This study develops and substantiates a polarization-interferometric Jones-matrix approach for revealing hidden multifractal optical anisotropy in dehydrated biological soft-matter films. The method integrates Mach-Zehnder interferometry, digital holographic reconstruction of complex amplitudes, phase-selective speckle-field analysis, and statistical-multifractal processing of Jones-matrix images. Unlike intensity-based Stokes polarimetry, it provides amplitude and phase information and enables selective analysis of the coherent ballistic or weakly scattered polarization-preserving field component. Analytical relationships between real and imaginary Jones-matrix components and linear/circular birefringence mechanisms establish their interpretation as markers of spatial heterogeneity, orientational consistency, and phase organization of supramolecular polycrystalline networks. Using bile films, phase-selective mapping revealed distinct anisotropy manifestations in dendritic and spherulitic structures. Higher-order statistical moments and multifractal spectra described coordinate- and scale-dependent transformations. Primary validation on bile, whole blood, and dental canal irrigation films showed comparable integral-field accuracy but higher Jones-matrix informativeness after minimally scattered component isolation, supporting label-free biomedical diagnostics requiring further clinical validation.
Fluorescence microscopy is essential for visualizing cellular and tissue structures. When combined with a hyperspectral modality, it enables the acquisition of emission spectra that provide insight into the composition of fluorophores. These spectra can be used for fluorophore-based image segmentation; however, accurate spectral separation becomes challenging when fluorophore emission spectra overlap and mix within individual pixels. We present a spatially-corrected density peak clustering (SC-DPC) method that combines phasor transformation with histogram-based density-peak detection and additional spatial correction to achieve accurate and fast clustering. SC-DPC effectively handles large datasets and clusters that are not separable linearly in phasor space while maintaining high clustering accuracy and computational efficiency. Results with synthetic data and experimental multiphoton microscopic data from the mouse retina demonstrate that SC-DPC provides a robust, high-performance approach for hyperspectral fluorescence data segmentation.
SIGNIFICANCE:This study leverages functional near-infrared spectroscopy (fNIRS) to elucidate optically derived cortical network signatures underlying combined sensory-motor interventions in stroke rehabilitation. AIM:To characterize the synergistic effects of peripheral electrical stimulation (PES) and bilateral arm training (BAT) on cortical hemodynamics and functional network architecture using fNIRS. APPROACH:fNIRS signals were acquired from 24 subacute stroke patients. Wavelet amplitude and wavelet phase coherence were employed to quantify task-related hemodynamic activation and interregional synchronization within the 0.01-0.08 Hz frequency band. RESULTS:Compared with BAT alone, the PES-BAT paradigm elicited augmented hemodynamic activation in ipsilesional prefrontal and motor regions. The combined intervention further enhanced phase synchronization across distributed cortical networks and preserved interhemispheric coherence, counteracting maladaptive contralesional dominance. CONCLUSIONS:The fNIRS-based wavelet metrics effectively detect intervention-dependent modulation of cortical hemodynamics and network organization, highlighting the value of optical neuroimaging in assessing neuroplasticity during stroke rehabilitation.
OBJECTIVES:Optical autofluorescence imaging is a noninvasive adjunct for detecting potentially malignant oral disorders, such as actinic cheilitis (AC). This study evaluated its use for early detection and for monitoring tissue response following methylene blue-mediated photodynamic therapy (MB-PDT). METHODS:Lip autofluorescence was assessed using a handheld device (405 ± 20 nm). Areas with altered fluorescence underwent biopsy for confirmation. Patients with AC received five MB-PDT sessions (660 nm, 100 mW, 120 s/point) after topical 1% MB. Grayscale intensity was quantified before treatment and at 30 days. RESULTS:Of 25 screened individuals, 19 had confirmed AC, and 17 completed follow-up. Lesions showed higher fluorescence intensity than healthy tissue. After MB-PDT, mean intensity and variability significantly decreased, indicating tissue response. Smokers showed a smaller reduction. CONCLUSION:Autofluorescence imaging enables early detection and noninvasive monitoring of AC. Combined with MB-PDT, it represents a practical strategy for managing high-risk patients and supporting early intervention.
In this study, the difference in behavior of the raw photoplethysmography (PPG) signal and the laser Doppler flowmetry (LDF) signal reflecting hemodynamics in the skin of upper extremities at brachial arterial occlusion is recorded and discussed. It is shown that at various locations on the hand, the raw PPG signal provides richer and previously little-known information on the redistribution of blood between the arterial, microcirculatory, and venous beds, while the conventional blood flow (BF) parameter recorded by LDF technique is less sensitive to it and largely does not capture this redistribution.
This study utilizes an integrated laser speckle (LSCI) and intrinsic optical signal imaging (IOSI) system to evaluate microvascular dynamics in murine pressure ulcer (PU) models. We compared a single prolonged compression (6 h) against repeated compressions (1.5 h/day for 7 days) using an enhanced spatiotemporal gradient analysis of LSCI data. In the repeated compression model, gradient analysis revealed a progressive perfusion decline by Day 4. By Day 7, perfusion gradients indicated near-complete flow loss, corresponding to severe hypoxia detected by IOSI, signifying sustained microvascular impairment. Conversely, the single compression model exhibited reversible alterations; LSCI gradients showed initial disruption followed by gradual recovery, with perfusion nearing baseline by Day 7. The LSCI-IOSI platform, emphasizing advanced gradient processing, systematically delineates microcirculatory compromise. This approach highlights the critical role of repeated ischemia-reperfusion in driving persistent dysfunction and demonstrates the utility of quantitative optical imaging for early detection and targeted intervention in PU progression.
Optical coherence tomography (OCT) enables non-invasive volumetric retinal imaging. Conventional tabletop and handheld systems rely on skilled operators and patient cooperation. Mobile robot-assisted OCT (RAOCT) systems can address these challenges, but many depend on complex visual servo modules for low-latency eye tracking. We present an intensity variance-guided RAOCT system integrated on a wheeled mobile platform. The system uses one depth camera for coarse eye localization and a single pupil camera for real-time tracking. By calibrating a lookup table between image variance and distance within the near-eye region, the pupil camera provides indirect depth estimation for robotic servoing. A motorized reference arm, an electrically tunable lens, and an automated polarization controller further enable image-quality optimization. Experiments demonstrated 103.50 μm axial and 20.46 μm lateral tracking accuracy. The pupil-camera response time was 10.53 ms. Automated retinal OCT imaging was achieved, demonstrating the system's potential for point-of-care diagnostics in resource-limited environments.
Acne is a common inflammatory skin condition and frequently leads to long-term adverse clinical outcomes including scarring and pigmentation, negatively impacting Health Related Quality of Life (HRQoL). Monitoring of acne progression can improve understanding of lesion evolution, support evaluation of treatment response and provide potential biomarkers for future investigation of acne sequelae. This study presents a multi-functional optical coherence tomography (OCT) protocol integrating structural imaging, OCT-based angiography (OCTA), and optical coherence elastography (OCE) for longitudinal in vivo monitoring of acne. Thirteen lesions were evaluated across eight time points over 18 days. Quantitative parameters, including Young's modulus and vascular metrics, captured biomechanical and microvascular changes during acne evolution. The system enables continuous multimodal assessment, showing that stiffness and vascular alterations reflect lesion progression. This pilot longitudinal study establishes a quantitative foundation for dermatological research and suggests that multimodal OCT monitoring may provide biomarkers for assessing lesion progression and long-term clinical outcomes.
Hyperspectral imaging combined with plasmonic nanoparticles offers powerful opportunities for nanoscale biological diagnostics, yet conventional push-broom systems are limited by slow acquisition and reduced spatial resolution. We report a wide-field hyperspectral imaging platform integrating a custom linear variable tunable filter (LVTF) with reflected light microscopy (RLM) for multiplexed plasmonic nanoparticle (NP) imaging. While LVTF-based systems have been used in industrial contexts, their adaptation to RLM microscopy enables high-resolution, high-contrast spectral imaging of NPs on biological samples. The system acquires data across 380-720 nm with 7-20 nm spectral resolution while preserving spatial detail. We demonstrate imaging of NPs bound to cancer cell membranes and classification of four distinct NP types. A trained support vector machine achieves an overall F-score of ~97%, significantly outperforming RGB-based approaches. Compared to push-broom systems, this platform provides faster acquisition, improved spatial resolution, and a compact, cost-effective solution for multiplex NP detection in bioimaging and immunoplasmonic applications.
The skin performs essential functions between the internal and external environments of the human body, such as protection against microorganisms, substances and radiation, maintenance of body temperature, prevention of excessive water loss, and production of vitamin D. However, many of these functions are reduced with aging and can be accentuated in photoaged skin. Photodynamic therapy (PDT) is a noninvasive technique used in the treatment of cancer, microbial infections, precancerous changes and for cosmetic purposes. Research on topical PDT suggests antibacterial, anti-inflammatory and immunomodulatory effects on keratinocytes, fibroblasts, sebaceous glands and hair follicles. Therefore, this pilot study evaluated PDT on the face using 5-aminolevulinic acid (ALA) and methyl 5-aminolevulinate (MAL), combined with amber LED and laser irradiation in women aged 40-55 years. PDT was effective in rejuvenating photoaged skin, reducing fine lines, smoothing wrinkles, and improving skin softness, firmness and sagging, with minimal side effects.
Polarization-resolved imaging provides a powerful, label-free means of visualizing anisotropic structural order in biological tissue, yet its quantitative exploitation remains limited in routine microscopy. Here, we present a polarization-resolved imaging approach based on polarized light microscopy (PLM) that enables automated, quantitative extraction of sarcomere-scale structural metrics from unstained cardiac tissue sections. Using experimental rat models of acute cardiorespiratory arrest as controlled test systems, we demonstrate that polarization-derived intensity profiles encode reproducible information on sarcomere length and band composition, with distinct patterns of structural compression observed across experimental conditions. Image-derived measurements were validated against conventional histological and immunohistochemical staining, highlighting the complementary value of polarization contrast for rapid, staining-free assessment of tissue anisotropy. Rather than addressing diagnostic specificity, this proof-of-concept study establishes PLM as a scalable quantitative imaging modality for polarization-resolved analysis of hierarchical structural order in biological tissue, with potential integration into multimodal imaging workflows in biomedical research.
Subtle differences between cancerous and normal regions in unstained tissue sections limit the performance of conventional diagnostic methods. Mueller matrix polarimetry provides comprehensive information on tissue polarization responses; however, the intrinsic coupling of optical effects in the original matrix elements complicates direct histological interpretation. In this study, a pixel-level polarization dataset from clinical lung cancer and basal cell carcinoma sections is established to systematically compare low-dimensional physical decomposition and high-dimensional combination mapping for cancer-region identification. Conventional decomposition approaches exhibit limited discriminative capability and significant class overlap in complex tissues. To address this limitation, a vectorial metric norm spectrum incorporating multi-order features is developed, enabling enhanced representation of polarization characteristics. The proposed high-dimensional mapping framework achieves accurate differentiation between cancerous and normal regions and demonstrates strong performance in cross-validated evaluations. This work establishes a progressive strategy from physical decomposition to high-dimensional representation for optical-assisted pathological analysis.
Clinical refractive surgeries for myopia correction generally entail stromal tissue removal with risks of postoperative complications. NIR femtosecond laser-induced corneal two-photon collagen cross-linking (two-photon CXL) through photochemical effects can lead to localized refractive index (RI) changes in the cornea, promising for non-ablative and non-incisional visual correction. However, previous studies mainly focused on hydrogels and animal corneal tissues, adopting a diffraction grating method that is difficult for biological tissue. Here we systematically investigate femtosecond laser-induced RI changes in human corneal tissue, demonstrate two-photon excitation of riboflavin leading to cross-linking, and employ direct interferometry to quantify RI changes. The maximum RI change is 3.80 ± 0.45 × 10-3 in collagen hydrogel and 5.14 ± 0.75 × 10-3 in corneal tissue. These findings illustrate that RI engineering by femtosecond laser two-photon CXL is promising for noninvasive refractive surgery.
Photodynamic therapy (PDT) is an established dermatologic therapeutic modality used to induce apoptosis within targeted tissue. Despite increasing clinical use, the genotoxic safety of blue light (BL) PDT has not yet been established. We examined whether combination BL (417 ± 5 nm) and 5-aminolevulinic acid (5-ALA) PDT induces cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) in human dermal fibroblasts. CRL-2617 and AG-13145 fibroblasts were treated with 0, 0.5, or 1 mM 5-ALA, then irradiated with BL at 10, 30, or 45 J/cm2. Unlike robust photolesion formation in the UVB-irradiated positive controls, no BL PDT experimental condition produced CPD or 6-4PP signal exceeding the empirically validated assay lower limit of quantification (LLOQ; 1.5625 ng/mL). However, sub-LLOQ DNA damage cannot be excluded. The minimum detectable effect was 2.42 ng/mL, ~1.55-fold the LLOQ. Linear mixed-effects sensitivity analysis confirmed assay responsiveness, demonstrating clear separation between UVB and BL PDT signals.
A compact reflection-mode optical sensor was developed and evaluated for noninvasive pulse waveform measurement using photoplethysmography (PPG). The sensor integrates an infrared light-emitting diode and photodetector, enabling real-time acquisition of PPG signals from subjects with diverse ages and health conditions. Despite a limited sample size, the device demonstrated reliable detection of physiologically relevant differences in pulse waveforms. The average systolic amplitude was 105.06 mV, with a mean pulse width of 0.14 s and an augmentation index of 0.19. Notably, subjects with identified health issues showed a trend toward higher augmentation index values and reduced compliance in pulse waveform morphology, consistent with diminished vascular elasticity. These findings highlight the potential of the proposed approach for early cardiovascular screening and personalized health monitoring. Future work will focus on validating the sensor in larger cohorts and enhancing robustness for real-world applications.
We tested walking interventions using adjustable air-insoles with hardness values of 80, 160, and 240 mmHg over walking durations of 10 and 20 min. Optical coherence tomography (OCT) was used to measure the thickness of the stratum corneum (SC) and living epidermis (ED) in three different locations: the big toe (T1), first metatarsal head (M1), and second metatarsal head (M2), and deep learning was used to compare the difference in thickness between SC and ED. The results indicate that SC thickness increases in M1 is statistically significant after 20 min walking interventions using 80 mmHg insole hardness, and SC thickness decreases in T1 and M1 are statistically significant after 20 min walking using 160 mmHg insole hardness. Changes in SC and ED thickness observed in this study highlight their potential relevance in evaluating plantar tissue health in the context of DFU prevention.
This study evaluated whether multimodal spectroscopic analysis of saliva can differentiate patients with lung cancer from healthy individuals. Unstimulated saliva samples were collected from 57 patients with lung cancer and 36 healthy controls. TEM and DLS revealed increased heterogeneity of the salivary colloidal fraction and a shift toward larger particle populations in lung cancer. UV-Vis spectroscopy showed a hypsochromic shift of the main absorption peak (279-261 nm), while fluorescence intensity at 510 nm increased 1.9-fold with additional emission bands at 617 and 680 nm. Reflectance decreased across the measured spectral range. ATR-FTIR identified the Amide III/asymmetric PO2 - region (1350-1180 cm-1) as the most discriminative interval (AUC = 0.854). Fluorescence-based classification achieved an AUC of 0.706, with 73.1% sensitivity and 76.3% specificity. 1H NMR revealed alterations in metabolites associated with metabolic reprogramming.
Raman Difference spectroscopy (RDS) presents a promising, non-invasive approach for facilitating rapid diagnosis of oral squamous cell carcinoma (OSCC). Many ex vivo studies rely on formalin-embedded tissue specimens. Spectroscopic changes and classification of formalin-fixed OSCC tissues were investigated. In an analysis of 47 specimens (n = 30 OSCC, n = 17 physiological mucosa), RDS was employed at 180 distinct measurement loci after storage in saline, and again at 125 measurement loci after storage in formalin. For classification, Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were utilized. In distinguishing OSCC from physiological mucosa, LDA revealed a higher sensitivity (97.6% for NaCl-stored vs. 90.9% for formalin-fixed tissues), specificity (93.0% vs. 78.6%), and overall classification accuracy (95.2% vs. 85.4%) for specimens stored in saline. While formalin fixation is valuable for tissue preservation in histopathology, Raman spectra of OSCC tissues were substantially altered, with implications for validation of innovative optical techniques such as Raman Spectroscopy.
Collagen XIV is a fibril-associated collagen with interrupted triple helices (FACIT) that helps regulate collagen fibril spacing, alignment, and extracellular matrix organization. Its role in corneal biomechanics remains incompletely understood. Here, we investigated murine wild-type (WT) and collagen XIV-deficient (Col14a1-/-) corneas using complementary optical elastography modalities: Brillouin microscopy and air-coupled ultrasound optical coherence elastography (ACUS-OCE). Brillouin microscopy generated high-resolution maps of Brillouin frequency shift in WT and Col14a1-/- corneas (N = 4 per group), while ACUS-OCE measured elastic wave speed in WT (N = 8) and Col14a1-/- (N = 7) corneas. Both methods showed reduced mechanical metrics in Col14a1-/- corneas, with lower Brillouin frequency shift and lower OCE-derived wave speed relative to WT controls. These findings support collagen XIV as a regulator of corneal stromal biomechanics and demonstrate the value of combining Brillouin microscopy with ACUS-OCE for detecting biomechanical alterations in murine corneas.
Fluorescence imaging (FI) is widely used in in vivo and cellular studies. However, accurate depth determination of fluorescent targets in vivo remains challenging due to strong photon scattering and absorption in biological tissues. In this study, we developed and validated a machine learning (ML)-based framework, supported by Monte Carlo (MC) simulations, for accurate depth estimation of near-infrared (NIR) fluorescent targets in turbid media. An optimized MC model was constructed to simulate NIR fluorescence photon propagation, generating datasets of fluorescence images corresponding to target depths between 0.1 and 1 cm. Experimental validation was conducted over a depth range of 0.1-0.7 cm using tissue-mimicking phantoms designed to replicate the optical properties of human skin, as well as on an in vivo model incorporating fluorescent gold nanostructures imaged with computed tomography (CT) and wide-field FI. The results were quantitatively validated using two performance metrics: rounded accuracy and root mean squared error (RMSE).
