurgery. In this prospective randomized controlled study, we evaluated the impact of SS microscope-integrated OCT (MI-OCT) on ophthalmology residents' performance of ophthalmic microsurgical maneuvers., Methods: Fourteen ophthalmology residents from a single institution were stratified by year of training and randomized to perform four anterior segment surgical maneuvers on porcine eyes with (MI-OCT+) or without (MI-OCT-) direct intraoperative OCT guidance. Subsequently, both groups repeated the same maneuvers without MI-OCT feedback to test whether initial MI-OCT experience affected subsequent surgical performance. Finally, the MI-OCT- group was crossed over and allowed to repeat the same maneuvers with direct MI-OCT guidance. Each resident completed a survey at the completion of the study., Results: With direct MI-OCT feedback, residents demonstrated enhanced performance in depth-based anterior segment maneuvers (corneal suture passes at 50% and 90% depth and corneal laceration repair) compared with the residents operating without MI-OCT. Microscope-integrated OCT+ residents continued to outperform the controls when both groups subsequently operated without MI-OCT. For clear corneal wound geometry, there was no statistically significant effect of MI-OCT as applied in this study. Overall, the resident surgeons rated their subjective experience of using MI-OCT very favorably., Conclusions: Microscope-integrated OCT feedback enhances performance of ophthalmology residents in select anterior segment surgical maneuvers. Microscope-integrated OCT represents a valuable tool in the surgical education of ophthalmology residents.

Magnification of the surgical field using the operating microscope facilitated profound innovations in retinal surgery in the 1970s, such as pars plana vitrectomy. Although surgical instrumentation and illumination techniques are continually developing, the operating microscope for vitreoretinal procedures has remained essentially unchanged and currently limits the surgeon's depth perception and assessment of subtle microanatomy. Optical coherence tomography (OCT) has revolutionized clinical management of retinal pathology, and its introduction into the operating suite may have a similar impact on surgical visualization and treatment. In this article, we review the evolution of OCT for retinal surgery, from perioperative analysis to live volumetric (four-dimensional, 4D) image-guided surgery. We begin by briefly addressing the benefits and limitations of the operating microscope, the progression of OCT technology, and OCT applications in clinical/perioperative retinal imaging. Next, we review intraoperative OCT (iOCT) applications using handheld probes during surgical pauses, two-dimensional (2D) microscope-integrated OCT (MIOCT) of live surgery, and volumetric MIOCT of live surgery. The iOCT discussion focuses on technological advancements, applications during human retinal surgery, translational difficulties and limitations, and future directions.

Current-generation software for rendering volumetric OCT data sets based on ray casting results in volume visualizations with indistinct tissue features and sub-optimal depth perception. Recent developments in hand-held and microscope-integrated intrasurgical OCT designed for real-time volumetric imaging motivate development of rendering algorithms which are both visually appealing and fast enough to support real time rendering, potentially from multiple viewpoints for stereoscopic visualization. We report on an enhanced, real time, integrated volumetric rendering pipeline which incorporates high performance volumetric median and Gaussian filtering, boundary and feature enhancement, depth encoding, and lighting into a ray casting volume rendering model. We demonstrate this improved model implemented on graphics processing unit (GPU) hardware for real-time volumetric rendering of OCT data during tissue phantom and live human surgical imaging. We show that this rendering produces enhanced 3D visualizations of pathology and intraoperative maneuvers compared to standard ray casting.

Purpose: To report the intraoperative use of microscope-integrated optical coherence tomography (MIOCT) to enable visualization for Descemet's stripping automated endothelial keratoplasty (DSAEK) in 2 patients with advanced bullous keratopathy., Methods: Patient 1 was an 83-year-old female and patient 2 was a 28-year-old male both with limited vision and significant pain from bullous keratopathy who underwent palliative DSAEK. Because of the severity and chronicity of the corneal decompensation in both patients, the view past the anterior cornea was negligible using standard microscope illumination techniques. We used spectral-domain (Patient 1) and swept-source (Patient 2) MIOCT, both of which rely on infrared illumination, to visualize key parts of the DSAEK procedure., Results: Graft insertion, unfolding, tamponade, and attachment could be dynamically visualized intraoperatively despite the nearly opaque nature of the host corneas. Postoperatively, the grafts remained attached with significant corneal clearing, and there was improvement in visual acuity, and pain relief for both patients., Conclusions: MIOCT is a valuable tool for the corneal surgeon, allowing for DSAEK to be successfully performed even when the surgical microscope view is limited from severe corneal edema, as is often the case in patients with advanced bullous keratopathy. By using MIOCT, these patients can benefit from the advantages of DSAEK despite a clinically opaque cornea, which would otherwise be treated with a penetrating keratoplasty.

We acquire the first experimental 3-D tomographic images with magnetic particle imaging (MPI) using projection reconstruction methodology, which is similar to algorithms employed in X-ray computed tomography. The primary advantage of projection reconstruction methods is an order of magnitude increase in signal-to-noise ratio (SNR) due to averaging. We first derive the point spread function, resolution, number of projections required, and the SNR gain in projection reconstruction MPI. We then design and construct the first scanner capable of gathering the necessary data for nonaliased projection reconstruction and experimentally verify our mathematical predictions. We demonstrate that filtered backprojection in MPI is experimentally feasible and illustrate the SNR and resolution improvements with projection reconstruction. Finally, we show that MPI is capable of producing three dimensional imaging volumes in both phantoms and postmortem mice.