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Dynamic Optical Coherence Tomography (DOCT) is an advanced imaging technique that uses temporal fluctuations in OCT signals to improve contrast and enhance visualization of dynamic processes such as motion and metabolic activity. Although various methods for implementing the DOCT algorithm have been proposed, the use of Principal Component Analysis (PCA), a commonly used technique in medical imaging, remains relatively underexplored in this area. Our study demonstrates that selecting only the most significant principal components in PCA can substantially reduce artifacts from strong specular reflections, particularly when high-numerical-aperture microscope objectives are used. Furthermore, by using a small number of principal components, we can isolate movement within the sample, successfully reconstruct volumetric images, and create thin, histology-like sections of bovine kidney tissue, avoiding the need for complex, time-consuming techniques used in clinical histopathology.

Optical Coherence Tomography (OCT) vibrometry provides sub-nanometer displacement sensitivity and has become a key technique for mapping complex vibration patterns, particularly in hearing research where frequency-dependent motion of middle-ear structures is central to diagnosing pathology. However, at high frequencies, OCT measurements often approach the noise floor, degrading the accuracy and interpretability of reconstructed displacement fields, which is especially critical for fast and reliable assessment. We introduce a robust, regularized finite-element (FE) global reconstruction framework that utilizes higher-order shape functions and L-curve optimization to recover continuous, high-fidelity displacement fields. Through comprehensive simulation and experimental validation, we demonstrate that this method significantly outperforms traditional unregularized filters. Statistical validation via two-sample t-tests indicates that the regularized approach achieves significantly lower mean reconstruction errors compared to lower-order methods (p < 0.01). Most importantly, variance testing proves that regularized filtering always improves the variance (p < 0.01), consistently reducing noise-propagation while preserving the underlying accuracy of the reconstructed field. This workflow provides an objective, reproducible method for quantitative vibration analysis, bridging the gap between raw OCT data and high-fidelity mechanical modeling.

We present a fully automated large-area OCT imaging procedure with realtime refocusing integrated with a combined OCT-Raman system. Scanning along the x-axis is achieved using a single galvanometer paired with a telecentric lens. Scanning along the y-axis is accomplished by translating a sample with a motorised horizontal stage over a much larger lateral size. The same translation stage is also moved along the y-axis to repeat the scanning over connecting columns. Automated refocusing at equidistant intervals along the y-axis is performed using a motorised vertical stage, which carries the combined OCTRaman imaging head. We also perform spatial calibration between the OCT and Raman optics to enable automated focusing of the Raman optics onto the sample surface. The procedure is validated on a large 5cm × 5cm biological sample, with assessment of scanning time and other imaging parameters. A surface map is generated to guide the subsequent Raman measurements, and a targeted Raman measurement is performed on selected sites on the sample. This combined OCT-Raman system is designed for fully automated intraoperative breast cancer diagnosis, integrating OCT imaging, AI-based classification, and Raman spectroscopy.

Optical coherence tomography (OCT) vibrometry enables non-invasive, high-resolution measurement of tissue motion with nanometer sensitivity. However, ex vivo measurements are limited by postmortem changes, and in vivo recordings are susceptible to patient motion artifacts. Therefore, accelerating OCT vibrometry acquisition is essential for advancing both fundamental research and clinical applications. To address this challenge, we introduce multisine OCT vibrometry. Using multisine stimulation, a single OCT dataset captures displacement information across a broad frequency range. Here, we present frequency-dependent displacement data for rubber membranes and rabbit eardrums. The multisine dataset results are consistent with pure-tone validation measurements. Furthermore, the multisine datasets offer insights into the relative mobility of the rubber membrane and eardrum samples, underscoring their potential for tissue characterization and diagnosis. Our findings demonstrate that multisine OCT vibrometry reduces acquisition, processing, and visualization time without compromising accuracy. This approach enables dense OCT data collection and represents a significant advancement toward rapid, reliable clinical assessment of middle ear mechanics.

Optical coherence tomography (OCT) vibrometry is a promising tool for middle-ear mechanics, but single-frequency approaches limit efficiency and diagnostic power. We introduce multisine OCT vibrometry in a rabbit model to capture broadband, frequency-dependent eardrum vibrations acquired in a single OCT volume. Multisine data revealed that control ears had maximal umbo displacement at 1.4 kHz with an amplitude of 86 ± 11 nm (N=5). Proof-of-concept measurements were performed to highlight the diagnostic value of detecting pathology related shifts in umbo displacement using multisines. Local thinning of the eardrum by ablation decreased the frequency of maximal displacement to 1.0 kHz and resulted in an umbo displacement of 84 ± 4 nm. In contrast, perforation of the eardrum caused an overall drop in displacement amplitude across frequencies, with a maximal displacement of 34 ± 3 nm reached at 2 kHz. Additionally, the single multisine OCT volume allowed visualization of the eardrum’s displacement across the surface for all multisine tones. Ablation and perforations caused localized changes of the eardrum’s displacement at frequencies above 4 kHz. Thus, multisine OCT vibrometry holds promise for improved diagnosis and surgical planning: umbo frequency-displacement curves can distinguish between healthy and pathological ears, while spatial displacement maps reveal lesion-specific displacement patterns at high frequencies.

Loss of focus in depth due to the mismatch between the coherence gate and the focus gate is a limiting factor in the achievable high lateral resolution in optical coherence tomography (OCT). This work adapts a simplified dynamic focus method, utilising only one mechanical element to a full-field OCT configuration, and demonstrates the capability to maintain the alignment of the coherence gate and the depth of the focus gates, at sample depths of up to 4 mm while using a high numerical aperture objective lens (NA = 0.5).

This paper comprehensively demonstrates the efficiency of balanced detection in a visible optical coherence tomography instrument employing a low-noise supercontinuum laser. By using an innovative technique for digitally aligning camera pixels, we achieved a noise floor reduction of up to 12.8 dB across the entire imaging depth range, particularly near the zero optical path difference between the interferometer arms. The instrument presented here operates at a central wavelength of 590 nm. It delivers high-resolution images with a sensitivity of up to 74 dB in a single spectrometer configuration and 92.8 dB in a balanced configuration. The enhancement in image contrast is exemplified through images of an optical phantom and in-vivo images of a human thumb and nail.

In this letter, a swept-source optical coherence tomography (SS-OCT) instrument employing an innovative scanning protocol for high-speed volumetric rate imaging is demonstrated. The optical source is a tuneable laser based on a supercontinuum source pumped with femtosecond pulses, followed by a time-stretched delay fibre. The instrument is equipped with an ultra-fast lateral scanner, based on a KTN crystal, driven at 100 kHz. The paper proves the utility of combining an ultra-fast lateral scanner with an ultra-fast swept laser to provide A-scans at a repetition rate of 40 MHz and an unprecedented 3D-OCT volume acquisition rate of 400 Hz.

In this paper, a fast dual resonance akinetic opticalswept source operating at 1550 nm is demonstrated. In-stead of modulating the optical amplifier gain reportedin our previous studies, here we employ a fiber intensitymodulator as a mode-locking element. A chirped fiberBragg grating is used to provide sufficient dispersion inthe laser cavity. A tuning range of 25 nm is obtained fora sweep frequency of ~900 kHz with a 6 dB drop-off insensitivity at 2.6 mm optical path difference.

Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography Authors Gheorghe Hutiu, Virgil-Florin Duma, Dorin Demian, Adrian Bradu and Adrian Podoleanu Coordinates Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography, Metals 8(2), 117 (2018). Abstract Some forensic in situ investigations, such as those needed in transportation (for aviation, maritime, road, or rail accidents) or for parts working under harsh conditions (e.g., pipes or turbines) would benefit from a method/technique that distinguishes ductile from brittle fractures of metals—as material defects are one of the potential causes of incidents. Nowadays, the gold standard in material studies is represented by scanning electron microscopy (SEM). However, SEM instruments are large, expensive, time-consuming, and lab-based; hence, in situ measurements are impossible. To tackle these issues, we propose as an alternative, lower-cost, sufficiently high-resolution technique, Optical Coherence Tomography (OCT) to perform fracture analysis by obtaining the topography of metallic surfaces. Several metals have been considered in this study: low soft carbon steels, lamellar graphite cast iron, an antifriction alloy, high-quality rolled steel, stainless steel, and ductile cast iron. An in-house developed Swept Source (SS) OCT system, Master-Slave (MS) enhanced is used, and height profiles of the samples’ surfaces were generated. Two configurations were used: one where the dimension of the voxel was 1000 μm^3 and a second one of 160 μm^3—with a 10 μm and a 4 μm transversal resolution, respectively. These height profiles allowed for concluding that the carbon steel samples were subject to ductile fracture, while the cast iron and antifriction alloy samples were subjected to brittle fracture. The validation of OCT images has been made with SEM images obtained with a 4 nm resolution. Although the OCT images are of a much lower resolution than the SEM ones, we demonstrate that they are sufficiently good to obtain clear images of the grains of the metallic materials and thus to distinguish between ductile and brittle fractures—especially with the higher resolution MS/SS-OCT system. The investigation is finally extended to the most useful case of fatigue fracture of metals, and we demonstrate that OCT is able to replace SEM for such investigations as well