Journal of Biomedical Optics最新文献

Significance: Prompt care is essential for burn wound recovery. Spatial frequency domain imaging (SFDI) has previously shown promise in predicting healing outcomes across burn severity grades. This study builds on that by demonstrating calibrated reflectance images ( $R_d$ ) from SFDI can estimate thermally induced collagen denaturation depth (CDD), a histology-based metric of burn severity linked to healing outcomes. These findings may simplify future hardware design by clarifying contrast sources in SFDI.

Aim: To develop predictive models for: 1) Day-1 postburn CDD using SFDI $R_d$ and 2) Day-28 healing outcomes using day-1 CDD.

Approach: Using a previously reported graded-severity porcine burn model ( $n=4$ ) with eight contact durations (5 to 40 s), we collected SFDI and color images on days 0, 1, 3, 7, 14, 21, and 28. Histological analysis using Picrosirius red staining and polarization microscopy was performed on days 1, 7, 14, 21, and 28 to assess CDD. Healing outcomes were clinically evaluated on day 28. For analysis, a two-step regression framework was applied:Step 1: Multiple linear regression, where day-1 SFDI R_d is used to predict same-day CDD.Step 2: Logistic regression, where day-1 CDD is used to predict day-28 healing outcome.Together, these steps established a regression framework to predict day-1 CDD and day-28 healing outcomes using day-1 SFDI R_d.

Results: The linear model using $R_d$ across eight wavelengths (471-851 nm) and five spatial frequencies (0 to $0.2{\mathrm{mm}}^{-1}$ ) predicted CDD with a root mean square error of $105\mu m$ and adjusted $R^2$ of 0.71. The logistic model predicted healing outcomes with an ROC-AUC of 0.88, supporting CDD as an early indicator for burn severity assessed by healing potential.

Conclusions: This two-step framework enables early prediction (as early as day 1) of burn severity and healing using SFDI $R_d$ .

Significance: Intralipid^® is widely used as a tissue-mimicking phantom due to its optical similarity to biological tissues, i.e., high scattering and low absorption of light. Accurate modeling of the optical behavior of phantoms requires detailed knowledge of the properties of its scatterers.

Aim: We aim to determine the particle size distribution (PSD), concentration, and refractive index (RI) of particles in Intralipid^® 20%.

Approach: Cryo-electron microscopy, three different flow cytometers, and microfluidic resistive pulse sensing were used to measure the size distribution and concentration of particles in Intralipid^® 20%. To select the most accurate technique, the measured volume fraction of lipid particles was calculated and compared with the expected volume fraction (0.227). The measured size distribution and RI of soybean oil and Dulbecco's phosphate-buffered saline were used to calculate key optical parameters for the independent, single scattering regime. Calculations were performed with Mie theory across the 400- to 700-nm-wavelength range. Analytical expressions were then fitted to describe the wavelength dependence of each optical parameter.

Results: The PSD, obtained from measurements of more than 10 million particles, spanned from 67 nm to over 2000 nm, with concentration decreasing continuously as diameter increased. The particle volume fraction calculated from the PSD deviated by less than 2% from the expected value, confirming the accuracy of the measurements. Optical parameters calculated from the PSD and RIs, including the scattering coefficient, phase function, anisotropy factor, and reduced scattering coefficient, showed good agreement with values reported in the literature. These parameters were also well described by empirical fits ( $R>0.97$ ).

Conclusions: The accurate measurement of particle size, concentration, and RI of Intralipid^® 20% supports the use of Intralipid^® as a reliable tissue-mimicking phantom and calibration sample in optical studies.

Significance: Colorectal cancer (CRC) remains a major cause of cancer-related mortality, with incomplete resection contributing to recurrence and poor survival. Improving intraoperative margin detection is critical to enhance surgical precision and patient outcomes.

Aim: We aim to evaluate the tumor-targeting specificity of cetuximab-IRDye800CW (Cet-IRDye800CW), an epidermal growth factor receptor (EGFR)-specific near-infrared probe, for fluorescence-guided surgery in CRC models.

Approach: Cet-IRDye800CW and IgG-IRDye800CW controls were synthesized and tested in LS174T and SW948 xenografts as well as patient-derived xenografts (PDXs). Mice received $200\mu g$ of the probe intravenously and underwent daily fluorescence imaging for 10 days. Tumor-to-background ratio (TBR) and mean fluorescence intensity (MFI) were quantified, and EGFR expression was analyzed by Western blot, reverse transcription quantitative polymerase chain reaction, and immunohistochemistry.

Results: Cetuximab-IRDye800CW significantly enhanced tumor fluorescence compared with controls in all models ( $p<0.05$ ). TBR increased progressively and peaked on day 10 (LS174T: $25.6\pm 2.94$ ; SW948: $21.6\pm 1.71$ ), whereas background MFI declined, resulting in improved tumor contrast. Tumor-specific fluorescence was detectable from day 1 and intensified over time. Similar findings were observed in PDX models, consistent with high EGFR expression.

Conclusion: Cetuximab-IRDye800CW provides stable, tumor-specific, high-contrast fluorescence imaging in EGFR-high CRC models. These findings validate its molecular targeting capability and support its translational potential for fluorescence-guided CRC surgery.

Significance: High-throughput live-cell imaging is crucial for biological applications, including organ-on-a-chip (OoaC) platforms, yet conventional optical systems face a fundamental trade-off between magnification and field of view (FOV). This limitation hinders the ability to capture large-scale biological dynamics while maintaining single-cell resolution. We address this gap by introducing a scalable, high-resolution imaging solution specifically tailored for OoaC platforms and other microfluidic-based systems.

Aim: We aim to develop a dual-mode multichannel optical imaging system capable of achieving single-cell resolution over an extended FOV while maintaining a working distance suitable for integration with microfluidic devices.

Approach: The system employs microlens arrays in conjunction with laser-fabricated micro-aperture arrays to optically isolate imaging channels, minimizing crosstalk. Two operational modes are implemented: (1) rapid sampling mode for instantaneous, partial-area imaging and (2) full-field imaging mode, utilizing micro-scanning and computational stitching to generate a seamless high-resolution composite. The system's performance was validated through experimental imaging and theoretical modeling.

Results: The system achieves an FOV of $8.4\times 6m{m}^2$ at 4× magnification with single-cell resolution while preserving a 14 mm working distance. Experimental results closely align with theoretical expectations, confirming high-fidelity imaging without requiring a large sensor. Dual-mode functionality enables both rapid assessments and detailed, large-area imaging, enhancing its applicability in biological research.

Conclusions: This compact and scalable imaging system overcomes the traditional magnification-FOV trade-off, offering a powerful tool for drug screening, cellular dynamics studies, and microfluidic-based biological analyses. Its high-resolution capability and adaptability make it a valuable asset for advancing OoaC technologies.

Significance: Tumor tissues exhibit contrast with healthy tissue in circular degree of polarization (DOP) images via higher magnitude circular DOP values and increased helicity-flipping. This phenomenon may enable polarimetric tumor detection and surgical/procedural guidance applications.

Aim: Depolarization metrics have been shown to exhibit differential responses to healthy and cancer tissue, whereby tumor tissues tend to induce less depolarization; however, the understanding of this depolarization-based contrast remains limited. Therefore, we investigate depolarization signals from tumor tissue and non-tumor tissue.

Approach: Mice ( $n=3$ ) with human pancreatic ductal adenocarcinoma (PDAC) xenografts enable polarimetric comparison between tumor tissue and non-tumor tissues. Modified signed-value DOP equations aid in the interpretation of DOP images, which encode helicity-flipping and co-linearity as negative values, but still yield the same magnitudes as conventional DOP calculations.

Results: Linear DOP is greater in magnitude than circular DOP across both tissue types; however, circular DOP yields greater contrast between tumor and non-tumor tissues. Circular DOP values are higher in magnitude and more negative (i.e., more helicity-flipping) in tumors, whereas linear DOP values exhibit similar behavior; however, they are only slightly higher in magnitude and slightly more negative (i.e., more co-linearity) in tumors.

Conclusions: Circular DOP images yield useful contrast between human PDAC xenografts and surrounding healthy skin in live mice. Each tumor region exhibited higher magnitude circular DOP (and total DOP) values, as previously observed. We noted three indications of Rayleigh scattering in the tumor tissue: (1) linear DOP > circular DOP, (2) helicity-flipping > helicity-preservation, and (3) co-linear intensity > cross-linear intensity. Rayleigh scatterers have been found to be highly polarization preserving; thus, we posit that higher DOP in tumor tissues may arise from an increased presence of Rayleigh scatterers. Furthermore, circular DOP may yield greater contrast between tumor and non-tumor via its well-observed sensitivity to scatterer size. Further investigation is warranted to test these hypotheses.

Significance: Addressing the challenges of accurate dosimetry in photodynamic therapy has motivated some of the earliest work in tissue optics, which then enabled the broader development of biomedical optics. Inadequate use of dosimetry-informed treatments may contribute to heterogeneity in tumor response and variable clinical outcomes that need to be addressed.

Aim: This perspective paper seeks to understand the current status of photodynamic therapy (PDT) dosimetry in preclinical and clinical applications and identify opportunities for improvement. We also identify the "elephant in the room" of photodynamic immune stimulation that presents additional dosimetry challenges and opportunities.

Approach: The origins of PDT dosimetry based on biophysical metrics are considered, and major scientific and technological advances that have underpinned biological and clinical studies are highlighted. The question is posed: "Has the inadequacy of dosimetry for PDT been a major factor in this treatment not achieving widespread adoption into clinical practice, particularly in oncology?" It may be the case that, in the clinic and also frequently in preclinical (especially, in vivo) research, PDT dosimetry is often necessary, occasionally used, sometimes effective, and rarely sufficient. The rapid emergence of research on PDT immune stimulation poses existential challenges for PDT dosimetry as practiced to date, which is based on purely biophysical considerations, and possible approaches are suggested that incorporate immunological factors.

Results: Different clinical situations require different PDT dosimetry approaches, depending on medical complexity and technical dosimetry requirements.

Conclusions: This article is not a comprehensive review, but rather intended to recognize past advances and current limitations, and to stimulate discussion of future directions in PDT dosimetry. Inadequate dosimetry may be a potential impediment to PDT adoption and may have contributed to the failure of some previous and ongoing clinical trials.

Significance: Confocal endomicroscopic image stitching can expand the field of view and improve examination efficiency. However, due to interference from the rolling shutter effect, traditional stitching methods may produce misalignments, leading to structural distortion and artifacts. Suppressing the rolling shutter effect in confocal endomicroscopic images can effectively enhance stitching quality.

Aim: We propose a Dual-Path Gaussian U-Net (DGU-Net)-based framework for confocal endomicroscopic image stitching. The parallel dual-encoder paths of DGU-Net extract Gaussian features and conventional features at different resolutions, respectively, achieving more precise gland segmentation masks. Based on these masks, we filter stable frames and optimize feature matching to effectively suppress rolling shutter interference and improve stitching quality.

Approach: We annotated a segmentation dataset comprising 80 rat confocal laser endomicroscopy (CLE) images to train the segmentation network and validated the frame selection method's effectiveness in suppressing the rolling shutter effect on consecutively acquired rat CLE video sequences. The stitching results generated from the filtered stable image sequences were compared with conventional methods.

Results: Experimental results demonstrate that DGU-Net achieves superior performance with a Dice score of 85.17 on CLE datasets, significantly outperforming existing segmentation networks. Compared with Auto-Stitching, our method improves regional consistency across the panoramic image by eliminating artifacts caused by mismatches while delivering enhanced stitching accuracy and image quality.

Conclusions: The proposed method effectively accomplishes confocal image stitching tasks, significantly enhancing endomicroscopic examination efficiency and contributing to improved diagnostic outcomes.

Significance: Current optical health-sensing devices rely on simplified homogeneous tissue models or semi-empirical ratiometric methods, which inadequately address anatomical complexity and inter-individual optical variability. This introduces systematic errors in light propagation modeling, compromising measurement accuracy and clinical robustness, necessitating organ-specific optical models for reliable physiological sensing.

Aim: To develop a standard optical digital wrist (DW) model by integrating magnetic resonance imaging (MRI) and diffuse optical imaging (DOI), enabling anatomically accurate and optically realistic modeling of wrist tissues for improved precision in wearable optical health monitoring applications.

Approach: The multimodal MRI-DOI framework was implemented, comprising three key components: (1) statistical integration of high-resolution MRI datasets generated a population-averaged anatomical DW template; (2) region-based time-domain diffuse optical tomography (TD-DOT) with MRI-derived anatomical priors, extracted depth-resolved optical properties of subsurface tissues; (3) spatial frequency domain imaging (SFDI) supplemented high-resolution optical properties of superficial skin layers.

Results: Simulation experiments demonstrated the high accuracy of region-based TD-DOT reconstruction, with mean errors below 8.57% ( ${\mu }_a$ ) and 9.63% ( ${\mu }_s^{\text{'}}$ ), quantitatively supporting the precision of the proposed approach. Phantom experiments with wrist-mimicking phantoms yielded mean reconstruction errors of 10.52% ( ${\mu }_a$ ) and 13.23% ( ${\mu }_s^{\text{'}}$ ) for TD-DOT, and the SFDI top-layer quantification yielded lower errors of 4.48% ( ${\mu }_a$ ) and 8.69% ( ${\mu }_s^{\text{'}}$ ), validating the performance of the TD-DOT system and the SFDI system. Furthermore, in vivo optical property measurements showed strong agreement with literature values, further validating the reliability and practicality of the methodology.

Conclusions: We establish a standard DW template and develop an in vivo optical structure acquisition methodology, transitioning biosensing models from homogeneous approximations to anatomically layered models. The approach can enhance the customization, dynamic adaptability, and clinical validity of biosensing technologies.

Significance: Estimating biomechanical properties of the in vivo crystalline lens remains a challenge and is a barrier to evaluating novel lens softening therapies. There is a need to estimate quantitative biomechanical properties of the human anterior and mid segments of the eye in vivo for conditions such as presbyopia.

Aim: We aim to develop a multimodal elastography device that enables high-performance sequential 3D imaging with both Brillouin microscopy and optical coherence elastography (OCE).

Approach: We combined Brillouin spectroscopy and OCE on a modified slit lamp platform for human measurements. The multimodal system was first characterized and then tested on both a porcine eye and a human subject.

Results: Both OCE and Brillouin microscopy were characterized at peak operating performance for clinical imaging. Successful measurements of an in situ porcine lens and a human in vivo lens are reported.

Conclusion: We demonstrated the first successful multimodal OCE and Brillouin microscopy measurement in a human subject. This instrument offers the potential to characterize the biomechanical status of presbyopia with age.