Optical Coherence Tomography Technique Research Articles

Optical coherence tomography: a novel imaging approach to visualize and quantify cutaneous microvascular structure and function in patients with diabetes

IntroductionThe pathophysiology of microvascular disease is poorly understood, partly due to the lack of tools to directly image microvessels in vivo.Research design and methodsIn this study, we deployed a novel...

Initial Study for the Determination of the Sequence of Intersecting Lines between Gel Pens and Seals by Optical Coherence Tomography.

Determining the sequence of intersecting lines is a significant issue in the forensic document examination that can reveal the fraud or distinguish between different allegations. Optical coherence tomography (OCT) is a high-resolution cross-sectional imaging technique that has been introduced into forensic science field recently. The potential of OCT as a novel method to determine the sequence of intersecting lines was examined for the first time. In this study, a spectral-domain OCT system with a center wavelength of 900nm was employed to perform nondestructive examination on determining the sequence of 18 heterogeneous intersecting line samples produced using three types of gel pens and three brands of stamp pad ink seals. Two-dimensional (2D) cross-sectional, and three-dimensional (3D) volumetric images of the intersecting lines were obtained by the OCT system. Several features were noted and analyzed to successfully determine the sequence of all the 18 samples. Blind tests were also conducted to demonstrate the effectiveness of OCT technique. The results illustrate that OCT technology can provide an effective and accurate method for sequencing intersecting lines of gel pen ink and seal ink, which may complement the conventional methods used in the examination of questioned documents.

Three-dimensional imaging with reflection synthetic confocal microscopy.

Biomedical imaging lacks label-free microscopy techniques able to reconstruct the contour of biological cells in solution, in 3D and with high resolution, as required for the fast diagnosis of numerous diseases. Inspired by computational optical coherence tomography techniques, we present a tomographic diffractive microscope in reflection geometry used as a synthetic confocal microscope, compatible with this goal and validated with the 3D reconstruction of a human effector T lymphocyte.

Cascade optical coherence tomography (C-OCT).

Significant advances for optical systems in terms of both performance and packaging are enabled by freeform optical components. Yet, surface form metrology for freeform optics remains a challenge. We developed and investigated a point-cloud cascade optical coherence tomography (C-OCT) technique to address this metrology challenge. The mathematical framework for the working principle of C-OCT is presented. A novel detection scheme is developed to enable high-speed measurements. Experimental results validate the C-OCT technique with the prototype setup demonstrating single-point precision of ±26 nm (∼λ/24 at the He-Ne wavelength), paving the way towards full surface measurements on freeform optical components.

Optical coherence tomography and its applications in experimental mechanics: A review

Optical coherence tomography (OCT) is a low-coherence interferometry based optical technique capable of imaging internal structures of transparent/semitransparent objects with micrometer resolution and millimeter range. It features distinct advantages of non-invasive and fast-imaging, and has been widely applied in biology, medicine, and material science. After combining with digital image/volume correlation (DIC/DVC) or phase-contrast, OCT can also be used as an elastography method, known as OCT elastography, for measuring full-field displacements and strains inside objects. Recently, OCT elastography has already been developed as an effective tool for investigating mechanical behaviors of inside bio-tissues and materials, such as cornea, skin, tumor, polymer, and polymer composite. In this work, we introduce the basic principles of OCT elastography, summarize the typical experimental mechanics applications of OCT elastography, and finally discuss the remaining problems and limitations of the technique. OCT was originally developed by D. Huang et al. in 1991. The early OCT technique detects depth information of a specimen by means of mechanical scanning, and therefore it is also called time-domain OCT (TD-OCT). Owing to the limitation of mechanical scanning manner, the imaging speed and signal-to-noise (SNR) of this first-generation OCT is relatively low, which makes it unable to meet the requirements of most measurement situations. In 1995, A. F. Fercher et al. developed another type of OCT, called Fourier-domain OCT (FD-OCT). This second-generation OCT uses parallel detection instead of mechanical scanning to improve the imaging speed and SNR, and greatly accelerated the extension of OCT application. Recently, OCT has also been combined with some other techniques and forms a lot of functional OCT methods, including Doppler OCT, polarization-sensitive OCT, OCT elastography, and spectroscopic OCT. Among them, OCT elastography can realize displacement and strain fields measurement inside objects, which is a promising technique in the field of experimental mechanics. The development of OCT elastography can be traced back to 1998, J. M. Schmitt et al. measured the in-plane and out-of-plane displacement fields inside specimens by using the combination of OCT and DIC. However, owing to the low resolution and poor SNR of the early OCT systems, the imaging quality of the method is unsatisfactory. In addition, the displacement sensitivity of the method is at sub-pixel level (micrometer or sub-micrometer level), which is insufficient for most measurement scenarios. For these reasons, DIC-based OCT elastography hasn’t been widely accepted by the researchers. In 2006, R. K. Wang et al. proposed an alternative method that combines OCT and phase-contrast for achieving OCT elastography. The method uses phase sensitive characteristic of OCT for measuring displacements, and makes the displacement sensitivity reach to nanometer level or even higher. Benefiting from the significant improved displacement sensitivity, OCT elastography has received increasing attention in the last decade. Though OCT elastography developed rapidly in recent years, there still remain some problems: (1) Current OCT elastography is only available of measuring transparent and semitransparent objects. For measuring non-transparent objects, it is helpless. Therefore, in the future work, improving penetrating capability is required for OCT elastography. (2) Despite the fact that the development of FD-OCT greatly improved the imaging speed of OCT elastography, it is still insufficient for measuring full-field deformations of inside objects dynamically. Therefore, improving the imaging speed of OCT elastography is also on demand. (3) The employment of phase-contrast can significantly improve the displacement measurement sensitivity of OCT elastography, but it also makes the method lose its in-plane displacement measurement capability. Therefore, developing a novel OCT elastography enabling both in-plane and out-of-plane displacement measurements with high sensitivity is required in the further research.

Dual-band infrared optical coherence tomography using a single supercontinuum source.

Recent developments and commercial availability of low-noise and bright infrared (IR) supercontinuum sources initiated intensive applied research in the last few years. Covering a significant part of near- and mid-infrared spectral ranges, supercontinuum radiation opened up unique possibilities and alternatives for the well-established imaging technique of optical coherence tomography (OCT). In this contribution, we demonstrate the development, performance, and maturity of a cost-efficient dual-band Fourier-domain IR OCT system (2 µm and 4 µm central wavelengths). The proposed OCT setup is elegantly employing a single supercontinuum source and a pyroelectric linear array. We discuss adapted application-oriented approaches to signal acquisition and post-processing when thermal detectors are applied in interferometers. In the experimental part, the efficiency of the dual-band detection is evaluated. Practical results and direct comparisons of the OCT system operating within the employed sub-bands are exhibited and discussed. Furthermore, we introduce the 2 µm OCT sub-system as an affordable alternative for art diagnosis; therefore, high resolution and sensitive measurements of the painting mock-ups are presented. Finally, potentials of the dual-band detection are demonstrated for lithography-based manufactured industrial ceramics.

Internal fouling during microfiltration with foulants of different surface charges

In view of the inevitability of membrane fouling, it is critically important to understand the underlying mechanisms to alleviate fouling and thereby improve the feasibility of membrane-filtration for more applications. This study was targeted at understanding the internal membrane fouling mechanisms by three types of polystyrene (PS) particles (sized at ~ 0.45 μm; different surface charges) during microfiltration with the same polycarbonate track-etched (PCTE) membrane (nominal pore size of 2 μm). Optical coherence tomography (OCT) technique, which was employed to monitor membrane fouling, indicated greater extents of particle deposition in the case of the positive and less negative PS particles, which is consistent with the more severe flux declines relative to the more negative PS particles. The new fouling model developed that additionally accounts for internal cake filtration, on top of the well-reported pore constriction and pore blockage, revealed the fouling mechanisms at play. For the positive PS particles, the attractive particle-membrane interaction led to a more homogeneous layer-by-layer cake growth, which resulted in denser packing in the pore and higher internal cake resistance, and thereby the worst flux decline. In contrast, for the negative PS particles, the repulsive particle-particle and particle-membrane interactions resulted in more random deposition of the particles inside the pores, resulting in more extensive pore constriction and blockage, as well as lower resistance of the internal cake. This study underscored the importance of surface charge in internal fouling and provided insights on the lesser reported internal fouling mechanisms.

OCT-Diagnostik beim Glaukom: Tipps & Tricks

High-resolution optical coherence tomography (OCT) with spectral-domain or swept-source techniques has become a mainstay in glaucoma and progression diagnosis. Imaging and morphometry of ganglion cell (GCL) and retinal nerve fiber (RNF) layer thickness and Bruch's membrane based minimum neuroretinal rim width (BMO-MRW) measurement allow the detection of pathologic changes. Graphic display of these measurements facilitate a comparison with normative data. False positive (red disease) and false negative (green disease) results represent pitfalls in OCT diagnosis. Pathologies of the posterior pole either caused by glaucoma or non-glaucoma associated changes of optic disc and retina play an important role. Epiretinal gliosis, age related macular degeneration and cystoid retinal changes cause measuring artefacts. A careful inspection of OCT B-scans is mandatory to detect these changes. Highly myopic eyes, underrepresented in normative databases cause changes resembling glaucoma and challenge the OCT glaucoma diagnosis. Neurological diseases present an important differential diagnosis when atrophy of neuroretinal tissue and ganglion cells occur. The location of the atrophy and the relationship of GCL, RNF and BMO-MRW changes may help in differential diagnosis. Sensory tests and imaging of the brain are mandatory in these cases. Drusen and disc edema cause thickening of BMO-MRW and may be followed by loss of RNF and GCL. Again a close observation of OCT B-scans and fundus may help to find the correct diagnosis. Good image quality, knowledge of OCT pathologies and technique of OCT imaging may help to avoid pitfalls in OCT glaucoma diagnosis.

Quantification of structural and microvascular changes for diagnosing early-stage oral cancer.

Changes in mucosal microvascular networks, called intraepithelial papillary capillary loops (IPCL), are an important key factor for diagnosing early-stage oral cancer in vivo. Nevertheless, there are a lack of tools to quantify these changes objectively. This is the first study to quantify the IPCL changes in vivo to differentiate benign or malignant oral lesions by the optical coherence tomography (OCT) technique. K14-EGFP-miR-211-GFP transgenic mice were inducted by 4-Nitroquinoline-1-oxide to produce oral carcinogenesis in different stages, including normal, premalignancy and cancer. The results showed significant differentiation between benign or malignant lesions by OCT quantitative parameters, including epithelial thickness, IPCL density, radius and tortuosity.

Fast Retinal Segmentation Based on the Wave Algorithm

The retinal layer segmentation technique of optical coherence tomography (OCT) data is essential for the diagnosis of ophthalmic and systemic diseases. To achieve fast and accurate retinal layer segmentation, a new medical image segmentation method (wave algorithm) is proposed based on the mathematical model of the fluid potential energy equation in fluid mechanics. A change in the gray value in the image is converted into a change in the potential energy in the ideal fluid (wave), thereby transforming the image segmentation problem into a problem that solves the potential energy based on the fluid potential energy equation. In the process of solving the fluid energy, it is necessary to constrain the potential energy according to the prior knowledge of the medical image. The method consists of two parts: the wave potential energy equation and the potential energy correction equation. When the method is applied to the retinal layer segmentation of an OCT image, the method first detects the boundary area of the retinal layer according to the wave potential energy equation and then uses the potential energy correction equation to accurately extract the boundary line from the boundary area. The proposed method is tested on publicly available datasets. The results show that compared with other advanced segmentation methods, the method achieved slightly superior segmentation accuracy and speed. When the mean unsigned positioning error of the retinal layer segmentation is less than 1.5 pixels, the method can quickly segment the retinal layer at a speed of 1.19 per B-scan/seconds.

EVALUATION OF POROSITY AND BIOFILM FORMATION IN RELINE RESINS THROUGH OPTICAL COHERENCE TOMOGRAPHY

Objective To evaluate the porosity and adhesion of mixed colony microorganisms in reline resins by means of optical coherence tomography (OCT). Study Design Two commercial brands of reline resins (Soft-Comfort and Coe-Comfort) were used, divided into 2 groups, and 10 samples were made for each group. Samples were submitted to OCT scanning before and after 96 hours inoculation with Candida albicans. The OCT images were composed of 2000 columns and 512 lines, obtained from a commercial model, Callisto SD-OCT (Thorlabs, USA), operating at 930 nm of central wavelength and 7 μm of axial resolution in the air. After the images were acquired, they were submitted to qualitative and quantitative analysis. Results It was possible to verify differences between OCT images before and after inoculation of microorganisms (MO). These differences suggest the observation of fluid absorption and presence of biofilm in the resins. As for the porosity, the Soft-Comfort resin presented higher values compared with the Coe-Comfort resin. Conclusions The OCT technique allows to evaluate the adhesion of microorganisms and porosity in reline resins. To evaluate the porosity and adhesion of mixed colony microorganisms in reline resins by means of optical coherence tomography (OCT). Two commercial brands of reline resins (Soft-Comfort and Coe-Comfort) were used, divided into 2 groups, and 10 samples were made for each group. Samples were submitted to OCT scanning before and after 96 hours inoculation with Candida albicans. The OCT images were composed of 2000 columns and 512 lines, obtained from a commercial model, Callisto SD-OCT (Thorlabs, USA), operating at 930 nm of central wavelength and 7 μm of axial resolution in the air. After the images were acquired, they were submitted to qualitative and quantitative analysis. It was possible to verify differences between OCT images before and after inoculation of microorganisms (MO). These differences suggest the observation of fluid absorption and presence of biofilm in the resins. As for the porosity, the Soft-Comfort resin presented higher values compared with the Coe-Comfort resin. The OCT technique allows to evaluate the adhesion of microorganisms and porosity in reline resins.

Advances in Doppler optical coherence tomography and angiography.

Since the first demonstration of Doppler optical coherence tomography (OCT) in 1997, several functional extensions of Doppler OCT have been developed, including velocimetry, angiogram, and optical coherence elastography. These functional techniques have been widely used in research and clinical applications, particularly in ophthalmology. Here, we review the principles, representative methods, and applications of different Doppler OCT techniques, followed by discussion on the innovations, limitations, and future directions of each of these techniques.

Assessment of the Adaptation of Interim Crowns using Different Measurement Techniques.

To compare the internal fit and marginal discrepancy of acrylic resin interim crowns fabricated by different manufacturing methods, and to test the consistency of measuring marginal discrepancy and internal fit between different measuring techniques. A dentoform mandibular left first molar was prepared for an all-ceramic crown. Thirty-six interim crowns were fabricated and divided into three groups (n = 12): group BAC (Bis-acrylic composite, fabricated manually), group CAM (CAD/CAM polymethylmethacrylate resin, milled), and group 3DP (3D printed methacrylic oligomers, printed). The internal fit of the interim crowns was evaluated by the silicone replica technique and by X-ray microcomputed tomography (µCT) technique. The marginal discrepancy of the interim crowns was evaluated by the vinyl polysiloxane (VPS) (Aquasil Ultra XLV) impression technique and by optical coherence tomography (OCT) technique. Data were statistically analyzed using ANOVA and Turkey tests at α = 0.05. Pearson correlation test was used to evaluate the correlation between the different measurement techniques and marginal discrepancy/internal fit. The manually fabricated interim crowns (group BAC) had significantly greater discrepancy of internal fit than did the digitally fabricated crowns (group CAM and group 3DP) measured by both silicone replica technique and µCT 2-dimensional (2D) image measurement. There were no statistically significant differences in the cement space volume values obtained by the µCT image technique between group BAC and group 3DP (p = 0.285). The coefficientof determination between the two volumetric measurement techniques was low (R2 = 0.30). For marginal discrepancy, the manually fabricated interim crowns had a wider absolute marginal discrepancy than both digitally fabricated groups (p < 0.05). In both the VPS impression and OCT assessment, there was no statistically significant difference between group CAM and group 3DP (p = 0.798 and 0.994, respectively). The coefficientof determination between the VPS impression and OCT techniques for marginal discrepancy measurement was low (R2 = 0.23). Digitally fabricated interim crowns (group CAM and group 3DP) had better internal fit and smaller marginal discrepancy than manually fabricated interim crowns (group BAC). For comparison of the different evaluation techniques, the silicone replica technique and µCT measurements had low correlation for internal fit assessment, as did the PVS impression and OCT techniques for marginal discrepancy test.

Assessing internal fouling during microfiltration using optical coherence tomography and evapoporometry

The internal fouling of membranes is typically presumed and inferred, but the direct characterization of representative samples is challenging. This study targeted to assess internal fouling using the Optical Coherence Tomography (OCT) and Evapoporometry (EP) techniques for real-time monitoring during filtration and off-line measurement of the pore size distributions (PSDs) of the fouled membranes, respectively. The results were validated by atomic force microscopy (AFM) measurements and also the three-mechanism fouling model. The foulant used was the well-studied bovine serum albumin (BSA), while the membranes were three commercially available polymeric microfiltration membranes with similar nominal pore sizes and porosities. Although the OCT affirmed the progressive worsening of internal fouling in real-time, the quantitative comparison of the extents of internal fouling among the three membranes was not possible. As for EP, it was able to quantitatively compare the pore size distributions and average pore diameters to ascertain the different extents of internal fouling. The phenomenological model available was effective in quantitatively comparing the extents of pore-constriction among the three membranes, while AFM tied the worst internal fouling to the most attractive BSA-membrane affinity. More in-depth understanding of internal fouling is warranted to not only recommend better membranes but also facilitate the advancement of models.

Gold Nanobipyramids as Second Near Infrared Optical Coherence Tomography Contrast Agents for in Vivo Multiplexing Studies.

Developing contrast-enhanced optical coherence tomography (OCT) techniques is important for specific imaging of tissue lesions, molecular imaging, cell-tracking, and highly sensitive microangiography and lymphangiography. Multiplexed OCT imaging in the second near-infrared (NIR-II) window is highly desirable since it allows simultaneous imaging and tracking of multiple biological events in high resolution with deeper tissue penetration in vivo. Here we demonstrate that gold nanobipyramids can function as OCT multiplexing contrast agents, allowing high-resolution imaging of two separate lymphatic flows occurring simultaneously from different drainage basins into the same lymph node in a live mouse. Contrast-enhanced multiplexed lymphangiography of a melanoma tumor in vivo shows that the peritumoral lymph flow upstream of the tumor is unidirectional, and tumor is accessible to such flow. Whereas the lymphatic drainage coming out from the tumor is multidirectional. We also demonstrate real-time tracking of the contrast agents draining from a melanoma tumor specifically to the sentinel lymph node of the tumor and the three-dimensional distribution of the contrast agents in the lymph node.

Espacio de Berger

Introduction and objectiveThe Berger's space (BS) is a space located between the posterior capsule of the lens and the anterior hyaloid of the vitreous, structures that adhere in a circular manner by means of the Wieger ligament, for which the outer limit is defined by Egger's line. The aim of this article is to perform a review of the BS, as well as to present three cases in which this BS could be demonstrated by optical coherence tomography (OCT). Material and methodA total of 90 patients from a general ophthalmology clinic were studied, on whom an anterior pole OCT was performed (Cirrus Lumera 700 Carl Zeiss Medicte, Dublin, California, United States). All patients were included consecutively, with an analysis being performed on the cornea, anterior chamber, iris, lens, and anterior vitreous, but excluding those in which the test could not be performed. ResultsThe posterior lens capsule, the anterior hyaloid, and the BS between both structures were observed in three patients. This is the first time in the current literature that three cases have been described, together with their characteristics (one phakic –case 1– and two pseudophakic, one of them vitreous destructuring –case 2– and the other with opacification of the posterior capsule of the lens –case 3–), using this previous pole OCT technique. ConclusionsKnowledge of the BS is essential to understand the vitreo-lenticular junction and any complications in some cataract surgeries, as well as to also understand the pathological origin of pigment dispersion syndrome.

Uveal Melanoma Biopsy: A Review.

Intraocular tumor diagnosis is based on clinical findings supported by additional imaging tools, such as ultrasound, optical coherence tomography and angiographic techniques, usually without the need for invasive procedures or tissue sampling. Despite improvements in the local treatment of uveal melanoma (UM), the prevention and treatment of the metastatic disease remain unsolved, and nearly 50% of patients develop liver metastasis. The current model suggests that tumor cells have already spread by the time of diagnosis, remaining dormant until there are favorable conditions. Tumor sampling procedures at the time of primary tumor diagnosis/treatment are therefore now commonly performed, usually not to confirm the diagnosis of UM, but to obtain a tissue sample for prognostication, to assess patient’s specific metastatic risk. Moreover, several studies are ongoing to identify genes specific to UM tumorigenesis, leading to several potential targeted therapeutic strategies. Genetic information can also influence the surveillance timing and metastatic screening type of patients affected by UM. In spite of the widespread use of biopsies in general surgical practice, in ophthalmic oncology the indications and contraindications for tumor biopsy continue to be under debate. The purpose of this review paper is to critically evaluate the role of uveal melanoma biopsy in ophthalmic oncology.

Spatio-Temporal Optical Coherence Imaging – a new tool for in vivo microscopy

Optical Coherence Imaging (OCI) including Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) uses interferometric detection to generate high-resolution volumetric images of the sample at high speeds. Such capabilities are significant for in vivo imaging, including ophthalmology, brain, intravascular imaging, as well as endoscopic examination. Instrumentation and software development allowed to create many clinical instruments. Nevertheless, most of OCI setups scan the incident light laterally. Hence, OCI can be further extended by wide-field illumination and detection. This approach, however, is very susceptible to the so-called crosstalk-generated noise. Here, we describe our novel approach to overcome this issue with spatio-temporal optical coherence manipulation (STOC), which employs spatial phase modulation of the incident light. Full Text: PDF ReferencesL. Wang, P. P. Ho, C. Liu, G. Zhang, and R. R. Alfano, "Ballistic 2-D Imaging Through Scattering Walls Using an Ultrafast Optical Kerr Gate", Science 253, 769-771 (1991). CrossRef D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and et al., "Optical coherence tomography", Science 254, 1178-1181 (1991). CrossRef J. A. Izatt, E. A. Swanson, J. G. Fujimoto, M. R. Hee, and G. M. Owen, "Optical coherence microscopy in scattering media", Opt. Lett. 19, 590-592 (1994). CrossRef D. Borycki, M. Nowakowski, and M. Wojtkowski, "Control of the optical field coherence by spatiotemporal light modulation", Opt. Lett. 38, 4817-4820 (2013). CrossRef D. Borycki, M. Hamkalo, M. Nowakowski, M. Szkulmowski, and M. Wojtkowski, "Spatiotemporal optical coherence (STOC) manipulation suppresses coherent cross-talk in full-field swept-source optical coherence tomography", Biomed. Opt. Express 10, 2032-2054 (2019). CrossRef P. Stremplewski, E. Auksorius, P. Wnuk, L. Kozon, P. Garstecki, and M. Wojtkowski, "In vivo volumetric imaging by crosstalk-free full-field OCT", Optica 6, 608-617 (2019). CrossRef L. Vabre, A. Dubois, and A. C. Boccara, "Thermal-light full-field optical coherence tomography", Opt. Lett. 27, 530-532 (2002). CrossRef M. Laubscher, M. Ducros, B. Karamata, T. Lasser, and R. Salathé, "Video-rate three-dimensional optical coherence tomography", Opt. Express 10, 429-435 (2002). CrossRef Dubois and A. C. Boccara, Full-Field Optical Coherence Tomography, (Springer Berlin Heidelberg, Berlin, Heidelberg, 2008), pp. 565-591. CrossRef O. Thouvenin, K. Grieve, P. Xiao, C. Apelian, and A. C. Boccara, "En face coherence microscopy [Invited]", Biomedical Opt. Express 8, 622-639 (2017). CrossRef F. Fercher, C. K. Hitzenberger, M. Sticker, E. Moreno-Barriuso, R. Leitgeb, W. Drexler, and H. Sattmann, "A thermal light source technique for optical coherence tomography", Optics Commun. 185, 57-64 (2000). CrossRef R. A. Leitgeb, "En face optical coherence tomography: a technology review [Invited]", Biomed Opt Express 10, 2177-2201 (2019). CrossRef J. Fujimoto and W. Drexler, Introduction to Optical Coherence Tomography, (Springer, Berlin, Heidelberg, 2008), pp. 1-45. CrossRef J. A. Izatt, M. A. Choma, and A.-H. Dhalla, Theory of Optical Coherence Tomography, (Springer International Publishing, Cham, 2015), pp. 65-94. CrossRef

Quantitative assessment of skin swelling using optical coherence tomography.

Preclinical and clinical studies suggest that optical coherence tomography (OCT) is a useful tool to visualize inflammatory conditions. The objective of this study was to evaluate the usefulness of combining OCT and various image processing techniques for quantitative assessment of histamine-induced tissue swelling. Both time-domain and frequency-domain OCT were used on a mouse ear model. The ear thickness and volume before and after histamine challenge were determined from pixel locations in 2D scans and voxel number counting in 3D scans. Swelling kinetics was analyzed on 3D contour mapping. Microvessel network was visualized using speckle decorrelation analysis. OCT images showed that the thickness and volume changes were histamine dose and contact time dependent. The 3D mapping showed that the histamine-induced swelling spread slowly and directionally. OCT data indicated that microvessel opening and vessel dilation occurred prior to tissue swelling. OCT is a robust and quantitative non-invasive imaging tool for assessing skin swelling.

Sub-surface imaging of soiled cotton fabric using full-field optical coherence tomography.

In the laundry industry, colorimetry is a common way to evaluate the stain removal efficiency of detergents and cleaning products. For ease of visualization, the soiling agent is treated with a dye before measurement. However, it effectively measures the dye removal rather than stain removal, and it cannot provide depth-resolved information of the sample. In this study, we show that full-field (FF) optical coherence tomography (OCT) technique is capable of measuring the cleaning effect on cotton fabric by imaging the sub-surface features of fabric samples. We used a broadband light-emitting diode (LED) source to power the FF-OCT system that achieves the resolution of 1 µm axially and 1.6 µm laterally. This allows the micron-sized cotton fibres/fibrils at different depth positions to be resolved. The clean, the soiled, and the washed samples can be differentiated from their cross-sectional images using OCT, where the cleaning effect can be correlated with the sub-surface fibre volume. The experimental results of the proposed method were found to be in good agreement with those of the standard colorimetry method. The proposed technique therefore offers an alternative way for measuring the stain removal from fabric substrate to assess the effectiveness of laundry detergent products.