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Quantification of collagen fiber structure using second harmonic generation imaging and two-dimensional discrete Fourier transform analysis: Application to the human optic nerve head
摘要： Second Harmonic Generation (SHG) microscopy is widely used to image collagen fiber microarchitecture due to its high spatial resolution, optical sectioning capabilities and relatively non-destructive sample preparation. Quantification of SHG images requires sensitive methods to capture fiber alignment. This paper presents a 2D Discrete Fourier Transform (DFT) based method for collagen fiber structure analysis from SHG images. The method includes integrated Periodicity Plus Smooth Image Decomposition (PPSID) for correction of DFT edge discontinuity artefact, avoiding the loss of peripheral image data encountered with more commonly used windowing methods. Outputted parameters are: the collagen fiber orientation distribution, aligned collagen content and the degree of collagen fiber dispersion along the principal orientation. We demonstrate its application to determine collagen microstructure in the human optic nerve head, showing its capability to accurately capture characteristic structural features including radial fiber alignment in the innermost layers of the bounding sclera and a circumferential collagen ring in the mid-stromal tissue. Higher spatial resolution rendering of individual lamina cribrosa beams within the nerve head is also demonstrated. Validation of the method is provided in the form of correlative results from wide-angle X-ray scattering (WAXS) and application of the presented method to other fibrous tissues.
关键词： Second Harmonic Generation,edge effect artefact correction,Discrete Fourier Transform,optic nerve head,collagen fiber structure,Non-linear microscopy
更新于2025-09-23 15:23:52
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Interaction of biologically relevant proteins with ZnO nanomaterials: A confounding factor for in vitro toxicity endpoints
摘要： The results of in vitro toxicological studies for manufactured nanomaterials (MNs) are often contradictory and not reproducible. Interference of the MNs with assays has been suggested. However, understanding for which materials and how these artefacts occur remains a major challenge. This study investigated interactions between two well-characterized ZnO MNs (NM-110 and NM-111) and lactate dehydrogenase (LDH), and two interleukins (IL-6 and IL-8). Particles (10 to 640 μg/mL) and proteins were incubated for 24 hours in routine in vitro assays test conditions. LDH activity (ODLDH), but not interleukins concentrations, decreased sharply in a dose-dependent manner within an hour after exposure (ODLDH < 60% of ODref for both MNs at 10 μg/mL). A Freundlich adsorption isotherm was successfully applied, indicating multilayer adsorption of LDH. ZnO MNs and LDH had neutral to slightly negative surface charges in dispersion, precluding electrostatic attachment. Particle sedimentation was not a limiting factor. Fast dissolution of ZnO MNs was shown and Zn2+ could play a role in the ODLDH drop. To summarize, ZnO MNs quickly reduced ODLDH due to concentration-dependent adsorption and LDH inhibition by interaction with dissolved Zn. The control of particle interference in toxicological in vitro assays should become mandatory to avoid misleading interpretation of results.
关键词： artefact,pH,interleukin,adsorption,lactate dehydrogenase,dissolution
更新于2025-09-23 15:23:52
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[ACM Press Proceedings of the 14th EAI International Conference - Melbourne, VIC, Australia (2017.11.07-2017.11.10)] Proceedings of the 14th EAI International Conference on Mobile and Ubiquitous Systems Computing Networking and Services - Sensor Agnostic Photoplethysmogram Signal Quality Assessment using Morphological Analysis
摘要： In this article, we propose a method to assess the clinical usability of fingertip Photoplethysmogram (PPG) waveform, collected from medical grade oximeter (train data) and smartphone (test data). We introduce a set of novel Signal Quality Indices (SQIs) to represent the noise characteristics of the PPG waveform. The SQIs are presented to a random forest classifier to discriminate between clean and noisy signals. The proposed method was evaluated on datasets annotated by four experts, resulting into a sensitivity and specificity of (92 + ? 4.7 % , 95 + ? 4.6 % , 95.4 + ? 3.1 %) on train and test data respectively. Further we applied the proposed method on PPG waveform of clinically proven control and disease population of Coronary Artery Disease (CAD), which resulted into (77 %,77 %) of sensitivity and specificity respectively.
关键词： Artefact,Noise Detection,Photoplethysmogram,Wearable Sensors,Morphology,Mobile Health
更新于2025-09-23 15:22:29
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[IEEE 2018 26th European Signal Processing Conference (EUSIPCO) - Rome (2018.9.3-2018.9.7)] 2018 26th European Signal Processing Conference (EUSIPCO) - Ear Presentation Attack Detection: Benchmarking Study with First Lenslet Light Field Database
摘要： Ear recognition has received broad attention from the biometric community and its emerging usage in multiple applications is raising new security concerns, with robustness against presentation attacks being a very active field of research. This paper addresses for the first time the ear presentation attack detection problem by developing an exhaustive benchmarking study on the performance of state-of-the-art light field and non-light field based ear presentation attack detection solutions. In this context, this paper also proposes an appropriate ear artefact database captured with a Lytro ILLUM lenslet light field camera, including both 2D and light field contents, using several types of presentation attack instruments, including laptop, tablet and two different mobile phones. Results show very promising performance for two recent light field based presentation attack detection solutions originally proposed for face presentation attack detection.
关键词： Ear Presentation Attack Detection,Feature Extraction,Light Field Imaging,Artefact Database
更新于2025-09-23 15:22:29
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Dielectric replica measurement: A new technique for obtaining the complex permittivity of irregularly shaped objects
摘要： Dielectric measurements provide valuable information about the properties of materials, and could be used to classify and identify the source of objects, in fields such as archaeology. Current methods of identification are all partly destructive, so an innovative electromagnetic method developed by the authors, based on resonant cavity perturbation (RCP), provides an attractive, non-destructive alternative. A problem with traditional RCP is that the changes in frequency and Q-factor vary with the object's shape; however we overcome this by creating a replica of the object, from a material whose dielectric properties are known. Then, by combining three separate perturbations with orthogonal field directions, due firstly to the object and then to its replica, we eliminate the shape dependency, and thus determine the object's dielectric constant and loss factor. After developing the theory of this novel DRM technique, we demonstrate the principle using a set of geometric shapes made in both polytetrafluoroethylene (PTFE) and a 3D printed material. Further measurements then enable second-order terms to be included in the model, improving its accuracy. Finally, DRM is shown to be capable of distinguishing two irregularly shaped objects of different materials. Potential applications of DRM include determining the provenance of pottery, glasses and flints, and distinguishing ivory from bone. These would be of interest to customs and environmental agencies, as well as museum curators and archaeologists.
关键词： resonant cavity,3D printing,artefact,network analyser,Dielectric measurement,archaeology,complex permittivity,non-destructive testing
更新于2025-09-19 17:15:36
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Ability to detect endodontic complications using three different CBCT units with and without artefact reduction modes: an ex vivo study
摘要： Aim To assess observer performance in detecting endodontic complications using three different CBCT units with and without the application of artefact reduction modes. Methodology The study involved 40 freshly extracted human mandibular teeth (n=10 per group) and divided randomly into four endodontic complication groups. Group 1) Instrument fracture; Group 2) Strip perforation; Group 3) Canal underfilling; Group 4) Canal overfilling. Images of each tooth were obtained using three different CBCT units offering artefact reduction algorithms: the ProMax 3D Max, the Pax Flex 3D, and the Dentri S. Four observers evaluated the images for the presence/absence of the four simulated endodontic complications. Weighted kappa coefficients and intra-class correlation coefficients (ICCs) were calculated to reveal the intra- and inter-observer agreement for each imaging mode, respectively. Receiver operating characteristic (ROC) analysis was used to evaluate the observers’performance. DeLong tests were used to compare the results for each image mode and observer using a significance level of α=0.05. Results In each of the four simulated endodontic complication groups, no significant differences were observed with and without application of artefact reduction for any of the three CBCT units tested. Only two significant differences were detected, and both were between the ProMax 3D Max at low mode AR and ProMax 3D Max without AR: observer 2 in group 1 (p=0.0001) and observer 4 in group 4 (p=0.0256). Conclusion For each of the three CBCT units tested, application of artefact reduction for detecting endodontic complications is not recommended as a routine tool.
关键词： endodontic complications,CBCT,artefact reduction algorithms
更新于2025-09-09 09:28:46