3D dynamic contrast optical coherence microscopy for organoid studies

PROJECT SUMMARY Optical coherence tomography (OCT) is an emerging biomedical imaging technology that provides label-free and depth-resolved images with micron-scale spatial resolution and sub-millisecond temporal resolution. Since its inception in 1991, OCT has revolutionized eye disease diagnosis with over 32 million ophthalmic OCT procedures performed world-wide annually. OCT-based technologies have also been exponentially adopted in a wide range of clinical applications, including cardiology, endoscopy, urology, dermatology, and dentistry. Traditionally, OCT only provides tissue-level morphological information. Recently, there is a surge in extending this label-free technology to also delineate the physiological information (e.g., cellular viability, necrotic regions, and growth dynamics) at the cellular level. The so-called dynamic contrast microscopic OCT (DyC- µOCT) or dynamic contrast optical coherence microscopy (DyC-OCM) is distinguished from traditional scattering-based OCT by its emphasis on dynamic fluctuations: the motions of viable cells are accented against the motionless regions in the OCT images, enhancing the image contrast and revealing both cellular morphological and physiological information. Today, there are two dominating DyC-OCM architectures: spectral-domain OCM (SD-OCM) and full-field OCM (FF-OCM), each optimized for temporal analysis of different 2D images. Unfortunately, none of the two dominating DyC-OCM architectures can support the 3D volumetric dynamic contrast analysis even though organelles and cells are naturally organized in 3D. This limitation mainly comes from the fact that both SD-OCM and FF-OCM can only provide a voxel rate of ~100 Mvoxel/s but a voxel rate exceeding 1 Gvoxel/s is necessary for 3D DyC-OCM. Such a high voxel rate has ever only been demonstrated with another OCM architecture, swept source OCM (SS-OCM). Even though SS-OCM can break through the voxel rate barrier, it suffers from poor axial resolution, and thus its ability to image cellular structure has been severely limited. In this program, we aim to develop the first 3D DyC-OCM technology that simultaneously breaks through the voxel rate and axial resolution barriers. We will accomplish the goal by introducing several key innovations in photonic integrated circuit technology to develop a novel swept source architecture (Aim 1) and a scalable parallel imaging platform (Aim 2). A dual-modality imaging system consisting of a widefield fluorescence microscope and the 3D DyC-OCM will be developed (Aim 3). Validation experiments will be conducted using in vitro 3D human heart and intestinal organoids (hHO and hIO, Aim 4). Given the non-invasive nature of 3D DyC- OCM, together with its high penetration and resolution, we expect to obtain a host of new information on the dynamics of hHO and hIO development over time. This information will be valuable to evaluate how similar (or dissimilar) in vitro organoid development is to embryonic and fetal heart and intestine development and guide new interventions to improve organoid modeling of human development.