PATIENT-SPECIFIC BLOOD DYNAMIC SIMULATIONS IN ASSESSING ENDOVASCULAR OCCLUSION OF INTRACRANIAL ANEURYSMS

According to recent studies, there are various potential predictors for surgical outcome for cerebral aneurysms. An accurate surgical outcome assessment would help make better-informed decisions and avoid the risk of rebleeding. It is well known that hemodynamic factors play an important role in the pathogenesis and treatment of intracranial aneurysms. In this article, a computational fluid dynamic analysis is applied to one patient-specific model of the cerebral aneurysm located at the tip of basilar artery, by which the differences of hemodynamic parameters before and after endovascular treatment may be evaluated. Based on the model, we show that the flow behavior near the neck of the aneurysm sees great differences after endovascular treatment as compared with that before treatment, which also affects the wall shear stress and the displacement distribution. In addition, our whole simulation process is based on a series of CFD commercial software packages, which are easily available for doctors to implement such a method in their daily practice. These results would be used to assess the outcome of endovascular treatment for the aneurysm occlusion.     

Numerical Simulation of Blood Pulsatile Flow in a DeBakey III Type of TVD

为探索胸主动脉夹层发展与血液动力学因素的关系,借助计算流体动力学,对DeBakeym型胸主动脉夹层血液脉动流在正常血压和高血压下进行三维数值模拟,获得了夹层血液流动在一个心动周期内不同时刻真假腔纵向切面流线分布、真假腔入口横断面流线分布以及血管壁面压力和剪应力分布．计算结果表明,尽管血压值对血管壁面剪应力分布影响较小,但血压与真假腔内血液动力学行为密切相关;心缩期夹层假腔内压力远大于真腔内压力,夹层可能继续向下延伸发展．     

Guidelines for Quantitative Evaluation of Medical Visualizations on the Example of 3D Aneurysm Surface Comparisons

Medical visualizations are highly adapted to a specific medical application scenario. Therefore, many researchers conduct qualitative evaluations with a low number of physicians or medical experts to assess the benefits of their visualization technique. Although this type of research has advantages, it is difficult to reproduce and can be subjectively biased. This makes it problematic to quantify the benefits of a new visualization technique. Quantitative evaluation can objectify research and help bringing new visualization techniques into clinical practice. To support researchers, we present guidelines to quantitatively evaluate medical visualizations, considering specific characteristics and difficulties. We demonstrate the adaptation of these guidelines on the example of comparative aneurysm surface visualizations. We developed three visualization techniques to compare aneurysm volumes. The visualization techniques depict two similar, but not identical aneurysm surface meshes. In a user study with 34 participants and five aneurysm data sets, we assessed objective measures (accuracy and required time) and subjective ratings (suitability and likeability). The provided guidelines and presentation of different stages of the evaluation allow for an easy adaptation to other application areas of medical visualization.     

大动脉调转手术规划的生物力学机理研究进展

大动脉调转术是治疗完全性大动脉转位的理想手术方式,其主要目的是矫正其畸形的解剖结构;手术近期和远期效果满意. 根据临床医生的经验和设想,提出了目前大动脉调转手术面临的问题. 综述了关于大动脉调转手术临床上的手术技巧;综述了国内外主动脉根部生物力学机理研究的有限元模型、实验研究等方面的最新研究进展;综述了几何构型因素对主动脉瓣关闭功能影响的研究进展. 在此基础上,对改进大动脉调转手术方案的生物力学机理研究进行了展望.     

用于数值模拟的带支架个性化主动脉弓动脉瘤有限元模型的构建

为了准确地分析动脉瘤壁面切应力及梯度变化,采用逆向工程的思想方法,借助Geomagic和Pro/E软件,以原始STL(stereo lithography)格式的表面模型为依据,建立了一个个性化主动脉弓动脉瘤实体模型,并在其内部创建理想化支架;利用ANSYS有限元分析软件,最终完成实体模型的建立和分块,并针对边界层和支架进行分区域网格划分.结果表明:所建立的有限元模型可进行血流动力学模拟仿真;模型基本满足对特定区域网格细划分的需要,可以为支架介入治疗动脉瘤的血流动力学仿真提供基础;这种模型建立方法为建立其他类似模型提供了参考.     

Chemistryvis-à-vis maternalism in lace bugs (Heteroptera: Tingidae): Alarm pheromones and exudate defense inCorythucha andGargaphia species

The hawthorn lace bug,Corythucha cydoniae, and the eggplant lace bug,Gargaphia solani, possess alarm pheromones that are produced in dorsal abdominal glands (DAGs). WhenG. solani nymphs are grasped, they emit secretion from both DAGs; the posterior DAG secretion alone elicits alarm, but the anterior DAG secretion may hasten the response. InC. cydoniae, the response is due to a synergism between the anterior and posterior DAG secretions, and nymphs are apparently unable to voluntarily release their DAG secretions; both DAGs must be ruptured for the pheromone to escape. The alarm pheromones are interspecifically active in patterns matching the intraspecific activities. Compounds identified from tingid DAG secretions that are involved in the alarm messages are: (E)2-hexenal, (E)-4-oxo-2-hexenal, acetaldehyde, geraniol, and linalool. A new natural product of unknown function (designated nerolidol aldehyde) was identified from the anterior DAG secretions of both species.     

CT纹理分析对腹主动脉瘤腔内修补术后瘤体体积变化的评价意义

目的探讨CT纹理分析对腹主动脉瘤腔内修补术(endovascular aneurysm repair,EVAR)后瘤体体积变化的评价意义。方法回顾性收集2014年7月至2019年6月于北京协和医院放射科行腹盆部增强CT血管造影(computed tomography angiography,CTA)随访的EVAR术后患者的临床及影像学资料,患者于术后第3、12个月分别接受两次腹盆部CTA检查,以传统测量方法为分组依据,根据动脉瘤体积变化情况将患者分为动脉瘤体积增大组和体积未增大组。采用分割软件,手动勾勒所有动脉瘤术后第1次随访时轴位最大截面,提取动脉瘤支架外血栓部分的纹理特征,同时采用灰度共生矩阵(grey level co-occurrence matrix,GLCM)、灰度游程矩阵(grey level run length matrix,GLRLM)和灰度差分矩阵(grey level difference matrix,GLDM) 3种方法,分析其与动脉瘤体积增大的关系。结果共70例符合纳入和排除标准的患者入选本研究,其中29例(41. 4%,29/70) EVAR术后腹主动脉瘤体积增大,41例(58. 6%,41/70)瘤体未增大。GLCM、GLRLM和GLDM 3种方法预测动脉瘤体积增大的曲线下面积分别为0. 892、0. 888和0. 800,GLCM的预测效能最佳,灵敏度和特异度分别为86. 2%和85. 4%,GLDM的曲线下面积最小,灵敏度和特异度分别为86. 2%和68. 3%。结论 CT纹理分析能有效预测EVAR术后动脉瘤的体积变化。     

Fluid–structure interaction modeling of a patient-specific cerebral aneurysm: influence of structural modeling

Fluid–structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on patient-specific FSI simulations. The maximum displacement computed with the hyper-elastic model is 36% smaller compared to the linearly elastic material model, but the displacement patterns such as the site of local maxima are not sensitive to the wall models. The blood near the apex of an aneurysm is likely to be stagnant, which causes very low wall shear stress and is a factor in rupture by degrading the aneurysmal wall. In this study, however, relatively high flow velocities due to the interaction between the blood flow and aneurysmal wall are seen to be independent of the wall model. The present results indicate that both linearly elastic and hyper-elastic models can be useful to investigate aneurysm FSI.     

序贯法测定羟考酮皮下注射用于Stanford A型主动脉夹层撕裂患者术前镇痛的半数有效剂量

目的:采用序贯法测定羟考酮皮下注射用于Stanford A型主动脉夹层撕裂患者术前镇痛的半数有效剂量(ED50)。方法:Stanford A型主动脉夹层撕裂患者30例，美国麻醉医师协会(ASA)分级Ⅱ～Ⅲ级，拟于全身麻醉下行急诊手术。根据序贯法增减给药，麻醉前60 min时第一例患者皮下注射羟考酮5.0 mg，相邻剂量梯度为0.5 mg，若上一例患者镇痛效果满意，则下一例患者剂量减少0.5 mg；若上一例患者镇痛效果不满意，则下一例患者剂量增加0.5 mg。序贯给药后采用视觉模拟评分法(VAS)评估镇痛效果，VAS≤3分为镇痛有效。采用Dixon and Massey序贯分配试验法公式计算羟考酮皮下注射用于Stanford A型主动脉夹层撕裂患者术前镇痛中的ED50和95%可信区间。结果:镇痛效果满意组患者总体满意度高于镇痛效果不满意组(P<0.05)，而两组补救镇痛率差异无统计学意义(P>0.05)。皮下注射羟考酮用于Stanford A型主动脉夹层撕裂患者术前镇痛的ED50为2.9 mg，95%可信区间为2.3～3.4 mg。结论:采用序贯法测得的皮下注射羟考酮用于Stanford A型主动脉夹层撕裂患者术前镇痛的ED50为2.9 mg，且此法简便、高效、准确性高。     

应用于推拿教学的气动式人体器官模拟装置设计研究

为了解决传统推拿训练引起医患纠纷等问题,设计一种新型的气动式人体器官模拟装置。研制一种气动驱动系统,建立胸/腹腔模拟器数学模型,仿真分析了压力和压缩位移等因素对胸/腹腔模拟器刚度特性的影响,实验验证了模型的有效性。结果表明:改变模拟器压力可模拟不同年龄段患者的胸/腹腔刚度。研究结果可为设计新型的推拿教学训练装置提供依据。