In this presentation, we introduce a novel imaging system that combines optical coherence tomography (OCT) and angle-resolved low-coherence interferometry (a/LCI) for enhanced detection of esophageal dysplasia. By integrating wide area imaging with high-resolution OCT and depth-resolved a/LCI measurements, we aim to provide a sensitive and specific screening method. This innovative approach overcomes the limitations of traditional techniques and enables real-time imaging guidance for accurate coverage of at-risk tissue surfaces. Our pilot clinical study shows promising results, suggesting that this combined system holds great potential in improving early detection and diagnosis of esophageal dysplasia in patients at risk.

The issue of radiation damage to skin in conventional radiotherapy (RT) has motivated pre-clinical studies to demonstrate reduced skin toxicity and overall improved normal tissue sparing in high-dose rate FLASH RT. We address the critical need for diagnostic tools to evaluate radiobiological response mechanisms produced with FLASH RT by using low-coherence light scattering to quantify skin and tumor tissue response to FLASH versus conventional radiotherapy. A study of melanoma growth in dorsal skin window chambers on rodents in vivo following separate regiments of RT treatment was conducted with optical coherence tomography (OCT), followed by parametric texture analysis of volumetric OCT images to delineate viable and dead cell clusters in tissue. Longitudinal quantification of viable and dead cell proportion demonstrates the severity of conventional RT damage to skin in comparison with higher epidermal structural integrity preserved by FLASH radiotherapy, highlighting potential of OCT for microstructural imaging in this first-of-its-kind study.

Nanoscale nuclear architecture mapping (nanoNAM), leveraging spectral interferometry, identifies local alterations in cell nuclei's optical density. This technique successfully detected early carcinogenesis in the gastrointestinal tract, even in histologically non-cancerous tissue, indicating its potential for cancer risk stratification. We demonstrate the potential of nanoNAM as a label-free method for stratifying cancer risk in patients predisposed to developing cancer such as conditions like Barrett’s esophagus and ulcerative colitis. Its biological basis will also be discussed. As nanoNAM can be integrated into clinical pipelines using existing formalin-fixed, paraffin-embedded tissue sections, it holds promise as an auxiliary tool for precision cancer prevention, identifying high-risk patients who require extensive surveillance.

Particle sizing of cellular structures may have significant diagnostic utility. We introduce a laser Speckle PARticle SizEr (SPARSE) that harnesses the spatio-temporal analysis of polarized speckle to estimate scattering particle sizes in opaque biofluids and tissues. SPARSE measurements significantly correlate with dynamic light scattering (DLS) in polybead suspensions (R2=0.91, p<.0001) and milk samples (R2=0.93, p<.0001). Similarly, in whole blood samples of increasing tonicities, SPARSE tracks RBC shrinkage in concordance with DLS (R2=0.84, p<.0001). Moreover, SPARSE maps of breast carcinoma reveal distinct sizes for adipose, fibrous, and epithelial compartments. These findings highlight the diagnostic potential of SPARSE in multiple conditions.

The vertebrate retina detects light primarily using an array of elongated rod and cone photoreceptor neurons that are oriented toward the pupil of the eye. The optical consequences of this anatomical specialization have long been a subject of curiosity for vision research, especially because this array of photoreceptors lines the back of the eye, forcing photons to pass through the inner layers of the retina before detection. A long-held belief is that the tapered shape of especially the cone photoreceptor allows it to function as a waveguide to enhance photon capture. However, an often overlooked aspect of this phenomenon is that numerous cone mitochondria—necessary to provide an energy supply for the needs of phototransduction—tightly congregate in the cone inner segment, forming the final scattering structure for photons prior to detection. Using the thirteen-lined ground squirrel, a cone-dominant mammal with a retinal anatomy similar to that of humans, we showed both experimentally and computationally that such tight bundles of mitochondria form microlenses that provide multiple optical benefits for vision, the insights from which will be valuable for imaging diagnostics.

This presentation will describe PyMieSim, a Python package developed to estimate the collection efficiency of incoherent and coherent imaging techniques with respect to various scatterer geometries. In particular, it will focus on few-mode optical coherence tomography (FM-OCT), in which a photonic lantern separates projections of a backscattered wavefront onto the different linearly polarized (LP) modes of a few-mode fiber. Each mode is converted by the lantern into the fundamental mode of a single-mode fiber to produce a distinct OCT image. PyMieSim was used to predict how different scatterer geometries would affect the OCT images acquired from the different LP modes collected by the lantern, thus paving the way for sub-resolution OCT.

In recent years, cell fate and phenotype can be affected without altering the underlying genetic sequence by the control of three-dimensional structure of chromatin packing domains. Many imaging methods have been developed to try to resolve the 3D chromatin organization. Here, we propose using the Finite Difference Time Domain (FDTD) method to compare and bridge the knowledge of spatial information regarding chromatin packing domains from different imaging modalities. We validated the ability of PWS, a label free high throughput live cell imaging method, to characterize spatial information of chromatin packing, making way for high spatial and temporal resolution chromatin imaging.

In many biological tissues such as muscles, dental enamel and mucosa that exhibit macroscopic and/or microscopic spatially anisotropic structures the nature of light scattering becomes anisotropic. This well-known property of tissues is usually neglected, which is rooted in the fact that the available open-source numerical solutions to the radiative transfer equation based on the stochastic Monte Carlo (MC) method do not allow simulations with anisotropic optical properties. In this contribution, we present an extension to our massively parallel PyXOpto (https://github.com/xopto/pyxopto) simulation engine that enables highly efficient and user-friendly MC simulations for layered or voxelated sample geometries with anisotropic scattering properties, both in the steady state and time-resolved domain.

We propose a novel approach to use OCT speckle analysis to quantify absolute flow speed in skin blood vessels. Using a bespoke scan acquisition pattern, we empirically compute a probability density function for the L1-norm decorrelation measure as a function of displacement. During clinical scanning, we calculate the decorrelation value within a small window at each point. By inverting the probability function, we are able to calculate a probability distribution over the possible values of blood displacement, and hence flow speed. We demonstrate the algorithm on 10 human patients who have suffered heart failure and 10 age-matched healthy control subjects.

Non-invasive optical blood flow monitoring systems for disease diagnosis and healthcare monitoring have been studied. Diffuse Speckle Contrast Analysis (DSCA) system can measure deep-tissue blood flow with a relatively simple system configuration, high speed, and high sensitivity. However, the relative blood flow index (BFI) is acquired with the system, and it changes with every acquisition. In this study, we adopt machine learning to overcome this limitation. DSCA system was established with a micro-size camera, and the correlation between conventional BFI and ML-based BFI was analyzed. This work will be the first step toward a quantitative Diffuse Speckle Contrast Velocimetry (DSCV).

Reef-building corals are a vital part for the health and biodiversity of marine ecosystems. However, they are facing grave challenges from climate change. Despite the urgent need to understand the mechanism of light collection in corals, many key questions remain open largely due to the lack of techniques to measure the optical properties in live corals. Here we used a recently developed extension of OCT, Inverse Spectroscopic Optical Coherence Tomography (ISOCT), to image vast varieties of coral species, acquiring 4D cubes containing spectral information alongside 3D geometry. A full set of optical parameters that inherently linked with key optical components of coral are calculated in both coral tissue and skeleton. Using a spectroscopic OCT imaging system, our study expands current knowledge of coral physiology.

Computational Scattered Light Imaging (ComSLI) is a novel, non-destructive, whole-slide imaging method with the unique ability to precisely disentangle densely interwoven fiber structures in biological tissues. ComSLI can be performed on microscopy slides regularly prepared within the histopathological routine. Although it is a label-free method and does not require any staining, it also works on stained tissues for various stains. So far, ComSLI has been used to visualize nerve fibers in brain tissues [1-3]. In this study, we visualize muscle and collagen fibers in oral tissues for the first time. REFERENCES: [1] Menzel, M., et al. "Using light and X-ray scattering to untangle complex neuronal orientations and validate diffusion MRI." Elife 12 (2023). [2] Menzel, M., et al. "Scattered Light Imaging: Resolving the substructure of nerve fiber crossings in whole brain sections with micrometer resolution." NeuroImage 233 (2021). [3] Menzel, M., et al. "Toward a high-resolution reconstruction of 3D nerve fiber architectures and crossings in the brain using light scattering measurements and finite-difference time-domain simulations." Physical Review X 10.2 (2020).

Brillouin spectroscopy uses the interaction of a laser light with picosecond timescale density fluctuations in the sample. It gives access to the mechanical properties (stiffness, viscosity…) on a sub-micrometer scale and at GHz frequencies. Since 2015, BLS has been successfully used for mechanical phenotyping and imaging with a contrast based on the stiffness in single cells using spectroscopic and time-resolved implementations, live organisms, plant tissues and teeth. Because it is label-free, all-optical and non-destructive, BLS has gained interest in the pharmaceutical and biomedical fields as a promising tool to investigate the mechanobiology of different pathologies. However, its relevance from a physiological standpoint remains debated due to the ultrashort timescales involved. Since the probing mechanism involves coupling of photons to longitudinal phonons, variations in the scattering spectra can be interpreted as the response of the sample to an infinitesimal uniaxial compression. With a few examples and some fundamental concepts, I will give some insights on how to interpret such data in biological samples, and offer new perspectives.

The function of orthopedic tissues such as cartilage and bones are particularly susceptible to aberrant mechanical transformation, which has long been associated with changes to the solid tissue components. There is, however, a growing appreciation for the role of interstitial fluid and tissue water content in degenerative mechanical transformation associated with orthopedic diseases. Yet, the contribution of viscous fluid-like behavior to the overall mechanical integrity of orthopedic tissues remains largely unexplored. We demonstrate wideband laser Speckle rHEologicAl micRoscopy (SHEAR) that harnesses speckle fluctuation induced by natural thermal motion of native light scattering tissue structures for microrheological investigation of orthopedic tissues.

The cerebral microcirculation plays a crucial role in maintaining cerebral homeostasis and facilitating optimal neuronal activity. Perturbations in this intricate microcirculatory system have been observed in neurological conditions such as Alzheimer's disease or systemic inflammation. However, changes occurring at the level of the capillary are difficult to translate to biomarkers that could be measured macroscopically. In this study, we employed a combined spectral optical coherence tomography (OCT) and intrinsic signal optical imaging (ISOI) system to investigate the capillary stalling and transit time of cerebral blood vessels in a mouse model of systemic inflammation induced by the intraperitoneal injection of lipopolysaccharide (LPS). Our findings reveal that LPS administration significantly increases both the percentage and duration of capillary stalling compared to mice receiving 0.9% saline injection. Moreover, LPS-induced mice exhibit significantly prolonged transit time of cerebral blood vessels compared to control mice. These observations suggest that capillary stalling, induced by inflammation, modulate transit time, a measure that has translational potential.

We present a single-shot laser speckle optical micro-rheology technique that measures tissue viscoelasticity from a single elongated speckle image, avoiding the need for high-speed cameras used in traditional optical micro-rheology. By calculating the intensity autocorrelation between rows of a rolling shutter speckle image with different inter-row delays, we can extract the decorrelation time of dynamic speckles, which directly related to the viscoelastic modulus of multiple scattering samples. Our method extends the range of measured viscoelastic modulus in optical micro-rheology by capturing speckle images with equivalent frame rates over 100,000 frame per second. This enables precise viscoelasticity assessments of diverse biological tissues and tissue phantoms.

Measurements of human milk fat content are essential for lactation care and research. We propose to quantify milk fat in non-homogenized human milk based on angular light scattering. Therefore, we measured the angular scattering profiles of milk from five donors using a goniometric light scattering setup. We also measured the milk fat globule (MFG) size distributions with 3D confocal laser scanning microscopy and use this as input in a Monte Carlo simulation. Both experimental and simulated angular scattering profiles are strongly dependent on fat concentration. The effect of the MFG size distribution on the scattering profiles will be discussed.