Characterizing the performance of fluorescence microscopy and nonlinear imaging systems is an essential step required for imaging system optimization and quality control during longitudinal experiments. Emerging multimodal nonlinear imaging techniques require a new generation of microscopy calibration targets that are not susceptible to bleaching, and can provide a contrast across the multiple modalities. Here, we present a nanodiamond-based calibration target for microscopy, designed for facilitating reproducible measurements at the object plane. Since fluorescent nanodiamonds are not prone to bleaching shelf-stable sample can provide a rapid reference measurements for ensuring consistent performance of microscopy systems in microscopy laboratories and imaging facilities.

3D printed reference targets with ICG-matching spectral characteristics allow for characterization and performance monitoring of fluorescence-guided surgery (FGS) systems. The developed 3D printing methodology allowed for manufacturing of standardized geometrical shapes and anatomical mimicking structures to test the concentration sensitivity, depth sensitivity, fluorescence resolution, and signal detail characteristics of FGS systems. Incorporation of various fluorophores and tuning of the optical properties of the 3D printed materials enables production of application-specific targets that can help develop new indications and provide characterization tools for novel imaging systems.

Computational modeling provides a powerful tool for identifying optimal phantom-based test methods in NIRS oximetry. We implemented a Monte Carlo model to enable the simulation of NIRS devices with specific illumination-collection geometries and to identify appropriate performance test methods. Initially, we validated that our in silico approach provided adequate convergence and identified a phantom size that was optically semi-infinite. We then assessed the impact of NIRS sensor orientations and positions on a simulated channel-array phantom. Additional simulations are currently underway to extract oxygen saturation and determine the effect of phantom layer thicknesses, vessel spacing, and diameter.

While photoacoustic imaging (PAI) continues to undergo clinical translation, evaluation of PAI devices remains challenging. Computational modeling offers an inexpensive and convenient approach to study fundamentals of device performance. Our objective was to develop a model to accurately predict PAI out-of-plane sensitivity effects. We combined 3D optical Monte Carlo simulations with the 2D and 3D acoustic propagation models in the k-Wave toolbox. Reconstructed images of an in silico phantom using 3D data showed that longer targets had higher contrast than shorter targets due to out-of-plane signal contributions. 3D computation modeling provided insights into PAI working mechanisms and performance limitations.

During the first peak of the COVID-19 pandemic, we have set up a clinical campaign in ten hospitals worldwide to assess the endothelial health of COVID-19 patients using commercial continuous-wave near-infrared spectroscopy (CW-NIRS) devices (PortaMon, Artinis, NL). In spite of the wide range of clinical applications, the reliability of common CW-NIRS systems for absolute oxygenation measurements was often questioned, opening issues of standardization. In addition, a multi-center trial itself opens issues about how to compare measurements performed by different operators, in different conditions and longitudinally over more than a year. Here, we present how we address these challenges by characterizing and comparing the performance of the devices, with phantom and in vivo experiments.

Endothelial dysfunction represents a key factor in the worsening of the COVID-19 disease in up to 20% of the cases of infection from acute respiratory distress syndrome coronavirus-2 (SARS-CoV-2). The combination of diffuse optics and vascular occlusion tests makes the assessment of endothelial and microvasculature health possible by accessing information about microvascular metabolism, reactivity and tissue perfusion just by performing a localized ischemia at the forearm of the patient. In this framework, we will present a smart platform integrating time-domain near-infrared spectroscopy and diffuse correlation spectroscopy alongside an automatized tourniquet and a pulse-oximeter for personalizing therapies targeting endothelial function and avoid ventilator-induced lung injuries.

High-resolution, extended depth-of-field (EDOF) optical coherence tomography (OCT) in tethered capsules can be achieved using a mirror-tunnel design, and then further modeled and optimized for enhanced performance. In this work, a model with initial dimensions yielded 13 µm full-width-at-half-maximum (FWHM) spot size over 1.5 mm DOF. An optimization algorithm produced a design that attained 8 µm FWHM over 1.5 mm DOF. The initial and optimized probes were fabricated, beam-profiled and integrated into capsules connected to a swept-source OCT system, for imaging swine esophagus in experiments. The resulting data comparison and analysis show the lateral resolution improvement achievable in optimized probes.

A novel photoacoustic remote sensing (PARS) microscopy architecture is explored which replaces the traditional continuous-wave detection source with a pulse-sampling approach. This novel optical processing method is demonstrated on live vasculature networks with significant reductions in detection-source sample exposure by around two orders of magnitude. This architecture paves the way forward for more advanced proposed single-wavelength PARS architectures that may provide drastically improve performance in chromatic-sensitive scenarios such as posterior ophthalmic imaging and micro-endoscopy devices. Both the current pulsed-detection PARS and the proposed single-wavelength PARS are discussed and explored in detail.

The goal towards developing faster and minimally damaging quantitative MPM involves keeping the exposure time per pixel as low as possible. Both the excitation and detection parameters affect the number of measurements required for quantification and therefore, the overall efficiency of the setup. We present our estimation for the minimum number of photons needed and our ability to resolve them to quantify label-free MPM of NAD(P)H and FAD using their intensity, fluorescence lifetime, and optical redox ratio. We not only utilize these results to guide the imaging parameters for in vitro and ex vivo studies, but also to normalize the results from different setups.

Hyperspectral imaging collects spatio-spectral information of objects useful in a wide range of applications including biomedical imaging. We propose a compact lensless snapshot HSI system, composed only of a monochromatic CMOS image sensor, a transparent phase-mask and a linear variable filter (LVF). The combination of a phase mask and an LVF generates wavelength-dependent transfer functions, and we can computationally recover the hyperspectral image stack from a single measurement. We report on the construction of the device, image reconstruction algorithm and spectral calibration methods and show the hyperspectral imaging performance of our prototype device the entire visible wavelengths.