Ultra-high-magnification zoom electronic endoscopes are highly susceptible to stray light because compact optomechanical layouts and zoom-dependent optical reconfiguration strongly affect non-imaging light propagation. In compact systems with a small-aperture moving lens group, indiscriminate barrel blackening is not always desirable because coating degradation or peeling may compromise imaging reliability. This study presents a simulation-guided, state-dependent stray light analysis and suppression strategy for a compact ultra-high-magnification zoom endoscope. Monte Carlo ray tracing was performed at different zoom positions to identify the dominant stray light paths in the conventional, low-magnification, and high-magnification modes. The results show that the dominant sources vary significantly with zoom state; as the system moves toward near-focus and high-magnification operation, changes in group position, back focal distance, and ray geometry increase interaction with critical surfaces, leading to stronger ghosting and background stray light. Based on this analysis, targeted suppression measures were implemented at the corresponding critical locations, including reflectance optimization of key optical interfaces, selective blackening of lens edges and mechanical surfaces, and local baffling. Both simulation and experiment confirm that the proposed strategy effectively suppresses ghost artifacts and background stray light while improving image contrast, luminance uniformity, and detail visibility, especially in the high-magnification mode. This work provides a practical framework for state-dependent stray light control in compact ultra-high-magnification zoom endoscopes.

Early assessment of the severity of frostbite injuries is critical for guiding clinical management and improving patient outcomes; however, tissue damage evolves dynamically and is difficult to predict during the acute phase. Terahertz time-domain spectroscopy (THz-TDS) has previously demonstrated high accuracy in the early triage of thermal burn injuries. In this study, we evaluate the potential of the THz-TDS modality using a portable handheld scanner to assess the depth of frostbite wounds. A standardized in vivo porcine frostbite model was employed, and injury classification was performed using a support vector machine algorithm. We demonstrate that the area under the receiver operating characteristic (ROC) curves was 0.94, 0.85, and 0.87 for healthy tissue, partial-thickness frostbite, and full-thickness injuries. In addition, we explored the use of the double Debye dielectric relaxation model of tissue to reduce the data dimensionality. We observed significant statistical differences between the double Debye parameters of the three groups. These results demonstrate the potential of THz-TDS imaging for early, non-destructive assessment of the depth of frostbite injuries and suggest its potential utility in improving clinical decision-making and surgical outcomes.

Singlet oxygen (1O2) is the primary cytotoxic agent in Type-II photodynamic therapy (PDT). Single-photon avalanche diode (SPAD)-based time-resolved singlet oxygen luminescence detection (TSOLD) systems enable direct detection of the near-infrared 1O2 phosphorescence (∼1270 nm) during PDT, offering a powerful tool for treatment monitoring. However, the efficiency of detection depends strongly on the acquisition parameters. Here, we present a comprehensive evaluation of a TSOLD system with 630 nm and 690 nm nanosecond pulsed diode lasers developed for in vivo PDT monitoring. The influence of acquisition time (1-300 s), SPAD dead time (5-40 µs), and temporal bin width (1-100 ns) on the fidelity of 1O2 lifetime measurements and signal-to-noise ratio (SNR) was quantitatively investigated. Measurements were performed using liquid phantoms containing the photosensitizers Photofrin or benzoporphyrin derivative, with acquisition time further validated in vivo in murine tumor models. The results demonstrate that both acquisition time and detector dead time significantly affect the signal vs. time histogram shape and the accuracy of the 1O2 and photosensitizer triplet-state lifetime measurements, while an optimal bin width minimizes photon-count noise without compromising temporal resolution. The optimized parameters enable reliable 1O2 lifetime extraction within 100 s from the mouse model in vivo. This systematic evaluation establishes quantitative design guidelines for compact TSOLD systems tailored to in vivo applications.

Aging induces structural and functional changes in the cerebral microvasculature. However, in vivo characterization of remodeling in cerebral penetrating vessels (PVs) remains limited. In this study, we employed optical coherence tomography angiography (OCTA) to investigate age-related alterations in cortical PVs in adult (2-4 months) and aged (15-16 months) mice. Using three-dimensional OCTA imaging, we quantified PV tortuosity and local flow dynamics through Doppler frequency variance (DFV) mapping. PV tortuosity was slightly but significantly increased in aged mice, reflecting geometric remodeling of the vertical microvascular network. DFV in aged PVs decreased by more than 15% relative to adults, suggesting reduced flow complexity that may be associated with increased vascular stiffness and altered perfusion dynamics. These findings provide in vivo evidence that aging alters the geometry and hemodynamics of PVs and support the use of OCTA-derived metrics as noninvasive biomarkers of cerebrovascular aging.

Visible-light optical coherence tomography (vis-OCT) provides ultrahigh axial resolution and intrinsic spectroscopic contrast, but its performance in deep tissues is fundamentally limited by strong scattering and absorption at short wavelengths. Here, we report the use of tartrazine-an FDA-approved, water-soluble food dye-as a rapid, biocompatible contrast enhancer to improve vis-OCT penetration and structural visibility across multiple tissue types. We systematically evaluated tartrazine-assisted imaging in postmortem chicken muscle, optic nerve, and brain cortex, as well as in vivo at the ocular limbus and mouse ear. Topical or surface immersion with low-concentration tartrazine solutions significantly improved the vis-OCT signal in deep tissue with increased signal-to-noise ratio, extended penetration, and enhanced structure contrast. These results establish Tartrazine as an inexpensive, safe, and effective optical clearing and contrast-enhancing agent for vis-OCT, enabling deeper and higher-fidelity imaging of biological tissues both ex vivo and in vivo.

Colorimetry camera-based single-molecule localization microscopy (CC-STORM) employs a simple optical setup to facilitate the simultaneous imaging of two or more targets at the nanoscale, but it suffers from a high data rejection rate. A recently reported deep learning-based algorithm (called CC-DeepSTORM) reduced the data rejection rate of two-color CC-STORM from 70% to 40%, while achieving crosstalk of 1%. However, when applying this algorithm to regions with dense emitters, it faces challenges with structural artifacts and low detection rates. Here, we propose CC-DenseSTORM, featuring an attention-gated standard-convolution U-Net to eliminate structural artifacts and a dual-channel adaptive classification network for robust dye classification. Simulations demonstrate that, even at a high density of 5 emitters/µm2, CC-DenseSTORM improves the detection rate by 2-fold compared to CC-DeepSTORM, while maintaining the data rejection rate below 30%. In experimental imaging of multiple myeloma cells, CC-DenseSTORM achieves <1% crosstalk (matching the state of the art), thus enabling simultaneous quantification of the densities of CD38 and BCMA, offering great potential for advancing dual-target immunotherapy.

Astrocytes are star-shaped glial cells whose elaborate soma-process architecture supports neuronal functions, regulates ions as well as water homeostasis, and contributes to brain structural organization. This paper presents a quantitative imaging technique for comprehensive morphological analysis of astrocytes, including their somata and branches, using a custom-built common-path quantitative phase microscope. The microscope employs a common-path off-axis configuration, splitting the sample beam using a grating, and a dual-lens system combined with a spatial filter to produce a reference beam required for hologram generation. This microscope enables a label-free, high-temporal-stability, and real-time 3D visualization of biological samples by measuring optical path length difference (OPD). Astrocyte cells were imaged, and their morphometric properties were quantified in near real time using the developed microscope. The reconstructed optical path length difference (OPD) maps were used to perform multistage deep learning segmentation of entire astrocyte cells, and the corresponding soma and branches were segmented using an optical thickness-based clustering approach. The segmented soma and process regions were compared as well as correlated by their phase-derived and geometrical morphological parameters. To the best of our knowledge, this is the first report of using the proposed digital holographic approach with an AI model to segment and measure the morphometrics of astrocyte cells, including their somata and branches separately.

Photoacoustic (PA) imaging is capable of visualizing the three-dimensional structures of light-absorbing objects, such as blood vessels, and it is often integrated with ultrasound (US) imaging for comprehensive anatomical and functional imaging of biological tissues. For wide field-of-view imaging, volumetric PA or US data from multiple scans are merged to image large objects, such as the entire organ of humans or the entire body of small animals. This study investigated improvements in the volumetric data-merging process of wide-field PA/US imaging using the dual-tree complex wavelet transform (DT-CWT) technique. First, it was shown to effectively suppress boundary seam artifacts in the combined scan data, enabling smooth fusion while preserving critical features. Second, a noise-reduction imaging method based on this technique was applied to effectively enhance the image contrast and spatial resolution. Finally, we demonstrated the DT-CWT-based fusion of vascular images from PA and US volumes, which provided an integrated visualization of the peripheral vasculature. These results demonstrate that DT-CWT has the potential to improve wide-field PA/US images in terms of seamless fusion of multi-scan or multi-modal volume data, enhanced visualization of structures, noise reduction, and contrast improvement.