Purpose
To design and construct a three‐dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) ...algorithms for adaptive radiation therapy (ART).
Method
Organ molds, including liver, kidney, spleen, stomach, vertebra, and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate. Gels with different densities were obtained by a polynomial fitting curve that described the relation between the Hounsfield unit (HU) and PVC‐softener blending ratio. The rigid vertebras were constructed by molding of white cement and cellulose pulp. The final abdominal phantom was assembled by arranging all the fabricated organs inside a hollow dummy according to their anatomies, and sealed by deformable gel with averaged HU of muscle and fat. Fiducial landmarks were embedded inside the phantom for spatial accuracy and dose accumulation accuracy studies. Two channels were excavated to facilitate ionization chamber insertion for dosimetric measurements. Phantom properties such as deformable gel elasticity and HU stability were studied. The dosimetric measurement accuracy in the phantom was performed, and the DIR accuracies of three DIR algorithms available in the open source DIR toolkit‐DIRART were also validated.
Results
The constructed deformable gel showed elastic behavior and was stable in HU values over times, proving to be a practical material for the deformable phantom. The constructed abdominal phantom consisted of realistic anatomies in terms of both anatomical shapes and densities when compared with its reference patient. The dosimetric measurements showed a good agreement with the calculated doses from the treatment planning system. Fiducial‐based accuracy analysis conducted on the constructed phantom demonstrated the feasibility of applying the phantom for organ‐wise DIR accuracy assessment.
Conclusions
We have designed and constructed an anthropomorphic abdominal deformable phantom with satisfactory elastic property, realistic organ density, and anatomy. This physical phantom can be used for routine validations of DIR geometric accuracy and dose accumulation accuracy in ART.
The aim of the present study was to investigate the role of CTVision in interfractional setup errors during intensity‐modulated radiation therapy (IMRT) in 12 nasopharyngeal carcinoma (NPC) patients. ...The trend of setup errors as a function of time during a fractionated radiotherapy course was investigated, and the influence of reconstructive thickness on image reconstruction for setup errors was analyzed. The appropriate planning target volume (PTV) margin and planning risk volume (PRV) margin were defined to provide a reference for the design of IMRT for NPC. Based on CTVision, online CT was performed weekly for each patient. Setup errors were measured by registration between the CT reconstructed image and reference image. Mean of setup errors, estimated population systematic (:), and population random (σ) errors were calculated using SPSS (v15.0). Optimum PTV and PRV margins were calculated. In the clinical data, for the LR (left–right), SI (superior–inferior), and AP (anterior–posterior) directions, : was 0.8, 0.8, and 1.0 mm, respectively, and σ was 1.0, 1.3, and 0.8 mm, respectively. In the LR, SI, and AP directions, PTV margins were at least 2.7, 2.9, and 3.0 mm, respectively, and PRV margins were at least 1.5, 1.7, and 1.7 mm, respectively. No significant differences in setup errors were observed during the fractionated radiotherapy course (p>0.05). However, CT image reconstruction with different thicknesses affected the accuracy of measurements for setup errors, particularly in the SI direction. The application of CTVision to correct setup errors is important and can provide reasonable margins to guarantee the coverage of PTVs and spare organs at risk. A thickness of 3 mm in the reconstructed image is appropriate for the measurement of setup errors by image registration.
PACS number(s): 87.55.Qr
With the purpose of reducing stray radiation dose (SRD) in out‐of‐field region (OFR) during radiotherapy with 6 MV intensity‐modulated radiation therapy (IMRT), a body‐shielding device (BSD) was ...prepared according to the measurements obtained in experimental testing. In experimental testing, optimal shielding conditions, such as 1 mm lead, 2 mm lead, and 1 mm lead plus 10 mm bolus, were investigated along the medial axis of a phantom using thermoluminescent dosimeters (TLDs). The SRDs at distances from field edge were then measured and analyzed for a clinical IMRT treatment plan for nasopharyngeal carcinoma before and after shielding using the BSD. In addition, SRDs in anterior, posterior, left and right directions of phantom were investigated with and without shielding, respectively. Also, the SRD at the bottom of treatment couch was measured. SRD decreased exponentially to a constant value with increasing distance from field edge. The shielding rate was 50%–80%; however, there were no significant differences in SRDs when shielded by 1 mm lead, 2 mm lead, or 1 mm lead plus 10 mm bolus (P>0.05). Importantly, the 10 mm bolus absorbed back‐scattering radiation due to the interaction between photons and lead. As a result, 1 mm lead plus 10 mm bolus was selected to prepare the BSD. After shielding with BSD, total SRDs in the OFR decreased to almost 50% of those without shielding when irradiated with IMRT beams. Due to the effects of treatment couch and gantry angle, SRDs at distances were not identical in anterior, posterior, left and right direction of phantom without BSD. As higher dose in anterior and lower dose in posterior, SRDs were substantial similarities after shielding. There was no significant difference in SRDs for left and right directions with or without shielding. Interestingly, SRDs in the four directions were similar after shielding. From these results, the BSD developed in this study may significantly reduce SRD in the OFR during radiotherapy, thus decreasing the risk of secondary cancers.
Objective: To investigate the relationship between genetic characteristics of pivotal driver genes and clinicopathological features in pancreatic ductal adenocarcinoma(PDAC). Methods: Mutations in ...related genes in 269 PDAC patients were detected with targeted sequencing, and the relationship between the genetic status of pivotal driver genes (KRAS、TP53、SMAD4 and CDKN2A) and clinicopathological features (including age, tumor differentiation, and prognosis, etc) were analyzed. Results: Among 269 patients, KRAS, TP53, SMAD4 and CDKN2A mutations were identified in 222 cases (82.53%), 148 cases (55.02%), 41 cases (15.24%) and 30 cases (11.15%) respectively. KRAS mutations were missense mutations, of which 94.59% occurred in codon 12 of exon 2 and 5.41% in codon 61 in exon 3. KRAS mutation might be correlated with age, with a mutation rate of 80.09% in patients younger than 70 years old and 93.75% in patients older than 70 years old (P<0.05); TP53 mutation was correlated with the tumor differentiation, with a mutat
Lithium-ion batteries (LIBs) have become one of the most prevalent techniques for feasible and fascinating energy storage devices used in portable electronics and electric vehicles; however, they ...still face a significant challenge due to the complicated electrode–electrolyte interface (EEI), which is closely related to the chemical/electrochemical instability of high-capacity high-voltage electrodes and electrolytes. In particular, the decomposition of an electrolyte on the electrode surface is unambiguously regarded as a crucial controlling factor for the obtainable capacity, rate capacity, and interfacial chemistries of batteries. Previously, significant efforts have been devoted toward modifying the EEI with remarkable progress. The incorporation of a small dose of foreign molecules, called film-forming additives, is regarded as one of the most economical and effective approaches to circumvent these predicaments. In this regard, this review provides an overview of various film-forming additives used for classified anodes and cathodes, aiming at emphasizing the state-of-the-art developments in the electrolyte research. Moreover, the authors intend to help the readers arouse new ideas and easily identify the additives suitable for their target materials, paving the way for greater progress in the lithium-ion battery community.
This paper presents an interval multi-objective path planning (PP) scheme for patrol robot in nuclear power plant. The purpose of this PP scheme is to find collision-free paths with the shortest ...length and smallest risk degree. Firstly, a novel workspace modeling method is proposed to describe the static PP environment of patrol robot in nuclear power plant. Then considering the conflicts of the shortest length and smallest risk degree, an interval multi-objective particle swarm optimization (IMOPSO) method is used. In the IMOPSO, an ingenious interval update law for the particle’s global best position and local best position based on the crowding distance of each risk degree interval is used to increase the diversity of population, and an iterative procedure is adopted to update the particle’s position when the found paths are collided with some existing obstacles. Finally, three representative simulation tests are used to verify the validity of proposed IMOPSO method. Results show that comparing with other three well-known multi-objective evolutionary algorithms, our proposed method has the advantages of finding a better Pareto optimal paths.
•A new workspace modeling method is proposed for patrol robot in nuclear power plant.•The path length and interval risk degree are selected as two objective functions.•An interval MOPSO-based method is proposed to solve the robot path planning problem.•Three representative simulation tests prove the effectiveness of our proposed method.
Introduction Transmission of COVID-19 within families and close contacts accounts for the majority of epidemic growth. Community mask wearing, hand washing and social distancing are thought to be ...effective but there is little evidence to inform or support community members on COVID-19 risk reduction within families. Methods A retrospective cohort study of 335 people in 124 families and with at least one laboratory confirmed COVID-19 case was conducted from 28 February to 27 March 2020, in Beijing, China. The outcome of interest was secondary transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within the family. Characteristics and practices of primary cases, of well family contacts and household hygiene practices were analysed as predictors of secondary transmission. Results The secondary attack rate in families was 23.0% (77/335). Face mask use by the primary case and family contacts before the primary case developed symptoms was 79% effective in reducing transmission (OR=0.21, 95% CI 0.06 to 0.79). Daily use of chlorine or ethanol based disinfectant in households was 77% effective (OR=0.23, 95% CI 0.07 to 0.84). Wearing a mask after illness onset of the primary case was not significantly protective. The risk of household transmission was 18 times higher with frequent daily close contact with the primary case (OR=18.26, 95% CI 3.93 to 84.79), and four times higher if the primary case had diarrhoea (OR=4.10, 95% CI 1.08 to 15.60). Household crowding was not significant. Conclusion The study confirms the highest risk of transmission prior to symptom onset, and provides the first evidence of the effectiveness of mask use, disinfection and social distancing in preventing COVID-19. We also found evidence of faecal transmission. This can inform guidelines for community prevention in settings of intense COVID-19 epidemics.
A dense neutrino medium can support flavor oscillation waves which are coherent among different momentum modes of the neutrinos. The dispersion relation (DR) branches of such a wave with complex ...frequencies and/or wave numbers can lead to the exponential growth of the wave amplitude which in turn will engender a collective flavor transformation in the neutrino medium. In this work, we propose that the complex DR branches of the neutrino oscillation wave should be bound by the critical points of the DR. We demonstrate how this theory can be applied to the neutrino medium with an (approximate) axial symmetry about the propagation direction of the neutrino oscillation wave. We also show how the flavor instabilities in this medium can be identified by tracing the critical points of the DR as the electron lepton number distribution of the neutrino medium is changed continuously.
Lithium‐ion batteries (LIBs) have been occupying the dominant position in energy storage devices. Over the past 30 years, silicon (Si)‐based materials are the most promising alternatives for graphite ...as LIB anodes due to their high theoretical capacities and low operating voltages. Nevertheless, their extensive volume changes in battery operation causes the structural collapse of Si‐based electrodes, as well as severe side reactions. In this review, the preparation methods and structure optimizations of Si‐based materials are highlighted, as well as their applications in half and full cells. Meanwhile, the developments of promising electrolytes, binders and separators that match Si‐based electrodes in half and full cells have made great progress. Pre‐lithiation technology has been introduced to compensate for irreversible Li+ consumption during battery operation, thereby improving the energy densities and lifetime of Si‐based full cells. More importantly, almost all related mechanisms of Si‐based electrodes in half and full cells are summarized in detail. It is expected to provide a comprehensive insight on how to develop high‐performance Si‐based full cells. The work can help us understand what happens during the lithiation process, the primary causes of Si‐based half and full cells failure, and strategies to overcome these challenges.
Promising Si‐based batteries should have outstanding and balanced performance between energy density and lifetime. Specifically, the development of cathodes, the modification of Si anodes, electrolytes, binders, and separators, as well as state of the art pre‐lithiation technologies are critical to facilitate the practical application of Si‐based batteries.
Solid‐state electrolytes (SSEs), being the key component of solid‐state lithium batteries, have a significant impact on battery performance. Rational materials structure and composition engineering ...on SSEs are promising to improve their Li+ conductivity, interfacial contact, and mechanical integrity. Among the fabrication approaches, the electrospinning technique has attracted tremendous attention due to its own merits in constructing a three‐dimensional framework of SSEs with precise porosity structure, tunable materials composition, easy operation, and superior physicochemical properties. To this end, in this review, we provide a comprehensive summary of the recent development of electrospinning techniques for high‐performance SSEs. Firstly, we introduce the historical development of SSEs and summarize the fundamentals, including the Li+ transport mechanism and materials selection principle. Then, the versatility of electrospinning technologies in the construction of the three main types of SSEs and stabilization of lithium metal anodes is comprehensively discussed. Finally, a perspective on future research directions based on previous work is highlighted for developing high‐performance solid‐state lithium batteries based on electrospinning techniques.
Solid‐state lithium batteries have attracted wide attention owing to their evident merits of high safety and high energy density. Rational materials structure and composition engineering on solid‐state electrolytes (SSEs) is promising to improve Li+ conductivity, interfacial contact, and mechanical integrity of SSEs. To this end, a comprehensive review related to the state‐of‐the‐art development of electrospinning technique toward high‐performance solid‐state lithium batteries is given to guild the rational design of advanced SSEs.
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