Segmentation Enhanced Elastic Image Registration for 2D Speckle Tracking Echocardiography—Performance Study In Silico

Although the two dimensional Speckle Tracking Echocardiography has gained a strong position among medical diagnostic techniques in cardiology, it still requires further developments to improve its repeatability and reliability. Few works have attempted to incorporate the left ventricle segmentation results in the process of displacements and strain estimation to improve its performance. We proposed the use of mask information as an additional penalty in the elastic image registration based displacements estimation. This approach was studied using a short axis view synthetic echocardiographic data, segmented using an active contour method. The obtained masks were distorted to a different degree, using different methods to assess the influence of the segmentation quality on the displacements and strain estimation process. The results of displacements and circumferential strain estimations show, that even though the method is dependent on the mask quality, the potential loss in accuracy due to the poor segmentation quality is much lower than the potential accuracy gain in cases where the segmentation performs well.

Live 3D imaging and mapping of shear stresses within tissues using incompressible elastic beads

To investigate the role of mechanical constraints in morphogenesis and development, we develop a pipeline of techniques based on incompressible elastic sensors. These techniques combine the advantages of incompressible liquid droplets, which have been used as precise in situ shear stress sensors, and of elastic compressible beads, which are easier to tune and to use. Droplets of a polydimethylsiloxane (PDMS) mix, made fluorescent through specific covalent binding to a rhodamin dye, are produced by a microfluidics device. The elastomer rigidity after polymerization is adjusted to the tissue rigidity. Its mechanical properties are carefully calibrated in situ, for a sensor embedded in a cell aggregate submitted to uniaxial compression. Thelocal shear stress tensor is retrieved from the sensor shape, accurately reconstructed through an active contour method. In vitro, within cell aggregates, and in vivo, in the prechordal plate of the Zebrafish embryo during gastrulation,our pipeline of techniques demonstrates its efficiency to directly measure the three dimensional shear stress repartition within a tissue.

Changes of Rat Embryon Nephrogenesis during Cadmium Salt Intoxication in Pregnant Females

The purpose of the experimental study was to determine morphogenetic disorders of embryonic and fetal kidney development in chronic intragastric exposure to cadmium salts (cadmium chloride, cadmium citrate) in pregnant females. Materials and methods. Low doses of cadmium salts were selected for the study, which can be compared with the actual concentration of cadmium in the daily diets of women, including pregnant women, in industrial regions. In the experiment, female rats with a given gestational age were divided into groups as follows: Group 1 – control (number of females – n = 16, of which 8 left the experiment on the 13th day of pregnancy, and 8 on the 20th; the number of embryos – n13 = 76; n20 = 77); Group 2 – administration of cadmium chloride at a dose of 1.0 mg/kg body weight of the female (number of females – n = 16; number of embryos – n13 = 65; n20 = 62); Group 3 – administration of cadmium citrate at a dose of 1.0 mg/kg body weight of the female (number of females – n = 16; number of embryos – n13 = 69; n20 = 70). Results and discussion. New quantitative data on the effect of cadmium salts were obtained on the thickness of the cortical and cerebral layers of the kidneys, the diameter and area of the cavity of the nephron capsule in the prenatal period of development in chronic female intoxication. On the 13th day, the effect of cadmium salts on the development of embryonic kidneys was multidirectional: the effect of cadmium chloride led to an increase in the thickness of the mesonephros and mesonephric duct, and the effect of cadmium citrate reduced the studied parameters. On the 20th day of rat embryogenesis in the group exposed to cadmium chloride, the renal weights increased, and when exposed to cadmium citrate, the weight of the kidneys decreased significantly (p˂0.05) both in comparison with control values and in the group exposed to cadmium chloride. On the 20th day of development, in order to exclude an error in estimating the dynamics of changes in the weight of embryo mass and kidney mass, the nephrofetal index was calculated, i.e. the ratio of wet kidney mass to wet weight of fixed fetus. Histological parameters of nephron diameters were also compared. Conclusion. Cadmium citrate has been shown for the first time to be less non-photoxic than cadmium chloride. Calculation of the area of the cavity of the nephron capsule by the spline contour method showed a 2.6-fold decrease in the average area of the capsule cavity in the group exposed to cadmium chloride relative to the control mean values, indicating a violation of nephrogenesis. When exposed to cadmium citrate, there was also a decrease in the area of the cavity of the nephron capsule by 1.8 times, which indicates a lower level of nephrotoxic cadmium citrate compared to cadmium chloride, despite the identity of the dose of exposure

COMPARISON OF SEGMENTATION METHODS USED FOR BONE FRACTURE IMAGES

The usage of computers and software in the biomedical field has been increasing and applications for doctors, clinicians, scientists and other users have been developed in the recent times. Manual, semi-automatic and fully automatic applications developed for bone fracture detection are one of the important studies in this field. Image segmentation, which is one of the image preprocessing steps in bone fracture detection, is an important step to obtain successful results with high accuracy. In this study, Otsu thresholding method, active contour method, k-means method, fuzzy c-mean method, Niblack thresholding method and max min thresholding range (MMTR) method are used on bone images obtained by Karabük University Training and Research Hospital. When any filters are not applied on images to remove noises, the most successful method is obtained by K-means method based on specificity and accuracy as 89,55% and 83,31% respectively. Niblack thresholding method has the highest sensitivity result as 92,45%.

Comparative Multi-Modal, Multi-Scale Residual Stress Evaluation in SLM 3D-Printed Al-Si-Mg Alloy (RS-300) Parts

SLM additive manufacturing has demonstrated great potential for aerospace applications when structural elements of individual design and/or complex shape need to be promptly supplied. 3D-printable AlSi10Mg (RS-300) alloy is widely used for the fabrication of different structures in the aerospace industry. The importance of the evaluation of residual stresses that arise as a result of the 3D-printing process’ complex thermal history is widely discussed in literature, but systematic assessment remains lacking for their magnitude, spatial distribution, and comparative analysis of different evaluation techniques. In this study, we report the results of a systematic study of residual stresses in 3D-printed double tower shaped samples using several approaches: the contour method, blind hole drilling laser speckle interferometry, X-ray diffraction, and Xe pFIB-DIC micro-ring-core milling analysis. We show that a high level of tensile and compressive residual stresses is inherited from SLM 3D-printing and retained for longer than 6 months. The stresses vary (from −80 to +180 MPa) over a significant proportion of the material yield stress (from −⅓ to ¾). All residual stress evaluation techniques considered returned comparable values of residual stresses, regardless of dramatically different dimensional scales, which ranged from millimeters for the contour method, laser speckle interferometry, and XRD down to small fractions of a mm (70 μm) for Xe pFIB-DIC ring-core drilling. The use of residual stress evaluation is discussed in the context of optimizing printing strategies to enhance mechanical performance and long-term durability.

Comparative Residual Stress Evaluation in SLM 3D-printed Al-Si-Mg alloy (RS-300) Using the Contour Method, Hole Drilling Laser Speckle Interferometry, X-ray Diffraction and Xe pFIB-DIC Micro-ring-core Milling

SLM Additive Manufacturing has demonstrated great potential for aerospace applications when structural elements of individual design and/or complex shape need to be promptly supplied. 3D-printable AlSi10Mg (RS-300) alloy is widely used for the fabrication of different structures in aerospace industry. The importance of the evaluation of residual stresses that arise as a result of complex 3D-printing process thermal history is widely discussed in literature, but systematic assessment remains lacking for their magnitude, spatial distribution, and comparative analysis of different evaluation techniques. In this study we report the results of a systematic study of residual stresses in a 3D-printed double tower shaped samples using several approaches: the contour method, blind hole drilling laser speckle interferometry, X-ray diffraction, and Xe pFIB-DIC micro-ring-core milling analysis. We show that a high level of tensile and compressive residual stresses is inherited from SLM 3D-printing and retained for longer than 6 months. The stresses vary over a significant proportion of the material yield stress. All residual stress evaluation techniques considered returned comparable values of residual stresses even regardless of dramatically different dimensional scales from millimeters for the Contour Method down, laser speckle interferometry and XRD and down to small fractions of a mm (70 μm) for Xe pFIB-DIC ring-core drilling. The use of residual stress evaluation is discussed in the context of optimizing the printing strategy to enhance the mechanical performance and long-term durability.

Effects of Simulation Length and Flexible Foundation on Long-Term Response Extrapolation of a Bottom-Fixed Offshore Wind Turbine

This paper deals with statistical and modeling uncertainty on the estimation of long-term extrapolated extreme responses in a monopile offshore wind turbine. The statistical uncertainty is addressed by studying the effect of simulation length. Modeling uncertainty is explored by evaluating the effects of considering a rigid and flexible foundation. The soil's flexibility is taking into account by considering the improved apparent fixity method. To identify the most relevant environmental conditions, the modified environmental contour method is used. The analysis focuses on the fore-aft shear force (FASF) and the fore-aft bending moment (FABM) at the mudline. The results show that using a simulation length of 10-min, does not provide sufficient accuracy. It was found that for the FASF, simulation lengths of at least 30-min are required to achieve an accuracy of about +/-5%. For the FABM, it was found that both the extrapolations made with 20-min and 30-min simulations achieved similar levels of accuracy of about 20%. Meanwhile, the results obtained from 10-min simulations reached deviations of about 40%. Finally, from the comparison made between a rigid and flexible foundation, it was found that the extrapolated responses exhibit maximum deviations up to around 5% and 10% for the FASF and the FABM, respectively. Also, for the FABM, it was observed that the consideration of a flexible foundation causes the critical wind speed to shift from 16.5 m/s (rigid) to 18 m/s (flexible).

A new method for structural safety and reliability analysis of offshore wind turbines

With the motivation to overcome the shortcomings of the Rosenblatt Inverse-First-Order Reliability environmental contour method, in this study, the use of bivariate kernel density estimation with smoothed cross-validation bandwidth selection method is proposed for generating more accurate environmental contour lines. The environmental contour lines at a chosen offshore site obtained by using the proposed new method were compared with those obtained by using the Rosenblatt Inverse-First-Order Reliability environmental contour method, and the accuracy and effectiveness of the proposed new method have been fully and clearly substantiated. Next, the 50-year extreme structural dynamic responses of a monopile-supported 5MW offshore wind turbine installed at this chosen offshore site based on the proposed new method and the Rosenblatt Inverse-First-Order Reliability environmental contour approach were calculated. Analyzing the calculating results, it can be found that the 50-year extreme fore-aft shear force value based on the 50-year extreme sea state obtained using the proposed new method is 78.9% larger than the corresponding value obtained based on the Rosenblatt Inverse-First-Order Reliability contour method. The calculation results in this paper were further systematically analyzed and compared, and the necessity and importance of using more realistic environmental contour lines (such as those generated using the proposed new method) have been finally highlighted.