This PDF file contains the front matter associated with SPIE Proceedings Volume 11954 including the Title Page, Copyright information, and Table of Contents.

The unique advantage of visible resonance Raman (VRR) spectroscopy using 532 nm excitation wavelength for biological samples is the resonance enhancement of vibrational modes of chemical bonds from cells and tissues. The aim of this study is specifically to reveal the VRR characteristic spectra of different organs in mice, find the molecular alterations in the development of white matter and gray matter of mouse embryos at different ages and study the VRR spectral information of the mouse embryo head using VRR technology.

Confocal Raman spectroscopy (CRS) technology has wide applications, especially in the biomedical field. CRS provides non-destructive, contrast-free and molecule-specific quantitative measurement of samples, including biological tissues. These advantages make it ideal for human skin characterization. We present a portable dual-wavelength CRS system with a handheld measurement probe which connected to the console by optical fibers. To achieve fast switching between the two wavelengths, a fast 2-to-1 fiber array multiplexing module was used. A large bandwidth could be covered at each measurement point in real time. We performed system characterization for this proposed CRS system and measured different samples.

Colorectal cancer (CRC) is the second most deadly and third most common type of cancer worldwide. In this study, we assessed the improvement of the diagnostic potential of diffuse reflectance spectroscopy (DRS) for CRC detection upon extending the tissue probed depth (up to 2mm) and wavelength ranges (350-1919 nm) investigated in previous studies. We analyzed almost 3000 DR spectra (7.5 times more than previous studies) collected with 630-µm and 2500-µm source-detector distance probes by using support vector machines with potential to automate tissue classification. We achieved 96.1% sensitivity and 95.7% specificity and 0.987±0.005 AUC on tissue classification.

Cancer related deaths remain among the most common in the US with laryngeal cancer being among the most complicated to diagnose and treat. Most cancers in the larynx begin on the mucosal surface which yields cell morphology and biomechanical changes. Existing techniques that allow elastic properties measurements are incapable of achieving this goal in vivo. The main objective of a present study is to evaluate viability of Brillouin microscpectroscopy application to in vivo differentiation of various tissue types inside the larynx based on elasticity measurements. Here we are reporting successful application of Brillouin spectroscopy to characterization of postmortem porcine larynx’ Inferior Vocal Fold, Superior Vocal Fold, and Supraglottal Wall regions. Acquired data correlated well with previously reported results, indicating viability of Brillouin spectroscopy application to in vivo tissue imaging, morphological and mechanical characterization as a substitute for tissue biopsy.

We present a method for designing and fabricating 'HyperPixels': pixel filter arrays with custom spectral transmission properties that enable efficient imaging of specific chromophores or fluorophores. Multispectral imaging typically targets particular spectral bands to uncover the spectral properties of tissue in combination with spatial resolution. Unmixing spectral properties can uncover the type and quantity of chromophores or fluorophores due to their unique spectral absorption or emission. Pixelated filter arrays atop imaging sensors are low-cost techniques used to achieve multispectral imaging. Typically, the filter pixels exhibit bandpass spectral behaviour, allowing only a fraction of the incident light to reach the sensor. As a result, narrowband filter pixels trade off high spectral resolution with optical power loss. A way to avoid this issue and improve the signal to noise ratio (SNR) for individual targets is to use a filter array where individual pixels are matched to a target chemical compound's reflectance or emission spectrum. Simulations show a >5-fold improvement in SNR under realistic noise conditions. These matched optical filters can also reduce the complexity of software or hardware spectral unmixing algorithms, offering the potential for real-time imaging of target compounds. We present a method for tailoring spectral transmission of individual pixels by building HyperPixels comprising multiple Fabry-Perot resonator subpixels with varying bandpass properties (FWHM = approximately 50-60 nm, thicknesses 75-150 nm) that collectively have the desired transmission spectrum. We used a numerical optimization process to design filter arrays for simultaneous detection of methylene blue and indocyanine green, commonly used in cancer diagnostics by clinicians. We then fabricated filters for indocyanine green detection using grayscale lithography with pixel sizes down to 5 μm and individual subpixels down to 0.5 μm and characterized them for their spectral properties.

Approximately 34% of people with diabetes will experience a diabetic foot ulcer (DFU) at some point throughout their lifetime. The perfusion of oxygen to the DFU is critical for promoting wound healing and closure. However, complications from diabetes can compromise the oxygenated flow to the wound site. Techniques such as transcutaneous oximetry and laser Doppler imaging have been used to assess perfusion to DFUs at discrete point-locations in the peri-wound. Widearea measurements of temporal oxygenation changes, as an indirect measure of perfusion, can provide additional insight of the oxygenated flow in the (peri-)wound and background tissue. Herein, our objective is to assess the differences in oxygenation flow patterns in and around the DFU regions and in the feet of control subjects as a potential biomarker for monitoring wound healing. Breath-holding (BH), as a stimulus, holds the potential to induce oxygenated flow pattern changes in the presence of wounds. In this study, 10 DFU and 3 control subjects were imaged using a hand-held nearinfrared optical scanner (NIROS). Spatial-temporal oxygenation maps of hemoglobin-based parameters were acquired across an 120-second paradigm with 20 seconds of breath-hold. The oxygenation flow patterns obtained from Pearson'sbased correlation maps across controls, healing DFU, and non-healing DFU indicated that flow patterns varied distinctly. Ongoing work is to correlate oxygenated flow patterns to clinical assessment of healing status in DFUs.

Hyperspectral endoscopy can offer multiple advantages as compared to conventional endoscopy. Our goal is to design and develop a real-time hyperspectral endoscopic imaging system for the diagnosis of gastrointestinal (GI) tract cancers using a micro-LED array as an in-situ illumination source. The wavelengths of the system range from ultraviolet to visible and near infrared. To evaluate the use of the LED array for hyperspectral imaging, we designed a prototype system and conducted ex vivo experiments using normal and cancerous tissues of mice, chicken, and sheep. We compared the results of our LED-based approach with our reference hyperspectral camera system. The results confirm the similarity between the LED-based hyperspectral imaging system and the reference HSI camera. Our LED-based hyperspectral imaging system can be used not only as an endoscope but also as a laparoscopic or handheld devices for cancer detection and surgery.