199 research outputs found
Optical coherence tomography angiography for chronic venous insufficiency and venous leg ulcer
No full textChronic venous insufficiency (CVI) ranks among the most common health care issues worldwide. The current diagnosis of CVI is done by clinical examination and duplex ultrasound, which can only detect visible physical changes and deeper vascular structures whereas the superficial cutaneous vasculature cannot be resolved. There is indeed a lack of information that can potentially be extracted from the cutaneous microvasculature of patients affected by CVI. In this work, we designed and applied an optical coherence tomography angiography (OCTA) system, which is customized for
lower extremity imaging of patients. Featuring fast imaging speed, large field of view, high spatial resolution, and most importantly non-invasiveness, this OCTA system was successfully applied in CVI and venous leg ulcer patient imaging. Using the OCTA results acquired from a cohort of 27 human subjects, we can clearly distinguish the vascular patterns uniquely associated with various stages of CVI. The findings of this study give an unexplored indicator to the disease of CVI and venous leg ulcer. With more patients to be recruited, we believe that OCTA imaging results for CVI can be
used as a powerful tool in CVI screening and diagnosis
Impact of image preprocessing on dermatological OCTA vessel segmentation: a DERMA-OCTA study
No full textSignificance: Optical coherence tomography angiography (OCTA) offers dye-free, three-dimensional views of skin microvasculature, yet progress in developing reliable and quantitative solutions for vessel architecture analysis is slowed by heterogeneous preprocessing practices, scarce annotated data, and limited evaluation metrics. Aim: We assess how typical OCTA preprocessing steps influence the accuracy of deep learning vessel segmentation, and we identify network designs and metrics best suited to OCTA dermatological data. Approach: Experiments use the open DERMA-OCTA dataset containing 330 volumes from different skin conditions; each volume is additionally provided in five progressively pre-processed versions: original, Bscan normalization, projection artifact attenuation, contrast enhancement, and vesselness filtering. Segmentation is performed with representative 2D and 3D deep learning approaches. Besides standard segmentation metrics, evaluation includes the connectivity-area-length index, which proved particularly effective for assessing dermatological vessel segmentation. Results: The analysis shows that Bscan normalization, projection artifact attenuation, and contrast enhancement incrementally improve segmentation accuracy, whereas vesselness enhancement can impair segmentation performance. Among the tested architectures, 2D models achieved the highest segmentation performance, although 3D approaches proved more effective for deeper tissue layers. Testing across different pathologies revealed challenges in model generalization to varied vascular patterns. Conclusions: Combining 2D and 3D models and using topology-aware indices provide a full, clinically relevant evaluation of algorithm performance
Hotspots of academic misconduct and misrepresentations among academics in the Republic of Poland, a European Union member state
No full textAcademic misconduct, misrepresentations, and gaming are a set of variable malpractices eroding public trust in scientific achievements and institutions of higher education. Here, the author analysed data on academic misconduct and misrepresentations in the Republic of Poland. The results presented here have based on the analysis of the records on academic malpractices revealed to the public by professor Marek Wronski, writing in the Academic Forum magazine regularly about academic integrity in Poland. Three or more examples of academic malpractices conducted by scholars working in the same institution of higher education cannot be explained by coincidence. Hence, an analysis of Marek Wronski's writing on academic integrity has revealed the existence of the hotspots of academic misconduct and misrepresentations in the Polish institutions of higher education. In addition, the Science Ethics Committee of the Polish Academy of Science, the Disciplinary Committee at the Central Council of Science and Higher Education, the Ministry of Education and Science, and the Council of Scientific Excellence have been asked to provide data on academics accused of misconduct. Moreover, Polish institutions responsible for investigating allegations of academic misconduct and misrepresentation be reluctant to disclose information about academics accused of misconduct and misrepresentation. Data presented in that paper may suggest the organisational research climate in the Polish institutions of higher education, and research may favour academic malpractices
Lissajous-trajectory scanning optical coherence photoacoustic microscopy for zebrafish larva imaging
No full textAs an important vertebrate animal model for development and human disease, research on zebrafish has been using many different imaging methods. Among them, optical coherence microscopy and photoacoustic microscopy (PAM) are gradually gaining popularity due to their complementary contrast mechanisms and non-invasive nature. This work demonstrates a combined optical coherence PAM system using Lissajous scanning trajectories for zebrafish imaging. The system configuration enables a large field of view (up to 11.8 mm × 25.2 mm) with uniform high resolution (1.8 μm lateral) and uniform sensitivity across the entire scanning area. The voice-coil-enabled Lissajous trajectories yield high scanning speed, while maintaining precise coregistration between modalities. A specially designed deep learning-based upsampling model has been trained to leverage unique characteristics of the Lissajous scanning pattern, reducing acquisition time by up to 70% while preserving image quality. The system’s capabilities are demonstrated through high-resolution imaging of zebrafish larvae, revealing detailed vascular networks and tissue structures. This novel approach provides a powerful tool for non-invasive, multimodal imaging of zebrafish development and disease models beyond typical size boundaries
Optical coherence photoacoustic microscopy for 3D cancer model imaging with AI-assisted organoid analysis
No full textCancer organoids and cancer spheroids are 3D cell culture models with distinct yet overlapping purposes in cancer research. Various commercially available optical imaging techniques have been employed to study these cell cultures, but these methods suffer from various limitations such as the requirement of fluorescence labeling, complicated sample handling, and limited image volume size. In this work, we demonstrate a multimodal optical coherence photoacoustic microscopy (OC-PAM) system for the study of these models, overcoming these limitations. We first performed a longitudinal study using optical coherence microscopy (OCM) for breast cancer organoids. Using the OCM imaging results, artificial intelligence (AI)-based algorithms were developed to automatically segment individual organoids and classify their viability over time using a radiomics texture feature approach, enabling robust, quantitative tracking and classification at the single-organoid level. To supplement OCM’s contrast, we then performed OC-PAM imaging of spheroid models with both melanin positive and melanin negative cells. In the second study, the OC-PAM images clearly mapped the distribution of melanin positive cells hidden amongst melanin negative cells. These results suggest that OC-PAM coupled with AI techniques can be a powerful tool to study cancer organoids and cancer spheroids
Agents of seed dispersal : animal--zoochary / Wind--anemonochory
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2004.Includes bibliographical references (leaves 91-98).Agents of seed dispersal is a project designed to address the increase of environmental degradation, which occurs as a result of the perpetual spread of the asphalt and concrete of the contemporary urban situation. Agents of Seed Dispersal proposes that the city is a natural ecosystem within the greater context of earth's environment. The city as an ecosystem challenges the common notion that the urban setting is artificial and the environment outside of its boundaries is the sole representation of nature. The metropolis as an ecosystem requires that earth's occupants address it as a natural system and as an ecosystem it requires environmental thought and action. Through the Agents of Seed Dispersal project the author initiates two separate but corresponding projects, which focus on urban environmental degradation by reversing the spread of the asphalt surface and it's corresponding suffocation of plant life by propagating the distribution and growth of specific plant life within the city.by Lukasz Kamil Lysakowski.S.M
Shear capacity of steel fibre reinforced concrete beams
No full textThe Critical Shear Displacement Theory (CSDT) was developed to determine the shear capacity of reinforced concrete beams based on the different shear-carrying mechanisms (concrete in the compression zone, aggregate interlock, and dowel action). This research aims at extending the CSDT to Steel Fibre Reinforced Concrete (SFRC) by adding the contribution of steel fibres. The model extension was developed based on formulations for the contribution of steel fibres to the shear capacity from the literature. With this extension to the CSDT, the shear strength of steel fibre reinforced concrete beams without stirrups could be estimated. An extensive database is developed from the literature in order to evaluate, compare, and analyse the shear capacity of SFRC beams. The analysis indicates that two models are capable of predicting the shear strength of SFRC beams with reasonable accuracy. The mean, standard deviation, and coefficient of variation are 0.9, 0.28, 0.31 and 1.1, 0.33 and 0.30 respectively. The main geometric variables of the steel fibres that influenced the shear strength are the length, diameter, and fibre type (hooked, crimped, and straight). From the comparison between the results in the database and the proposed extensions to the CSDT it is found that the critical shear displacement of Δcr = 0.025 mm, gives reasonable results for SFRC. As such, this proposed method can be used to estimate the shear strength of SDRC based on a mechanical model.Accepted Author ManuscriptConcrete Structure
Optical coherence tomography angiography enables visualization of microvascular patterns in chronic venous insufficiency
No full textChronic venous insufficiency (CVI) is a global health concern with significant public health and individual
impact. Currently available diagnostic methods cannot visualize microvenous pathologies that have
shown to result in severe forms of CVI and also affect the skin. Optical coherence tomography angiography (OCTA) may close the CVI diagnostic gap by providing a fast, label-free, and non-invasive solution
to visualize cutaneous microvasculature. The study enlisted 66 subjects, including 53 CVI patients spanning all clinical-etiology-anatomic-pathophysiologic (CEAP) C stages and 13 healthy controls. The high
spatial resolution OCTA system used was specifically designed for skin imaging. Significant microangiographic pattern variations emerged, both in qualitative and quantitative terms. OCTA provided valuable
insights into cutaneous microvascular changes among different CVI stages. Thereby, OCTA may enable
the selection of patient populations at risk for disease progression in the future
Motion Control Strategies for Smart Floating Cranes
No full textFloating structures have raised interest in the recent years for different applications, from living and farming at sea to renewable energy production. To support the logistics on the floating structures, floating cranes are necessary and their designs are constantly improved. Increasing developments in the automation industry paved the way for automated crane operations. In this work, motion control of a smart crane is presented with particular attention to the performance under wave motion. In this research, a scaled down, two-dimensional mathematical model of a gantry crane is derived using Lagrangian mechanics and DC motors dynamics. This results in a nonlinear system that is capable of simultaneous traversing and hoisting a container. The system is simulated in MATLAB Simulink environment and a proportional-derivative control and a state feedback control are designed and implemented. Their robustness is explored by modelling sensor behavior, external disturbances and floating platform dynamics. Both control strategies were able to keep stability in a disturbed system. During simulation, the sway angles never exceed 10°. Smaller oscillations occurred using the state feedback control. Therefore, it creates a smoother response compared to the proportional derivative control, which ultimately translates to increased safety, turnover rate and durability of the crane.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
Motion control strategies for smart floating cranes
No full textFloating structures have raised interest in the recent years for different applications, from living and farming at sea to renewable energy production. To support the logistics on the float- ing structures, floating cranes are necessary and their designs are constantly improved. In- creasing developments in the automation industry paved the way for automated crane opera- tions. In this work, motion control of a smart crane is presented with particular attention to the performance under wave motion. In this research, a scaled down, two-dimensional math- ematical model of a gantry crane is derived using Lagrangian mechanics and DC motors dy- namics. This results in a nonlinear system that is capable of simultaneous traversing and hoist- ing a container. The system is simulated in MATLAB Simulink environment and a proportional-derivative control and a state feedback control are designed and implemented. Their robustness is explored by modelling sensor behavior, external disturbances and floating platform dynamics. Both control strategies were able to keep stability in a disturbed system. During simulation, the sway angles never exceed 10 degrees. Smaller oscillations occurred us- ing the state feedback control. Therefore, it creates a smoother response compared to the pro- portional derivative control, which ultimately translates to increased safety, turnover rate and durability of the crane.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
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