Journal of Biomedical Optics最新文献

Significance: Given the rapidly ageing global population and the projected rise in dementia cases, research into Alzheimer's disease (AD) has become an urgent scientific and medical priority. Continued investigation into the molecular mechanisms and early detection of AD is therefore essential to mitigate its growing personal and societal impact. Most current AD therapies in advanced phases of development target amyloid $\beta$ -peptide ( $A\beta$ ) production, aggregation, or accumulation.

Aim: Mueller Matrix Polarimetry (MMP) has evolved into a prominent research subject, with a focus on identifying microstructural changes in biotissues. This is done by investigating light properties, which is especially useful in the early detection of brain cell degradation, among others. We set up and employed experimental MMP at three illuminating laser wavelengths (i.e., 445, 532, and 632 nm).

Approach: We investigated the application of MMP to mouse brain tissue containing $A\beta$ plaques. The investigated samples on glass slides consisted of paraffin-embedded brain and paraffin-embedded tissue slices. The tissues were taken at various stages of ageing, i.e., 75, 100, 125, 150, 175, 200, and 225 days. Paraffin tissue blocks were used as an additional sample set for comparison.

Results: We performed a comparative analysis based on the Mueller matrix elements for each age category and highlighted the importance of certain elements, e.g., $m_{44}$ , for further analysis. We also compared the trends of decomposition parameters and could correlate them with the ageing. Contrary to previous studies, we also report on retardation, diattenuation, and polarizance changes for later AD changes.

Conclusions: From the higher-order statistics, we concluded that the mean and standard deviation remained constant across the ages. Skewness values were positive and increased as the age progressed, whereas kurtosis decreased with age. The large available dataset opens the possibility of implementing machine learning methods to assist clinical diagnosis in the future.

Significance: Short-wave infrared (SWIR) light has recently gained popularity in tissue spectroscopy and imaging applications for a wide range of biomedical applications, primarily due to advancements in hardware (e.g., cameras).

Aim: We aim to provide a detailed review of SWIR-based biomedical optics studies from the past decade, during which there has been a proliferation of SWIR-based tissue-optics studies.

Approach: We report literature occurring after the publication of our previous (2015) review of this space, describing next-generation SWIR-based techniques that hold significant promise for enhanced in vivo tissue characterization and clinical translation.

Results: Interest from the biophotonics field in SWIR technology is typically attributable to (1) the capability of SWIR light to provide greater sensitivity to chromophores such as water and lipids, with absorption peaks not as prominent in the visible-to-near-infrared (VIS-NIR) spectral region, and (2) the potential for SWIR photons to penetrate through superficial tissue layers due to lower scattering in the SWIR than in the VIS-NIR, as well as substantially reduced attenuation from hemoglobin and melanin.

Conclusion: This review of emerging SWIR biophotonic technologies illustrates the rapid growth in the use of SWIR light for in vivo tissue spectroscopy and imaging.

Significance: Integrating ultrasound (US) with multiphoton microscopy (MPM) enables comprehensive tissue characterization by combining contrast mechanisms across spatial scales. However, prior implementations suffer from degraded US image quality at the glass optical window arising from off-axis acoustic noise (clutter).

Aim: We aimed to reduce clutter near the optical window without compromising the MPM image quality using different optical window materials combined with different ultrasound beamforming techniques.

Approach: Clutter in B-mode images was measured for glass and several optically clear polymer films using physically or synthetically focused US beamforming with varied focal configurations ( $f/\#$ ) and with acoustic coupling beneath the window. MPM image quality with the material optical windows was assessed via second harmonic generation (SHG) point spread function (PSF) measurements. We evaluated SHG-based automated collagen fiber alignment quantification with the optical windows in rat tail tendon samples and collagen gels.

Results: Candidate materials included polymethyl pentene (PMP), cyclin olefin copolymer (COC), polycarbonate (PC), polyethylene terephthalate, polymethyl methacrylate, and an Ibidi^® polymer coverslip. At receive $f/\#\ge 2$ , COC and Ibidi^® reduced acoustic clutter by $>40\%$ compared with glass with physical focusing regardless of physically or synthetically focused beams or acoustic coupling. Collagen gel imaged with COC and high $f/\#$ showed clearer ultrasound speckle close to the optical windows. COC, Ibidi^®, PMP, and PC showed minimal SHG PSF differences from glass and collagen alignment errors $<5\%$ relative to glass.

Conclusions: COC or Ibidi^® optical windows significantly improve US image quality without compromising MPM quality. These enhancements support future multimodal studies with high-quality, co-registered US and MPM data.

[This corrects the article DOI: 10.1117/1.JBO.30.3.036007.].

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.