The VESSEL12 (VESsel SEgmentation in the Lung) challenge objectively compares the performance of different algorithms to identify vessels in thoracic computed tomography (CT) scans. Vessel segmentation is fundamental in computer aided processing of data generated by 3D imaging modalities. As manual vessel segmentation is prohibitively time consuming, any real world application requires some form of automation. Several approaches exist for automated vessel segmentation, but judging their relative merits is difficult due to a lack of standardized evaluation. We present an annotated reference dataset containing 20 CT scans and propose nine categories to perform a comprehensive evaluation of vessel segmentation algorithms from both academia and industry. Twenty algorithms participated in the VESSEL12 challenge, held at International Symposium on Biomedical Imaging (ISBI) 2012. All results have been published at the VESSEL12 website http://vessel12.grand-challenge.org. The challenge remains ongoing and open to new participants. Our three contributions are: (1) an annotated reference dataset available online for evaluation of new algorithms; (2) a quantitative scoring system for objective comparison of algorithms; and (3) performance analysis of the strengths and weaknesses of the various vessel segmentation methods in the presence of various lung diseases.

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Dual stimuli-sensitive star polypeptide was for the first time synthesized and self-assembled into reduction- and thermo-sensitive micelles and hydrogels, demonstrating tunable size, mechanical and triggered drug-release properties useful for on-demand drug delivery.

Pulmonary fissures are important landmarks for recognition of lung anatomy. In CT images, automatic detection of fissures is complicated by factors like intensity variability, pathological deformation and imaging noise. To circumvent this problem, we propose a derivative of stick (DoS) filter for fissure enhancement and a post-processing pipeline for subsequent segmentation. Considering a typical thin curvilinear shape of fissure profiles inside 2D cross-sections, the DoS filter is presented by first defining nonlinear derivatives along a triple stick kernel in varying directions. Then, to accommodate pathological abnormality and orientational deviation, a [Formula: see text] cascading and multiple plane integration scheme is adopted to form a shape-tuned likelihood for 3D surface patches discrimination. During the post-processing stage, our main contribution is to isolate the fissure patches from adhering clutters by introducing a branch-point removal algorithm, and a multi-threshold merging framework is employed to compensate for local intensity inhomogeneity. The performance of our method was validated in experiments with two clinical CT data sets including 55 publicly available LOLA11 scans as well as separate left and right lung images from 23 GLUCOLD scans of COPD patients. Compared with manually delineating interlobar boundary references, our method obtained a high segmentation accuracy with median F1-scores of 0.833, 0.885, and 0.856 for the LOLA11, left and right lung images respectively, whereas the corresponding indices for a conventional Wiemker filtering method were 0.687, 0.853, and 0.841. The good performance of our proposed method was also verified by visual inspection and demonstration on abnormal and pathological cases, where typical deformations were robustly detected together with normal fissures.

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Hyperbranched poly(ε-benzyloxycarbonyl-L-lysine) (HPlys) with multiple alkyne peripheries was synthesized through the click polycondensation of an AB2 type Plys macromonomer with α-thiol and ω-alkyne terminal groups (thiol is the A unit, and each π bond in alkyne is the B unit), and the resulting HPlys was further conjugated with thiol-termined poly(ethylene oxide) (PEO) to generate HPlys-b-PEO block copolymer by consecutive thiol-yne chemistry. Their molecular structures and physical properties were characterized in detail by FT-IR, (1)H NMR, gel permeation chromatography, differential scanning calorimetry, wide-angle X-ray diffraction, and polarized optical microscopy. HPlys and HPlys-b-PEO mainly assumed an α-helix conformation similar to the linear precursors, while the liquid crystalline phase transition of Plys segment disappeared within HPlys and HPlys-b-PEO. HPlys-b-PEO self-assembled into nearly spherical micelles in aqueous solution, while it gave a 5-fold lower critical aggregation concentration (8.9 × 10(-3) mg/mL) than a linear counterpart (4.5 × 10(-2) mg/mL), demonstrating a dendritic topology effect. Compared with a linear counterpart, HPlys-b-PEO gave a higher drug-loading capacity and efficiency for the anticancer drug doxorubicin (DOX) and a slower drug-release rate with an improved burst-release profile, enabling them useful for drug delivery systems. Importantly, this work provides a versatile strategy for the synthesis of hyperbranched polypeptides and related block copolymers by utilizing thiol-yne chemistry.

Excitation of nonlinear ion acoustic wave (IAW) by an external electric field is demonstrated by Vlasov simulation. The frequency calculated by the dispersion relation with no damping is verified much closer to the resonance frequency of the small-amplitude nonlinear IAW than that calculated by the linear dispersion relation. When the wave number kλ De increases, the linear Landau damping of the fast mode (its phase velocity is greater than any ion's thermal velocity) increases obviously in the region of T i /T e < 0.2 in which the fast mode is weakly damped mode. As a result, the deviation between the frequency calculated by the linear dispersion relation and that by the dispersion relation with no damping becomes larger with kλ De increasing. When kλ De is not large, such as kλ De = 0.1, 0.3, 0.5, the nonlinear IAW can be excited by the driver with the linear frequency of the modes. However, when kλ De is large, such as kλ De = 0.7, the linear frequency can not be applied to exciting the nonlinear IAW, while the frequency calculated by the dispersion relation with no damping can be applied to exciting the nonlinear IAW.

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