Optical coherence tomography (OCT) is widely used in dermatology, but conventional OCT-based angiography and elastography are performed independently, limiting real-time assessment of vascular and mechanical properties within the same region. As microvascular and biomechanical changes often occur simultaneously during inflammation, fibrosis, and tumor progression, separate measurements may introduce spatial mismatch and reduce diagnostic accuracy. Here, we present a multifunctional OCT approach that enables the simultaneous acquisition of structural and elasticity information within a single scan, utilizing a streamlined sample arm and a customized protocol. Vascular networks are extracted using an intensity-based Doppler variance algorithm, while elasticity maps are generated through phase-based strain analysis. The method was validated using a bilayer tissue-mimicking phantom and tumor-bearing mouse skin, demonstrating simultaneous mapping of vascular and elastic features within the same region. This compact system offers an efficient tool for non-invasive skin assessment, with strong potential for enhancing diagnostic accuracy and functional evaluation.

The elasticity of luminal tissues is closely associated with disease progression and functional status. Endoscopic optical coherence elastography (OCE) has emerged as a promising technique for assessing the mechanical properties of luminal tissues. However, previous endoscopic OCE approaches typically measure elasticity along only a single direction-either laterally or in depth-thereby potentially leading to an inaccurate estimation of anisotropic tissue mechanics. In this study, we propose a forward-scanning endoscopic OCE method that enables quantitative measurement of tissue elasticity in both the lateral and depth directions, allowing direct characterization of anisotropic mechanical properties in luminal tissues. An air-pulse excitation was applied to generate Rayleigh waves and longitudinal shear waves in agar phantoms and ex vivo gastric tissues. Elastic wave propagation was detected using phase-resolved Doppler optical coherence tomography. Experimental results demonstrate that the proposed method can quantitatively assess anisotropic elasticity with a forward-viewing configuration, highlighting its potential for clinical diagnosis and biomechanical characterization of luminal tissues.

Optical coherence tomography (OCT) faces a fundamental trade-off between transverse resolution and depth of focus (DOF). While diffractive optical elements (DOEs) have been utilized to extend the DOF, existing designs are typically customized for specific objective lenses, limiting their versatility. We propose an extended-DOF OCT system utilizing a configuration-independent DOE. By modulating the incident wavefront to evenly distribute beam energy along the optical axis, the DOE extends the DOF without requiring redesign when applied to different optical setups. Simulations and experiments demonstrate that the integration of a single DOE across different sample arms more than doubles the effective DOF while maintaining diffraction-limited lateral resolution. The improved deep-tissue and large-field-of-view imaging capabilities are validated through resolution targets, cleared tissues, and in vivo OCT angiography of the murine cerebral cortex and human nailfold microcirculation. Quantitative evaluations reveal significant improvements in the contrast-to-noise ratio and vascular density (VD). The proposed system offers a highly adaptable solution for high-resolution, extended-DOF OCT imaging, demonstrating significant potential for preclinical and clinical applications.

Strain-based optical coherence elastography (OCE) is a functional imaging modality derived from optical coherence tomography (OCT), which evaluates biomechanical properties by measuring tissue strain. However, conventional Doppler phase-based strain estimation is highly susceptible to phase wrapping, particularly under conditions of unstable scanning speed, which is often exacerbated by non-uniform rotational distortion (NURD) in proximally driven endoscopic probes. To overcome these limitations, we propose a distal rotary scanning endoscopic OCE system integrated with a balloon catheter. By combining balloon inflation-induced excitation with circumferential scanning, the system enables stable and uniform elastography imaging of intestinal tissue while mitigating NURD-related artifacts. Displacement fields are estimated by calculating inter-frame phase differences of OCT images, based on which radial strain maps are reconstructed, thereby simplifying the phase-unwrapping process. Experiments conducted on tissue-mimicking phantoms and ex vivo porcine intestines confirm the feasibility of the proposed method. The results indicate that the system can simultaneously capture high-resolution structural images and radial strain information from localized intestinal tissues, demonstrating significant potential for clinical applications in the early diagnosis and therapeutic monitoring of intestinal diseases.

Gastrointestinal tissues in the digestive system support a wide range of essential physiological functions. However, conventional endoscopic imaging techniques are limited in their ability to detect alterations in tissue mechanical properties, which poses significant challenges for timely and accurate gastric health assessment. Endoscopic optical coherence elastography (OCE), an advanced functional extension of optical coherence tomography (OCT), offers a high-resolution approach for evaluating tissue biomechanical characteristics. While rotary-scanning configurations in endoscopic OCE have been explored, they are less effective for intraluminal applications, such as gastrointestinal imaging, due to the large internal diameter of the lumen. In this study, we present a forward-scanning endoscopic OCE system designed for quantitative elasticity measurements. The system incorporates a miniaturized endoscopic probe with a piezoelectric tube actuator that drives fiber scanning in the forward direction. The sample is stimulated using an air pulse, and the resulting mechanical responses are analyzed via Doppler OCT measurements. Spatiotemporal maps of elastic wave propagation are constructed to quantify wave velocities, providing insight into the biomechanical properties of the sample. Experimental results demonstrate that the proposed forward-scanning endoscopic OCE technique, combined with the air-pulse excitation, effectively quantifies the elasticity and holds strong potential for the detection and characterization of gastrointestinal pathologies.

Non-invasive and high-resolution blood flow velocity (BFV) measurement using Doppler optical coherence tomography (DOCT) is critical in diagnosing and monitoring clinical diseases. However, the inherent phase wrapping problem with inevitable noise in the acquired phase data severely limits the accuracy of flow quantification. To overcome this challenge, this paper takes phase unwrapping as a regression task and proposes a deep neural network called Transformer-enhanced residual network (TRNet) for automatic and noise-robust phase unwrapping in DOCT flow measurement. Considering the importance of long-range dependency for resolving phase discontinuities in noisy environments, TRNet integrates a Transformer block after each convolutional block, which is equipped with a residual strategy and row attention mechanism in the encoder path, forming a hybrid network that synergizes local feature extraction with global contextual awareness through self-attention mechanisms. To mitigate the lack of paired phase images used for network training, we construct a practically representative dataset with DOCT real phase images by leveraging Mamba-YOLO-based object detection and morphological image processing, avoiding reliance on simulated or synthetic data. Extensive evaluations on the rat middle cerebral artery (MCA) Doppler images demonstrate that TRNet outperforms traditional and other deep learning methods under varying signal-to-noise ratios (0-25 dB) in both visual inspection and quantitative evaluation. Notably, TRNet-derived flow velocities exhibit near-perfect correlation with the actual flow velocities in phantom milk flow experiments and show strong agreement with manual measurements in in vivo blood flow experiments, further validating the effectiveness of the proposed phase unwrapping method and its clinical feasibility for precision hemodynamic analysis.

Optical coherence elastography (OCE) is a functional imaging modality derived from optical coherence tomography (OCT), offering non-invasive and high-resolution assessment of tissue elasticity. In previous studies, endoscopic OCE imaging has primarily relied on proximal rotary scanning, which is susceptible to non-uniform rotational distortion and limits image fidelity. To overcome these limitations, we developed a distal rotary scanning endoscopic probe integrated with a balloon catheter, capable of simultaneously acquiring structural OCT images and elastic properties from luminal tissue models. Circumferential scanning is achieved via rotation of a reflective mirror driven by a compact brushless servo motor. Controlled inflation of the balloon is realized by adjusting airflow through an injection pump, providing tunable mechanical stimulation to the luminal wall. A vector-based phase analysis method is employed to process the complex OCT signal sequences, enabling accurate extraction of phase shifts and the construction of radial strain maps. This approach effectively mitigates phase wrapping artifacts, enhancing strain quantification accuracy. The feasibility of the proposed system was validated using vascular phantoms. Experimental results demonstrate its capability to simultaneously capture co-registered structural and radial strain information at the same imaging location. This technique shows strong potential for clinical applications in disease diagnosis and therapeutic monitoring within hollow organs.

Blood vessels are essential for transporting substances and supporting metabolic exchange. Vessel elasticity is a key biomechanical parameter for evaluating vascular health and plays a vital role in assessing plaque vulnerability in coronary artery disease. Acoustic radiation force optical coherence elastography (ARF-OCE) enables remote and non-invasive quantification of tissue elasticity and has been successfully applied to ocular tissues. However, its application to endoscopic elasticity measurements remains challenging due to the difficulty of miniaturized probe designs and the complexity of assessing the elasticity of tube-like structures. In this study, we propose an endoscopic ARF-OCE technique for elasticity assessment of the vessel-mimicking phantoms. A miniature ultrasound transducer was integrated into an endoscopic probe to excite the inner wall. The probe was coupled to a fiber-optic rotary joint, with a motor enabling precise control. The deformation of the phantom was recorded using an M-scan protocol and analyzed with a phase-resolved Doppler method. Vibration characteristics were then extracted to quantify elasticity based on resonance frequency. Experimental results demonstrate that endoscopic ARF-OCE can effectively measure the elasticity of vessel-mimicking phantoms, offering a promising approach for evaluating vessel function and identifying vulnerable plaques in coronary artery disease.

Scleral plaque spots and pigmentation dots have significant potential for non-invasive disease diagnosis. However, the high intra-class variability in their size, shape, and distribution across individuals poses a critical challenge for automated and robust detection in complex scleral images. This study presents an integrated system that combines sclera imaging and object detection to overcome these challenges. First, a specially designed sclera imaging device is employed to obtain the high quality and shadowless scleral images. Then, an improved YOLOv5 model is proposed, incorporating three key enhancements: a CBAM module to suppress redundant information, a series of Mamba blocks to expand the model's receptive field in scleral images, and a small head strategy to enhance the detection effectiveness on small objects. The proposed detection algorithm was validated on three disparate scleral datasets. The experimental results demonstrate that the proposed method can effectively detect scleral spots and dots, featuring robust and generalizable performance.

Optical coherence tomography (OCT) provides high-resolution, non-invasive visualization of biological tissues, enabling structural imaging and the visualization of microvascular networks. However, tissue scattering remains a significant limitation for achieving deeper imaging penetration and improved image quality. Optical clearing agents help minimize this scattering, enhancing OCT imaging capabilities. This study investigates the optical clearing effects of tartrazine, a commonly used food dye, to improve OCT and OCT angiography imaging. In ex vivo chicken breast, tartrazine solution demonstrated enhanced penetration depth and reversible optical clearing. In vivo mouse skin was evaluated using parameters such as extinction coefficient, signal-to-noise ratio, contrast-to-noise ratio, and vessel density. The results revealed substantial reductions in light scattering, improved imaging penetration, and enhanced visualization of vascular networks after applying tartrazine solution.

Accurate measurement of corneal viscoelasticity is essential for diagnosing ocular diseases and understanding corneal biomechanics. Optical coherence elastography (OCE) is a promising technique for high-resolution imaging and quantitative assessment of tissue elasticity. However, existing OCE methods often struggle to provide comprehensive viscoelastic measurements of the cornea under varying intraocular pressures (IOPs). In this study, we present a method based on elastic wave dispersion for measuring corneal viscoelasticity using a handheld OCE system integrating non-contact air-puff excitation and a compact probe design. The elastic wave dispersion method, validated through experiments on agar phantoms, enables precise quantification of both elastic and viscous properties of the cornea. The system's effectiveness was further demonstrated by measuring corneal viscoelasticity in ex vivo porcine corneas at different IOPs. Our results show that the elastic wave dispersion method, combined with the handheld OCE system, provides a flexible and effective approach for assessing corneal viscoelasticity, offering valuable insights into corneal biomechanics under clinically relevant conditions.

Optical coherence tomography (OCT) is a non-invasive, label-free imaging modality that generates high-resolution three-dimensional images. Based on OCT imaging, optical coherence tomography angiography (OCTA) and optical coherence elastography (OCE) can visualize vascular networks and measure the elastic properties of biological tissues. In previous studies, OCTA and OCE were performed separately, providing either vascular network information or elasticity properties of the tissue. We have developed a simultaneous angiography and elastography method using a simplified sample arm structure. After mechanical pressure is loaded on the sample by a glass plate, the deformation is analyzed by the OCT phase changes, and the elasticity is assessed. Meanwhile, the vascular network is visualized by intensity-based Doppler variance analysis. A transparent flexible reference layer is placed between the glass plate and the tissue, which closely contacts the tissue. Better elasticity measurements can be achieved without affecting vascular imaging. The simultaneous elastography and angiography method was demonstrated by the phantom experiments and rat skin measurements. The results show that the information on the microvascular networks and mechanical properties can be obtained at the same imaging location. The method can provide more comprehensive information on biological tissue for disease diagnosis and treatment monitoring.

Anisotropic elasticity measurements of the retina are essential for retinal disease diagnosis and function assessment. Optical coherence elastography (OCE) is a high-resolution imaging technique for mapping the elasticity distribution of tissues. However, previous OCE measurements quantified the tissue elasticity in a single direction, resulting in a biased estimation of the elastic properties. In this study, we propose an OCE method with acoustic radiation force (ARF) excitation to map the retinal anisotropic elasticity in the depth and lateral directions. The axial elasticity was analyzed using the natural frequency of free vibration, and the lateral elasticity was quantified using the elastic wave velocity. After evaluating the feasibility of the OCE method on the phantoms, the anisotropic elasticity of ex vivo porcine retinas was mapped. The results show that the OCE method with ARF excitation can assess the elasticity in orthogonal directions and provide a comprehensive understanding of the elasticity of the anisotropic tissues.

The viscoelasticity of the retina can reflect its function and state. Accurate assessment of retinal viscoelasticity can assist in early diagnosis of retinal diseases. With high-resolution and non-contact features, optical coherence elastography (OCE) has been used to evaluate the retinal elasticity based on the elastic wave velocity measurement. Nonetheless, the retinal viscosity cannot be assessed. In this study, a shear wave dispersion OCE method was proposed to measure the retinal viscosity and elasticity. After acoustic radiation force (ARF) induces a shear wave, optical coherence tomography (OCT) visualizes shear wave propagation in the retina. The wave velocities at different frequencies are analyzed, and the viscoelasticity is quantified based on the dispersion analysis. The accuracy of the method was verified on phantoms with different glycerol concentrations. The viscosity of the phantom is related to the concentration of glycerin, and its elasticity is adjusted by the agar concentration. The OCE results closely matched the elasticity measured by a mechanical testing system. Furthermore, the retinal shear wave velocity dispersion on the ex-vivo porcine eye was analyzed to determine its viscoelasticity. Our results demonstrate that ARF-OCE can quantitatively evaluate the viscoelasticity of the retina. The shear wave dispersion OCE method has great potential for diagnosing retinal diseases.

Objective The structural characteristics of biological tissues can provide essential information for diagnosing clinical diseases. Medical imaging methods, such as X-ray imaging, computed tomography, magnetic resonance imaging, positron emission tomography, and ultrasound imaging, can obtain the structure and function of the tissues; however, these methods cannot detect small lesions due to low imaging resolutions. A biopsy, the gold standard for tumor diagnosis, is painful and invasive, and some tissues cannot be sampled. Optical coherence tomography (OCT) is a label-free, noninvasive, three-dimensional optical imaging method with micrometer resolution and is used for optical biopsy. In the traditional benchtop OCT system, the large scanning probe fixed on a bench cannot reach into a narrow cavity, and the detection process requires a high degree of patient cooperation. Therefore, the use of benchtop OCT systems for clinical applications is limited to a certain extent. A handheld OCT system has a separated sample arm packaged into a miniaturized handheld probe, which is connected to the main OCT system via an optical fiber. The miniaturized probe can be held conveniently and inserted into the narrow cavity, increasing the applicability and flexibility. We propose a video-guided handheld high-speed OCT system with an A-line speed of 200 kHz. The compact handheld probe is easy to hold and can be inserted into narrow cavities. A camera integrated into the probe can capture real-time video for guiding OCT imaging. An image registration method is also developed to eliminate image misalignment due to hand tremors during OCT imaging. Methods A handheld OCT system based on a swept source was built for tissue imaging, as shown in Figure 1. The handheld probe was connected to the main system through an optical fiber. The handheld probe was made to have a smaller size and lower power consumption by employing a microelectromechanical system-based scanner for beam scanning. A visible imaging camera integrated inside the handheld probe allows for real- time imaging, facilitating rapid localization of the region of interest, and guiding OCT imaging. The system has a high scanning speed with an A- line rate of 200 kHz, a lateral resolution of 31.4 mu m, and an axial resolution of 5.2 mu m in tissue. To improve the image quality, an image registration method was developed to eliminate image dithering. The handheld OCT system was validated using ex-vivo porcine cornea and tooth. The images obtained by the handheld OCT system were also compared with those obtained by the benchtop OCT system. Results and Discussions The ex- vivo porcine cornea and tooth were imaged using the handheld OCT system, as shown in Figure 2. Figures 2(a) and 2( d) show the images of the cornea and tooth, respectively, captured by a cell phone. Real- time videos can be captured to guide the imaging location and determine the region of interest using the camera in the handheld OCT system. The images of the cornea and tooth captured by the video camera are shown in Figures 2( b) and 2( e), respectively. Single B-scan images of the cornea and tooth are captured by the handheld OCT system, as shown in Figures 2(c) and 2(f), respectively. The results show that the handheld OCT system can acquire high-resolution cross-sectional structural images for the cornea and tooth. During imaging using the handheld probe, the hand tremor causes OCT image misalignment, and image registration is required. Figure 3 shows the OCT images of the porcine cornea and tooth with/ without image registration. After multiple rounds of B- scanning at the same location, the images were averaged, as shown in Figures 3( a) and 3(c). The averaged images are blurry, showing image misalignment. After image registration, the image misalignment is corrected, and the averaging B- scan images present a clear tissue structure, as shown in Figures 3( b) and 3(d). To evaluate the imaging performance, the images obtained from the handheld OCT system were compared with those from the benchtop OCT system, as shown in Figure 4. Figures 4(a) and 4(b) show the single B-scan images of the ex- vivo porcine tooth from the benchtop and handheld OCT systems, respectively. The results show that there are no significant differences between the images acquired by the two systems. The CNRs of the images from the handheld and benchtop OCT systems are 3.28 +/- 0.01 and 3.30 +/- 0.02, respectively. As there is no image misalignment during imaging using the benchtop OCT system, it can provide a reference for evaluating the image registration method. After image registration, the averaging B-scan images from the handheld OCT system show a structure similar to that of the images from the benchtop OCT system. Moreover, the registered images from the handheld OCT system have a quality similar to that of the images from the benchtop OCT system. Conclusions In this study, a video-guided high-speed handheld OCT system with an A-line scanning rate of 200 kHz is designed and constructed. Compared with the traditional benchtop OCT system, the handheld system has a compact and easy-to- hold handheld probe, which extends the applications and increases the flexibility of OCT imaging. A video camera inside the probe allows real-time imaging to quickly localize the region of interest and guide the OCT image. An image registration method can eliminate image misalignment during OCT imaging. The imaging performance of the system was verified by imaging ex-vivo porcine cornea and tooth. The results show that the handheld OCT system can provide a more convenient method for tissue imaging, thus exhibiting great potential for imaging the tissues in a narrow cavity and serving the needs of less-cooperative patients.

Optical coherence tomography angiography (OCTA) is a label-free, high-resolution imaging technique used to detect blood flow by combining optical coherence tomography (OCT) with time-series signal analysis. In OCTA, time-series signals from the same position are captured, and fluctuations in the signals are analyzed to detect the blood flow. In this study, we evaluated different OCTA scan protocols in terms of image quality and sampling time, including the dense A-scans, dense B-scans, and multiple B-scans. In the protocols of dense A-scans and dense B-scans, the beam continues scanning with a slight change between adjacent positions. Whereas, the B-scans are repeated at each position along the slow scan direction in the protocol of the multiple B-scans. After capturing the time-series signals using different scan protocols and analyzing them with an OCTA algorithm, we visualized the vasculature of the rat cerebral cortex. The image quality and the sampling time were then analyzed to assess the efficiency of each scan protocol. The quantitative evaluation of these protocols allows for optimizing sampling schemes in OCTA imaging of biological tissues.

Alteration in the elastic properties of biological tissues may indicate changes in the structure and components. Acoustic radiation force optical coherence elastography (ARF-OCE) can assess the elastic properties of the ocular tissues non-invasively. However, coupling the ultrasound beam and the optical beam remains challenging. In this Letter, we proposed an OCE method incorporating homolateral parallel ARF excitation for measuring the elasticity of the ocular tissues. An acoustic-optic coupling unit was established to reflect the ultrasound beam while transmitting the light beam. The ARF excited the ocular tissue in the direction parallel to the light beam from the same side of the light beam. We demonstrated the method on the agar phantoms, the porcine cornea, and the porcine retina. The results show that the ARF-OCE method can measure the elasticity of the cornea and the retina, resulting in higher detection sensitivity and a more extensive scanning range.

Optical coherence tomography (OCT) enables high-resolution, label-free cross-sectional and volumetric imaging of biological tissues. Combining OCT imaging with external force excitation, optical coherence elastography (OCE) provides noninvasive elasticity quantification for the pathological analysis of tissues and early diagnosis of diseases. However, the OCE system with a fixed OCT sample arm cannot be used for elasticity measurements of tissues located in a narrow space, such as an oral cavity and an ear canal, because the OCT beam and external force cannot easily reach the tissues. In this study, we developed a handheld OCE method for the elasticity measurements based on elastic wave imaging. The handheld probe integrated an air pulse excitation unit and a microelectromechanical system-based scan imaging unit. The short air pulse induced the elastic wave in a sample. Then, the OCT data was captured by an M-B scan protocol, and the tissue vibration was analyzed by Doppler phase shifts. After elastic wave visualization, the elastic wave velocity was measured for the elasticity quantification. The results show that the handheld OCE method can quantify the elastic modulus with high flexibility for the tissue in a narrow, deep space.

Pathological changes in ocular tissues can cause differences in tissue elasticity. Therefore, tissue elasticity is a valuable indicator of early ocular diseases. To measure the elasticity of ocular tissues, we proposed a whole-eye optical coherence elastography (OCE) method. To image the whole eye, an electrically tunable lens (ETL) was integrated into the system to adjust the focal plane. For inducing elastic waves in an entire eye, the acoustic radiation force (ARF) from one transducer stimulated the anterior segment from the side of the eye, and another transducer excited the retina from the front of the eye. The elastic waves in the porcine cornea and retina were visualized by Doppler phase shift analysis. Then, we measured the elastic wave propagation velocities and calculated Young's moduli of the tissues. In the ex-vivo experiments of porcine eyes, the elastic moduli of the cornea and retina were quantified, respectively. The experimental results demonstrate the feasibility and potential clinical value of the proposed method for assessing tissue elasticity in ocular structures.