NOVEL TECHNOLOGIES AND APPLICATIONS FOR FLUORESCENT LAMINAR OPTICAL TOMOGRAPHY

Laminar optical tomography (LOT) is a mesoscopic three-dimensional (3D) optical imaging technique that can achieve both a resolution of 100-200 µm and a penetration depth of 2-3 mm based either on absorption or fluorescence contrast. Fluorescence laminar optical tomography (FLOT) can also provide large field-of-view (FOV) and high acquisition speed. All of these advantages make FLOT suitable for 3D depth-resolved imaging in tissue engineering, neuroscience, and oncology. In this study, by incorporating the high-dynamic-range (HDR) method widely used in digital cameras, we presented the HDR-FLOT. HDR-FLOT can moderate the limited dynamic range of the charge-coupled device-based system in FLOT and thus increase penetration depth and improve the ability to image fluorescent samples with a large concentration difference. For functional mapping of brain activities, we applied FLOT to record 3D neural activities evoked in the whisker system of mice by deflection of a single whisker in vivo. We utilized FLOT to investigate the cell viability, migration, and bone mineralization within bone tissue engineering scaffolds in situ, which allows depth-resolved molecular characterization of engineered tissues in 3D. Moreover, we investigated the feasibility of the multi-modal optical imaging approach including high-resolution optical coherence tomography (OCT) and high-sensitivity FLOT for structural and molecular imaging of colon tumors, which has demonstrated more accurate diagnosis with 88.23% (82.35%) for sensitivity (specificity) compared to either modality alone. We further applied the multi-modal imaging system to monitor the drug distribution and therapeutic effects during and after Photo-immunotherapy (PIT) in situ and in vivo, which is a novel low-side-effect targeted cancer therapy. A minimally-invasive two-channel fluorescence fiber bundle imaging system and a two-photon microscopy system combined with a micro-prism were also developed to verify the results

Novel Endoscope for Surgical Guidance and Functional Brain Imaging

Optical imaging methods have become very powerful tools in biomedical research since they can achieve both high spatial and temporal resolutions. However, due to the effects of light scattering, the penetration depth of optical imaging methods is usually limited. Gradient refractive index (GRIN) lens that are 350–2,000 μm in diameter and provide micron-scale resolution have been shown to enable minimally invasive in vivo imaging of deep tissues. Based on GRIN lens, we developed a small hand-held optical coherence tomography (OCT) forward-imaging needle device for real-time epidural anesthesia surgery guidance and demonstrated its feasibility through ex vivo and in vivo animal experiments. Besides, to access subcortical brain structures, we combined voltage-sensitive dye imaging (VSDi) with GRIN lens to image neural activities evoked in thalamic barreloids by deflection of whiskers in vivo in the whisker system of rodents

A pilot study on biaxial mechanical, collagen microstructural, and morphological characterizations of a resected human intracranial aneurysm tissue

Intracranial aneurysms (ICAs) are focal dilatations that imply a weakening of the brain artery. Incidental rupture of an ICA is increasingly responsible for significant mortality and morbidity in the American’s aging population. Previous studies have quantified the pressure-volume characteristics, uniaxial mechanical properties, and morphological features of human aneurysms. In this pilot study, for the first time, we comprehensively quantified the mechanical, collagen fiber microstructural, and morphological properties of one resected human posterior inferior cerebellar artery aneurysm. The tissue from the dome of a right posterior inferior cerebral aneurysm was first mechanically characterized using biaxial tension and stress relaxation tests. Then, the load-dependent collagen fiber architecture of the aneurysm tissue was quantified using an in-house polarized spatial frequency domain imaging system. Finally, optical coherence tomography and histological procedures were used to quantify the tissue’s microstructural morphology. Mechanically, the tissue was shown to exhibit hysteresis, a nonlinear stress-strain response, and material anisotropy. Moreover, the unloaded collagen fiber architecture of the tissue was predominantly aligned with the testing Y-direction and rotated towards the X-direction under increasing equibiaxial loading. Furthermore, our histological analysis showed a considerable damage to the morphological integrity of the tissue, including lack of elastin, intimal thickening, and calcium deposition. This new unified characterization framework can be extended to better understand the mechanics-microstructure interrelationship of aneurysm tissues at different time points of the formation or growth. Such specimen-specific information is anticipated to provide valuable insight that may improve our current understanding of aneurysm growth and rupture potential

Characterization and quantification of necrotic tissues and morphology in multicellular ovarian cancer tumor spheroids using optical coherence tomography

The three-dimensional (3D) tumor spheroid model is a critical tool for high-throughput ovarian cancer research and anticancer drug development in vitro. However, the 3D structure prevents high-resolution imaging of the inner side of the spheroids. We aim to visualize and characterize 3D morphological and physiological information of the contact multicellular ovarian tumor spheroids growing over time. We intend to further evaluate the distinctive evolutions of the tumor spheroid and necrotic tissue volumes in different cell numbers and determine the most appropriate mathematical model for fitting the growth of tumor spheroids and necrotic tissues. A label-free and noninvasive swept-source optical coherence tomography (SS-OCT) imaging platform was applied to obtain two-dimensional (2D) and 3D morphologies of ovarian tumor spheroids over 18 days. Ovarian tumor spheroids of two different initial cell numbers (5,000- and 50,000- cells) were cultured and imaged (each day) over the time of growth in 18 days. Four mathematical models (Exponential-Linear, Gompertz, logistic, and Boltzmann) were employed to describe the growth kinetics of the tumor spheroids volume and necrotic tissues. Ovarian tumor spheroids have different growth curves with different initial cell numbers and their growths contain different stages with various growth rates over 18 days. The volumes of 50,000-cells spheroids and the corresponding necrotic tissues are larger than that of the 5,000-cells spheroids. The formation of necrotic tissue in 5,000-cells numbers is slower than that in the 50,000-cells ones. Moreover, the Boltzmann model exhibits the best fitting performance for the growth of tumor spheroids and necrotic tissues. Optical coherence tomography (OCT) can serve as a promising imaging modality to visualize and characterize morphological and physiological features of multicellular ovarian tumor spheroids. The Boltzmann model integrating with 3D OCT data of ovarian tumor spheroids provides great potential for high-throughput cancer research in vitro and aiding in drug development.Histology service provided by the Tissue Pathology Shared Resource was supported in part by the National Institute of General Medical Sciences Grant P20GM103639 and National Cancer Institute Grant P30CA225520 of the National Institutes of Health. Research reported in this publication was supported in part by a Stephenson Cancer Center Trainee Research Award funded by the National Cancer Institute Cancer Center Support Grant P30CA225520 awarded to the University of Oklahoma Stephenson Cancer Center. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Real-time Epidural Anesthesia guidance using optical coherence tomography needle probe

Epidural anesthesia is one of the most widely used anesthesia methods. Due to lack of visual feedback to guide needle navigation, failure rate of epidural anesthesia is up to 20%, and the complication rate of peripheral nerve block approaches 10%, with the potential of permanent nerve damage. To address these difficulties, needle insertion under ultrasound guidance and fluoroscopy has been introduced. However, they do not provide adequate resolution and contrast to distinguish the tissue layers that the needle travels through or to specifically identify the epidural space. To improve the accuracy of epidural space identification, we developed a small hand-held optical coherence tomography (OCT) forward-imaging needle device for real-time epidural anesthesia surgery guidance and demonstrated its feasibility through ex vivo and in vivo animal experiments. With tissue structures visualized and differentiated at the needle tip, OCT needle imaging device will enhance clinical outcomes with regards to complication rates, induced pain, and procedure failure when compared to standard practice. Furthermore, this technology could be used in combination with ultrasound/fluoroscopy to enhance outcomes

Media 1: Quantitative single-mode fiber based PS-OCT with single input polarization state using Mueller matrix

Originally published in Biomedical Optics Express on 01 May 2015 (boe-6-5-1828

Media 3: Quantitative single-mode fiber based PS-OCT with single input polarization state using Mueller matrix

Originally published in Biomedical Optics Express on 01 May 2015 (boe-6-5-1828

A pilot study on biaxial mechanical, collagen microstructural, and morphological characterizations of a resected human intracranial aneurysm tissue.

Intracranial aneurysms (ICAs) are focal dilatations that imply a weakening of the brain artery. Incidental rupture of an ICA is increasingly responsible for significant mortality and morbidity in the Americans aging population. Previous studies have quantified the pressure-volume characteristics, uniaxial mechanical properties, and morphological features of human aneurysms. In this pilot study, for the first time, we comprehensively quantified the mechanical, collagen fiber microstructural, and morphological properties of one resected human posterior inferior cerebellar artery aneurysm. The tissue from the dome of a right posterior inferior cerebral aneurysm was first mechanically characterized using biaxial tension and stress relaxation tests. Then, the load-dependent collagen fiber architecture of the aneurysm tissue was quantified using an in-house polarized spatial frequency domain imaging system. Finally, optical coherence tomography and histological procedures were used to quantify the tissues microstructural morphology. Mechanically, the tissue was shown to exhibit hysteresis, a nonlinear stress-strain response, and material anisotropy. Moreover, the unloaded collagen fiber architecture of the tissue was predominantly aligned with the testing Y-direction and rotated towards the X-direction under increasing equibiaxial loading. Furthermore, our histological analysis showed a considerable damage to the morphological integrity of the tissue, including lack of elastin, intimal thickening, and calcium deposition. This new unified characterization framework can be extended to better understand the mechanics-microstructure interrelationship of aneurysm tissues at different time points of the formation or growth. Such specimen-specific information is anticipated to provide valuable insight that may improve our current understanding of aneurysm growth and rupture potential

Intravital imaging of adriamycin-induced renal pathology using two-photon microscopy and optical coherence tomography

Adriamycin (doxorubicin), a common cancer chemotherapeutic drug, can be used to induce a model of chronic progressive glomerular disease in rodents. In our studies, we evaluated renal changes in a rat model after Adriamycin injection using two-photon microscopy (TPM), optical coherence tomography (OCT) and Doppler OCT (DOCT). Taking advantage of deep penetration and fast scanning speed for three-dimensional (3D) label-free imaging, OCT/DOCT system was able to reveal glomerular and tubular pathology noninvasively and in real time. By imaging renal pathology following the infusion of fluorophore-labeled dextrans of different molecular weights, TPM can provide direct views of glomerular and tubular flow dynamics with the onset and progression of renal disease. Specifically, glomerular permeability and filtration, proximal and distal tubular flow dynamics can be revealed. 6–8 weeks after injection of Adriamycin, TPM and OCT/DOCT imaging revealed glomerular sclerosis, compromised flow across the glomerular wall, tubular atrophy, tubular dilation, and variable intra-tubular flow dynamics. Our results indicate that TPM and OCT/DOCT provide real-time imaging of renal pathology in vivo that has not been previously available using conventional microscopic procedures