Optical coherence tomography: an emerging technology for biomedical imaging and optical biopsy

Portable boom-type ultrahigh-resolution OCT with an integrated imaging probe for supine position retinal imaging

To expand the clinical applications and improve the ease of use of ultrahigh-resolution optical coherence tomography (UHR-OCT), we developed a portable boom-type ophthalmic UHR-OCT operating in supine position that can be used for pediatric subjects, bedridden patients and perioperative conditions. By integrating the OCT sample arm probe with real-time iris display and automatic focusing electric lens for easy alignment, coupling the probe on a self-locking multi-directional manipulator to reduce motion artifacts and operator fatigue, and installing the OCT module on a moveable cart for system mobility, our customized portable boom-type UHR-OCT enables non-contact, high-resolution and high-stability retinal examinations to be performed on subjects in supine position. The spectral-domain UHR-OCT operates at a wavelength of 845 nm with 130 nm FWHM (full width at half maximum) bandwidth, achieving an axial resolution of ≈2.3µm in tissue with an A-line acquisition rate up to 128 kHz. A high-definition two-dimensional (2D) raster protocol was used for high-quality cross-sectional imaging while a cube volume three-dimensional (3D) scan was used for three-dimensional imaging and en-face reconstruction, resolving major layer structures of the retina. The feasibility of the system was demonstrated by performing supine position 2D/3D retinal imaging on healthy human subjects, sedated infants, and non-sedated awake neonates.

Automated counting of cerebral penetrating vessels using optical coherence tomography images of a mouse brain in vivo

RATIONALE AND OBJECTIVES

Penetrating blood vessels emanating from cortical surface vasculature and lying deep in the cortex are essential vascular conduits for the shuttling of blood from superficial pial vessels to the capillary beds in parenchyma for the nourishment of neuronal brain tissues. Locating and counting the penetrating vessels is beneficial for the quantification of a course of ischemia in blood occlusive events such as stroke. This paper seeks to demonstrate and validate a method for automated penetrating vessel counting that uses optical coherence tomography (OCT).

MATERIALS AND METHODS

This paper proposes an OCT method that effectively identifies and grades the cortical penetrating vessels in perfusion. The key to the proposed method is the harnessing of vascular features found in the penetrating vessels, which are distinctive from those of other vessels. In particular, with an increase in the light attenuation and flow turbulence, the contrast in the mean projection of the OCT datacube decreases, whereas that in the maximum projection of the Doppler frequency variance datacube increases. By multiplying the inversion of the former with the latter, its binary thresholding is sufficient to highlight the penetrating vessels and allows for their counting over the projection image.

RESULTS

A computational method that leverages the decrease in mean OCT projection intensity and the increase in Doppler frequency variance at the penetrating vessel is developed. It successfully identifies and counts penetrating vessels with a high accuracy of over 87%. The penetrating vessel density is observed to be significantly reduced in the mouse model of focal ischemic stroke.

CONCLUSION

The OCT analysis is effective for counting penetrating blood vessels in mice brains and may be applied to the rapid diagnosis and treatment of stroke in stroke models of small animals. This article is protected by copyright. All rights reserved.

Research Techniques Made Simple: Emerging Imaging Technologies for Noninvasive Optical Biopsy of Human Skin

Over the past few years, high-resolution optical imaging technologies such as optical coherence tomography (OCT), reflectance confocal microscopy (RCM), and multiphoton microscopy (MPM) have advanced significantly as new methodologies for clinical research and for real-time detection, diagnosis, and therapy monitoring of skin diseases. Implementation of these technologies into clinical research and practice requires clinicians to have an understanding of their capabilities, benefits, and limitations. This concise review provides insights on the application of OCT, RCM, and MPM for clinical skin imaging through images acquired in vivo from the same lesions. The presented data are limited to pigmented lesions and basal cell carcinoma.

Biophotonics in Dentistry

The aim of this review paper is to concentrate on the use and application of photonics in dentistry. More than one hundred review and research articles were comprehensively analysed in terms of applications of photonics in dentistry, including surgical applications, as well as dental biomaterials, diagnosis and treatments. In biomedical engineering, various fields, such as biology, chemistry, material and physics, come together in to tackle a disease/disorder either as a diagnostic tool or an option for treatment. Engineers believe that biophotonics is the application of photonics in medicine, whereas photonics is simply a technology for creating and connecting packets of light energy, known as photons. This review paper provides a comprehensive discussion of its main elements, such as photoelasticity, interferometry techniques, optical coherence tomography, different types of lasers, carbon nanotubes, graphene and quantum dots.

Laboratory system for optical coherence tomography (OCT) using a laser plasma source of soft x-rays and extreme ultraviolet and focusing ellipsoidal optics

Optical coherence tomography (OCT) with the use of soft x-rays (SXR) and extreme ultraviolet (EUV) has been recently demonstrated [Fuchs et al. Sci. Rep.6, 20658 (2016)10.1038/srep20658; Fuchs et al. Optica4, 903 (2017)10.1364/OPTICA.4.000903]. This new imaging technique, named XCT, makes it possible to obtain cross-sectional and tomographic images of objects with nanometer spatial resolution. The article presents a newly developed laboratory system for XCT using a compact laser plasma light source operating in the SXR and EUV spectral ranges. The source is based on a gas puff target containing Kr gas or a Kr/Xe gas mixture irradiated with nanosecond laser pulses from an Nd:YAG laser. The use of the gas puff target enables efficient emission of SXR and EUV radiation without generating target debris associated with laser ablation when using a solid target. The system is equipped with an ellipsoidal mirror to collect radiation from the source and focus on the imaged object. The XCT measurements are made by processing the spectrum of the radiation reflected from the object recorded with a transmission grating spectrometer equipped with an identical focusing mirror and a CCD camera. The paper presents the characterization and optimization of the new XCT system and its application to the measurements of layered nanostructures.

An Overview of Terahertz Imaging with Resonant Tunneling Diodes

Terahertz (THz) imaging is a rapidly growing application motivated by industrial demands including harmless (non-ionizing) security imaging, multilayer paint quality control within the automotive industry, insulating foam non-invasive testing in aerospace, and biomedical diagnostics. One of the key components in the imaging system is the source and detector. This paper gives a brief overview of room temperature THz transceiver technology for imaging applications based on the emerging resonant tunneling diode (RTD) devices. The reported results demonstrate that RTD technology is a very promising candidate to realize compact, low-cost THz imaging systems.

Organic fluorescent nanoprobes with NIR-IIb characteristics for deep learning

Illumination of biological events with near-infrared II sub-channel (NIR-IIb, 1500-1700 nm) enhances the transparency of biological tissues, which is very attractive for deep imaging. Due to the long-wavelength, which reduces optical damage, suppresses autofluorescence, and obviates light scattering, NIR-IIb nanoprobes afford deep tissue penetration with unprecedented spatiotemporal resolution. Hence, NIR-IIb imaging facilitates deep learning and decipherment of biological proceedings in living organisms with astounding high clarity. In comparison to its predecessors in the visible-near-infrared spectrum, imaging in the NIR-IIb has shown great potential for tissue imaging and extrapolating imaging applications for clinical studies. However, the use of organic fluorescent nanoprobes (OFNPs) in the NIR-IIb region is still rare since it is in its early stages. Thus, herein we aim to survey the recent development of different organic fluorescent nanomaterials with NIR-IIb characteristics, their unique photophysical properties, and their utilization in deep imaging in animal models. Further, practical researches on organic fluorescent nanoprobes with NIR-IIb emission and their transition to clinical applications are highlighted.

Performance evaluation of various deep learning based models for effective glaucoma evaluation using optical coherence tomography images

Glaucoma is the dominant reason for irreversible blindness worldwide, and its best remedy is early and timely detection. Optical coherence tomography has come to be the most commonly used imaging modality in detecting glaucomatous damage in recent years. Deep Learning using Optical Coherence Tomography Modality helps in predicting glaucoma more accurately and less tediously. This experimental study aims to perform glaucoma prediction using eight different ImageNet models from Optical Coherence Tomography of Glaucoma. A thorough investigation is performed to evaluate these models' performances on various efficiency metrics, which will help discover the best performing model. Every net is tested on three different optimizers, namely Adam, Root Mean Squared Propagation, and Stochastic Gradient Descent, to find the best relevant results. An attempt has been made to improvise the performance of models using transfer learning and fine-tuning. The work presented in this study was initially trained and tested on a private database that consists of 4220 images (2110 normal optical coherence tomography and 2110 glaucoma optical coherence tomography). Based on the results, the four best-performing models are shortlisted. Later, these models are tested on the well-recognized standard public Mendeley dataset. Experimental results illustrate that VGG16 using the Root Mean Squared Propagation Optimizer attains auspicious performance with 95.68% accuracy. The proposed work concludes that different ImageNet models are a good alternative as a computer-based automatic glaucoma screening system. This fully automated system has a lot of potential to tell the difference between normal Optical Coherence Tomography and glaucomatous Optical Coherence Tomography automatically. The proposed system helps in efficiently detecting this retinal infection in suspected patients for better diagnosis to avoid vision loss and also decreases senior ophthalmologists' (experts) precious time and involvement.

Finite Element Analysis of the Epiretinal Membrane Contraction

The epiretinal membrane is a thin sheet of fibrous tissue that can form over the macular area of the retina, and may result in the loss of visual acuity or metamorphopsia, due to superficial retinal folds. A vitrectomy surgery, the current treatment procedure for this pathology, is only performed after symptoms are present. However, sometimes the patients do not present any vision improvements after the surgery. The use of computational methods for a patient-specific biomechanical analysis can contribute to better understanding the mechanisms behind the success or failure of a vitrectomy. Using medical data from two patients who underwent a vitrectomy, one with substantial improvements and another with no improvements, an analysis of the retinal displacement due to the contraction of the epiretinal membrane was performed. Our results suggest a causal effect between the magnitude of the retinal displacements caused by the epiretinal membrane contraction and the outcome of the vitrectomy procedure.

Role of Anterior Segment-Optical Coherence Tomography Angiography in Acute Ocular Burns

Acute ocular burns have varied manifestations which require prompt diagnosis and management to prevent chronic sequelae. Of these, the detection of limbal ischemia poses a challenge because of the subjective nature of its clinical signs. Anterior segment optical coherence tomography angiography (AS-OCTA) offers an objective method of assessing ischemia in these eyes. This review provides an overview of the technology of AS-OCTA and its applications in acute burns. AS-OCTA generates images by isolating the movement of erythrocytes within blood vessels from sequentially obtained b-scans. Limbal ischemia manifests in these scans as absent vasculature and the extent of ischemia can be quantified using different vessel-related parameters. Of these, the density of vessels is most commonly used and correlates with the severity of the injury. Incorporation of the degree of ischemia in the classification of acute burns has been attempted in animal studies and its extension to human trials may provide an added dimension in determining the final prognosis of these eyes. Thus, AS-OCTA is a promising device that can objectively evaluate limbal ischemia. This will facilitate the identification of patients who will benefit from revascularization therapies and stem cell transplants in acute and chronic ocular burns, respectively.

Is Real-Time Microscopy on the Horizon? A Brief Review of the Potential Future Directions in Clinical Breast Tumor Microscopy Implementation

We will briefly review the current paradigm and some recent developments in the area of clinical breast microscopy, highlighting several promising commercially available, and research-based platforms. Confocal microscopy (reflectance, fluorescence, and spectrally encoded), optical coherence tomography (wide field and full field), stereomicroscopy, open-top light sheet microscopy, microscopy with ultraviolet surface excitation, nonlinear microscopy, Raman scattering microscopy, photoacoustic microscopy, and needle microendoscopy will be discussed. Non-microscopic methods for breast pathology assessment are beyond the scope of this review. These microscopic technologies have to varying degrees the potential for transforming breast cancer care, but in order for any of these to be integrated into clinical practice there are several hurdles to overcome. In our review we will focus on what needs to be done in order for the commercially available technologies to become more established, what the technologies in the research domain need to do in order to reach the commercial realm; and finally, what the field of breast pathology might look like if these technologies were to be widely adopted.

Comparison of Long-Wave and Mid-Wave Infrared Imaging Modalities for Photothermal Coherence Tomography of Human Teeth

The ability to detect dental caries at early stages lies at the heart of minimal intervention dentistry, enabling the curing or arresting of carious lesions before they advance to the cavity stage. Enhanced truncated-correlation photothermal coherence tomography (eTC-PCT) using mid-wave infrared (MWIR) cameras has recently been shown to offer tomographic visualization of early caries. The tomographic slicing ability of such systems, however, is believed to be limited by direct radiative thermal emission through the translucent dental enamel in the 3-5 m MWIR spectral range. Such radiative emissions can dominate the delayed conductive thermal contributions needed for tomographic reconstruction of internal dental defects. It has been hypothesized that long-wave infrared (LWIR) eTC-PCT systems may offer better tomographic performance by taking advantage of the intrinsic attenuation of direct radiative emission by dental enamel in the LWIR spectral range, enabling more effective delayed conductive thermal contributions from subsurface caries. More than an order of magnitude lower cost of the system is another key attribute of LWIR eTC-PCT which can open the door for downstream translation of the technology to clinics. In this report, we offer a systematic comparison of the performance/effectiveness of caries detection with LWIR and MWIR eTC-PCT systems for detecting natural caries, bacterial caries, and artificially demineralized enamel surfaces. Our results suggest that the low-cost LWIR based eTC-PCT system provides 3D visualization and 2D slice-by-slice images of early caries and internal micro-cracks similar to those obtained from the more expensive MWIR-based eTC-PCT system, albeit with ~1.3dB lower signal-to-noise ratio.

Imaging Modalities for Intracranial Aneurysm: More Than Meets the Eye

Intracranial aneurysms (IA) are often asymptomatic and have a prevalence of 3 to 5% in the adult population. The risk of IA rupture is low, however when it occurs half of the patients dies from subarachnoid hemorrhage (SAH). To avoid this fatal evolution, the main treatment is an invasive surgical procedure, which is considered to be at high risk of rupture. This risk score of IA rupture is evaluated mainly according to its size and location. Therefore, angiography and anatomic imaging of the intracranial aneurysm are crucial for its diagnosis. Moreover, it has become obvious in recent years that several other factors are implied in this complication, such as the blood flow complexity or inflammation. These recent findings lead to the development of new IA imaging tools such as vessel wall imaging, 4D-MRI, or molecular MRI to visualize inflammation at the site of IA in human and animal models. In this review, we will summarize IA imaging techniques used for the patients and those currently in development.

Directional analysis of intensity changes for determining the existence of cyst in optical coherence tomography images

Diabetic retinopathy (DR) is an important cause of blindness in people with the long history of diabetes. DR is caused due to the damage to blood vessels in the retina. One of the most important manifestations of DR is the formation of fluid-filled regions between retinal layers. The evaluation of stage and transcribed drugs can be possible through the analysis of retinal Optical Coherence Tomography (OCT) images. Therefore, the detection of cysts in OCT images and the is of considerable importance. In this paper, a fast method is proposed to determine the status of OCT images as cystic or non-cystic. The method consists of three phases which are pre-processing, boundary pixel determination and post-processing. After applying a noise reduction method in the pre-processing step, the method finds the pixels which are the boundary pixels of cysts. This process is performed by finding the significant intensity changes in the vertical direction and considering rectangular patches around the candidate pixels. The patches are verified whether or not they contain enough pixels making considerable diagonal intensity changes. Then, a shadow omission method is proposed in the post-processing phase to extract the shadow regions which can be mistakenly considered as cystic areas. Then, the pixels extracted in the previous phase that are near the shadow regions are removed to prevent the production of false positive cases. The performance of the proposed method is evaluated in terms of sensitivity and specificity on real datasets. The experimental results show that the proposed method produces outstanding results from both accuracy and speed points of view.

Review on Laser Technology in Intravascular Imaging and Treatment

Blood vessels are one of the most essential organs, which nourish all tissues in our body. Once there are intravascular plaques or vascular occlusion, other organs and circulatory systems will not work properly. Therefore, it is necessary to detect abnormal blood vessels by intravascular imaging technologies for subsequent vascular treatment. The emergence of lasers and fiber optics promotes the development of intravascular imaging and treatment. Laser imaging techniques can obtain deep vascular images owing to light scattering and absorption properties. Moreover, photothermal and photomechanical effects of laser make it possible to treat vascular diseases accurately. In this review, we present the research progress and applications of laser techniques in intravascular imaging and treatment. Firstly, we introduce intravascular optical coherent tomography and intravascular photoacoustic imaging, which can obtain various information of plaques. Multimodal intravascular imaging techniques provide more information about intravascular plaques, which have an essential influence on intravascular imaging. Secondly, two laser techniques including laser angioplasty and endovenous laser ablation are discussed for the treatment of arterial and venous diseases, respectively. Finally, the outlook of laser techniques in blood vessels, as well as the integration of laser imaging and treatment are prospected in the section of discussions.

Deep-learning approach for automated thickness measurement of epithelial tissue and scab using optical coherence tomography

SIGNIFICANCE

In order to elucidate therapeutic treatment to accelerate wound healing, it is crucial to understand the process underlying skin wound healing, especially re-epithelialization. Epidermis and scab detection is of importance in the wound healing process as their thickness is a vital indicator to judge whether the re-epithelialization process is normal or not. Since optical coherence tomography (OCT) is a real-time and non-invasive imaging technique that can perform a cross-sectional evaluation of tissue microstructure, it is an ideal imaging modality to monitor the thickness change of epidermal and scab tissues during wound healing processes in micron-level resolution. Traditional segmentation on epidermal and scab regions was performed manually, which is time-consuming and impractical in real time.

AIM

We aim to develop a deep-learning-based skin layer segmentation method for automated quantitative assessment of the thickness of in vivo epidermis and scab tissues during a time course of healing within a rodent model.

APPROACH

Five convolution neural networks were trained using manually labeled epidermis and scab regions segmentation from 1000 OCT B-scan images (assisted by its corresponding angiographic information). The segmentation performance of five segmentation architectures was compared qualitatively and quantitatively for validation set.

RESULTS

Our results show higher accuracy and higher speed of the calculated thickness compared with human experts. The U-Net architecture represents a better performance than other deep neural network architectures with 0.894 at F1-score, 0.875 at mean intersection over union, 0.933 at Dice similarity coefficient, and 18.28  μm at an average symmetric surface distance. Furthermore, our algorithm is able to provide abundant quantitative parameters of the wound based on its corresponding thickness maps in different healing phases. Among them, normalized epidermal thickness is recommended as an essential hallmark to describe the re-epithelialization process of the rodent model.

CONCLUSIONS

The automatic segmentation and thickness measurements within different phases of wound healing data demonstrates that our pipeline provides a robust, quantitative, and accurate method for serving as a standard model for further research into effect of external pharmacological and physical factors.

Multimodality Imaging Trials Evaluating the Impact of Omega-3 Fatty Acids on Coronary Artery Plaque Characteristics and Burden

Treatment of established risk factors, especially low-density lipoprotein (LDL) cholesterol, is the cornerstone of preventing atherosclerotic coronary artery disease. Despite reducing LDL cholesterol, there remains a significant risk of cardiovascular disease. Inflammatory and metabolic pathways contribute to recurrence of cardiovascular events, and are often missed in clinical practice. Eicosapentaenoic acid (EPA) may play a crucial role in reducing residual risk of cardiovascular disease. In this review we discuss the clinical applications of omega-3 fatty acids (OM3FAs), their mechanism of action, the difference between pure EPA and docosahexaenoic acid components, and the latest cardiovascular outcome trials and imaging trials evaluating coronary plaque. PubMed and EMBASE were searched to include all the remarkable clinical trials investigating OM3FAs and cardiovascular disease. Beyond statins, additional medications are required to reduce the risk of cardiovascular disease. EPA has shown cardiovascular benefit in addition to statins in large outcome trials. Additionally, multiple serial-imaging studies have demonstrated benefits on plaque progression and stabilization. Due to its pleotropic properties, icosapent ethyl outperforms other OM3FAs in decreasing cardiovascular disease risk in both patients with and without high triglycerides, and is currently recommended as an adjunct to statins. To further strengthen the current evidence, additional research is required to elucidate the inconsistencies between the effects of pure EPA and EPA plus docosahexaenoic acid.

Scanning interferometric near-infrared spectroscopy

In diffuse optics, quantitative assessment of the human brain is confounded by the skull and scalp. To better understand these superficial tissues, we advance interferometric near-infrared spectroscopy (iNIRS) to form images of the human superficial forehead blood flow index (BFI). We present a null source-collector (S-C) polarization splitting approach that enables galvanometer scanning and eliminates unwanted backscattered light. Images show an order-of-magnitude heterogeneity in superficial dynamics, implying an order-of-magnitude heterogeneity in brain specificity, depending on forehead location. Along the time-of-flight dimension, autocorrelation decay rates support a three-layer model with increasing BFI from the skull to the scalp to the brain. By accurately characterizing superficial tissues, this approach can help improve specificity for the human brain.

The diagnostic accuracy and prognostic value of OCT for the evaluation of the visual function in children with a brain tumour: A systematic review

Purpose

To systematically review the evidence on the diagnostic accuracy and prognostic value of retinal optical coherence tomography (OCT) to detect visual acuity (VA) or visual field (VF) loss in children with a brain tumour.

Methods

PubMed, Embase and Cochrane Library databases were searched from inception to February 2021. We included studies evaluating retinal OCT and standard visual function parameters (VA and or VF) in children with a brain tumour. Two authors independently extracted data from each included study. They also assessed the methodological quality of the studies using the QUADAS-2 or QUIPS tool. The diagnostic accuracy of OCT was evaluated with receiver operating characteristic analysis, sensitivity, specificity, positive predictive value and negative predictive value. The prognostic value of OCT was evaluated with predictive measures (odds ratio).

Results

We included five diagnostic studies, with a total of 186 patients, all diagnosed with optic pathway glioma. No prognostic studies were eligible for inclusion. Included studies evaluated either retinal nerve fiber layer (RNFL) thickness or ganglion cell layer—inner plexiform layer (GCL-IPL) thickness. There was considerable heterogeneity between OCT devices, OCT protocols, visual function parameters and threshold values. Sensitivity and specificity for RNFL thickness measurement ranged from 60.0% to 100.0% and 76.6% to 100%, respectively. For GCL-IPL thickness measurement, area under the curve ranged from 0.91 to 0.98 for different diameters.

Conclusion

The literature regarding the diagnostic accuracy and prognostic value of OCT parameters in children with a brain tumour is scarce. Due to heterogeneity and a considerable risk of bias of included studies, we cannot draw solid conclusions regarding the accuracy of retinal OCT. Future research should investigate the potential of OCT as diagnostic and prognostic tool for the evaluation of the visual function and detection of visual impairment in children with any type of brain tumour.

The effect of branch retinal vein occlusion on the vascular structure of the choroid

OBJECTIVE

Our aim is to examine choroidal structural changes in eyes with branch retinal vein occlusion (BRVO).

MATERIAL AND METHOD

This retrospective, comparative study included 34 newly diagnosed unilateral BRVO patients and 40 healthy controls. Subfoveal choroidal thickness (SFCT) measurement was performed with enhanced depth imaging optical coherence tomography (EDI-OCT). The images were binarized using the ImageJ software program. Total choroidal area (TCA), stromal area (SA), and luminal area (LA) were calculated from the 1500 µm area. The choroidal vascular index (CVI) was determined as the LA/TCA ratio. All parameter values were compared between the BRVO eye and the fellow eye, and the control group eyes.

RESULTS

Eyes with BRVO had a greater SA compared to both fellow and control eyes; hence, the CVI was lower (p < 0.001). LA did not differ between eyes. TCA, although not statistically significant, was larger in eyes with BRVO than in both fellow and control eyes. SFCT was also greater in eyes with BRVO. No correlation was observed between CVI and SFCT and best-corrected visual acuity (BCVA).

CONCLUSION

BRVO affects the stromal part of the choroid rather than its vascular structure. SA increases due to choroidal exudation that occurs in response to retinal ischemia, and CVI decreases accordingly.

Is Computer-Assisted Tissue Image Analysis the Future in Minimally Invasive Surgery? A Review on the Current Status of Its Applications

Purpose: Computer-assisted tissue image analysis (CATIA) enables an optical biopsy of human tissue during minimally invasive surgery and endoscopy. Thus far, it has been implemented in gastrointestinal, endometrial, and dermatologic examinations that use computational analysis and image texture feature systems. We review and evaluate the impact of in vivo optical biopsies performed by tissue image analysis on the surgeon’s diagnostic ability and sampling precision and investigate how operation complications could be minimized. Methods: We performed a literature search in PubMed, IEEE, Xplore, Elsevier, and Google Scholar, which yielded 28 relevant articles. Our literature review summarizes the available data on CATIA of human tissues and explores the possibilities of computer-assisted early disease diagnoses, including cancer. Results: Hysteroscopic image texture analysis of the endometrium successfully distinguished benign from malignant conditions up to 91% of the time. In dermatologic studies, the accuracy of distinguishing nevi melanoma from benign disease fluctuated from 73% to 81%. Skin biopsies of basal cell carcinoma and melanoma exhibited an accuracy of 92.4%, sensitivity of 99.1%, and specificity of 93.3% and distinguished nonmelanoma and normal lesions from benign precancerous lesions with 91.9% and 82.8% accuracy, respectively. Gastrointestinal and endometrial examinations are still at the experimental phase. Conclusions: CATIA is a promising application for distinguishing normal from abnormal tissues during endoscopic procedures and minimally invasive surgeries. However, the efficacy of computer-assisted diagnostics in distinguishing benign from malignant states is still not well documented. Prospective and randomized studies are needed before CATIA is implemented in clinical practice.

Role of Optical Coherence Tomography Imaging in Predicting Progression of Age-Related Macular Disease: A Survey

In developed countries, age-related macular degeneration (AMD), a retinal disease, is the main cause of vision loss in the elderly. Optical Coherence Tomography (OCT) is currently the gold standard for assessing individuals for initial AMD diagnosis. In this paper, we look at how OCT imaging can be used to diagnose AMD. Our main aim is to examine and compare automated computer-aided diagnostic (CAD) systems for diagnosing and grading of AMD. We provide a brief summary, outlining the main aspects of performance assessment and providing a basis for current research in AMD diagnosis. As a result, the only viable alternative is to prevent AMD and stop both this devastating eye condition and unwanted visual impairment. On the other hand, the grading of AMD is very important in order to detect early AMD and prevent patients from reaching advanced AMD disease. In light of this, we explore the remaining issues with automated systems for AMD detection based on OCT imaging, as well as potential directions for diagnosis and monitoring systems based on OCT imaging and telemedicine applications.

Flush Flow Behaviour Affected by the Morphology of Intravascular Endoscope: A Numerical Simulation and Experimental Study

Background: Whilst intravascular endoscopy can be used to identify lesions and assess the deployment of endovascular devices, it requires temporary blockage of the local blood flow during observation, posing a serious risk of ischaemia. Objective: To aid the design of a novel flow-blockage-free intravascular endoscope, we explored changes in the haemodynamic behaviour of the flush flow with respect to the flow injection speed and the system design. Methods: We first constructed the computational models for three candidate endoscope designs (i.e., Model A, B, and C). Using each of the three endoscopes, flow patterns in the target vessels (straight, bent, and twisted) under three different sets of boundary conditions (i.e., injection speed of the flush flow and the background blood flowrate) were then resolved through use of computational fluid dynamics and in vitro flow experiments. The design of endoscope and its optimal operating condition were evaluated in terms of the volume fraction within the vascular segment of interest, as well as the percentage of high-volume-fraction area (PHVFA) corresponding to three cross-sectional planes distal to the microcatheter tip. Results: With a mild narrowing at the endoscope neck, Model B exhibited the highest PHVFA, irrespective of location of the cross-sectional plane, compared with Models A and C which, respectively, had no narrowing and a moderate narrowing. The greatest difference in the PHVFA between the three models was observed on the cross-sectional plane 2 mm distal to the tip of the microcatheter (Model B: 33% vs. Model A: 18%). The background blood flowrate was found to have a strong impact on the resulting volume fraction of the flush flow close to the vascular wall, with the greatest difference being 44% (Model A). Conclusion: We found that the haemodynamic performance of endoscope Model B outperformed that of Models A and C, as it generated a flush flow that occupied the largest volume within the vascular segment of interest, suggesting that the endoscope design with a diameter narrowing of 30% at the endoscope neck might yield images of a better quality.

Polypoidal Choroidal Vasculopathy Diagnosis and Neovascular Activity Evaluation Using Optical Coherence Tomography Angiography

Purpose

To examine choroidal neovascularization (CNV) characteristics in patients with exudative age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV), using swept-source optical coherence tomography angiography (SS-OCTA), and investigate agreement with OCT B-scan, fundus fluorescein angiography (FFA), and indocyanine green angiography (ICGA) by two different examiners.

Methods

This is a retrospective multicentric study that involved patients with a history of AMD and PCV. Examiner A, who had access to OCTA, B-scan OCT, FFA, and ICGA imaging, had to differentiate between AMD and PCV, study the activity of AMD using Coscas' criteria (active vs. quiescent), and categorize PCV subtypes, while examiner B had only access to OCTA. Then, the diagnostic concordance was assessed between both examiners.

Results

A total of 27 patients (11 females (40.7%) and 16 males (59.3%), P = 0.231) were included in the analysis. Among those, 13 patients presented with neovascular AMD and 14 patients with PCV. There were 92.3% of correct answers regarding appropriate diagnosis and lesion characterization among AMD patients, against 61.5% of correct answers among PCV patients. The overall interrater reliability agreement between examiners, using Cohen's kappa coefficient (κ) was 0.70 (0.5082-0.8916). Disagreement was found with one active AMD misdiagnosed as inactive AMD, three inactive PCV misdiagnosed as inactive AMD, and one inactive PCV misdiagnosed as active AMD.

Conclusion

SS-OCTA alone remains limited in some specific phenotypes of PCV, which suggests the ongoing role of B-scan OCT associated with FFA and ICGA in the diagnosis of these conditions.

High-Resolution Imaging for the Analysis and Reconstruction of 3D Microenvironments for Regenerative Medicine: An Application-Focused Review

The rapid evolution of regenerative medicine and its associated scientific fields, such as tissue engineering, has provided great promise for multiple applications where replacement and regeneration of damaged or lost tissue is required. In order to evaluate and optimise the tissue engineering techniques, visualisation of the material of interest is crucial. This includes monitoring of the cellular behaviour, extracellular matrix composition, scaffold structure, and other crucial elements of biomaterials. Non-invasive visualisation of artificial tissues is important at all stages of development and clinical translation. A variety of preclinical and clinical imaging methods-including confocal multiphoton microscopy, optical coherence tomography, magnetic resonance imaging (MRI), and computed tomography (CT)-have been used for the evaluation of artificial tissues. This review attempts to present the imaging methods available to assess the composition and quality of 3D microenvironments, as well as their integration with human tissues once implanted in the human body. The review provides tissue-specific application examples to demonstrate the applicability of such methods on cardiovascular, musculoskeletal, and neural tissue engineering.

Comparison of image quality of corneal and retinal optical coherence tomography using sedation and general anesthesia protocols with or without retrobulbar anesthesia in horses

OBJECTIVE

To compare image quality and acquisition time of corneal and retinal spectral domain optical coherence tomography (SD-OCT) under 3 different sedation-anesthesia conditions in horses.

ANIMALS

6 middle-aged geldings free of ocular disease.

PROCEDURES

1 randomly selected eye of each horse was evaluated via SD-OCT under the following 3 conditions: standing sedation without retrobulbar anesthetic block (RB), standing sedation with RB, and general anesthesia with RB. Five regions of interest were evaluated in the cornea (axial and 12, 3, 6, and 9 o'clock positions) and fundus (optic nerve head). Three diagnostic scans of predetermined quality were obtained per anatomical region. Image acquisition times and total scans per site were recorded. Corneal and retinal SD-OCT image quality was graded on a subjective scale from 0 (nondiagnostic) to 4 (excellent).

RESULTS

Mean values for the standing sedation without RB, standing sedation with RB, and general anesthesia conditions were 24, 23, and 17, respectively, for total cornea scan attempts; 23, 19, and 19 for total retina-scan attempts; 14.6, 13.2, and 9.2 minutes for total cornea scan time; 19.1, 9.2, and 13.0 for total retina scan time; 2.0, 2.3, and 2.5 for cornea grade; and 2.7, 2.9, and 2.5 for retina grade.

CONCLUSIONS AND CLINICAL RELEVANCE

The RB facilitated globe akinesia and improved the percentage of scans in frame and region of interest accuracy for retinal imaging via OCT in horses. Retrobulbar blocks improved clinical image acquisition while minimizing motion artifact.

Measures of disease activity in glaucoma

Glaucoma is the leading cause of irreversible blindness globally which significantly affects the quality of life and has a substantial economic impact. Effective detective methods are necessary to identify glaucoma as early as possible. Regular eye examinations are important for detecting the disease early and preventing deterioration of vision and quality of life. Current methods of measuring disease activity are powerful in describing the functional and structural changes in glaucomatous eyes. However, there is still a need for a novel tool to detect glaucoma earlier and more accurately. Tear fluid biomarker analysis and new imaging technology provide novel surrogate endpoints of glaucoma. Artificial intelligence is a post-diagnostic tool that can analyse ophthalmic test results. A detail review of currently used clinical tests in glaucoma include intraocular pressure test, visual field test and optical coherence tomography are presented. The advanced technologies for glaucoma measurement which can identify specific disease characteristics, as well as the mechanism, performance and future perspectives of these devices are highlighted. Applications of AI in diagnosis and prediction in glaucoma are mentioned. With the development in imaging tools, sensor technologies and artificial intelligence, diagnostic evaluation of glaucoma must assess more variables to facilitate earlier diagnosis and management in the future.

FULL-THICKNESS MACULAR HOLE SIZE BY HYPERTRANSMISSION SIGNAL ON SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To assess the full-thickness macular hole (FTMH) size using the choroidal hypertransmission signal on spectral-domain optical coherence tomography and to compare this method to the standard aperture measurement of the minimum aperture size at the level of the neurosensory retina.

DESIGN

Cross-sectional study of retrospective data.

METHODS

Eyes with FTMH imaged on spectral-domain optical coherence tomography were included. Two independent masked graders used the device's built-in caliper tool to measure the FTMH minimum aperture size at the level of the neurosensory retina and the size of the corresponding hypertransmission signal below the level of the retinal pigment epithelium/Bruch membrane complex. To assess the reproducibility of the hypertransmission measurement in tilted scans, two measurements were obtained and compared; the first was traced parallel to the retinal pigment epithelium (parallel hypertransmission), and the second was horizontal to the image frame (horizontal hypertransmission), both using Image J software.

RESULTS

A total of 31 eyes were enrolled. The mean FTMH minimum aperture size was smaller compared with both the choroidal parallel hypertransmission and horizontal hypertransmission measurements (mean ± SD: 335.7 ± 139.5 µm, 376.7 ± 150.6 µm, 375.1 ± 150.0 µm, respectively. P < 0.001 for both comparisons).

CONCLUSION

The proposed hypertransmission measurement is a feasible and reproducible alternative to assess FTMH size and could provide the basis for an automated FTMH measurement on cross-sectional spectral-domain optical coherence tomography scans, as presented in this study, or on the spectral-domain optical coherence tomography volumetric data set by using an en face projection.

In vivo optical molecular imaging of inflammation and immunity

Inflammation is the phenotypic form of various diseases. Recent development in molecular imaging provides new insights into the diagnostic and therapeutic evaluation of different inflammatory diseases as well as diseases involving inflammation such as cancer. While conventional imaging techniques used in the clinical setting provide only indirect measures of inflammation such as increased perfusion and altered endothelial permeability, optical imaging is able to report molecular information on diseased tissue and cells. Optical imaging is a quick, noninvasive, nonionizing, and easy-to-use diagnostic technology which has been successfully applied for preclinical research. Further development of optical imaging technology such as optoacoustic imaging overcomes the limitations of mere fluorescence imaging, thereby enabling pilot clinical applications in humans. By means of endogenous and exogenous contrast agents, sites of inflammation can be accurately visualized in vivo. This allows for early disease detection and specific disease characterization, enabling more rapid and targeted therapeutic interventions. In this review, we summarize currently available optical imaging techniques used to detect inflammation, including optical coherence tomography (OCT), bioluminescence, fluorescence, optoacoustics, and Raman spectroscopy. We discuss advantages and disadvantages of the different in vivo imaging applications with a special focus on targeting inflammation including immune cell tracking.

Emerging Minimally Invasive Technologies for the Detection of Skin Cancer

With the increasing incidence of skin cancer, many noninvasive technologies to detect its presence have been developed. This review focuses on reflectance confocal microscopy (RCM), optical coherence tomography (OCT), high-frequency ultrasound (HFUS), electrical impedance spectroscopy (EIS), pigmented lesion assay (PLA), and Raman spectroscopy (RS) and discusses the basic principle, clinical applications, advantages, and disadvantages of each technology. RCM provides high cellular resolution and has high sensitivity and specificity for the diagnosis of skin cancer. OCT provides lower resolution than RCM, although its evaluable depth is deeper than that of RCM. RCM and OCT may be useful in reducing the number of unnecessary biopsies, evaluating the tumor margin, and monitoring treatment response. HFUS can be mainly used to delineate tumor depths or margins and monitor the treatment response. EIS provides high sensitivity but low specificity for the diagnosis of skin malignancies. PLA, which is based on the genetic information of lesions, is applicable for the detection of melanoma with high sensitivity and moderate-to-high specificity. RS showed high accuracy for the diagnosis of skin cancer, although more clinical studies are required. Advances in these technologies for the diagnosis of skin cancer can lead to the realization of optimized and individualized treatments.

A narrative review of therapies for scalp dermatomyositis

Cutaneous involvement of the scalp is a common manifestation of dermatomyositis (DM), occurring in up to 82% of adults with DM. Scalp DM predominantly affects women and is characterized by dermatitis, alopecia, pruritus, and/or burning. While cutaneous DM negatively impacts quality-of-life, scalp symptoms in particular are often severe, debilitating, and recalcitrant to standard DM therapies. Currently, there is a paucity of guidelines to inform management of scalp symptoms in patients with cutaneous DM. In this narrative review, we summarize the treatments utilized to manage scalp DM and highlight potential areas for future research. We identified eight studies that reported on 27 treatments focused on cutaneous DM and described outcomes on scalp symptoms. A majority of the treatments were standard therapies for cutaneous DM and resulted in no or minimal improvement in scalp symptoms. Five therapies did result in complete resolution of scalp symptoms and were recommended as potential areas of future research. These included low-dose naltrexone and platelet-rich plasma, as well as two frequent and one less common therapy for cutaneous DM respectively: intravenous immunoglobulin, rituximab, and apremilast. Though the literature was not systematically assessed in this review, these findings illustrate not only that strategies for refractory scalp DM are lacking, but also that those demonstrating potential efficacy are limited by low levels of evidence. Additional studies, especially randomized controlled trials, are needed to better inform management of scalp DM.

Noninvasive monitoring of suprachoroidal, subretinal, and intravitreal implants using confocal scanning laser ophthalmoscope (cSLO) and optical coherence tomography (OCT)

To address the need for noninvasive monitoring of injectable preformed drug delivery implants in the eye, we developed noninvasive methods to monitor such implants in different locations within the eye. Cylindrical polymeric poly(lactide-co-glycolide) or metal implants were injected into isolated bovine eyes at suprachoroidal, subretinal, and intravitreal locations and imaged noninvasively using the cSLO and OCT modes of a Heidelberg Spectralis HRA + OCT instrument after adjusting for the corneal curvature. Length and diameter of implants were obtained using cSLO images for all three locations, and the volume was calculated. Additionally, implant volume for suprachoroidal and subretinal location was estimated by integrating the cross-sectional bleb area over the implant length in multiple OCT images or using the maximum thickness of the implant based on thickness map along with length in cSLO image. Simultaneous cSLO and OCT imaging identified implants in different regions of the eye. Image-based measurements of implant dimensions mostly correlated well with the values prior to injection using blade micrometer. The accuracy (82-112%) and precision (1-19%) for noninvasive measurement of length was better than the diameter (accuracy 69-130%; precision 3-38%) using cSLO image for both types of implants. The accuracy for the measurement of volume of both types of implants from all three intraocular locations was better with cSLO imaging (42-152%) compared to those obtained using OCT cross-sectional bleb area integration (117-556%) or cSLO and thickness map (32-279%) methods. Suprachoroidal, subretinal, and intravitreal implants can be monitored for length, diameter, and volume using cSLO and OCT imaging. Such measurements may be useful in noninvasively monitoring implant degradation and drug release in the eye.

Theranostic applications of optical coherence tomography in neurosurgery?

In light of our own experiences, we value the existing literature to critically point out possible “near” future applications of optical coherence tomography (OCT) as an intraoperative neurosurgical guidance tool. “Pub Med”, “Cochrane Library”, “Crossref Metadata Search”, and “IEEE Xplore” databases as well as the search engine “Google Scholar” were screened for “optical coherence tomography + neurosurgery”, “optical coherence tomography + intraoperative imaging + neurosurgery”, and “microscope integrated optical coherence tomography + neurosurgery”. n = 51 articles related to the use of OCT as an imaging technique in the field of neurosurgery or neurosurgical research. n = 7 articles documented the intraoperative use of OCT in patients. n = 4 articles documented the use of microscope-integrated optical coherence tomography as a neurosurgical guidance tool. The Results demonstrate that OCT is the first imaging technique to study microanatomy in vivo. Postoperative analysis of intraoperative scans holds promise to enrich our physiological and pathophysiological understanding of the human brain. No data exists to prove that OCT-guided surgery minimizes perioperative morbidity or extends tumor resection. But results suggest that regular use of microscope-integrated OCT could increase security during certain critical microsurgical steps like, e.g., dural dissection at cavernous sinus, transtentorial approaches, or aneurysm clip placement. Endoscopy integration could aid surgery in regions which are not yet accessible to real-time imaging modalities like the ventricles or hypophysis. Theranostic instruments which combine OCT with laser ablation might gain importance in the emerging field of minimal invasive tumor surgery. OCT depicts vessel wall layers and its pathologies uniquely. Doppler OCT could further visualize blood flow in parallel. These abilities shed light on promising future applications in the field of vascular neurosurgery.

Rapid pseudo-H&E imaging using a fluorescence-inbuilt optical coherence microscopic imaging system

A technique using Linnik-based optical coherence microscopy (OCM), with built-in fluorescence microscopy (FM), is demonstrated here to describe cellular-level morphology for fresh porcine and biobank tissue specimens. The proposed method utilizes color-coding to generate digital pseudo-H&E (p-H&E) images. Using the same camera, colocalized FM images are merged with corresponding morphological OCM images using a 24-bit RGB composition process to generate position-matched p-H&E images. From receipt of dissected fresh tissue piece to generation of stitched images, the total processing time is <15 min for a 1-cm² specimen, which is on average two times faster than frozen-section H&E process for fatty or water-rich fresh tissue specimens. This technique was successfully used to scan human and animal fresh tissue pieces, demonstrating its applicability for both biobank and veterinary purposes. We provide an in-depth comparison between p-H&E and human frozen-section H&E images acquired from the same metastatic sentinel lymph node slice (∼10 µm thick), and show the differences, like elastic fibers of a tiny blood vessel and cytoplasm of tumor cells. This optical sectioning technique provides histopathologists with a convenient assessment method that outputs large-field H&E-like images of fresh tissue pieces without requiring any physical embedment.

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

In this review, the roles of detectors in various medical imaging techniques were described. Ultrasound, optical (near-infrared spectroscopy and optical coherence tomography) and thermal imaging, magnetic resonance imaging, computed tomography, single-photon emission tomography, positron emission tomography were the imaging modalities considered. For each methodology, the state of the art of detectors mainly used in the systems was described, emphasizing new technologies applied.

Non-Invasive Optical Coherence Tomography Data-Based Quantitative Algorithm for the Assessment of Residual Adhesive on Bracket-Removed Dental Surface

The aim of this study was to quantitatively assess the residual adhesive on orthodontic ceramic bracket-removed dental surface. In orthodontic process, ceramic bracket was repeated debonding physically, then the adhesive remained on the dental surface. The residual adhesive caused a lack of adhesive strength between dental and ceramic bracket. Since commonly used adhesive in orthodontics is translucent, residual adhesive is hard to be detected with conventional microscopes. Therefore, 1310 nm center wavelength swept-source OCT system based on laboratory customized image processing algorithm was used for the precise detection of residual adhesive on tooth surface. The algorithm separates residual adhesive from dental surface by comparing the height of adjacent B-scan images, while providing color-scaled images emphasizing the thickness information of residual adhesive. Finally, the acquired results were compared with microscopic and adhesive remnant index scoring gold standards, while the comparison confirmed the potential merits and the improvements of the proposed method over gold standards.

Microparticle-Based Biochemical Sensing Using Optical Coherence Tomography and Deep Learning

Advancing continuous health monitoring beyond vital signs to biochemistry will revolutionize personalized medicine. Herein, we report a biosensing platform to achieve remote biochemical monitoring using microparticle-based biosensors and optical coherence tomography (OCT). Stimuli-responsive, polymeric microparticles were designed to serve as freely dispersible biorecognition units, wherein binding with a target biochemical induces volumetric changes of the microparticle. Analytical approaches to detect these submicron changes in 3D using OCT were devised by modeling the microparticle as an optical cavity, enabling estimations far below the resolution of the OCT system. As a proof of concept, we demonstrated the 3D spatiotemporal monitoring of glucose-responsive microparticles distributed throughout a tissue mimic in response to dynamically fluctuating levels of glucose. Deep learning was further implemented using 3D convolutional neural networks to automate the vast processing of the continuous stream of three-dimensional time series data, resulting in a robust end-to-end pipeline with immense potential for continuous in vivo biochemical monitoring.

Imaging methods to evaluate tumor microenvironment factors affecting nanoparticle drug delivery and antitumor response

Standard small molecule and nanoparticulate chemotherapies are used for cancer treatment; however, their effectiveness remains highly variable. One reason for this variable response is hypothesized to be due to nonspecific drug distribution and heterogeneity of the tumor microenvironment, which affect tumor delivery of the agents. Nanoparticle drugs have many theoretical advantages, but due to variability in tumor microenvironment (TME) factors, the overall drug delivery to tumors and associated antitumor response are low. The nanotechnology field would greatly benefit from a thorough analysis of the TME factors that create these physiological barriers to tumor delivery and treatment in preclinical models and in patients. Thus, there is a need to develop methods that can be used to reveal the content of the TME, determine how these TME factors affect drug delivery, and modulate TME factors to increase the tumor delivery and efficacy of nanoparticles. In this review, we will discuss TME factors involved in drug delivery, and how biomedical imaging tools can be used to evaluate tumor barriers and predict drug delivery to tumors and antitumor response.

Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness. The main risk factor is advancing age, with the severity of vision loss ranging from mild to severe. There is a 25% risk of early AMD and 8% risk of late AMD in patients over the age of 75, with the number of cases expected to increase because of the aging population. Diagnosis of the disease requires a dilated fundus examination. Physicians should be aware of the symptoms, risk factors, and treatment options for AMD to refer appropriately for ophthalmologic evaluation. Early detection can be helpful to prevent disease progression.

Noninvasive and real-time in vivo characterization of Inflammation skin. A feasibility of animal study

BACKGROUND

Inflammatory skin diseases were the most common problem in dermatology. This study aimed to develop a circuit by using a simple method for noninvasive, objective, and real-time skin inflammation screening.

MATERIALS AND METHODS

Sprague-Dawley rats were used in this study. The rats were chemically induced to suffer from skin inflammation at the back of their left-hand side while the right-hand side of their back remained untreated serving as a control. Impedance (Z) spectrum of the rat's skin was recorded.

RESULTS

Two characteristic frequencies (4.5 and 48.3 kHz) were found. At the two frequencies, the impedance of inflammatory skin tissue (Z_IST ) was found to be significantly (P < .05) smaller than that of normal healthy skin tissue (Z_NHST ). Moreover, the ratio of the impedance measured at 4.5 kHz (Z_f = 4 ._5 kHz ) to the impedance measured at 48.3 kHz (Z_{f = 48.3 kHz} ), that is, Z_{f = 4.5 kHz} /Z_{f = 48.3 kHz} , was capable of skin inflammation screening. It was observed that the inflammatory skin tissue (IST) had the smaller value of Z_f = 4 ._5 kHz /Z_{f = 48.3 kHz} (value < 8.5) and normal healthy skin tissue (NHST) had the higher value of Z_f = 4 ._5 kHz /Z_{f = 48.3 kHz} (value ≈ 10) which almost remained constant.

CONCLUSION

A circuit was developed which was used for measuring the skin impedance accurately at the two characteristic frequencies for skin inflammation screening.

Utilization potential of intraluminal optical coherence tomography for the Eustachian tube

Imaging the Eustachian tube is challenging because of its complex anatomy and limited accessibility. This study fabricated a fiber-based optical coherence tomography (OCT) catheter and investigated its potential for assessing the Eustachian tube anatomy. A customized OCT system and an imaging catheter, termed the Eustachian OCT, were developed for visualizing the Eustachian tube. Three male swine cadaver heads were used to study OCT image acquisition and for subsequent histologic correlation. The imaging catheter was introduced through the nasopharyngeal opening and reached toward the middle ear. The OCT images were acquired from the superior to the nasopharyngeal opening before and after Eustachian tube balloon dilatation. The histological anatomy of the Eustachian tube was compared with corresponding OCT images, The new, Eustachian OCT catheter was successfully inserted in the tubal lumen without damage. Cross-sectional images of the tube were successfully obtained, and the margins of the anatomical structures including cartilage, mucosa lining, and fat could be successfully delineated. After balloon dilatation, the expansion of the cross-sectional area could be identified from the OCT images. Using the OCT technique to assess the Eustachian tube anatomy was shown to be feasible, and the fabricated OCT image catheter was determined to be suitable for Eustachian tube assessment.

Optical coherence tomography microscopy in experimental traumatic brain injury

Worldwide elderly traumatic brain injury (TBI) patients tend to become an increasing burden to the society. Thus, a faster and less expensive way of evaluating TBI victims is needed. In the present study we investigated if optical coherence tomography (OCT) could be used as such a method. By using an animal model, we established if OCT can detect cortical changes in the acute phase of a penetrating TBI, in young (5-7 months) and old (20-22 months) rats. Due to the long-term evolution of TBI's, we wanted to investigate to what extent OCT could detect changes within the cortex in the chronic phase. Adult (7-12 months) male rats were used. Surprisingly, OCT imaging of the normal hemisphere was able to discriminate age-related differences in the mean gray values (MGV) of recorded pixels (p = .032). Furthermore, in the acute phase of TBI, OCT images recorded at 24 hr after the injury showed differences between the apparent damaged area of young and aged animals. Changes of MGV and skewness were only recorded 48 hr after injury. Monitoring the chronical evolution of the TBI with OCT revealed changes over time exceeding the normal range recorded for MGV, skewness and kurtosis, 14 and 21 days after TBI. Although in the present study we still used an extremely invasive approach, as technology improves, less invasive and non-harmful ways of recording OCT may allow for an objective way to detect changes within the brain structure after brain injuries.

Utilisation of Chick Embryo Chorioallantoic Membrane as a Model Platform for Imaging-Navigated Biomedical Research

The fertilised chick egg and particularly its chorioallantoic membrane (CAM) have drawn continuing interest in biomedicine and bioengineering fields, especially for research on vascular study, cancer, drug screening and development, cell factors, stem cells, etc. This literature review systemically introduces the CAM's structural evolution, functions, vascular features and the circulation system, and cell regulatory factors. It also presents the major and updated applications of the CAM in assays for pharmacokinetics and biodistribution, drug efficacy and toxicology testing/screening in preclinical pharmacological research. The time course of CAM applications for different assays and their advantages and limitations are summarised. Among these applications, two aspects are emphasised: (1) potential utility of the CAM for preclinical studies on vascular-disrupting agents (VDAs), promising for anti-cancer vascular-targeted therapy, and (2) modern imaging technologies, including modalities and their applications for real-time visualisation, monitoring and evaluation of the changes in CAM vasculature as well as the interactions occurring after introducing the tested medical, pharmaceutical and biological agents into the system. The aim of this article is to help those working in the biomedical field to familiarise themselves with the chick embryo CAM as an alternative platform and to utilise it to design and optimise experimental settings for their specific research topics.

Integrated Quad-Scanner Strategy-Based Optical Coherence Tomography for the Whole-Directional Volumetric Imaging of a Sample

Whole-directional scanning methodology is required to observe distinctive features of an entire physical structure with a three dimensional (3D) visualization. However, the implementation of whole-directional scanning is challenging for conventional optical coherence tomography (OCT), which scans a limited portion of the sample by utilizing unidirectional and bidirectional scanning methods. Therefore, in this paper an integrated quad-scanner (QS) strategy-based OCT method was implemented to obtain the whole-directional volumetry of a sample by employing four scanning arms installed around the sample. The simultaneous and sequential image acquisition capabilities are the conceptual key points of the proposed QS-OCT method, and were implemented using four precisely aligned scanning arms and applied in a complementary way according to the experimental criteria. To assess the feasibility of obtaining whole-directional morphological structures, a roll of Scotch tape, an ex vivo mouse heart, and kidney specimens were imaged and independently obtained tissue images at different directions were delicately merged to compose the 3D volume data set. The results revealed the potential merits of QS-OCT-based whole-directional imaging, which can be a favorable inspection method for various discoveries that require the dynamic coordinates of the whole physical structure.

Getting Your Neutrophil: Neutrophil Transepithelial Migration in the Lung

Neutrophil transepithelial migration is a fundamental process that facilitates the rapid trafficking of neutrophils to inflammatory foci and occurs across a diverse range of tissues. For decades there has been widespread interest in understanding the mechanisms that drive this migratory process in response to different pathogens and organ systems. This has led to the successful integration of key findings on neutrophil transepithelial migration from the intestines, lungs, liver, genitourinary tract, and other tissues into a single, cohesive model. However, recent studies have identified organ specific differences in neutrophil transepithelial migration. These findings support a model where the tissue in concert with the pro-inflammatory stimuli dictate a unique collection of signals that drive neutrophil trafficking. This review focuses on the mechanisms that drive neutrophil transepithelial migration in response to microbial infection of a single organ, the lung. Herein we provide a detailed analysis of the adhesion molecules and chemoattractants that contribute to the recruitment of neutrophil into the airways. We also highlight important advances in experimental models for studying neutrophil transepithelial migration in the lung over the last decade.