Rationale Airway smooth muscle (ASM) remodelling is a central feature of asthma pathology but cannot currently be measured in vivo with adequate coverage, limiting the development of targeted therapies. The objective of the present study was to trial bronchoscopic polarisation-sensitive optical coherence tomography (PS-OCT) to assess ASM remodelling and its distribution in vivo throughout the lungs in individuals with and without asthma. Methods Participants with (n=7) and without (n=13) doctor-diagnosed asthma undergoing bronchoscopy were recruited to obtain PS-OCT imaging data during the procedure. ASM area in large and small airways was measured and normalised for airway size (lumen perimeter). ASM remodelling was defined as ASM mass (ASM area/perimeter 2 ) >1.96 sd above a histological reference control group. Measurements and main results PS-OCT quantified ASM mass was greater in participants with asthma (median 0.0072, Q1–Q3 0.0064–0.0089) compared with the control group (0.0039, 0.0035–0.0049), (p=0.012). ASM remodelling was also more prevalent in the asthma group (44% of airways examined, 24–53%) than in the control group (0%, 0–4%) (p=0.007). ASM mass was heterogeneously distributed within airways, lungs and the sample population. Phenotypes of ASM remodelling (based on location in small or large airways) were apparent in the asthma group, compared with the control group where participants were all classified as non-remodelled. Conclusions PS-OCT is a minimally invasive, accurate, efficient and effective modality to measure ASM mass. Visualising and quantifying ASM in patients with asthma provides an opportunity to make ASM remodelling a treatable trait and may facilitate the development of novel therapeutics for the treatment of asthma.

Optical coherence tomography (OCT) enables visualization and quantification of the cutaneous microvasculature, yet no study has compared responses to distinct forms of heating in humans. We hypothesized that local skin heating (LH) would evoke larger responses in microvascular diameter, velocity, flow and density than passive whole-body heating (PH) or heated exercise (HE), and that HE responses would exceed PH. Twelve healthy young adults completed four interventions: baseline (33°C; BL), LH, PH (seated) and HE (ergometer cycling) in a climatic chamber (50 min, 40°C, 50% relative humidity). OCT was used to quantify microvascular variables immediately after each intervention. Microvascular responses differed across conditions (P < 0.001). LH induced the largest responses in all OCT indices (all P < 0.001): diameter (67 µm), velocity (195 µm s-1), flow (687 picolitres s-1) and density (56.0%), compared with BL (42 µm, 106 µm s-1,154 picolitres s-1 and 26.6%, respectively), PH (45 µm, 99 µm s-1, 165 picolitres s-1 and 34.4%, respectively) and HE (49 µm, 105 µm s-1, 208 picolitres s-1 and 34.5%, respectively). Although the diameter response was higher after HE (P = 0.046), no differences were documented for PH and HE relative to 33°C BL for other OCT measures (all P > 0.05). Comparable responses were observed between PH and HE across all variables (all P > 0.05). Local heating elicited substantially greater increases in all OCT-derived microvascular metrics compared with PH and HE. Although both PH and HE activate the cutaneous microvasculature, neither stimulus approaches the magnitude of response achieved with local heating. These findings demonstrate that OCT provides quantifiable insights into the distinct ways in which the skin microvasculature responds to different heat exposures.

Objective: This study presents a fiber-optic needle probe to detect malignant tissue prior to removal from the brain. Methods: The probe comprises separate multimode optical fibers for excitation and detection of fluorescence. A higher numerical aperture was used in the collection fiber to provide a larger acceptance angle for fluorescence emission light. Using a dual-bore ferrule to simplify fabrication and ensure optical alignment, the fibers were angle-polished and silver-coated using Tollens' reagent to produce a side-facing needle probe, which was integrated into a 16-gauge needle (outer diameter 1.65 mm). Sensitivity of the probe was assessed using a tissue-mimicking fluorescent brain phantom, with optical scattering, absorption and fluorescence properties comparable to brain tissue. To demonstrate feasibility in a clinical environment, experiments were performed on fresh brain tissue obtained from patients undergoing surgical resection for glioblastoma. Results: When the tissue-mimicking fluorescent phantom was obscured by a thin layer of non-fluorescent material, sensitivity was found to be comparable to a free-space fluorescence surgical microscope. Fluorescence was detectable through an obscuring thickness of 0.4 mm of low absorption, non-fluorescent material, and 0.3 mm of high absorption, non-fluorescent material. When evaluated on fresh human brain tissue, the probe detected the characteristic fluorescence signal of protoporphyrin IX, with a stronger signal detected in tissue with an increased density of malignant cells. Conclusion: These findings show feasibility of using a dual-fiber fluorescence needle probe to identify malignant brain tissue. Significance: This work contributes to advancing the use of optical methods for surgical guidance.

Murine models are essential for cardiovascular translational research for developing new therapies to reduce the risk of heart attacks. However, assessment of murine atherosclerotic plaques by traditional histological methods fails to capture the entirety of plaque development across the length of a blood vessel over time. Here, the authors have developed and validated the first longitudinal molecular and microstructural intravascular imaging approach to study murine atherosclerosis. This approach combines a unique murine surgical model and a miniaturized multimodal intravascular imaging device with optical coherence tomography (OCT) and fluorescence imaging capabilities able to detect infused indocyanine green (ICG), a marker of macrophages. This multimodal device could identify important plaque features and their changes over multiple time points across the length of vessels containing atherosclerosis in high-cholesterol diet-fed apolipoprotein E knockout mice. It is found that OCT-derived plaque lipid measures correlate closely with histologically assessed plaque lipid (Oil Red O) in co-registered sections. Plaque ICG fluorescence also correlates with CD68+ macrophages, measured by immunofluorescence in co-registered sections. This novel approach maximizes data acquisition of plaque evolution dynamics within individual vessels. It represents a paradigm shift over the current need to compare disparate atherosclerosis plaques histologically across multiple timepoints and in multiple animals.

Fluorescence‐guided surgery is an increasingly common technique in neurosurgery, where 5‐aminolevulinic acid induces fluorescence in high‐grade gliomas, aiding in tumor resection and improving surgical outcomes. Reliable detection of malignant tissue fluorescence depends critically upon the clinical imaging system. Factors such as nonuniform excitation light and the presence of non‐fluorescent tissue layers over the tumor can reduce sensitivity. Characterizing imaging system performance in these scenarios is important to ensure clinical reliability. However, there are a lack of practical calibration standards available for this purpose. This study proposes a novel calibration standard to assist in characterizing a clinical fluorescence imaging system. The calibration standard uses multiple glass‐based phantoms fabricated to mimic the optical properties of tissue. Silver nanoparticles mimic the absorption spectrum of hemoglobin; small air‐filled cavities and crystals in the glass generate controlled levels of scattering; and samarium ions provide fluorescence to mimic malignant tissue. Single‐layer and bilayer glass phantoms enable assessment of fluorescence across the field of view, including characterization of the sensitivity to detect fluorescence through layers of non‐fluorescent glass, mimicking non‐malignant tissue. The glass‐based phantoms demonstrate excellent photo‐stability, homogeneity, and long‐term shelf‐life. Utility of this calibration standard is demonstrated with a commercial surgical fluorescence imaging system.

This pilot study characterizes the spectrum of atherosclerotic coronary artery pathologies in a porcine model of streptozotocin-induced diabetes, with a particular focus on the natural progression of atherosclerotic plaques. Four pigs (designated P01 - P04) were subjected to an identical streptozotocin regimen to induce diabetes and studied using blood biochemistry, lipid profiling, coronary angiography, optical coherence tomography, and histological analysis of the coronary arteries to assess for the development of coronary atherosclerosis. All animals developed sustained hyperglycemia and dyslipidemia, with total cholesterol levels ranging from 14.9 to 36.7 mmol/L and low-density lipoprotein concentrations reaching up to 32 mmol/L. Notably, the study captured the full pathological continuum: from nearly no coronary abnormality in P01 and early atheromatous plaque formation in P02, to advanced atherosclerosis in P03, and finally, in P04, severe fibrofatty atheroma, and myocardial infarction. Unlike conventional animal myocardial infarction models that rely on interventional triggers, the infarction in P04 occurred spontaneously, demonstrating the natural cascade of plaque development and acute plaque rupture with thrombosis. These findings demonstrate the feasibility of using streptozotocin-treated pigs to model key stages of diabetic coronary artery disease.

Brillouin spectroscopy is a powerful technique for non-invasive micromechanical analysis of biological materials such as tissues and cells. Conventional bulk-optical Brillouin spectroscopy systems, however, face challenges in translation to endoscopic applications due to strong parasitic background signals using single optical fibers. To overcome this issue, dual fiber approaches have been proposed, but they suffer from poor overlap of excitation and collection beam paths. In this work, we present a dual fiber-integrated probe with a tip diameter below 300 μm. Using tailored freeform 3D-printed micro-optics, we achieve a precise overlap of the foci to map mechanical properties with a resolution below 10 μm in lateral and 45 μm in axial direction. We detail the probe's design, fabrication, and optical simulations and present experimental results demonstrating high-resolution Brillouin measurements from polymer and protein solution samples. Our findings indicate that this dual fiber probe could significantly advance fiber-integrated Brillouin spectroscopy, with promising applications in materials science and biomedical diagnostics.

A fundamental challenge in endoscopy is how to fabricate a small fiber-optic probe that can achieve comparable function to devices with large, complicated optics. To achieve high resolution over an extended depth of focus (DOF), the application of needle-like beams has been proposed. However, existing methods for miniaturized needle-beam designs fail to adequately correct astigmatism and other monochromatic aberrations, limiting the resolution of at least one axis. Here, we describe an approach to realize freeform beam-shaping endoscopic probes via two-photon polymerization three-dimensional (3D) printing. We present a design achieving <8 mu m lateral resolution with a DOF of similar to 800 mu m. The probe has a diameter of <260 mu m (without the torque coil and catheters) and is fabricated using a single printing step directly on the optical fiber. The probe was successfully utilized for intravascular imaging in living diabetic swine at multiple time points, as well as human atherosclerotic plaques ex vivo. To the best of our knowledge, this is the first report of a 3D-printed micro-optic for in vivo imaging of the coronary arteries. These results are a substantial step to enable the clinical adoption of both 3D-printed micro-optics and beam-tailoring devices.

Background In‐stent neoatherosclerosis is a complication of percutaneous coronary intervention with stenting. Although similar to de novo atherosclerosis, it develops rapidly within 1 to 5 years rather than over a lifetime. No preclinical small animal model exists to fully elucidate neoatherosclerosis biology or evaluate targeted therapies. This study aimed to establish and validate a novel murine model of in‐stent neoatherosclerosis. Methods Murine stainless‐steel stents (2.5×0.7 mm) were deployed into donor descending aortas of atherosclerosis‐prone (Apo)e−/− (apolipoprotein E) mice, then carotid‐interposition grafted into Apoe−/− recipients. Mice (n=6–8/group) received chow or a high‐cholesterol diet for 7 or 28 days post surgery. A novel miniaturized probe was used to image the stented vessel of a mouse fed high‐cholesterol diet for 28 days. Neointimas in stented vessels were histologically and flow cytometrically assessed. Results Bimodal intravascular imaging combined optical coherence tomography (plaque burden) with fluorescence detection of indocyanine green (plaque instability) to visualize in‐stent neoatherosclerosis along the entire stented segment. Histological analyses revealed that stented vessels from mice fed high‐cholesterol diet had neointimas with prominent lipid cores and abundant CD68+ macrophages, reminiscent of human neoatherosclerosis. Mice fed chow post stenting had distinctly different neointimas that were smooth muscle cell rich, resembling neointimal hyperplasia. Flow cytometry revealed a higher content of monocytes/macrophages in stented aortas from mice fed high‐cholesterol diet than in nonstented aortas. Conclusions We have developed and validated the first murine model that replicates the unique characteristics of human in‐stent neoatherosclerosis. This has implications for exploring the mechanisms that promote neoatherosclerosis and testing targeted new therapies.

We investigated the effect of exercising in hot conditions on cerebral blood flow and systolic left ventricular (LV) function in males and females, to explore sex differences. The experimental condition consisted of walking on a treadmill at 5 km/h and 2% incline, inside a heat chamber at 40°C (50% relative humidity), for 90 min. Middle cerebral artery velocity (MCAv) and LV global longitudinal strain (GLS) were assessed at baseline and every 30 min by means of transcranial Doppler and speckle-tracking echocardiography, respectively. Thirty-eight individuals (19♀, 19♂) were recruited. Both males and females exhibited non-significant increases in MCAv from baseline at 30 min (♂ Δ = 2.55 ± 2.15, P > 0.05; ♀ Δ = 0.54 ± 2.53 cm s-1, P > 0.05; interaction P = 0.63). This was followed by a significant decrease at 60 (♂ Δ = -4.0 ± 1.23 P = 0.04; ♀ Δ = -5.41 ± 1.56 cm s-1, P = 0.03) and 90 min (♂ Δ = -6.08 ± 1.37 P < 0.01; ♀ Δ = -7.39 ± 1.40 cm s-1, P < 0.01). In males, there was a significant decrease in GLS from baseline at 60 (Δ = 2.17 ± 0.66%, P = 0.049) and 90 (Δ = 2.60 ± 0.77%, P = 0.036) min; no significant changes were observed in females. The correlation between changes in GLS and MCAv was higher for males (r = -0.631, P = 0.069) than for females (r = 0.252, P = 0.513). Males and females exhibited similar patterns of change in MCAv in response to a heat and exercise challenge. An exercise-related reduction in GLS, and a higher correlation between changes in GLS and MCAv, were more apparent in males. These data suggest that sex differences may exist in the relationships between cerebrovascular and cardiac responses to exercise in the heat in humans.

We present a novel, robust, miniaturized 3D printed encapsulated probe for endoscopic optical coherence tomography, featuring improved mechanical stability, high-resolution, large-depth-of-focus in vivo imaging, demonstrated in a pig's intrathecal space, offering potential to advance diagnostics. (c) 2025 The Author(s)

Vulnerable atherosclerotic plaques, which are prone to rupture, can result in life-threatening events, such as strokes and heart attacks. These plaques are distinguished by features including a large necrotic core, macrophage infiltration, spotty calcification, intraplaque hemorrhage, and a thin fibrous cap. While current intravascular optical coherence tomography (OCT) is capable of visualizing structural characteristics of plaques, such as the fibrous cap thickness, it has limitations in reliably identifying vulnerable plaques. Previous studies have demonstrated that intraplaque hemorrhage and oxidized lipids in the necrotic core and of vulnerable plaques generate autofluorescence when excited at 633 nm. Our team has designed and developed a 3D-printed micro-lens probe that utilizes a photoresist, IP-Visio, with low background fluorescence. This photoresist is ideal for autofluorescence detection of vulnerable plaques in the visible range, without the need for externally injected fluorophores. The micro-lens on the tip of a double clad fiber has two apertures that address the threefold purpose of our probe: OCT imaging, fluorescence excitation, and fluorescence collection by a combination of focal and afocal optical design. With this dual aperture design, we have achieved in capturing the weak autofluorescence signals and high-resolution OCT images from ex vivo human carotid plaques, using the IP-Visio micro-lens intravascular probe. We validated these imaging results with histology and a commercial benchtop fluorescence imaging system. This work paves the way for the wider application of 3D-printed micro-lenses for multimodal OCT and fluorescence imaging in the visible and near-infrared range, especially with intravascular or endoscopic devices.

Objective: In-stent neoatherosclerosis is a phenomenon of percutaneous coronary intervention with stenting. Whilst similar to de novo atherosclerosis, it develops rapidly over 1-5 years rather than over a lifetime. No preclinical small animal models exist that allow full elucidation of neoatherosclerosis biology and future treatments. The aim of this study was to establish and validate a novel murine model of in-stent neoatherosclerosis. Approach and Results: Murine stainless-steel stents (2.5 x 0.7 mm) were deployed into donor descending aortas of atherosclerosis-prone apolipoprotein (Apo)e-/- mice, then carotid-interposition grafted into Apoe-/- recipients. Mice (n=6-8/group) received chow or a high cholesterol diet (HCD) for 7- or 28-days post-surgery. Multimodal intravascular imaging, simultaneously combining optical coherence tomography (OCT, plaque burden) and fluorescence for indocyanine green (ICG, plaque instability), visualized in-stent neoatherosclerosis across the entire length of the stented site. Histological analyses revealed that stented vessels from mice fed HCD had neointimas with prominent lipid cores and an elevated CD68+ macrophage content, similar to human neoatherosclerosis. Mice fed chow post-stenting had distinctly different neointimas that were smooth muscle cell rich, resembling neointimal hyperplasia. Consistent with this, flow cytometry revealed a higher content of monocytes/macrophages and dendritic cells in stented aortas from mice fed HCD than in non-stented aortas. Conclusion: We have developed and validated the first murine model that replicates the unique characteristics of human in-stent neoatherosclerosis. This project has implications for exploring the mechanisms that promote neoatherosclerosis and testing targeted new therapies. ### Competing Interest Statement The authors have declared no competing interest.

Due to a lack of technical capacity to directly visualise and quantify microvessels in the skin, little is known regarding regional and/or sex differences. We compared diameter, velocity, flow and density at four regional sites using a novel optical coherence tomography (OCT) approach. OCT and laser Doppler flowmetry (LDF) were performed on the back, forearm, foot and thigh in 30 healthy adults (15♂ 15♀; 31 ± 6years) at rest (33°C) and after 30 min of local heating (LH; 44°C). At baseline, larger diameter, speed, flow, density and LDF flux were recorded on the back than other sites ( P < 0.017). In response to LH, the smallest changes in OCT‐derived diameter were observed on the back (Δ12 ± 6 µm) and foot (Δ13 ± 6 µm vs. forearm 17 ± 5 µm; thigh Δ18 ± 5 µm, all P < 0.005 vs. foot, back). The back exhibited the smallest change in density (back Δ19 ± 7%, forearm Δ24 ± 5%, thigh Δ26 ± 6%, foot Δ26 ± 8%, P < 0.02 vs. back) whilst the foot exhibited the smallest changes in speed (foot Δ27 ± 14, back Δ58 ± 22, forearm Δ47 ± 17, thigh Δ48 ± 11 µm/s, P < 0.001 vs. foot) and flow (Δ135 ± 60, back Δ204 ± 76, forearm Δ212 ± 60, thigh Δ247 ± 51 µL/s, P < 0.001 vs. foot). When sites were grouped, males had larger baseline diameters (♂ 45 ± 3 vs. ♀ 42 ± 3 µm, P = 0.019) and flows (♂ 109 ± 20 vs. ♀ 93 ± 17 µL/s, P = 0.025) whilst females exhibited larger LH‐induced changes in speed in the thigh (♀ Δ53 ± 10 vs. ♂ Δ43 ± 10 µm/s, P = 0.014) and density in the forearm (♀ Δ26 ± 4 vs. ♂ Δ21% ± 6%, P = 0.006). Regional differences exist in OCT‐derived cutaneous microvascular diameter, speed, flow and density at baseline and in response to LH. Males showed larger cutaneous diameter and flow at baseline, while females exhibited larger changes in the speed and density outcomes in response to local heating.

Miniaturized fiber-optic fluorescence endoscopes play a crucial role in medical diagnostics and research, but system-induced autofluorescence remains a significant challenge, particularly in single-fiber setups. While recent advances, such as double-clad fiber (DCF) and DCF couplers, have reduced background noise, complete elimination remains challenging. Research on the various sources of system-induced autofluorescence and the methods to remove them is scarce. This study seeks to fulfill this need by proposing practical approaches to the removal of system-induced autofluorescence. This study presents the methods to suppress static background noise and proposes an algorithm based on least-squares linear spectral unmixing to remove variable system-induced autofluorescence artifacts. The algorithm was evaluated on a single-fiber DCF intravascular imaging system, with phantom and rodent in vivo experiments confirming its effectiveness. Results showed accurate differentiation between true sample fluorescence and system-induced autofluorescence artifacts through the validation with optical coherence tomography images and histology results, further verified by statistical analysis. Unlike simple background subtraction, the method addresses both background noise and incidental artifacts, providing robust performance under varying conditions. Our method may be adapted to various fiber-based endoscopy setups and be compatible with different fluorescent agents and autofluorescence imaging, broadening its applicability in biomedical imaging.

Quantifying airway smooth muscle (ASM) in patients with asthma raises the possibility of improved and personalized disease management. Endobronchial polarization-sensitive optical coherence tomography (PS-OCT) is a promising quantitative imaging approach that is in the early stages of clinical translation. To date, only animal tissues have been used to assess the accuracy of PS-OCT to quantify absolute (rather than relative) ASM in cross sections with directly matched histological cross sections as validation. We report the use of whole fresh human and pig airways to perform a detailed side-by-side qualitative and quantitative validation of PS-OCT against gold-standard histology. We matched and quantified 120 sections from five human and seven pig (small and large) airways and linked PS-OCT signatures of ASM to the tissue structural appearance in histology. Notably, we found that human cartilage perichondrium can share with ASM the properties of birefringence and circumferential alignment of fibers, making it a significant confounder for ASM detection. Measurements not corrected for perichondrium overestimated ASM content several-fold (P < 0.001, paired t test). After careful exclusion of perichondrium, we found a strong positive correlation (r = 0.96, P < 0.00001) of ASM area measured by PS-OCT and histology, supporting the method's application in human subjects. Matching human histology further indicated that PS-OCT allows conclusions on the intralayer composition and in turn potential contractile capacity of ASM bands. Together these results form a reliable basis for future clinical studies.NEW & NOTEWORTHY Polarization-sensitive optical coherence tomography (PS-OCT) may facilitate in vivo measurement of airway smooth muscle (ASM). We present a quantitative validation correlating absolute ASM area from PS-OCT to directly matched histological cross sections using human tissue. A major confounder for ASM quantification was observed and resolved: fibrous perichondrium surrounding hyaline cartilage in human airways presents a PS-OCT signature similar to ASM for birefringence and optic axis orientation. Findings impact the development of automated methods for ASM segmentation.

The fabrication of a stable, reproducible optical imaging phantom is critical to the assessment and optimization of optical imaging systems. We demonstrate the use of an alternative material, glass, for the development of tissue-mimicking phantoms. The glass matrix was doped with nickel ions to approximate the absorption of hemoglobin. Scattering levels representative of human tissue were induced in the glass matrix through controlled crystallization at elevated temperatures. We show that this type of glass is a viable material for creating tissue-mimicking optical phantoms by providing controlled levels of scattering and absorption with excellent optical homogeneity, long-term stability and reproducibility.

Single-fiber-based sensing and imaging probes enable the co-located and simultaneous observation and measurement (i.e., ‘sense’ and ‘see’) of intricate biological processes within deep anatomical structures. This innovation opens new opportunities for investigating complex physiological phenomena and potentially allows more accurate diagnosis and monitoring of disease. This prospective review starts with presenting recent studies of single-fiber-based probes for concurrent and co-located fluorescence-based sensing and imaging. Notwithstanding the successful initial demonstration of integrated sensing and imaging within single-fiber-based miniaturized devices, the realization of these devices with enhanced sensing sensitivity and imaging resolution poses notable challenges. These challenges, in turn, present opportunities for future research, including the design and fabrication of complex lens systems and fiber architectures, the integration of novel materials and other sensing and imaging techniques.

The oxygen saturation level in the blood (SaO2) is crucial for health, particularly in relation to sleep-related breathing disorders. However, continuous monitoring of SaO2 is time-consuming and highly variable depending on patients’ conditions. Recently, optical coherence tomography angiography (OCTA) has shown promising development in rapidly and effectively screening eye-related lesions, offering the potential for diagnosing sleep-related disorders. To bridge this gap, our paper presents three key contributions. Firstly, we propose JointViT, a novel model based on the Vision Transformer architecture, incorporating a joint loss function for supervision. Secondly, we introduce a balancing augmentation technique during data preprocessing to improve the model’s performance, particularly on the long-tail distribution within the OCTA dataset. Lastly, through comprehensive experiments on the OCTA dataset, our proposed method significantly outperforms other state-of-the-art methods, achieving improvements of up to 12.28% in overall accuracy. This advancement lays the groundwork for the future utilization of OCTA in diagnosing sleep-related disorders.

Skin microvasculature is essential for cardiovascular health and thermoregulation in humans, yet its imaging and analysis pose significant challenges. Established methods, such as speckle decor relation applied to optical coherence tomography (OCT) B-scans for OCT-angiography (OCTA), often require a high number of B-scans, leading to long acquisition times that are prone to motion artifacts. In our study, we propose a novel approach integrating a deep learning algorithm within our OCTA processing. By integrating a convolutional neural network with a squeeze-and-excitation block, we address these challenges in microvascular imaging. Our method enhances accuracy and reduces measurement time by efficiently utilizing local information. The Squeeze-and-Excitation block further improves stability and accuracy by dynamically recalibrating features, highlighting the advantages of deep learning in this domain.