Tissue metabolism is an inter-and intra-cellular process, which is essential to maintain the living state of tissue. Functional abnormality of such cellular processes initiates several metabolic diseases including non-alcoholic-fatty-liver-disease (NAFLD), liver fibrosis, cancer, chronic kidney disease, and so on. To understand the metabolic processes and how tissue metabolism changes from healthy to diseased conditions, it is required to investigate tissue metabolic activity in animal models in a label-free manner. Since the metabolic structures in animal organs extend into the deep region, deep tissue metabolism imaging is necessary. In this paper, we demonstrate the investigation of ex vivo animal organ models’ metabolism including mouse liver and kidney tissues using OCT-based dynamics imaging method. The dynamics imaging method is based on logarithmic intensity variance (LIV) analysis that enables volumetric metabolic imaging with a 50-kHz swept-source OCT system. NAFLD model mouse livers and obstructed mouse kidney model were investigated ex vivo. In the normal liver, highly dynamic vessel-like structures were observed and they might correspond to high metabolic activity in the periportal/perivenous zones. In the 1-week NAFLD model, a macroscopic, ring-shaped dynamic structure was observed which may indicate highly-motile lipid droplets. In the 2-week NAFLD model, highly-dynamic fragmented vessel-like structures were observed, which are believed to correspond to inflammatory cells around large vessels. In the normal mouse kidney, superficial pipe-like metabolic structures were observed that may correspond to the kidney renal tubules. The pipe-like structures did not appear in the obstructed kidney model.
We present three-dimensional, label-free renal tubular metabolism imaging by functional optical coherence tomography (OCT) including dynamics imaging method so-called “logarithmic intensity variance (LIV)” and OCT angiography (OCTA). Normal mouse kidneys and obstructed kidney models were investigated ex vivo. In the normal kidney, several vertical tails of high-LIV and hyper-OCTA signals were observed in the corresponding cross-sectional images. These signals formed pipe-like structures in the en face slab average projection images. In the obstructed kidneys, such anatomical pipe-like structures disappeared and instead, a circular shell at the edge of the renal cortex region was observed in the LIV.
We present 3D intracellular motility imaging in MCD-diet induced non-alcoholic fatty liver disease (NAFLD) model by OCT-based dynamics imaging method, logarithmic intensity variance (LIV). LIV imaging visualizes the label-free intracellular activity. A 1-week and 2-week NAFLD model were investigated. In 1-week NAFLD, formation of large number of highly dynamic small particles at the beneath of the tissue surface were observed in LIV volume rendering image. In 2-week NAFLD model, a thin high LIV layer signal appeared in cross-sectional LIV image just beneath the tissue surface. The LIV projection and volume rendering images also reveal several discontinuous vessel-like structures.
We demonstrate label-free imaging of renal function with a unilateral ureteral obstruction (UUO) kidney mouse model. The imaging was performed by optical coherence microscopy which is capable of measuring tissue dynamics. Two different studies comprising of 1-week and 2-week UUO models were performed. A circular ring-shape high dynamics appearance at the periphery of the tissue surface was found in the 1-week UUO model for both obstructed and contralateral non-obstructed kidneys. In the 2-week UUO model, several vertical high dynamics regions were observed in cross-sectional dynamics images for both obstructed and non-obstructed kidneys. The results were validated by histological analysis.
A multi-functional optical coherence microscopy capable of computational refocusing, tissue dynamics and birefringence imaging, and scatterer density estimation is demonstrated. It is applied to cell spheroid, ex vivo animal tissues.
A three-dimensional multi-contrast tissue dynamics imaging method based on polarization-sensitive optical coherence tomography is presented to visualize microvascular tissue activity of mouse livers. Temporal variance of birefringence, temporal polarization uniformity and logarithmic OCT intensity variance are used to access the tissue dynamics. These methods are applied to time-course microvasculature activity visualization of dissected normal and inflammatory mouse liver. Multi-contrast projection images are generated to visualize vascular network of the liver. Cross-sectional and en face dynamics images show high activity around the periportal region of mouse liver at initial time point. Degradation of tissue activity is demonstrated by time-lapse imaging.
In this paper, we demonstrate polarization-sensitive optical coherence tomography (PS-OCT) based tissue dynamics imaging methods to investigate the activity of mouse livers. The methods include logarithmic intensity variance (LIV), temporal variance of birefringence, temporal degree-of-polarization-uniformity. Portal veins appeared as hypo-scattering structure in static OCT intensity. High dynamics appearance around the portal veins in all the dynamics contrasts was found just after the dissection of mouse liver. Although, high activity around the vessels reduced by time, a bright and high dynamics spot appeared in the vessel in LIV cross-sectional and en face image after 28-hours of the dissection.
A new method for quantitative assessment of tissue dynamics and activity is presented. The method is based on polarizationsensitive optical coherence tomography. Temporal variance of birefringence and temporal polarization uniformity are used to assess the tissue dynamics. These methods are applied to hourly time-course evaluation of tissue activity of ex-vivo dissected mouse heart.
We present a new OCT-based tissue dynamics/subcellular motion analysis method to visualize tissue dynamics, where we increase the functionality of OCT to be sensitive for tissue dynamics by utilizing rapid-time-sequence analysis of OCT signals. These analysis includes log intensity variance (LIV) and OCT time-correlation analysis (OCT decorrelation speed; OCDS). In addition to LIV and OCDS methods, attenuation coefficient (AC), birefringence, and degree of polarization uniformity (DOPU) analysis were performed. These methods used to visualize and quantify long-term tissue dynamics degradation of different tissue types such as dissected mouse liver and tumor spheroids. These methods were quantitative, so the time-course tissue dynamics degradation has been not only visualized as an image, but also quantitative analysis of the dynamics degradation were performed.
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