Line-field Optical Coherence Tomography Research Articles

Non-Invasive Imaging Including Line-Field Confocal Optical Coherence Tomography (LC-OCT) for Diagnosis of Cutaneous Lymphomas.

Background/Objectives: Primary cutaneous lymphomas (PCL) are a heterogeneous group of non-Hodgkin lymphomas arising from malignant T (CTCL) or B (CBCL) cells, often mimicking other skin conditions. Recently, non-invasive diagnostic imaging modalities, including dermoscopy, Reflectance Confocal Microscopy (RCM), and Line-field Optical Coherence Tomography (LC-OCT), have become increasingly important, supporting clinicians in clinical practice. Hence, our study aimed to describe dermoscopic, RCM, and LC-OCT features of PCL and to explore their role in PCL management. Methods: Between December 2022 and January 2024, 40 lesions of 25 patients with PCL were retrospectively analyzed at the Dermatologic Unit of the University of Siena, Italy. Predefined dermoscopic, LC-OCT, and RCM criteria were assessed and their frequencies were calculated. Results: At dermoscopy, CTCL lesions were characterized by pinkish structureless areas (58,6%) and homogeneous distributed dotted vessels (35,7%), whereas 57.1% of CBCL presented with orange-yellow structureless areas. Considering CTCL, lymphocytes in the epidermis, dermal-epidermal junction, and dermis were detected by LC-OCT in 73.1%, 66.7%, and 51.9% and by RCM in 72.2%, 55.6%, and 61.1% of cases, respectively. The detection of lymphocytes was more precise using RCM than LC-OCT in CTCL (p < 0.001). Dermal infiltration of medium-reflective cells was visible in 80% and 40% of CBCL cases by LC-OCT and RCM, respectively. Conclusions: Non-invasive imaging techniques may support clinicians in managing PCL; however, further studies are mandatory in this field.

Novel imaging techniques for tumor margin detection in basal cell carcinoma: a systematic scoping review of FDA and EMA-approved imaging modalities.

Mohs micrographic surgery (MMS) is the gold standard for removing basal cell carcinomas (BCCs) due to its ability to guarantee 100% margin evaluation through frozen section histopathology, offering the highest cure rate among current treatments. However, noninvasive imaging technologies have emerged as promising alternatives to clinical assessment for defining presurgical margins. This systematic scoping review examines the efficacy of these imaging modalities, focusing on those approved for clinical use by the United States Food and Drug Administration (FDA) or the European Medicines Agency (EMA). A systematic search of EMBASE, Scopus, PubMed, and the Cochrane Public Library databases identified 11 relevant studies out of 2123 records, encompassing 644 lesions across five imaging techniques. The findings suggest that dermoscopy, high-frequency ultrasound (HFUS), optical coherence tomography (OCT), line-field optical coherence tomography (LC-OCT), and reflectance confocal microscopy (RCM) show potential in detecting BCC margins, which could enhance MMS by providing better preoperative planning, informing patients of expected defect size, aiding in reconstruction decisions, and reducing overall procedure costs. This review discusses the benefits and limitations of each technique, offering insights into how these innovations could influence the future of BCC management. Emerging imaging techniques could enhance MMS by improving BCC margin assessment and reducing costs. Their adoption will depend on price and ease of use.

Computational approach for correcting defocus and suppressing speckle noise in line-field optical coherence tomography images.

The trade-off between transverse resolution and depth-of-focus (DOF) typical for optical coherence tomography (OCT) systems based on conventional optics, prevents "single-shot" acquisition of volumetric OCT images with sustained high transverse resolution over the entire imaging depth. Computational approaches for correcting defocus and higher order aberrations in OCT images developed in the past require highly stable phase data, which poses a significant technological challenge. Here, we present an alternative computational approach to sharpening OCT images and reducing speckle noise, based on intensity OCT data. The novel algorithm uses non-local priors to model correlated speckle noise within a maximum a posteriori framework to generate sharp and noise-free images. The performance of the algorithm was tested on images of plant tissue (cucumber) and in-vivo healthy human cornea, acquired with line-field spectral domain OCT (LF-SD-OCT) systems. The novel algorithm effectively suppressed speckle noise and sharpened or recovered morphological features in the OCT images for depths up to 13×DOF (depth-of-focus) relative to the focal plane.

Integrated line-field optical coherence tomography and scheimpflug imaging for corneal imaging

Previously we demonstrated a combined scanning-point optical coherence tomography (OCT) and Scheimpflug Imaging (SI) system, to provide cross-section images of the corneal layers and the whole anterior segment of the eye simultaneously. However, to fully realise the benefits of this dual imaging modality concept towards clinical practice, it is required that the OCT part of the system can achieve ultra-high axial resolution (<3 µm in air) and faster imaging speeds, without using prohibitively expensive components. To achieve this, a new imaging device integrating line-field OCT and SI, using a supercontinuum light source, is demonstrated. This line-field configuration enables both OCT and SI B-scan to be captured using the same light illumination in a single shot, which is the most significant improvement over single point scanning. This achieves an OCT axial resolution down to 2.1 µm in air (1.6 µm in corneal tissue) and an imaging speed up to 213 kA-Scans/s. Since the OCT and SI capture the identical corneal position and serve as cross-validation, this technique offers a great method for accurately determining the individual corneal thickness and refractive index, thereby minimizing individual variations, which can help determine the extent of cutting or correction needed in vision correction. Moreover, the precise measurement of corneal thickness provided by this technique allows for a better understanding of the biomechanical properties of the cornea. We demonstrate the efficacy of the proposed system by evaluating porcine and bovine eyes ex-vivo for determining the corneal refractive index and thickness.

LC-OCT as a tool to visualize in vivo location of dermal fillers.

Dermal fillers have emerged as a popular non-surgical solution for facial rejuvenation and enhancement. Apart from botulinum toxin injections, they are the most common non-surgical procedure performed in the US. Line-field optical coherence tomography (LC-OCT; deepLive system Damae Medical, France) represents one of the most recent developments in non-invasive skin imaging technologies. We performed LC-OCT image acquisition on six patients that were treated with hyaluronic acid (HA) dermal fillers in various locations on the face. The images were acquired before the application of the fillers (T0), immediately after (T1), and at a 6- to 8-week (T2) follow-up visit. At T0, we were able to appreciate a normal-appearing epidermis, dermoepithelial junction, and dermis. At T1, the intradermal filler deposits appeared as homogeneously hyporeflective areas, clearly discernible from surrounding vessels and other structures. At T2, the deposits were distinguishable as hyporeflective areas, although they were diminished in size compared to T1. On enface view, collagen fibers had increased thickness and were more homogeneously organized and hyperreflective. We established the usefulness of LC-OCT in the non-invasive evaluation of dermal HA fillers to visualize both short-term and medium-term effects. LC-OCT may be a valuable tool in evaluating the precise location of filler placement and follow-up of resulting in vivo changes.

Line-Field Optical Coherence Tomography: Usefulness in the Non-Invasive Differential Diagnosis of Congenital Alopecia of Infancy.

Soon after birth, the clinical differential diagnosis between sebaceous of Jadassohn (NSJ), congenital triangular alopecia (CTA) and aplasia cutis congenita (ACC) may be challenging. A certain overlap of standard dermoscopic features can occur, especially in atypical cases, depending on scalp skin morphology and maturation age. The recently developed line-field confocal optical coherence tomography (LC-OCT) can provide morphological skin details with cellular resolution trough a rapid non-invasive examination. To assess the LC-OCT features of 6 cases of congenital alopecia of different aetiologies, with both typical and atypical clinical appearance. A non-invasive imaging examination combining standard dermoscopy, high-resolution videodermoscopy (HRVD) and LC-OCT was realized in 7 babies presenting for congenital alopecia with overlapping features, aged between 5 months and 5 years. Based on the specific LC-OCT features, and supported by HRVD features, a diagnosis of NSJ, congenital triangular alopecia (CTA) and AC) were made in 4, 2 and 1 case, respectively. The combined LC-OCT plus HRVD non-invasive imaging bring the advantage to have a real time diagnosis, to set the proper management and allows to avoid a skin biopsy in the perinatal age/first years of life at delicate skin site.

Real-time line-field optical coherence tomography for cellular resolution imaging of biological tissue.

A real-time line-field optical coherence tomography (LF-OCT) system is demonstrated with image acquisition rates of up to 5000 B-frames or 2.5 million A-lines per second for 500 A-lines per B-frame. The system uses a high-speed low-cost camera to achieve continuous data transfer rates required for real-time imaging, allowing the evaluation of future applications in clinical or intraoperative environments. The light source is an 840 nm super-luminescent diode. Leveraging parallel computing with GPU and high speed CoaXPress data transfer interface, we were able to acquire, process, and display OCT data with low latency. The studied system uses anamorphic beam shaping in the detector arm, optimizing the field of view and sensitivity for imaging biological tissue at cellular resolution. The lateral and axial resolution measured in air were 1.7 µm and 6.3 µm, respectively. Experimental results demonstrate real-time inspection of the trabecular meshwork and Schlemm's canal on ex vivo corneoscleral wedges and real-time imaging of endothelial cells of human subjects in vivo.

Understanding the anatomy of dermoscopy of melanocytic skin tumours: Correlation invivo with line-field optical coherence tomography.

Early melanoma detection is the main factor affecting prognosis and survival. For that reason, non-invasive technologies have been developed to provide a more accurate diagnosis. Recently, line-field confocal optical coherence tomography (LC-OCT) was developed to provide an invivo, imaging device, with deep penetration and cellular resolution in three dimensions. Combining the advantages of conventional OCT and reflectance confocal microscopy, this tool seems to be particularly suitable for melanocytic lesions. The objective of this study was to identify and describe the correlation between specific dermoscopic criteria and LC-OCT features in three dimensions associated with melanocytic lesions. Dermoscopic and LC-OCT images of 126 melanocytic lesions were acquired in three different centres. The following dermoscopic criteria have been considered: reticular pattern, dots and globules, structureless areas, blue-whitish veil, regression structures, negative network, homogeneous pattern, streaks and blotches. 69 (55%) benign and 57 (45%) malignant lesions were analysed. A regular reticular pattern was found associated in the 75% of the cases with the presence of elongated rete ridges with pigmented cells along the basal layer, while atypical reticular pattern showed an irregular organization of rete ridges with melanocytic hyperplasia, broadened and fused ridges and elongated nests. Both typical and atypical dots and globules were found associated with melanocytic nests in the dermis or at the dermoepidermal junction (DEJ), as well as with keratin cysts/pseudocysts. Grey globules corresponded to the presence of melanin-containing dermal inflammatory cells (melanophages) within the papillae. Structureless brown/black areas correlated with alterations of the DEJ. We observed the same DEJ alterations, but with the presence of dermal melanophages, in 36% of the cases of blue/white/grey structureless areas. A description of each LC-OCT/dermoscopy correlation was made. LC-OCT permitted for the first time to perform an invivo, 3D correlation between dermoscopic criteria and pathological-like features of melanocytic lesions.

SmartOCT: smartphone-integrated optical coherence tomography.

Smartphone devices have seen unprecedented technical innovation in computational power and optical imaging capabilities, making them potentially invaluable tools in scientific imaging applications. The smartphone's compact form-factor and broad accessibility has motivated researchers to develop smartphone-integrated imaging systems for a wide array of applications. Optical coherence tomography (OCT) is one such technique that could benefit from smartphone-integration. Here, we demonstrate smartOCT, a smartphone-integrated OCT system that leverages built-in components of a smartphone for detection, processing and display of OCT data. SmartOCT uses a broadband visible-light source and line-field OCT design that enables snapshot 2D cross-sectional imaging. Furthermore, we describe methods for processing smartphone data acquired in a RAW data format for scientific applications that improves the quality of OCT images. The results presented here demonstrate the potential of smartphone-integrated OCT systems for low-resource environments.

35406 Characterization of photodamaged skin using 3D line-field optical coherence tomography and histopathologic correlation

Noninvasive imaging techniques morphologically characterize photoaging and generate qualitative analysis in photodamaged skin. Optical coherence tomography (OCT) allows a deep laser penetration in the surface, reaching a good quality image of dermis visualization. A new 3-dimensional technology, 3D line field confocal OCT (LC-OCT) has been introduced, allowing a vertical and horizontal reconstruction of the complete skin with cellular resolution. The objective of this study was to observe in an in vivo 3-dimensional mode (3D LC-OCT) the morphologic and cytologic changes of photodamaged skin, to better understand the changes of the different skin layers induced by chronic sun exposure and responsible for chronic sun damage. 9 phototype II-III subjects were included. Dermoscopy and LC-OCT were performed on 2 zones: the sun-damaged area on the dorsal forearm and the non-sun-damaged area on the ventral side of the same forearm. Skin biopsies were obtained from both areas. All metrics were compared as paired data. LC OCT analysis showed increased epidermal thickness (mean: 5.39 μm, P = .0078) and higher number of keratinocytes (mean = 0.997; P = .002) in exposed vs nonexposed areas. The volume of the different keratinocyte layers seemed to be larger in the exposed area. Histology comparisons also showed an increased epidermal thickness on exposed areas. Significant differences were observed for the number of keratinocyte layers that was higher in photodamaged skin. This study provides for the first time a 3D quantitative analysis of photodamaged skin. There was a good correlation with histopathologic evaluation.

Accurate In Vivo Bowman's Thickness Measurement Using Mirau Ultrahigh Axial Resolution Line Field Optical Coherence Tomography.

PurposeThe purpose of this study was to assess the accuracy, repeatability, and performance limits of in vivo Mirau ultrahigh axial resolution (UHR) line field spectral domain (LF-SD) optical coherence tomography (OCT) for the measurement of Bowman's and epithelial thickness, and to provide a reference range of these values for healthy corneas.MethodsVolunteers with no history and evidence of corneal disease were included in this study. An in vivo graph search image segmentation of the central cornea was obtained at the normal interface vector orientation. The Mirau-UHR-LF-SD-OCT system used has an axial resolution down to 2.4 µm in air (1.7 µm in tissue), with an A-scan speed of 204.8 kHz and a signal to noise ratio (sensitivity) of 69 (83) dB.ResultsNine volunteers were included, one of whom wore contact lenses. The repeatability of mean Bowman's and epithelial thicknesses were 0.3 and 1.0 µm, respectively. The measured 95% population range for healthy in vivo thickness was 13.7 to 19.6 µm for the Bowman's layer, and 41.9 to 61.8 µm for the epithelial layer.ConclusionsThe measured thicknesses of Bowman's layer and the corneal epithelium using the Mirau-UHR-LF-SD-OCT were both accurate, with the range for healthy in vivo thicknesses matching prior confocal and OCT systems of varying axial resolutions, and repeatable, equaling the best value prior reported.Translational RelevanceT1. Development of a commercially viable clinical UHR OCT technology, enabling accurate measurement and interpretation of Bowman's and epithelial layer thickness in clinical practice.

Micron-resolution high-performance line field optical coherence tomography and its application

A line-field scanning Fourier-domain optical coherence tomography (OCT) system (LF-FDOCT) that makes high-resolution and large-dynamic-range imaging possible was demonstrated. Unlike the conventional flying-spot OCT system, the x-axis parallel imaging (one B-scan) has a coherent imaging mode. A theoretical simulation of parallel interference imaging was derived, and the anisotropic resolution along two orthogonal directions was achieved. Validated by experimental results, the spatial resolutions along the x and y axis directions were 2.46 and 2.19 μm, and the theoretical resolutions were 1.8 and 1.34 μm, respectively. The field of view (FOV) in the lateral direction was 900 μm ( x ) × 850 μm ( y ) , and the axial resolution and FOV in the experiment were 2.5 and 700 μm, respectively. The maximal axial sensitivity was measured to be 90.5 dB when the sample was a specula. The en face of tomato and the cross-section of multilayer glass were demonstrated based on the LF-FDOCT system. The three-dimensional image of adherend sample including gels and microelectrodes was realized, proving the LF-FDOCT system had the capability of high resolution and high-dynamic-range imaging.

Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

A method combining phase-contrast technique and spectral-domain optical coherence tomography (OCT) has been recently proposed for visualizing curing behaviors inside polymers (2020 Appl. Phys. Lett. 116 054103). Here, based on the method, a non-contact and highly-sensitive optical sensor is further developed to monitor the photocuring process of light-cured polymers. Compared with the existing method, the proposed optical sensor features two distinct advantages: (a) the sensor uses a point-detection OCT, rather than a line-field OCT, to capture the interference signal, which significantly improves its practicability and the measuring speed; (b) the sensor can simultaneously monitor the shrinkage strains and refractive index variations during a photocuring process, featuring enhanced functionality in practical applications. For validation, a cure monitoring experiment was carried out, proving that the sensor can accurately monitor the shrinkage strain and refractive index variation during the polymer photocuring process. The polymer coating fabrication process and the polymer adhesive process were also monitored, showing the effectiveness and practicability of the sensor.

Characterization of Electrical–Thermal–Mechanical Deformation of Bonding Wires Under Silicone Gel Using LF-OCT

Bonding wires are one of the most failure-prone components of power electronics’ modules, and silicone gel is usually employed to encase bonding wires. To study the deformation of silicone gel-encased bonding wires, in this article, we report the use of line-field optical coherence tomography (LF-OCT) technique to precisely measure the electrical–thermal–mechanical (ETM) deformation of bonding wires. An LF-OCT system was developed to capture the whole cross-sectional image (B-scan) of the bonding wire sample in a single-shot fashion due to its advantageous parallel detection scheme. This, together with the Fourier phase self-referencing technique, allows the deformation of the bonding wires to be quantitatively measured down to the range of 0.1 nm. The maximum sampling rate (framerate) of the deformation measurement achieved was 400 Hz when setting camera imaging size to 1920 × 200 pixels, providing a temporal resolution of 2.5 ms for monitoring the ETM deformation dynamics of the bonding wire. We found that the ETM deformation of the gel-encased bonding wire was about three times smaller than that of the bare bonding wire. These results represent the first experimental demonstration that the LF-OCT could be a useful analytical tool for studying the time-dependent ETM deformation of bonding wires encased by silicone gel.

Design and optimization of line-field optical coherence tomography at visible wavebands.

Parallel line-field Fourier-domain optical coherence tomography (LF-FDOCT) has emerged to enable relatively higher speeds than the conventional FDOCT system. In the LF-FDOCT, one B-scan is captured at a time instead of scanning the beam to acquire hundreds of A-scans. On the other hand, spectroscopic OCT using the visible waveband provides absorption information over multiple wavelengths at each voxel. This information of spectral absorption enables quantitative measurement of blood oxygenation, voxel by voxel. Here, we presented the design and optimization of a LF-FDOCT system at the visible waveband (520-620 nm), especially using a generic Camera Link area sensor (2048 × 1088 pixels). To optimize the axial resolution and depth of imaging volume, we simulated various parameters and found that two Nyquist optima can exist, the origin and implication of which has been discussed. As a result, our system acquired 1088 A-scans in parallel at the camera's frame rate of 281 frame per second, achieving an equivalent rate of over 300,000 A-scan/s, while minimizing sacrifice in the point spread function (2.8 × 3.1 × 3.2 µm3, x × y × z) and the field of view (750 × 750 × 750 µm3). As an example of application, we presented high-speed imaging of blood oxygenation in the rodent brain cortex.

Delayed Tattoo Reaction From Red Dye With Overlapping Clinicopathological Features: Examination With High-Frequency Ultrasound and Line-Field Optical Coherence Tomography.

Delayed Tattoo Reaction From Red Dye With Overlapping Clinicopathological Features: Examination With High-Frequency Ultrasound and Line-Field Optical Coherence Tomography.

Line-Field Optical Coherence Tomography as a tool for In vitro characterization of corneal biomechanics under physiological pressures

There has been a lot of interest in accurately characterising corneal biomechanical properties under intraocular pressure (IOP) to help better understand ocular pathologies that are associated with elevated IOP. This study investigates the novel use of Line-Field Optical Coherence Tomography (LF-OCT) as an elastographic tool for accurately measuring mechanical properties of porcine corneas based on volumetric deformation following varying IOPs. A custom-built LF-OCT was used to measure geometrical and corneal surface displacement changes in porcine corneas under a range of IOPs, from 0–60 mmHg. Corneal thickness, elastic properties and hysteresis were calculated as a function of pressure. In addition, the effects of hydration were explored. We found that the elastic modulus increased in a linear fashion with IOP. Corneal thickness was found to reduce with IOP, decreasing 14% from 0 to 60 mmHg. Prolonged hydration in phosphate buffered saline (PBS) was found to significantly increase the elastic modulus and corneal hysteresis. Our study demonstrates that LF-OCT can be used to accurately measure the elastic properties based on volumetric deformation following physiological pressures. Furthermore, we show that prolonged hydration in PBS has a significant effect on the measured corneal properties.

Synthetic subaperture-based angle-independent Doppler flow measurements using single-beam line field optical coherence tomography in vivo.

We demonstrate a synthetic subaperture-based angle-independent Doppler flow calculation, using a line field spectral domain optical coherence tomography system. The high speed of the system features a high phase stability over the volume, which is necessary to apply synthetic subapertures in the aperture plane. Thus, the flow component for each subaperture can be reconstructed in postprocessing. Capillary phantom and in vivo retinal imaging experiments were performed to validate and demonstrate angle-independent Doppler flow calculation.

Energetic efficiency assessment of spectral coherence tomograph optical-electronic system

Subject of Research.The paper considers the methods of optical coherence tomography (OCT) based on illuminating a sample by optical radiation with subsequent determination of light reflection degree through a sample depth. Illumination method defines basic characteristics of OCT system such as sensitivity and speed in studies of biological samples. In mechanical scanning-free OCT systems, line- and full-field illumination methods are applied utilizing object illumination by laser source with tunable wavelength. The study is aimed at energetic efficiency quantitative assessment of line-field OCT system with tunable radiation source and in comparison of line-field illumination method with full-field one. Method. Based on the model of OCT optical system, ray tracing has been carried out, and spatial distribution of energy reflected from a sample and registered by photo detector has been determined. Photoelectrical signal and signal-to-noise ratio have been evaluated.Main Results. It has been shown that line-field OCT system providessignificantly higher sensitivity (97 dB) compared to full-field system (78 dB). In addition, line-field system allows obtaining B-scan without moving of mechanical parts. Original scheme of lighting channel has been proposed providing uniform illumination spatial distribution along lighting line without sensitivity decay near edges of image field. Practical Relevance.The obtained results can be applied for creation of compact real-time spectral OCT system.

High speed parallel spectral-domain OCT using spectrally encoded line-field illumination

We report parallel spectral-domain optical coherence tomography (OCT) at 500 000 A-scan/s. This is the highest-speed spectral-domain (SD) OCT system using a single line camera. Spectrally encoded line-field scanning is proposed to increase the imaging speed in SD-OCT effectively, and the tradeoff between speed, depth range, and sensitivity is demonstrated. We show that three imaging modes of 125k, 250k, and 500k A-scan/s can be simply switched according to the sample to be imaged considering the depth range and sensitivity. To demonstrate the biological imaging performance of the high-speed imaging modes of the spectrally encoded line-field OCT system, human skin and a whole leaf were imaged at the speed of 250k and 500k A-scan/s, respectively. In addition, there is no sensitivity dependence in the B-scan direction, which is implicit in line-field parallel OCT using line focusing of a Gaussian beam with a cylindrical lens.