Usefulness of multidetector CT imaging to assess vascular stents in children with congenital heart disease: An in vivo and in vitro study

Objective : To evaluate varying CT settings to visualize pediatric vascular stents in comparison to digital angiography (DA). Background : There is a great clinical interest in substituting noninvasive methods to follow up children with congenital heart disease after interventional treatment. Materials and Methods : CT studies in small children with transcatheter placed stents were reviewed, retrospectively. Furthermore, eight stents were implanted in tubes and partially obstructed. CT exams were performed on varying scanners (4 up to 64 slices) with corresponding tube settings. The effects of dose on image quality were evaluated regarding stent size, strut thickness, and in‐stent stenoses in comparison to DA. Results : Fourteen children with 28 implanted stents were identified. Significant differences between higher and lower radiation settings were not found, corresponding with the phantom, where moderate tube setting showed the best results. In vitro, there was an improvement with increasing number of detector rows, which resulted in a decrease of stent strut overestimation (295% down to 201%; P < 0.0001) and a better agreement with DA measurements for mild (78% up to 91%; P = 0.003) and moderate in‐stent stenoses (80% up to 99%; P = 0.0001). Conclusion : Higher radiation exposure settings did not improve image quality, suggesting that the exams could be performed at a lower radiation dose. © 2008 Wiley‐Liss, Inc.     

Nature of curvature coupling of amphiphysin with membranes depends on its bound density

Cells are populated by a vast array of membrane-binding proteins that execute critical functions. Functions, like signaling and intracellular transport, require the abilities to bind to highly curved membranes and to trigger membrane deformation. Among these proteins is amphiphysin 1, implicated in clathrin-mediated endocytosis. It contains a Bin-Amphiphysin-Rvs membrane-binding domain with an N-terminal amphipathic helix that senses and generates membrane curvature. However, an understanding of the parameters distinguishing these two functions is missing. By pulling a highly curved nanotube of controlled radius from a giant vesicle in a solution containing amphiphysin, we observed that the action of the protein depends directly on its density on the membrane. At low densities of protein on the nearly flat vesicle, the distribution of proteins and the mechanical effects induced are described by a model based on spontaneous curvature induction. The tube radius and force are modified by protein binding but still depend on membrane tension. In the dilute limit, when practically no proteins were present on the vesicle, no mechanical effects were detected, but strong protein enrichment proportional to curvature was seen on the tube. At high densities, the radius is independent of tension and vesicle protein density, resulting from the formation of a scaffold around the tube. As a consequence, the scaling of the force with tension is modified. For the entire density range, protein was enriched on the tube as compared to the vesicle. Our approach shows that the strength of curvature sensing and mechanical effects on the tube depends on the protein density.     

On the origin of long-range correlations in texts

The complexity of human interactions with social and natural phenomena is mirrored in the way we describe our experiences through natural language. In order to retain and convey such a high dimensional information, the statistical properties of our linguistic output has to be highly correlated in time. An example are the robust observations, still largely not understood, of correlations on arbitrary long scales in literary texts. In this paper we explain how long-range correlations flow from highly structured linguistic levels down to the building blocks of a text (words, letters, etc..). By combining calculations and data analysis we show that correlations take form of a bursty sequence of events once we approach the semantically relevant topics of the text. The mechanisms we identify are fairly general and can be equally applied to other hierarchical settings.     

Sources of Uncertainty in Intuitive Physics

Recent work suggests that people predict how objects interact in a manner consistent with Newtonian physics, but with additional uncertainty. However, the sources of uncertainty have not been examined. In this study, we measure perceptual noise in initial conditions and stochasticity in the physical model used to make predictions. Participants predicted the trajectory of a moving object through occluded motion and bounces, and we compared their behavior to an ideal observer model. We found that human judgments cannot be captured by simple heuristics and must incorporate noisy dynamics. Moreover, these judgments are biased consistently with a prior expectation on object destinations, suggesting that people use simple expectations about outcomes to compensate for uncertainty about their physical models.     

Reply to Commentaries by Neil Altman and Thomas Menaker

Both commentaries address, from different perspectives, the controversies inherent in the idea of a transpersonal field. In response to Menaker, I examine the ways in which this territory cannot be adequately conceptualized from within the framework of existing theory and therefore is experienced as disruptive and destabilizing. I also focus on the gradual movement within contemporary psychoanalytic approaches toward realites that invite such a paradiamatic shift. In response to Altman, I agree that the intersubjective is not superseded by the transpersonal and emphasize that use of a transpersonal perspective to avoid intersubjective disruption is a form of perversion. I underscore Altman's use of contemporary scientific discoveries to substantiate the idea of a transcendent field yet emphasize that a transpersonal orientation also involves a willingness to encounter and tolerate the inexplicable.     

Certification in Medical Physics Imaging,The Workforce and Training Models

The pathway to becoming a qualified medical physicist (QMP) in the imaging physics disciplines includes several certification organizations. Imaging QMPs play an essential role in the safe practice of the diagnostic disciplines, and their qualifications are necessary for compliance with federal bodies and professional accreditation organizations. The future demand for imaging QMPs is largely unknown, but professional organizations that represent these groups agree that efforts should be made to increase the number of matriculating trainees. The number of imaging residency programs that provide the necessary professional experience to enter the certification pathway has increased substantially in recent years. Most of these programs follow a traditional academic hospital-based training model, but guidance on program construction from the accrediting body permits flexibility. Existing training models for medical physics imaging also include consortiums of affiliate partners and private consulting service groups. In this article, the authors briefly review the certification pathways for imaging QMPs, workforce estimates, and training models.     

医学物理学与医学课程相结合的研究

目的：从目前医学物理课程教学的现状出发,阐述在医学专业的课程设置和教学中加强医学和理工课程相结合的必要性。分析医学物理学与医学课程之间的关系,结合多年的教学实践探讨医学物理学与医学课程教学相结合的教学思想和方法,以期解决教学中实际问题,提高医学物理教学质量,提高物理学应用能力,培养具有扎实理工基础的创新医学人才。方法：采用理论分析和实践相结合的方法。医学物理学与医学课程教学相结合通过教学内容相融合、专题教学、医学案例讨论、医学拓展练习等形式具体实现。实践中分别对设立的两类班施行传统教学和医学与物理相结合的不同教学方法,然后进行比较。结果：医学物理学与医学课程相结合的教学能够提高学生学习《医学物理学》的积极性和效率,加深对医学课程内容的理解,增强医学应用能力,促进综合能力提升。结论：应当促使教学管理部门、教师、学生充分认识到物理学与医学课程存在紧密关联,意识到物理课程在医学生培养中的重要作用,通过医理结合教学提高课程的教学质量,提高医学生的医理结合能力。     

放射物理与防护本科课程双语教学的若干思考

文章总结了近年来作者在所在大学开展放射物理与防护本科双语教学工作的实践经验,从紧密结合放射物理专业知识结构特点采用点面结合的教学方式、理论和实践相结合避免填鸭式教学方式、以及合理运用现代媒体教学手段提高师生教学互动等几个方面重点总结了相关教学经验。结合双语教学理论和放射物理与防护专业课程的特点,从教学知识点分布以及考试权重分配等方面,对教学质量进行了全面的分析,给出了相应的教学质量分析方法,包括相关知识点分布全面性以及各个章节覆盖率分析、认知分类比例以及学生解决问题能力的考察分析、考试题目难易程度是否保持适中分析等方法。并进一步提出了根据每年考试成绩结果,分析总结优化教学知识点以及考试权重分配方案,最终逐步提高教学质量的方法。最后,从适当扩充与放射物理与防护关联紧密的其它专业课程知识、加强双语教学的实验和实践环节、加强学生用英语思考回答问题的习惯培养等三个方面就如何进一步提高放射物理与防护本科课程双语教学质量提出了建议。