Continuous Ultrasound Speckle Tracking with Gaussian Mixtures

Speckle tracking echocardiography (STE) is now widely used for measuring strain, deformations, and motion in cardiology. STE involves three successive steps: acquisition of individual frames, speckle detection, and image registration using speckles as landmarks. This work proposes to avoid explicit detection and registration by representing dynamic ultrasound images as sparse collections of moving Gaussian elements in the continuous joint space-time space. Individual speckles or local clusters of speckles are approximated by a single multivariate Gaussian kernel with associated linear trajectory over a short time span. A hierarchical tree-structured model is fitted to sampled input data such that predicted image estimates can be retrieved by regression after reconstruction, allowing a (bias-variance) trade-off between model complexity and image resolution. The inverse image reconstruction problem is solved with an online Bayesian statistical estimation algorithm. Experiments on clinical data could estimate subtle sub-pixel accurate motion that is difficult to capture with frame-to-frame elastic image registration techniques

Facile and Low-Cost Route for Sensitive Stretchable Sensors by Controlling Kinetic and Thermodynamic Conductive Network Regulating Strategies

Highly sensitive conductive polymer composites (CPCs) are designed employing a facile and low-cost extrusion manufacturing process for both low- and high-strain sensing in the field of, for example, structural health/damage monitoring and human body movement tracking. Focus is on the morphology control for extrusion-processed carbon black (CB)-filled CPCs, utilizing binary and ternary composites based on thermoplastic polyurethane (TPU) and olefin block copolymer (OBC). The relevance of the correct CB amount, kinetic control through a variation of the compounding sequence, and thermodynamic control induced by annealing is highlighted, considering a wide range of experimental (e.g., static and dynamic resistance/scanning electron microscopy/rheological measurements) and theoretical analyses. High CB mass fractions (20 m %) are needed for OBC (or TPU)–CB binary composites but only lead to an intermediate sensitivity as their conductive network is fully packed and therefore difficult to be truly destructed. Annealing is needed to enable a monotonic increase of the relative resistance with respect to strain. With ternary composites, a much higher sensitivity with a clearer monotonic increase results, provided that a low CB mass fraction (10–16 m %) is used and annealing is applied. In particular, with CB first dispersed in OBC and annealing, a less compact, hence, brittle conductive network (10–12 m % CB) is obtained, allowing high-performance sensing

Kinetic Modeling of Radical Thiol–Ene Chemistry for Macromolecular Design: Importance of Side Reactions and Diffusional Limitations

The radical thiol–ene coupling of thiol-functionalized polystyrene (PS-SH) with dodecyl vinyl ether (DVE) and the polystyrene-<i>b</i>-poly­(vinyl acetate) (PS-<i>b</i>-PVAc) polymer–polymer conjugation using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator are modeled to assess the importance of diffusional limitations and side reactions. Intrinsic chemical rate coefficients are determined based on a kinetic study of the coupling of benzyl thiol (BT) and DVE. The addition and transfer reactions are chemically controlled, whereas diffusional limitations on termination slightly increase the coupling efficiency. Termination by recombination of carbon-centered radicals and addition of DMPA derived radicals to DVE are shown to be mainly responsible for the reduced coupling efficiency in case polymeric species are involved. The obtained results confirm the idea to disregard radical thiol–ene chemistry as a true member of the family of “click” chemistry techniques for polymer–polymer conjugation and show that the initial conditions have a significant impact on the coupling efficiency

Predictive Factors and Risk Model for Positive Circumferential Resection Margin Rate after Transanal Total Mesorectal Excision in 2653 Patients with Rectal Cancer

The aim of this study was to determine the incidence of, and preoperative risk factors for, positive circumferential resection margin (CRM) after transanal total mesorectal excision (TaTME). Background: TaTME has the potential to further reduce the rate of positive CRM for patients with low rectal cancer, thereby improving oncological outcome. Methods: A prospective registry-based study including all cases recorded on the international TaTME registry between July 2014 and January 2018 was performed. Endpoints were the incidence of, and predictive factors for, positive CRM. Univariate and multivariate logistic regressions were performed, and factors for positive CRM were then assessed by formulating a predictive model. Results: In total, 2653 patients undergoing TaTME for rectal cancer were included. The incidence of positive CRM was 107 (4.0%). In multivariate logistic regression analysis, a positive CRM after TaTME was significantly associated with tumors located up to 1 cm from the anorectal junction, anterior tumors, cT4 tumors, extra-mural venous invasion (EMVI), and threatened or involved CRM on baseline MRI (odds ratios 2.09, 1.66, 1.93, 1.94, and 1.72, respectively). The predictive model showed adequate discrimination (area under the receiver-operating characteristic curve &gt;0.70), and predicted a 28% risk of positive CRM if all risk factors were present. Conclusion: Five preoperative tumor-related characteristics had an adverse effect on CRM involvement after TaTME. The predicted risk of positive CRM after TaTME for a specific patient can be calculated preoperatively with the proposed model and may help guide patient selection for optimal treatment and enhance a tailored treatment approach to further optimize oncological outcomes