Mohamed Tarek El-Haddad, Ph.D.
Research Scientist, Facebook Reality Labs
Ivan Bozic, M.S.
Ph.D. Candidate, Department of Biomedical Engineering, Tulane University
NSF Graduate Research Fellow, Department of Biomedical Engineering, Columbia University
Graduate Student, Department of Biomedical Engineering, Texas A&M University
Graduate Student, Department of Electrical and Computer Engineering, The Ohio State University
Graduate Student, Department of Biomedical Engineering, Duke University
Multimodality ophthalmic imaging technologies
Non-invasive biological imaging is crucial for understanding in vivo structure and function. Optical coherence tomography (OCT) and reflectance confocal microscopy are two of the most widely used optical modalities for exogenous contrast-free high-resolution three-dimensional imaging in non-fluorescent scattering tissues. However, sample motion remains a critical barrier to raster-scanned acquisition and reconstruction of wide-field anatomically accurate volumetric datasets. We introduce spectrally encoded coherence tomography and reflectometry (SECTR), a high-speed multimodality system for simultaneous OCT and spectrally-encoded reflectance (SER) imaging. SECTR utilizes a robust system design consisting of shared optical relays, scanning mirrors, swept-laser, and digitizer to achieve the fastest reported in vivo multimodal imaging rate of 2 gigapixels-per-second. Our optical design and acquisition scheme enable spatiotemporally co-registered acquisition of OCT cross-sections simultaneously with en face SER images for multi-volumetric mosaicking. Complementary axial and lateral translation and rotation are extracted from OCT and SER data, respectively, for full volumetric estimation of sample motion with micron spatial and millisecond temporal resolution.
Intraoperative imaging for ophthalmic surgical guidance
Translation of optical coherence tomography (OCT) technologies for intraoperative visualization enables in vivo micron-resolution imaging of subsurface tissue structures and image-guided clinical decision-making. Over the last decade, intraoperative OCT has evolved from two-dimensional imaging using handheld probes to include stereomicroscope integrated systems that provide real-time three- and four-dimensional visualization of surgical maneuvers. We have developed multimodal spectrally encoded coherence tomography and reflectometry (SECTR) technologies that allow for simultaneous and intrinsically co-registered en face spectrally encoded reflectance (SER) and cross-sectional OCT imaging. We also recently demonstrated an intraoperative SECTR (iSECTR) microscope-integrated scan-head and ex vivo and in vivo video-rate volumetric (4D) imaging at 18 volumes-per-second. SECTR overcomes the FOV and imaging speed trade-offs of current-generation ophthalmic iOCT by providing complementary en face spatial information to enable real-time image aiming, retinal tracking, bulk-motion compensation, and multi-volumetric averaging and mosaicking. We are actively working to develop novel technologies, feedback mechanisms, and maneuvers that integrate volumetric iSECTR data for image-guided ophthalmic surgery.
Machine-learning assisted imaging of surgical dynamics
Intraoperative optical coherence tomography (iOCT) enables volumetric imaging of surgical maneuvers. However, the lack of automated instrument-tracking remains a critical barrier to real-time surgical feedback and iOCT-guided surgery. We previously presented spectrally-encoded coherence tomography and reflectometry (SECTR), which provides simultaneous imaging of spatiotemporally co-registered orthogonal imaging planes at several gigapixels-per-second. Here, we demonstrate automated surgical instrument-tracking and adaptive-sampling of OCT using a combination of deep-learning and SECTR. We believe this method overcomes critical barriers to clinical translation of iOCT and offers several computational and system advantages over previous approaches.
Point-of-care ophthalmic diagnostic imaging
Optical coherence tomography (OCT) is the gold standard for quantitative ophthalmic imaging. The majority of commercial and research systems require patients to fixate and be imaged in a seated upright position, which limits the ability to perform ophthalmic imaging in bedridden or pediatric patients. Handheld OCT devices overcome this limitation, but image quality often suffers due to a lack of real-time aiming and patient eye and photographer motion. Here, we describe a handheld spectrally encoded coherence tomography and reflectometry (SECTR) system that enables simultaneous en face reflectance and cross-sectional OCT imaging. The handheld probe utilizes a custom double-pass scan lens for fully telecentric OCT scanning with a compact optomechanical design and a rapid-prototyped enclosure to reduce overall system size and weight. We also introduce a novel variable velocity scan waveform that allows for simultaneous acquisition of densely-sampled OCT angiography (OCTA) volumes and widefield reflectance images, which enables high-resolution vascular imaging with precision motion-tracking for volumetric motion-correction and multi-volumetric mosaicking. Finally, we demonstrate in vivo human retinal OCT and OCT angiography (OCTA) imaging using handheld SECTR on a healthy volunteer. Clinical translation of handheld SECTR will allow for high-speed, motion-corrected widefield OCT and OCTA imaging in bedridden and pediatric patients that may benefit ophthalmic disease diagnosis and monitoring.
Structural and functional imaging in rodent models of ophthalmic injury and repair
Rodent models are robust tools for understanding human retinal disease and function because of their similarities with human physiology and anatomy and availability of genetic mutants. Optical coherence tomography (OCT) has been well-established for ophthalmic imaging in rodents and enables depth-resolved visualization of structures and image-based surrogate biomarkers of disease. Similarly, fluorescence confocal scanning laser ophthalmoscopy (cSLO) has demonstrated utility for imaging endogenous and exogenous fluorescence and scattering contrast in the mouse retina.
Collaborators: Edward Levine, Ph.D.
Quantitative vascular imaging
Quantitative measurements of lung microvessels would benefit characterization of vascular function and remodeling in pulmonary vascular diseases. Here, we present a novel method for quantitative measurements of lung vasculature using multi-volumetric optical coherence microscopy (OCM). Murine lungs were perfused with scattering contrast, fixed, and optically cleared. OCM volumes were acquired and segmented in post-processing to quantify vessel diameters. This proof-of-concept demonstrates the utility of our OCM and tissue preparation approach, which can be extended to compare microvasculature changes in entire lung lobes in animal models of pulmonary disease.
Collaborators: Susan Majka, Ph.D.
- Tang, E. M., El-Haddad, M. T., Patel, S. N. and Tao, Y. K., “Automated instrument-tracking for 4D video-rate imaging of ophthalmic surgical maneuvers,” Biomedical Optics Express (2022).
- Rico-Jimenez, J. J., Hu, D., Tang, E. M., Oguz, I. and Tao, Y. K., “Real-time OCT image denoising using a self-fusion neural network,” Biomedical Optics Express (2022).
- Tang, E. M. and Tao, Y. K., “Modeling and optimization of galvanometric point-scanning temporal dynamics,” Biomedical Optics Express (2021).
- El-Haddad, M. T. and Tao, Y. K., "Non-contact characterization of compound optical elements using reflectance confocal microscopy, low-coherence interferometry, and computational ray-tracing," Scientific Reports (2019).
- Malone, J. D., El-Haddad, M. T., Yerramreddy, S. S., Oguz, I., and Tao, Y. K., “Handheld spectrally encoded coherence tomography and reflectometry for motion-corrected ophthalmic optical coherence tomography and optical coherence tomography angiography,” Neurophotonics (2019).
- Daniels, A. B., Froehler, M. T., Nunnally A. H., Pierce, J. M., Bozic, I., Stone, C. A., Santapuram, P. R., Tao, Y. K., Boyd, K. L., Himmel, L. E., Chen, S., Du, L., Friedman, D. L., and Richmond, A., “Rabbit model of intra-arterial chemotherapy toxicity demonstrates retinopathy and vasculopathy related to drug and dose, not procedure or approach,” IOVS (2019).
- Lapierre-Landry, M., Connor, T. B., Carroll, J., Tao, Y. K., and Skala, M. C., “Photothermal optical coherence tomography of indocyanine green in ex vivo eyes,” Optics Letters (2018).
- Bozic, I., Li, X., and Tao, Y. K., “Quantitative biometry of zebrafish retinal vasculature using optical coherence tomographic angiography,” Biomedical Optics Express (2018).
- El-Haddad, M. T., Bozic, I., and Tao, Y. K., “Spectrally Encoded Coherence Tomography and Reflectometry (SECTR): simultaneous en face and cross-sectional imaging at 2 gigapixels-per-second,” J Biophotonics (2017).
DIIGI Lab present research at SPIE Photonics West
Jose and Eric presented their research at the SPIE Photonics West conference in San Francisco, CA. Congrats Jose and Eric!
DIIGI Lab publishes work on optimization of galvanometric point-scanning temporal dynamics
Graduate student Eric Tang publishes his work on modeling and optimization of galvanometric point-scanning temporal dynamics in Biomedical Optics Express. Hardware and software optimizations are presented for improving optical point-scanning response times that can more than halve the settling time, which can directly improve imaging speed/field-of-views. Congrats Eric! [Link]
Incoming graduate student joins DIIGI Lab
Rachel Hecht graduated the University of Colorado Boulder in 2021 with a B.S. in Electrical Engineering and B.M. in Bassoon Performance and will be starting as a first-year graduate student in the Department of Biomedical Engineering. Welcome Rachel! [Link]
Incoming graduate student joins DIIGI Lab
Jake Watson graduated the University of Evansville in 2021 with a B.S. in Electrical Engineering and will be starting as a first-year graduate student in the Department of Biomedical Engineering. Welcome Jake! [Link]
Dr. Tao receives endowed SPIE Faculty Fellowship
SPIE, the international society for optics and photonics, and Vanderbilt University announced the establishment of the SPIE Faculty Fellowship in Optics and Photonics. Prof. Kenny Tao (Department of Biomedical Engineering) has been selected as the recipient of the first gift. [Link]
DIIGI Lab publishes work on non-contact optical metrology
Recent graduate Dr. El-Haddad publishes his work on non-contact characterization of compound optical elements in Scientific Reports. The method characterizes compound optical elements including curvatures, material and air-gap thicknesses, and glass types using a combination of reflectance confocal microscopy, low-coherence interferometry, and computational ray-tracing. Congrats Mohamed! [Link]
DIIGI Lab publishes work on handheld ophthalmic imaging technologies
Graduate student Joe Malone publishes his work on handheld spectrally encoded coherence tomography and reflectometry (SECTR) in Neurophotonics. SECTR is a multimodality ophthalmic imaging technology that combines optical coherence tomography and spectrally encoded reflectance imaging to enable volumetric motion-correction and multi-volumetric mosaicking. Congrats Joe! [Link]
DIIGI Lab: Stevenson Center SC5842