Motion‐compensated b‐tensor encoding for in vivo cardiac diffusion‐weighted imaging

Motion is a major confound in diffusion‐weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo‐based DWI commonly employs gradient moment‐nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2‐nulled). However, current M2‐nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b‐tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof‐of‐concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2‐nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2‐nulled LTE, where diffusion‐weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal‐to‐noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed.     

A Bipolar-Bisection Piecewise Encoding Scheme for Multi-Source Reverse Time Migration

Conventional shot-record reverse time migration (RTM) suffers from a high computational burden when dealing with massive data. The computational cost of RTM can be reduced by shot-encoding techniques, and plane-wave encoding is a commonly used and effective shot-encoding scheme. However, plane-wave encoding requires long time padding to avoid information loss, which decreases the efficiency of the time-domain wavefield extrapolator, and the time padding becomes longer with the increasing distance between multiple sources. The piecewise plane-wave encoding scheme cuts multiple sources into several segments prior to implementing plane-wave encoding, hence reduces the time padding, but brings new crosstalk due to the mutual interference between shots in different source segments. We suppress the crosstalk artifacts by a new bipolar-bisection amplitude encoding method, in which half of the encoding array of each migration is different from that of any other migrations to reduce the number of crosstalk terms with as few migrations as possible. We embed the bipolar-bisection method into piecewise plane-wave encoding. Compared with plane-wave encoding, the proposed scheme requires considerably shorter time padding and thus works more efficiently and can generate a qualified imaging result. The feasibility of the proposed method is tested on the 2D SEG/EAGE salt model and the Marmousi model.     

中医药文献语义标注系统研究与开发

目的研究和开发支持中医和现代生物医学本体和术语集的语义标注系统。方法以MedPortal本体库和中医临床术语集等为术语资源库,设计语义标注系统工作流程和功能框架,并开发Web应用系统。结果构建了一个基于Web的中医药文献语义标注系统,支持语料库管理与维护、术语词典管理、语义标注和语义检索等功能,既可以为基于机器学习的信息抽取算法研究提供训练集,又能实现语义层面的多来源数据集成与知识融合。结论该中医药文献语义标注系统设计方案已经过实际项目验证,可为其他同类系统研发提供参考。     

Early signal from the hippocampus for memory encoding

The mediotemporal lobe (MTL), including the hippocampus, is involved in all stages of episodic memory including memory encoding, consolidation, and retrieval. However, the exact timing of the hippocampus' involvement immediately after stimulus encounter remains unclear. In this study, we used high‐density 156‐channel electroencephalography to study the processing of entirely new stimuli, which had to be encoded, in comparison to highly overlearned stimuli. Sixteen healthy subjects performed a continuous recognition task with meaningful pictures repeated up to four consecutive times. Waveform and topographic cluster analyses of event‐related potentials revealed that new items, in comparison to repetitions, were processed significantly differently at 220–300 ms. Source estimation localized activation for processing new stimuli in the right MTL. Our study demonstrates the occurrence of a transient signal from the MTL in response to new information already at 200–300 ms poststimulus onset, which presumably reflects encoding as an initial step toward memory consolidation.     

中医哮喘领域本体的构建

目的:利用本体的方式实现中医哮喘领域的知识的共建共享及推理。方法:通过对中医文献中"哮喘"相关知识的提取,基于斯坦福大学的七步法构建了"哮喘"的疾病本体,实现了哮喘相关知识的领域建模,建立了部分概念与概念间的关系约束及公理。结果:中医哮喘领域本体构建完成能够实现知识的共享以及简单的推理。共有类120个,实例425个,对象属性18个,其中反向属性6个,数值属性2个,等价类公理1个,子类公理138个,基本实现了对哮喘领域知识的语义化表达。结论:本体的构建在知识的共建、共享及未来知识库的语义检索、数据挖掘中具有一定的参考与应用价值。     

Category fluency in schizophrenia: opposing effects of negative and positive symptoms?

Introduction: Category fluency is associated with speed-, executive- and semantic impairments in schizphrenia. It has traditionally been linked to negative symptoms, whereas the relation to positive symptoms is mixed. Associations to the consensus negative, positive and disorganisation factors have not been analysed before.

Methods: Animal fluency was administered to 81 patients with schizophrenia. Measures of overall performance and applied strategies were analysed in relation to the Wallwork five-factor PANSS-model.

Results: Negative and disorganisation symptoms were negatively related to overall fluency performance. Positive symptoms were positively related to overall performance when controlling for disorganisation symptoms. Negative symptoms were related to fewer switches, less repetitions, less single animals intrusions, and both less rare and common animals. Positive symptoms were related to more effective retrieval of sub-category exemplars following a sub-category title, whereas there were no relation between symptoms and exemplars when the title was not retrieved. The Beta values of negative and positive symptoms were opposite.

Conclusion: This is the first study showing that positive symptoms are related to increased fluency performance when disorganisation is controlled for. Like previous studies, negative symptoms were found to depress fluency. Strategy measures indicated that negative symptoms predispose for rigidity, whereas positive symptoms facilitate more efficient associative pathways.     

Inferior detection of information from collaborative versus individual crimes based on a P300 Concealed Information Test

The present study used a P300‐based Concealed Information Test (CIT) to detect individual and collaborative crimes and to explore whether or not the P300 index is effective in identifying collaborative crime members. Participants were divided into two groups to either steal a ring alone (individual group) or collaboratively with another companion participant (collaborative group) before taking the Complex Trial Protocol test that is regarded as an accurate version of the P300‐based CIT. The ERP results revealed that both groups showed significantly larger P300s to probe (the ring) than to all irrelevant stimuli (other jewelery), but the P300 amplitude difference of probe stimulus versus irrelevant stimuli in the collaborative group was significantly less than that in the individual group. For the individual diagnosis, using P300 index, the detection rate was significantly inferior for collaborative crime than individual crime, probably related to weakness of collaborative encoding. The ROC curve comparisons showed the individual guilty was effectively discriminated from the simulated‐innocent (AUC = .84) and from the collaborative guilty (AUC = .83), but the collaborative guilty was not discriminable from the simulated‐innocent (AUC = .66). These findings suggest that collaborative encoding of crime‐related information impacts the efficiency of the P300 index, and that the P300‐based CIT is not applicable when used to identify collaborative crime perpetrators.