Blueprint for a Semi-automated Image Processing Tool to Characterize Stent Features: Application to a Pediatric Growth-Adaptive Stent.

The goal of this work was to develop a general blueprint for a semi-automated image processing tool (SIPT) to measure small, complex features of stent prototypes that can replace the current gold standard of manual measurements. The stents were designed using CAD software and manufactured via laser cutting. Stent prototypes were imaged using a Keyence microscope in top and side view orientations.

Detection and mapping of specular surfaces using multibounce LiDAR returns.

We propose methods that use specular, multibounce LiDAR returns to detect and map specular surfaces that might be invisible to conventional LiDAR systems that rely on direct, single-scatter returns. We derive expressions that relate the time- and angle-of-arrival of these multibounce returns to scattering points on the specular surface, and then use these expressions to formulate techniques for retrieving specular surface geometry when the scene is scanned by a single beam or illuminated with a multi-beam flash. We also consider the special case of transparent specular surfaces, for which surface reflections can be mixed together with light that scatters off of objects lying behind the surface.

Field-Portable Microplastic Sensing in Aqueous Environments: A Perspective on Emerging Techniques.

Microplastics (MPs) have been found in aqueous environments ranging from rural ponds and lakes to the deep ocean. Despite the ubiquity of MPs, our ability to characterize MPs in the environment is limited by the lack of technologies for rapidly and accurately identifying and quantifying MPs. Although standards exist for MP sample collection and preparation, methods of MP analysis vary considerably and produce data with a broad range of data content and quality.

High-density speckle contrast optical tomography of cerebral blood flow response to functional stimuli in the rodent brain.

Noninvasive, three-dimensional, and longitudinal imaging of cerebral blood flow (CBF) in small animal models and ultimately in humans has implications for fundamental research and clinical applications. It enables the study of phenomena such as brain development and learning and the effects of pathologies, with a clear vision for translation to humans. Speckle contrast optical tomography (SCOT) is an emerging optical method that aims to achieve this goal by directly measuring three-dimensional blood flow maps in deep tissue with a relatively inexpensive and simple system.

Compact, multi-exposure speckle contrast optical spectroscopy (SCOS) device for measuring deep tissue blood flow.

Speckle contrast optical spectroscopy (SCOS) measures absolute blood flow in deep tissue, by taking advantage of multi-distance (previously reported in the literature) or multi-exposure (reported here) approach. This method promises to use inexpensive detectors to obtain good signal-to-noise ratio, but it has not yet been implemented in a suitable manner for a mass production. Here we present a new, compact, low power consumption, 32 by 2 single photon avalanche diode (SPAD) array that has no readout noise, low dead time and has high sensitivity in low light conditions, such as measurements.

Enhanced tagging of light utilizing acoustic radiation force with speckle pattern analysis.

In optical imaging, the depth and resolution are limited due to scattering. Unlike light, scattering of ultrasound (US) waves in tissue is negligible. Hybrid imaging methods such as US-modulated optical tomography (UOT) use the advantages of both modalities.

Near infrared spectroscopy for measuring changes in bone hemoglobin content after exercise in individuals with spinal cord injury.

Bone blood perfusion has an essential role in maintaining a healthy bone. However, current methods for measuring bone blood perfusion are expensive and highly invasive. This study presents a custom built near-infrared spectroscopy (NIRS) instrument to measure changes in bone blood perfusion.

High-density speckle contrast optical tomography (SCOT) for three dimensional tomographic imaging of the small animal brain.

High-density speckle contrast optical tomography (SCOT) utilizing tens of thousands of source-detector pairs, was developed for in vivo imaging of blood flow in small animals. The reduction in cerebral blood flow (CBF) due to local ischemic stroke in a mouse brain was transcanially imaged and reconstructed in three dimensions. The reconstructed volume was then compared with corresponding magnetic resonance images demonstrating that the volume of reduced CBF agrees with the infarct zone at twenty-four hours.

Human Corneal Fibroblast Pattern Evolution and Matrix Synthesis on Mechanically Biased Substrates.

In a fibroblast colony model of corneal stromal development, we asked how physiological tension influences the patterning dynamics of fibroblasts and the orientation of deposited extracellular matrix (ECM). Using long-term live-cell microscopy, enabled by an optically accessible mechanobioreactor, a primary human corneal fibroblast colony was cultured on three types of substrates: a mechanically biased, loaded, dense, disorganized collagen substrate (LDDCS), a glass coverslip, and an unloaded, dense, disorganized collagen substrate (UDDCS). On LDDCS, fibroblast orientation and migration along a preferred angle developed early, cell orientation was correlated over long distances, and the colony pattern was stable.

Diffusion model for ultrasound-modulated light.

Researchers use ultrasound (US) to modulate diffusive light in a highly scattering medium like tissue. This paper analyzes the US-optical interaction in the scattering medium and derives an expression for the US-modulated optical radiance. The diffusion approximation to the radiative transport equation is employed to develop a Green's function for US-modulated light.

Analysis and modeling of an ultrasound-modulated guide star to increase the depth of focusing in a turbid medium.

The effects of strong scattering in tissue limit the depth to which light may be focused. However, it has been shown that scattering may be reduced utilizing adaptive optics with a focused ultrasound (US) beam guidestar. The optical signal traveling through the US beam waist is frequency shifted and may be isolated with demodulation.

Error analysis of finite-spectral-linewidth illumination in optical oximetry systems.

Multi-spectral systems consisting of a small number of wavelengths are increasingly using light emitting diodes (LEDs) to reduce the overall costs of the system. However, LEDs typically have broad spectral bandwidths and cannot be modeled as having a single discrete wavelength. This paper puts forth a simple model to analyze the effects of using LEDs to illuminate a single layer of homogenous tissue.

Multiple-source optical diffusion approximation for a multilayer scattering medium.

A method for improving the accuracy of the optical diffusion theory for a multilayer scattering medium is presented. An infinitesimally narrow incident light beam is replaced by multiple isotropic point sources of different strengths that are placed in the scattering medium along the incident beam. The multiple sources are then used to develop a multilayer diffusion theory.

Computational microscopy in embryo imaging.

The growth of computing power has greatly improved our ability to extract quantitative information about complicated three-dimensional structures from microscope images. New hardware techniques are also being developed to provide suitable images for these tasks. However, a need exists for synthetic data to test these new developments.