Interobserver variability in target definition for stereotactic arrhythmia radioablation

BackgroundStereotactic arrhythmia radioablation (STAR) is a potential new therapy for patients with refractory ventricular tachycardia (VT). The arrhythmogenic substrate (target) is synthesized from clinical and electro-anatomical information. This study was designed to evaluate the baseline interobserver variability in target delineation for STAR.MethodsDelineation software designed for research purposes was used. The study was split into three phases. Firstly, electrophysiologists delineated a well-defined structure in three patients (spinal canal). Secondly, observers delineated the VT-target in three patients based on case descriptions. To evaluate baseline performance, a basic workflow approach was used, no advanced techniques were allowed. Thirdly, observers delineated three predefined segments from the 17-segment model. Interobserver variability was evaluated by assessing volumes, variation in distance to the median volume expressed by the root-mean-square of the standard deviation (RMS-SD) over the target volume, and the Dice-coefficient.ResultsTen electrophysiologists completed the study. For the first phase interobserver variability was low as indicated by low variation in distance to the median volume (RMS-SD range: 0.02–0.02 cm) and high Dice-coefficients (mean: 0.97 ± 0.01). In the second phase distance to the median volume was large (RMS-SD range: 0.52–1.02 cm) and the Dice-coefficients low (mean: 0.40 ± 0.15). In the third phase, similar results were observed (RMS-SD range: 0.51–1.55 cm, Dice-coefficient mean: 0.31 ± 0.21).ConclusionsInterobserver variability is high for manual delineation of the VT-target and ventricular segments. This evaluation of the baseline observer variation shows that there is a need for methods and tools to improve variability and allows for future comparison of interventions aiming to reduce observer variation, for STAR but possibly also for catheter ablation

Chemically Controlled Volatile and Nonvolatile Resistive Memory Characteristics of Novel Oxygen-Based Polymers

Recent advancements in modern microelectronics continuously increase the data storage capacity of modern devices, but they require delicate and costly fabrication processes. As alternatives to conventional inorganic based semiconductors, semiconducting polymers are of academic and industrial interest for their cost-efficiency, power efficiency, and flexible processability. Here, we have synthesized a series of novel oxygen-based polymers through the postmodification reactions of poly(ethylene-alt-maleate) with various oxybenzyl alcohol derivatives. The oxygen-based polymers are thermally stable up to 180 degrees C, and their nanoscale film devices exhibit reliable, power efficient p-type unipolar volatile and nonvolatile resistive memory characteristics with high ON/OFF current ratios. Additionally, when given a higher number of oxygen atoms in oxyphenyl side groups, the thin film polymer devices demonstrate a wide operational film thickness range. The memory characteristics depend on the oxyphenyl moieties functioning as charge trap sites, where a combination of Schottky emission and trap-limited space charge limited conductions in OFF-state and hopping conduction in ON-state are observed. This study demonstrates the chemical incorporation of oxyphenyl derivatives into polymer dielectrics as a powerful development tool for p-type resistive memory materials

Influence of Topological Confinement on Nanoscale Film Morphologies of Tricyclic Block Copolymers

This study is the first quantitative synchrotron grazing incidence X-ray scattering investigation of nanoscale film morphologies of tricyclic block copolymers based on poly (n-decyl glycidyl ether) (PDGE) and poly (2-(2-(2-methoxyethoxy)-ethoxy)ethyl glycidyl ether) (PTEGGE) blocks in equivalent volume fractions. Both PDGE and PTEGGE blocks of the tricyclic block copolymers are amorphous, but copolymers exhibit phase-separated lamellar nanostructures due to block immiscibility. The lamellar structures vary in their structural parameters such as lamellar orientation and structural integrity stability depending on the degree of topological confinement effect taking effect. Interestingly, sub-10 nm domain spacings are established by all nanostructures, which are remarkably shorter than that of the linear analogue. These exceptionally short domain spacings are evident that the tricyclic block copolymer approach is highly efficient for developing high-performance nanolithographic materials for future advanced semiconductor applications

Correlations of nanoscale film morphologies and topological confinement of three-armed cage block copolymers

The nanoscale film morphologies of three-armed cage block copolymers showing three different variations (Cage-A, -B, and -C) have been investigated for the first time via synchrotron grazing incidence X-ray scattering. For all cage block copolymers, the individual block components revealed amorphous characteristics. Nevertheless, they all exhibited either cylindrical or lamellar phase-separated nanostructures. Key structural parameters such as domain spacing (d-spacing), structural ordering, and orientation varied depending on the cage topologies. In particular, the d-spacing of nanostructures ranged from 6.50 to 10.85 nm. Compared to their linear block copolymer analogues, the cage block copolymers achieved a 54.8-74.5% d-spacing reduction. Overall, structural parameters such as d-spacing, structural ordering, and orientation were found to be correlated with the topological confinement which originated from the molecular cage topology

Highly Ordered Nanoscale Film Morphologies of Block Copolymers Governed by Nonlinear Topologies

Among many properties of cyclic block copolymers, the notable domain spacing (d-spacing) reduction offers nonlinear topology as an effective tool for developing block copolymers for nanolithography. However, the current consensus regarding the topology-morphology correlation is ambiguous and in need of more studies. Here we present the morphological investigation on nanoscale films of cyclic and tadpole-shaped poly(n-decyl glycidyl ether-block-2-(2-(2-methoxyethoxy)ethoxy)-ethyl glycidyl ether)s and their linear counterpart via synchrotron grazing-incidence X-ray scattering. All copolymers form phase-separated nanostructures, in which only the nonlinear copolymers form highly ordered and unidirectional nanostructures. Additionally, d-spacings of cyclic and tadpole-shaped block copolymers are 49.3-53.7% and 25.0-32.5% shorter than that of their linear counterpart, respectively, exhibiting greater or comparable d-spacing reductions against the experimentally and theoretically achieved values from the literature. Overall, this study demonstrates that cyclic and tadpole topologies can be utilized in developing materials with miniaturized dimensions, high structural ordering, and unidirectional orientation for various nanotechnology applications

Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

Ongoing efforts in materials science have resulted in linear block copolymer systems that generate nanostructures via the phase separation of immiscible blocks; however, such systems are limited with regard to their domain miniaturization and lack of orientation control. We overcome these limitations through the bicyclic topological alteration of a block copolymer system. Grazing incidence X-ray scattering analysis of nanoscale polymer films revealed that bicyclic topologies achieve 51.3-72.8% reductions in domain spacing when compared against their linear analogue, which is more effective than the theoretical predictions for conventional cyclic topologies. Moreover, bicyclic topologies achieve unidirectional orientation and a morphological transformation between lamellar and cylindrical domains with high structural integrity. When the near-equivalent volume fraction between the blocks is considered, the formation of hexagonally packed cylindrical domains is particularly noteworthy. Bicyclic topological alteration is therefore a powerful strategy for developing advanced nanostructured materials for microelectronics, displays, and membranes

Unimodal and Well-Defined Nanomicelles Assembled by Topology-Controlled Bicyclic Block Copolymers

This study provides first insights into the micellization behavior and micellar morphologies of bicyclic amphiphiles in four different topologies: bicy-BCP-A, bicy-BCP-B, bicy-BCP-C, and bicy-BCP-D, consisting of poly(n-decyl glycidyl ether) and poly(2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether) blocks in equivalent molar fractions. Quantitative synchrotron X-ray scattering analysis reveals that all bicyclic amphiphiles self-assemble into unimodal nanomicelles consisting of core, dense corona, and soft corona structural components. The micelles also demonstrate substantial size reductions (56.7-70.7%) compared to micelles of their linear counterpart (l-BCP). The critical micelle concentration, stability, and structural parameters (shape, size, and others) of nanomicelles are differentiated by controlling the bicyclic topology types. bicy-BCP-A, -B, and -C form oblate ellipsoidal micelles, whereas bicy-BCP-D and l-BCP assemble into prolate ellipsoidal micelles. The size is found to be in the following order: bicy-BCP-D < bicy-BCP-C < bicy-BCP-B < bicy-BCP-A << l-BCP. Furthermore, the structural stability is in the following order: l-BCP < bicyBCP-D << bicy-BCP-B < bicy-BCP-C < bicy-BCP-A. These results indicate that the topology-controlled bicyclic block copolymers can be used as a desirable platform for developing high-performance functional core-shell nanoparticles for advanced applications in various fields, including smart drug delivery, biomedical imaging, cosmetics, advanced coating appliances, and molecular electronics

Micelle Structure Details and Stabilities of Cyclic Block Copolymer Amphiphile and Its Linear Analogues

In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(-n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b-PEO and -l-PBA--b-PEO-b-PBA) by using synchrotron X-ray scattering and quantitative data analysis. The comprehensive scattering analysis gives details and insights to the micellar architecture through structural parameters. Furthermore, this analysis provides direct clues for structural stabilities in micelles, which can be used as a good guideline to design highly stable micelles. Interestingly, in water, all topological polymers are found to form ellipsoidal micelles rather than spherical micelles; more interestingly, the cyclic polymer and its linear triblock analog make oblate-ellipsoidal micelles while the linear diblock analog makes a prolate-ellipsoidal micelle. The analysis results collectively inform that the cyclic topology enables more compact micelle formation as well as provides a positive impact on the micellar structural integrity

One-Shot Intrablock Cross-Linking of Linear Diblock Copolymer to Realize Janus-Shaped Single-Chain Nanoparticles

Developing an efficient and versatile process to transform a single linear polymer chain into a shape-defined nanoobject is a major challenge in the fields of chemistry and nanotechnology to replicate sophisticated biological functions of proteins and nucleic acids in a synthetic polymer system. In this study, we performed one-shot intrablock crosslinking of linear block copolymers (BCPs) to realize single-chain nanoparticles (SCNPs) with two chemically compartmentalized domains (i.e., Janus-shaped SCNPs). Detailed structural characterizations of the Janus-shaped SCNP composed of polystyrene-block-poly(glycolic acid) revealed its compactly folded conformation and compartmentalized block localization, similar to the self-folded tertiary structures of natural proteins. Versatility of the one-shot intrablock crosslinking was demonstrated using several different BCP precursors. We further discovered the excellent self-assembling behavior of the Janus-shaped SCNP to produce miniscule microphase-separated structures, representing the significant potential of the presented compartmentalization protocol, for developing biomimetic synthetic-systems, as well as for industrial nanofabrication applications