Journal of Biomedical Optics最新文献

Significance: Optical coherence tomography vibrometry (OCTv) allows measuring the surface and subsurface nanometer vibrations of the mammalian ossicular chain. However, existing multidimensional OCTv setups remain expensive, complex, or limited in accuracy.

Aim: We developed a 3D OCTv setup with a rotational component and provided a theoretical framework that clarifies the main determinants of measurement accuracy in 3D vibrometry.

Approach: A commercially available OCTv system is mounted on a robotic arm to allow multidimensional measurements. The relative positions of measured structures and the optical axes orientation are defined with a custom volume registration algorithm.

Results: We present a mathematical framework for decomposing the measured motion components into a Cartesian space and identify key factors that influence the decomposition accuracy. The angular accuracy of optical axis estimation was 0.4 deg. Experimental validation was performed on an oscillating phantom and on the malleus-incus complex (MIC) of a fresh human temporal bone specimen, replicating previous evidence on the MIC's frequency-dependent vibratory behavior.

Conclusions: The robot-mounted 3D OCTv setup provides a cost-effective, robust, and integral solution for mapping middle ear 3D vibrations, accurately orienting optical axes across measurements. Future work should integrally map the ossicular chain to test the commonly assumed rigid-body behavior of ossicular motion.

Significance: Accurate intraoperative assessment of ablation completeness in liver radiofrequency ablation (RFA) remains a clinical challenge, as conventional imaging lacks real-time capability to delineate necrotic boundaries. Incomplete ablation increases recurrence risk, underscoring the need for real-time, high-resolution imaging with functional tissue differentiation.

Aim: We propose a robot-assisted photoacoustic (PA) imaging system employing a customized diffusing optical fiber to improve intraoperative monitoring of liver RFA.

Approach: The system integrates circumferential wide-field illumination for enhanced tissue coverage with robotic automated 3D scanning and co-registered ultrasound. Spectroscopic PA imaging differentiates necrotic from viable tissue based on optical absorption, whereas a standard Hough transform algorithm suppresses fiber-induced artifacts. Validation was performed using ex vivo and cadaveric swine liver studies.

Results: In cadaveric studies, 3D lesion mapping showed necrotic zones of $7.55\times 5.37\times 7.42\mathrm{mm}$ , closely matching gross pathology measurements (7.93 mm average diameter), confirming system accuracy.

Conclusions: The proposed system enables accurate, real-time visualization of ablation lesions in situ, offering a clinically viable approach to improve treatment precision and reduce recurrence in liver RFA procedures.

Significance: Biophotonics has advanced through many discoveries, yet challenges remain, including label-free biomolecular specificity, quantitative imaging, and single-molecule detection. Progress is further constrained by the need for cheaper, lighter, miniaturized materials that still meet strict optical, electrical, and mechanical specifications. This limitation can be overcome if bioinspired structures are developed. One of the developed areas in which solutions in nature are used is micro and nanostructures including nanosurfaces. It offers a way to increase biomolecular specificity and develop lightweight, low-cost devices for biomedicine. However, it requires measuring phenomena in materials and testing these materials in applications, e.g., sensing systems.

Aim: We offer a concise, authoritative overview of biophotonics-from nanoscale light-biomolecule interactions to bioinspired materials, phantoms, test methods, and sensor development.

Approach: A coherent and comprehensive analysis of the crucial problems related to the development of bioinspired materials and devices was carried out. Recent advances in light scattering by biological surfaces enable structure characterization, disease diagnosis, red-blood-cell analysis, drug discovery, and optical imaging and sensing. Structural and genetic bases of biological photonic surfaces were examined, alongside key performance factors in bio-inspired materials-biocompatibility, biodegradability, structure-optics coupling (e.g., dynamic color change), and scalability limits. We survey chiral nanomaterials, silica frustules, and artificial surfaces that emulate peacock feathers, butterfly wings, iridescent fruits, plant petals, and beetle cuticles, highlighting complementary diagnostics-omics, hyperspectral, and terahertz imaging-for structural analysis and material innovation. We examine bio-inspired phantoms for medical calibration, recent advances in Monte Carlo tissue light-transport modeling, and the resulting applications of these materials and diagnostic tools.

Results: Results confirm a broad set of tunable bio-inspired materials: key optical phenomena were mapped, structures fabricated and modeled, phantoms validated, and strong sensor potential demonstrated.

Conclusions: We survey emerging biophotonics, review material and system requirements, and emphasize simplifying and miniaturizing sensors for biomedical use.

Significance: Accurate monitoring of pupil size and gaze direction is critical in clinical and research contexts; however, current pupillometry methods require open eyes, limiting their use in patients under anesthesia, sedation, or sleep. Short-wave infrared (SWIR) imaging enables noninvasive closed-eye pupillometry, but challenges remain due to eyelid glare, gaze variability, and low signal-to-noise ratio (SNR).

Aim: We aimed to enhance closed-eye pupillometry by integrating polarization filters into the SWIR imaging system and developing improved algorithms for pupil localization and gaze direction estimation under natural closed-eye conditions.

Approach: Experiments were conducted on healthy volunteers using SWIR imaging with different polarizer configurations (parallel, partially crossed, crossed, and no polarizers). Pupillary light reflexes (PLR) were recorded under open- and closed-eye conditions with both forward fixation and varying gaze directions. Image analysis incorporated brightness difference imaging and statistical modeling to evaluate maximal brightness change and SNR.

Results: In open-eye settings, parallel polarizers produced the strongest PLR signal, but in closed-eye conditions, crossed polarizers significantly improved image quality by suppressing eyelid glare. The crossed configuration yielded the highest PLR brightness change and SNR compared with parallel or no polarizers, enabling reliable pupil localization across multiple gaze directions. Improved algorithms allowed robust PLR detection even under natural eyelid closure and variable gaze positions.

Conclusions: Integrating crossed polarizers into SWIR-based pupillometry substantially enhances signal fidelity and pupil localization through closed eyelids. This approach overcomes major limitations of previous methods and enables accurate, touchless pupillometry in clinically relevant conditions. These advances pave the way for applications in anesthesiology, sleep medicine, and neurocritical care.

Significance: Gold nanospheres (AuNSs) functionalized with DNA are powerful tools for studying nanoscale biomolecular interactions through fluorescence modulation. Understanding how DNA conformation influences fluorescence is essential for advancing biosensor design.

Aim: We examine how DNA strand length and surface loading govern the fluorescence behavior of Cy5-labeled single-stranded DNA (polyA-Cy5) bound to AuNSs and how these properties change upon hybridization with complementary polyT strands.

Approach: PolyA-Cy5 strands of different bases were conjugated to AuNSs and analyzed using steady-state and time-resolved fluorescence spectroscopy before and after polyT hybridization.

Results: Surface attachment induced strong fluorescence quenching, with intensity varying with strand length due to differences in DNA conformation. Short strands remained rigid and upright, whereas longer strands adopted more flexible geometries. Upon hybridization, longer duplexes exhibited fluorescence enhancement attributed to increased fluorophore-metal spacing as dsDNA becomes more upright. Lifetime measurements supported these conformational changes and suggest a Förster resonance energy transfer (FRET)-based quenching mechanism. Experiments in fetal bovine serum (FBS) confirmed that hybridization-induced enhancement persists in biologically relevant media.

Conclusions: The results reveal strand-length and density-dependent conformational dynamics of DNA on AuNSs and establish a robust fluorescence-based method for probing nanoscale assembly. The nanosystem can also be tracked intracellularly, as demonstrated by its detectable signal in fluorescence imaging.

Significance: Laser safety studies of the eye are well documented for visible wavelength and continuous wave lasers. There are fewer experimental results for infrared wavelengths and pulsed lasers.

Aim: We aim to fill the gap at 1645 nm for single nanosecond pulse duration exposures of rabbit cornea and determine the threshold radiant exposure to generate lesions 50% of the time (estimated dose ${\mathrm{ED}}_{50}$ ).

Approach: Images of the cornea during exposures were acquired using slit lamp microscopy and optical coherence tomography. A histological analysis helped provide dosimetry relationships with morphology and mechanisms of the damage.

Results: We measured the energy ${\mathrm{ED}}_{50}$ value at $3.86\pm 0.085\mathrm{mJ}$ utilizing the slit lamp biomicroscopy. Incorporating the experimental spot size diameter, this corresponds to a peak radiant exposure of $102J/{\mathrm{cm}}^2$ . By contrast, the average radiant exposure ${\mathrm{ED}}_{50}$ over a 1-mm diameter limiting aperture as per the ANSI Z.136 convention was $0.49J/{\mathrm{cm}}^2$ . Additional analysis via optical coherence tomography (OCT) and histology examined the severity and degree of damage.

Conclusion: This experimental approach performed well to characterize damage and identify damage thresholds to inform the laser safety standard community of the accuracy of current exposure limits.

Significance: Minimally invasive surgery (MIS) offers substantial benefits to patients, including reduced trauma and faster recovery. However, it limits visual and tactile feedback, which can affect surgical decision-making. Hyperspectral and multispectral imaging (HSI/MSI) are imaging technologies with the potential to provide detailed, real-time tissue characterization, enhancing minimally invasive intraoperative guidance.

Aim: This perspective aims to summarize the current state-of-the-art in the use of HSI/MSI in laparoscopy and endoscopy. It focuses on both technological development and clinical implementation, providing an overview of performance characteristics and translational state.

Approach: A structured literature search was conducted to identify relevant studies. These were analyzed for key system specifications (spectral range, resolution, and acquisition speed) and clinical applications. The studies were further categorized using a "bench-to-bedside" framework to evaluate their level of translational progress.

Results: The majority of studies fall within early translational stages (T1 to T2), with no reports of large-scale clinical trials. Most systems operate in the visible spectrum (450 to 650 nm), optimized for blood-related imaging. Applications include perfusion assessment, nerve visualization using short-wave infrared wavelengths, and tumor detection.

Conclusions: HSI/MSI for MIS is a rapidly developing field with demonstrated potential across a range of applications. Continued research and validation are essential to transition these technologies from experimental use to routine surgical practice.

Significance: Ureteral injuries represent a major concern during a range of surgical procedures, due to the proximity of the ureter to target surgical structures. Intraoperative identification of the ureter is critical to prevent this accidental damage.

Aim: We demonstrate the first known in vivo photoacoustic imaging of the ureter in swine following intravenous administration of FDA-approved methylene blue, enabled by a software-hardware integration that has not been previously reported in the literature.

Approach: Photoacoustic channel data from the ureters of two swine were acquired using a Vevo F2 ultrasound system and an Opotek Phocus Mobile laser. Images were beamformed using a delay-and-sum algorithm. Photoacoustic image quality was evaluated using contrast, signal-to-noise ratio (SNR), and generalized contrast-to-noise ratio (gCNR) metrics, measured 10 to 80 min after methylene blue injection.

Results: Across the 10- to 80-min imaging window, median contrast (3.46-11.43 dB), SNR (2.84-6.99), and gCNR (0.27-0.64) confirmed sustained ureter visibility with methylene blue. Maximum image quality was observed 20- to 30-min after methylene blue injection, with significantly higher contrast, SNR, and gCNR values compared with earlier or later time points ( $p<0.05$ ).

Conclusions: In vivo results demonstrate that methylene-blue-enhanced photoacoustic imaging can visualize the ureter over a time duration that is consistent with the length of surgical procedures, providing initial feasibility for real-time photoacoustic-guided surgery applications.