Journal of Biomedical Optics最新文献

{"title":"Polarizer-assisted pupillometry through closed eyelids, overcoming pupil position dependence.","authors":"Michal Tepper, Omer Ben Barak-Dror, David Haggiag, Israel Gannot, Yuval Nir","doi":"10.1117/1.JBO.31.6.064303","DOIUrl":"10.1117/1.JBO.31.6.064303","url":null,"abstract":"<p><strong>Significance: </strong>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).</p><p><strong>Aim: </strong>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.</p><p><strong>Approach: </strong>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.</p><p><strong>Results: </strong>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.</p><p><strong>Conclusions: </strong>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.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"064303"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12900575/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146201864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Macrophage volume analysis and real-time monitoring by digital holography.","authors":"Baodan Bai, Yanwei Lu, Geng Zhu, Feiyu Liu, Yubo Liu, Wen Wu, Dezhi Lu, Xiupin Wu","doi":"10.1117/1.JBO.31.6.066002","DOIUrl":"10.1117/1.JBO.31.6.066002","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Significance: &lt;/strong&gt;Cell volume serves as a macroscopic indicator of cellular metabolism, growth, and signal transduction. Understanding how cell volume varies across macrophage phenotypes is essential for interpreting their functional states and activation processes.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Aim: &lt;/strong&gt;We present a label-free, noninvasive method for 3D morphological characterization and volume quantification of macrophages and apply it to monitor volume variations during their biological behaviors.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Approach: &lt;/strong&gt;We employed a home-made off-axis digital holographic microscopy (DHM) system based on a Mach-Zehnder interferometric configuration to reconstruct the 3D morphology of cells. Using the mathematical relationship between the phase map and the cell thickness, we further calculated their cellular volume.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Our measurements show that M0 macrophages have a nearly spherical morphology with a volume of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;970.54&lt;/mn&gt; &lt;mo&gt;±&lt;/mo&gt; &lt;mn&gt;153.15&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;μ&lt;/mi&gt; &lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt; &lt;/msup&gt; &lt;/mrow&gt; &lt;/math&gt; . &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; macrophages exhibit a flattened, pancake-like morphology with pseudopodia, with a significantly larger volume of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;3822.00&lt;/mn&gt; &lt;mo&gt;±&lt;/mo&gt; &lt;mn&gt;437.45&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;μ&lt;/mi&gt; &lt;msup&gt;&lt;mi&gt;m&lt;/mi&gt; &lt;mn&gt;3&lt;/mn&gt;&lt;/msup&gt; &lt;/mrow&gt; &lt;/math&gt; . &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; macrophages present a morphology resembling that of &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; cells but with a volume of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;2743.10&lt;/mn&gt; &lt;mo&gt;±&lt;/mo&gt; &lt;mn&gt;254.67&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;μ&lt;/mi&gt; &lt;msup&gt;&lt;mi&gt;m&lt;/mi&gt; &lt;mn&gt;3&lt;/mn&gt;&lt;/msup&gt; &lt;/mrow&gt; &lt;/math&gt; . It indicates that the cell volume might be a potential parameter to distinguish different polarized macrophages. In addition, we successfully monitored the volume changes of macrophages during cell death, cell division, and the polarization process from &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; to &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; . The cell-death process behaved as expected, with the cell volume continuously decreasing and eventually reaching a plateau. The division event we observed occurred together with cell death; during division, the total volume of the cell cluster increased sharply and then gradually decreased as cell death progressed. During the 8-h &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; -to- &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; polarization process, two phases of gradual volume increase and two phases of rapid volume increase were observed. In the early stage (0 to 2 h), &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; macrophages were likely not fully activated, showing only mild volume changes but still exhibiting an increasing trend. At 6 to 8 h, the cells undergo a sharp increase in volume, reflecting their full activation and transition toward the &lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt; &lt;m","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"066002"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13233025/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148163323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time-of-flight fluorescence depth mapping using a spatiotemporal deep learning model.","authors":"Shiru Wang, Arthur Pétusseau, Claudio Bruschini, Edoardo Charbon, Petr Bruza","doi":"10.1117/1.JBO.31.6.066003","DOIUrl":"10.1117/1.JBO.31.6.066003","url":null,"abstract":"<p><strong>Significance: </strong>Fluorescence-guided surgery (FGS) utilizes molecular contrast agents to highlight critical structures or pathological tissues in real time. The premise of FGS is to enable precise surgical decision-making through accurate visualization and quantitative assessment of fluorophore distribution. However, strong effects of diffusion and absorption of fluorescent light in tissue confound fluorescence images, preventing accurate quantitative assessment of the concentration and distribution of fluorescent markers. These optical artifacts may lead to misinterpretation of tissue boundaries and compromised surgical precision, thereby diminishing the capabilities of FGS. Resolving topological depth maps of fluorophore distribution at the millimeter scale is an important first step in performing quantitative sub-surface fluorescence imaging.</p><p><strong>Aim: </strong>In this study, we present a spatiotemporal deep learning architecture that utilizes picosecond single-photon avalanche diode (SPAD) sensor images to rapidly recover the depth topology of a fluorophore distribution embedded in diffuse media. The network is designed to work with wide-field, epi-illumination geometry and millimeter spatial resolution.</p><p><strong>Approach: </strong>A ConvLSTM-UNet deep learning network was developed for picosecond time-resolved image analysis. This network was trained on 5000 spatiotemporal maps simulated by the optical Monte Carlo method and convolved with the instrument response function (IRF) of the imaging system. The experimental setup utilized a SwissSPAD2 sensor synchronized with a 635 nm picosecond laser diode. Using only 10 selected temporal gates as input, the network could recover depth maps. Reconstruction accuracy was evaluated using mean error metrics across various depths and background concentrations of a fluorophore with a simulated decay time of 100 ps.</p><p><strong>Results: </strong>A total of 75 different test fluorescence video data were evaluated. This set encompassed 15 unique inclusion shapes at five different depths. The network successfully reconstructed fluorescence topography up to 15 mm with a mean absolute error of less than 0.6 mm and mean depth variances below 0.5 mm. The inference time was <math><mrow><mo>∼</mo> <mn>30</mn> <mtext>  </mtext> <mi>ms</mi></mrow> </math> .</p><p><strong>Conclusions: </strong>Integrating temporal and spatial deep learning networks enabled depth mapping from time-resolved fluorescence data. Utilizing real IRF proved the applicability of SPAD sensors for sub-surface fluorescence mapping.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"066003"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13278904/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148295089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multimodal optical imaging for the assessment of the teratogenic effects of ethanol on zebrafish development.","authors":"Leah A Lewis, Md Mobarak Karim, Christian Zevallos-Delgado, Mahshid Babeli Nia, Sarah M Empie, Halpandeniya Hewage Helani N Alwis, Manmohan Singh, Salavat Aglyamov, Arne C Lekven, David Mayerich, Kirill V Larin","doi":"10.1117/1.JBO.31.6.066004","DOIUrl":"10.1117/1.JBO.31.6.066004","url":null,"abstract":"<p><strong>Significance: </strong>Prenatal alcohol exposure is a major cause of neurodevelopmental and growth impairments collectively termed fetal alcohol spectrum disorders (FASD). However, the mechanisms by which ethanol disrupts early embryonic development remain incompletely understood; for example, the potential link between ethanol treatment and biomechanical properties of tissues that lead to defects in development is not understood.</p><p><strong>Aim: </strong>To address this gap in knowledge, we used zebrafish (<i>Danio rerio</i>), a powerful vertebrate model with optical transparency and rapid development, to investigate ethanol-induced alterations during embryogenesis.</p><p><strong>Approach: </strong>Embryos were exposed to varying concentrations of ethanol and assessed using a multimodal imaging approach integrating light sheet fluorescence microscopy, optical coherence tomography, and optical coherence elastography.</p><p><strong>Results: </strong>This platform enabled high-resolution, noninvasive, and parallel visualization of structural, molecular, and biomechanical changes. We found that ethanol exposure disrupts Wnt ligand expression in the nervous system, which correlates with a cascade of morphological abnormalities consistently detected across imaging modalities and consistent with alterations to <math><mrow><mi>Wnt</mi> <mo>/</mo> <mi>β</mi></mrow> </math> -catenin signaling activity.</p><p><strong>Conclusions: </strong>These findings highlight the critical role of <math><mrow><mi>Wnt</mi> <mo>/</mo> <mi>β</mi></mrow> </math> -catenin signaling in alcohol-induced teratogenesis and underscore the value of zebrafish models and multimodal imaging for advancing our understanding of FASD pathogenesis.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"066004"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13322611/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148367983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-time fidelity assessment of fluorescence molecular imaging without reference images.","authors":"Elena Kriukova, Sarah Glasl, Vasilis Ntziachristos, Dimitris Gorpas","doi":"10.1117/1.JBO.31.6.066001","DOIUrl":"10.1117/1.JBO.31.6.066001","url":null,"abstract":"<p><strong>Significance: </strong>Fluorescence molecular imaging (FMI) has been approved for surgical guidance in several procedures. However, its interpretation still requires substantial clinician expertise due to variable signal levels. For FMI to gain wider clinical acceptance, image quality should be assessed automatically, thereby prompting clinicians to retake low-quality images when necessary. Yet, no user-friendly fidelity assessment tools currently address this need.</p><p><strong>Aim: </strong>Herein, we introduce a real-time, frame-by-frame FMI fidelity assessment method, termed no-reference fidelity assessment of fluorescence molecular imaging (NRFA-FMI).</p><p><strong>Approach: </strong>NRFA-FMI quantifies image fidelity using a combination of histogram-based and textural metrics. A central advantage of NRFA-FMI is that it operates without reference images, making it particularly suitable for clinical FMI workflows.</p><p><strong>Results: </strong>We show that NRFA-FMI outperforms two state-of-the-art no-reference image fidelity assessment methods, the blind/referenceless image spatial quality evaluator (BRISQUE) and the natural image quality evaluator (NIQE).</p><p><strong>Conclusions: </strong>The introduction of NRFA-FMI enables real-time FMI fidelity assessment, an essential step toward reducing data misinterpretation and preventing incorrect diagnosis. This approach provides clinicians with an intuitive, automated indicator of image reliability, supporting more consistent and accurate intraoperative decision-making.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"066001"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13237650/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148199146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectral dependence of lipofuscin fluorescence lifetimes revealed by FLIM with a superconducting nanowire single-photon detector.","authors":"Pavel Morozov, Vladislav Andreev, Marina Yakovleva, Alex Kostyukov, Tatiana Feldman, Anastasia Ryabova, Igor Romanishkin, Marina Shirmanova, Gregory Goltsman, Vladimir Kuzmin, Mikhail Ostrovsky, Alexandra Arkhipchenko, Eugene Maksimov, Wolfgang Becker, Vladislav Shcheslavskiy","doi":"10.1117/1.JBO.31.6.066501","DOIUrl":"10.1117/1.JBO.31.6.066501","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Significance: &lt;/strong&gt;The noninvasive assessment of oxidative stress in the retinal pigment epithelium (RPE), a key factor in the pathogenesis of age-related macular degeneration (AMD), is an important aspect in ophthalmic diagnostics. Although fundus autofluorescence (FAF) is clinically used, its diagnostic power is limited. Fluorescence lifetime imaging ophthalmoscopy shows promise, but the photophysical underpinnings of lifetime changes in lipofuscin-the dominant RPE fluorophore-remain poorly understood. Lipofuscin granules (LGs) in the RPE are a primary source of fundus autofluorescence and are critically involved in the pathogenesis of AMD. This study characterizes the spectral and lifetime properties of LGs using a fluorescence lifetime imaging microscopy (FLIM) system integrated with a wide-range sensitivity, large-active-area superconducting nanowire single-photon detector (SNSPD) coupled with a standard &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;50&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;μ&lt;/mi&gt; &lt;mtext&gt;m&lt;/mtext&gt;&lt;/mrow&gt; &lt;/math&gt; multimode fiber.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Aim: &lt;/strong&gt;We present experiments on multispectral fluorescence lifetime imaging with a detailed analysis of the fluorescence decays and spectral profiles of LGs in the RPE cells to probe the molecular oxidative state of RPE lipofuscin, aiming to improve AMD understanding and propose a method for early diagnosis of retinal pathologies.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Approach: &lt;/strong&gt;We use a cutting-edge FLIM system integrated via a multimode fiber with a large-active-area SNSPD. Unlike previous studies, our approach provides component-resolved and spatially resolved fluorescence decay kinetics across a broad spectral range (500 to 1000 nm), which is typically inaccessible to conventional detectors. LGs were isolated from 100 human (aged 50 to 75 years) donor RPE cells and subjected to &lt;i&gt;in vitro&lt;/i&gt; photo-oxidation to simulate AMD-like conditions. Steady-state spectroscopy revealed a blue shift in emission following photo-oxidation.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;FLIM analysis, employing a tri-exponential decay model, showed a significant increase in the mean fluorescence lifetime &lt;math&gt; &lt;mrow&gt; &lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;/math&gt; from &lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt; &lt;mn&gt;247&lt;/mn&gt;&lt;/mrow&gt; &lt;/math&gt; to &lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt; &lt;mn&gt;587&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;ps&lt;/mi&gt;&lt;/mrow&gt; &lt;/math&gt; after photo-oxidation. Crucially, we identified a pronounced direct spectral dependence of fluorescence lifetimes &lt;math&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;τ&lt;/mi&gt; &lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;/math&gt; versus wavelength: for native LGs, &lt;math&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;τ&lt;/mi&gt; &lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;/math&gt; increased from 136 to 319 ps at registration range 500 to 650 nm; for photo-oxidized LGs, it increased from 174 to 623 ps over the same region. High-performance liquid chromatography confirmed the degradation of the bisretinoid A2E and accumulation of oxidized derivatives, correlating with the observed photophysical ch","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"066501"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13292641/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148329911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Endoscopic iso-pathlength self-calibration for direction-resolved retrieval of tissue optical properties.","authors":"Natanel Ovadia, Hamootal Duadi, Dror Fixler","doi":"10.1117/1.JBO.31.6.064305","DOIUrl":"10.1117/1.JBO.31.6.064305","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Significance: &lt;/strong&gt;Medical examination of human tissue is preferably performed by imaging the tissue surface. Optical imaging techniques are limited by low penetration depth due to high tissue scattering, whereas sensing techniques can detect changes deeper inside the tissue. Near-infrared sensing methods such as oximetry and fNIRS are already used clinically but have not yet been applied in endoscopy.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Aim: &lt;/strong&gt;We investigate the existence of iso-pathlength (IPL) points in endoscopic geometry, with the goal of extending the concept of IPL points from cylindrical and half-infinite geometries into hollow cylindrical tissue relevant to endoscopy. In addition, we demonstrate the ability to extract the absorption properties of a tissue at this structure by the IPL and demonstrate it by &lt;i&gt;ex vivo&lt;/i&gt; experiment.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Approach: &lt;/strong&gt;The IPL point is a unique position in the full scattering profile, independent of tissue scattering and dependent only on the tissue absorption and geometry. We studied two directions in cylindrical endoscopic geometry: azimuthal and longitudinal. First, diffusion theory with extrapolated zero-boundary conditions was applied to predict IPL positions. These predictions were then tested using Monte Carlo simulations of photon distribution and validated experimentally using phantoms with cylindrical air holes measured by endoscopy. Finally, using the experimentally identified IPL point and applying the same procedure to a standard phantom, a hemoglobin-agar phantom, and chicken breast tissue, we were able to estimate the absorption coefficient of the chicken tissue.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Both azimuthal and longitudinal IPL points were identified. The experimental azimuthal IPL point was found at an angle of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;144&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;deg&lt;/mi&gt; &lt;mo&gt;±&lt;/mo&gt; &lt;mn&gt;3&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;deg&lt;/mi&gt;&lt;/mrow&gt; &lt;/math&gt; , whereas the longitudinal IPL point appeared at a distance of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;0.33&lt;/mn&gt; &lt;mo&gt;±&lt;/mo&gt; &lt;mn&gt;0.05&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;mi&gt;cm&lt;/mi&gt;&lt;/mrow&gt; &lt;/math&gt; from the laser spot center. These findings confirm the theoretical and simulation predictions. Moreover, from the &lt;i&gt;ex vivo&lt;/i&gt; experiment of a chicken breast, the IPL point enables us to calculate the absorption coefficient and get &lt;math&gt; &lt;mrow&gt; &lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mtext&gt;a&lt;/mtext&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;mo&gt;=&lt;/mo&gt; &lt;mn&gt;0.94&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mo&gt;-&lt;/mo&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/msup&gt; &lt;/mrow&gt; &lt;/math&gt; , within the range of &lt;math&gt;&lt;mrow&gt;&lt;mn&gt;0.2&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mo&gt;-&lt;/mo&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/msup&gt; &lt;mo&gt;≤&lt;/mo&gt; &lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mtext&gt;a&lt;/mtext&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;mo&gt;≤&lt;/mo&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mtext&gt;  &lt;/mtext&gt; &lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;/mrow&gt; &lt;mrow&gt;&lt;mo&gt;-&lt;/mo&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt; &lt;/msup&gt; &lt;/mrow&gt; &lt;/math&gt; .&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions: &lt;/strong&gt;The demonstration of IPL points in endoscopic geometry provides a ne","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"064305"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13005598/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147498756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Light sources and detectors: applications in nanoscale imaging, sensing, and actuation.","authors":"Sebastian Wachsmann-Hogiu, Monica Focşan, Dror Fixler","doi":"10.1117/1.JBO.31.6.064301","DOIUrl":"10.1117/1.JBO.31.6.064301","url":null,"abstract":"<p><p>The editorial provides an overview of the JBO Special Section Nanoscale Imaging, Sensing, and Actuation and reflects on the future of nanoscale biophotonics.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"064301"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13210876/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148042450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluorescence properties of collagen types I-V: a comprehensive study of spectral and lifetime characteristics.","authors":"Xuhui Liu, Alexandra C Adams, Xiangnan Zhou, Julien Bec, Laura Marcu","doi":"10.1117/1.JBO.31.6.065001","DOIUrl":"10.1117/1.JBO.31.6.065001","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Significance: &lt;/strong&gt;Collagen autofluorescence provides valuable intrinsic contrast for assessing tissue structure, composition, and pathology. However, a comprehensive understanding of the fluorescence properties across different collagen types remains limited. This knowledge gap may limit the development of advanced label-free fluorescence spectroscopy and imaging techniques for specific tissue characterization and diagnostic applications.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Aim: &lt;/strong&gt;This study aims to comprehensively characterize the fluorescence intensity excitation-emission matrices (I-EEMs) and time-resolved excitation-emission matrices (TR-EEMs) of collagen standards from types I, II, III, IV, and V obtained from various organ sources under both dry and hydrated conditions, to identify optimal excitation-emission parameters for each collagen type discrimination, and to establish a reference dataset that supports future research in label-free tissue characterization.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Approach: &lt;/strong&gt;We employed a time-resolved fluorescence spectroscopy system equipped with an optical parametric oscillator laser (excitation: 200 to 2000 nm, pulse width: 30 ps) as an excitation source to generate I-EEMs and TR-EEMs of human and bovine collagen types I-V. The fluorescence light was obtained by a multichannel plate photomultiplier tube through a monochromator (spectral range: 200 to 1000 nm). Measurements were conducted using collagen standards, under both dry and hydrated states. In addition, photobleaching effects were assessed to ensure the reliability and reproducibility of fluorescence data.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Each collagen type exhibited distinct I-EEM and TR-EEM signatures, with fluorescence lifetimes ranging from 2.5 ns (type III, bovine skin) to 5.3 ns (types II and V). Fibrillar collagens (types I and V) displayed broader I-EEMs, whereas basement membrane collagen (type IV) showed the narrowest spectral distribution. Organ-source-dependent variations were evident within the same collagen type. Type I collagen from human placenta exhibited an inverse lifetime-emission wavelength relationship compared with bovine sources. Hydration consistently red-shifted emission peaks into the 395 to 420 nm range and reduced fluorescence lifetimes across all collagen types (e.g., type I bovine Achilles tendon: 3.2 to 5.0 ns dry versus 3.0 to 4.5 ns hydrated). Despite excitation wavelength- and fluence-dependent photobleaching of fluorescence intensity, fluorescence lifetimes remained relatively stable, confirming the robustness of lifetime-based measurements.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions: &lt;/strong&gt;This study establishes a comprehensive reference dataset for the fluorescence properties of collagen types I-V and demonstrates the potential of combined I-EEMs and TR-EEMs analysis for tissue characterization. The results highlight species-, organ-, type-, and environment-specific optical fingerprints of similar collagens, which must be considered be","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"065001"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13309843/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148345514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DNA-hybridization on gold nanospheres: a dual-fluorescence investigation of surface loading and strand length effects.","authors":"Daria Stoia, Ana-Maria Craciun, Gabriela Chereches, Olga Soritau, Dana Maniu, Simion Astilean, Marc Lamy de la Chapelle, Monica Focsan","doi":"10.1117/1.JBO.31.6.064304","DOIUrl":"10.1117/1.JBO.31.6.064304","url":null,"abstract":"<p><strong>Significance: </strong>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.</p><p><strong>Aim: </strong>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.</p><p><strong>Approach: </strong>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.</p><p><strong>Results: </strong>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.</p><p><strong>Conclusions: </strong>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.</p>","PeriodicalId":15264,"journal":{"name":"Journal of Biomedical Optics","volume":"31 6","pages":"064304"},"PeriodicalIF":3.3,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12949946/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147344241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}