Biomedical Imaging

该项目使用成像科学技术来分析多种类型的生物、临床和生物医学图像。目前的研究主要集中在两个方面：(1)利用电子显微照片和核磁共振光谱的图像处理技术来研究大分子的结构生物学；(2)开发复杂的生物医学和实验室成像软件。 (1)成像科学实验室与各研究所进行了一项重要的合作研究工作，涉及使用结构生物学中的图像处理技术和先进的计算技术来分析电子显微照片和核磁共振光谱，目的是确定大分子结构。最近的工作集中在二十面体病毒衣壳结构的三维重建、分析和解释上。正在进行的研究包括分析与疱疹病毒和乳头瘤病毒以及其他二十面体病毒衣壳有关的结构。 乳头瘤病毒(如HPV-16)编码两种衣壳蛋白L1和L2。主要衣壳蛋白L1可以自发组装成一个72个五聚体的二十面体结构，与天然病毒粒子非常相似。虽然次要衣壳蛋白L2不是衣壳形成所必需的，但它被认为参与了病毒基因组的囊化，并在病毒感染进入途径中发挥了许多重要作用。L2的丰度及其在病毒粒子中的排列仍不清楚。冷冻电子显微镜和差值三维重建分析显示，每个L1胶囊的轴向内腔下都有一个二十面体有序的L2特定密度。L2特定密度的等面体有序的细丝也在L1衣壳的底部延伸，增加了组装的病毒粒子内同型L2相互作用的可能性。我们用时移低温电子显微镜和图像分析技术研究了293T细胞中组装的HPV-16衣壳的成熟过程。主要的衣壳蛋白L1最初形成一个松散连接的前衣壳，在体外条件下，它在几个小时内浓缩成更熟悉的直径60纳米的乳头瘤病毒衣壳。在这个过程中，Proapsid的直径缩小了~5%；它的五聚体胶囊结构发生了变化，最明显的是在其轴向区域；相邻胶囊之间的相互作用表面得到了巩固。这些结构变化伴随着二硫键交联物的形成，这些交联物增强了成熟衣壳的稳定性。C175S突变体没有交联，表现出类似的成熟相关结构变化，但在其他类似的条件下，衣壳明显更大。我们的结论是，观察到的结构尺寸变化有助于成熟，但需要交联剂的形成才能将衣壳锁定到成熟状态。 我们还一直在开发利用核磁共振数据研究生物大分子的结构和动力学的计算工具。我们正在积极支持使用Xplor-NIH生物分子结构测定软件包的校内外社区。继续在下列领域开发Xplor-NIH：(A)在使用PYTHON和TCL脚本接口方面取得进一步进展，并增加了大量文件；(B) 通过结合来自核磁共振和溶液X射线散射技术的信息，获得了关于DNA在溶液中的动力学性质的第一幅真实图像；(C)现在可以直接根据溶液X射线散射和小角中子散射数据来精炼分子结构。 (2)成像科学实验室致力于为NIH的各种临床和生物医学活动提供计算和工程专业知识。具体地说，PET、超声波、CT、MRI、EPR、显微镜、癌症研究中的成像以及与神经功能障碍相关的成像已经以多种方式得到了支持。为了在NIH内部计划中支持科学研究，CIT已经开发并继续增强与平台无关的、n维的、可扩展的图像处理和可视化应用程序。MIPAV(医学图像处理分析和可视化)是一个能够对生物医学成像模式(从微观到宏观)进行定量分析和可视化的应用程序，NIH和世界各地的研究人员都在使用该应用程序。在NIH，MIPAV已被用于分析CT数据集的解剖结构，协助与射频消融(RFA)相关的图像数据集的预处理分析(配准和分割)，分析NIMH的MRI数据集，并已被NCI用于2D和3D显微样本的分析。我们还继续通过眼部疾病的研究来支持NEI，并支持对骨关节炎倡议的图像数据进行分析，这是一项由美国国立卫生研究院赞助的全国性研究研究，将帮助我们更好地了解如何预防和治疗膝骨性关节炎。此外，我们管理和开发国家自闭症研究数据库(NDAR)项目的主要组成部分，该项目是由美国国立卫生研究院创建的协作生物医学信息学系统，为支持和加速自闭症研究提供国家资源。NDAR是一个信息系统的集合，支持自闭症研究的所有活动，包括基因组、成像、实验室、临床和行为数据源。它将为数据仓库、数据输入系统以及共同措施及其文件的集中来源提供核心技术。它将支持大型、多地点项目以及试验性研究和基础科学调查。

This project uses imaging science techniques to analyze many types of biological, clinical and biomedical images. Current research focuses on two general areas: (1) the structural biology of macromolecules using image processing of electron micrographs and NMR spectroscopy and (2) the development of sophisticated biomedical and laboratory imaging software. (1) The Imaging Sciences Laboratory has a major collaborative research effort with the Institutes involving the use of image processing techniques and advanced computational techniques in structural biology to analyze electron micrographs and NMR spectra with the goal of determining macromolecular structures. Recent efforts have concentrated on the 3D reconstruction, analysis and interpretation of the structures of icosahedral virus capsids. Ongoing research involves analyses of structures related to herpesvirus and papillomairus as well as other icosahedral virus capsids. Papillomaviruses (e.g. HPV-16) encode two capsid proteins, L1 and L2. The major capsid protein, L1, can assemble spontaneously into a 72-pentamer icosahedral structure that closely resembles native virions. Although the minor capsid protein L2 is not required for capsid formation, it is thought to participate in encapsidation of the viral genome, and plays a number of essential roles in the viral infectious entry pathway. The abundance of L2 and its arrangement within the virion remain unclear. Cryo-electron microscopy and difference 3D reconstruction analysis of purified capsids revealed an icosahedrally-ordered L2-specific density beneath the axial lumen of each L1 capsomer. Icosahedrally-ordered filaments of L2-specific density also extended under the floor of the L1 capsid shell, raising the possibility of homotypic L2 interactions within assembled virions. We have used time-lapse cryo-electron microscopy and image analysis to study the maturation of HPV-16 capsids assembled in 293T cells. The major capsid protein, L1, initially forms a loosely connected procapsid which, under in vitro conditions, condenses over several hours into the more familiar 60 nm-diameter papillomavirus capsid. In this process, the procapsid shrinks by ~ 5% in diameter; its pentameric capsomers change in structure, most markedly in their axial region; and the interaction surfaces between adjacent capsomers are consolidated. These structural changes are accompanied by the formation of disulfide crosslinks that enhance the stability of the mature capsid. The C175S mutant, which does not crosslink, shows similar maturation-related structural changes but capsids are significantly larger, under otherwise similar conditions. We conclude that the observed structural size changes facilitates maturation, but crosslink formation is required to lock the capsid into the mature state. We have also been developing computational tools for the study of the structure and dynamics of biological macromolecules using NMR data. We are actively supporting the intra- and extramural communities which use the Xplor-NIH biomolecular structure determination software package. Development of Xplor-NIH has continued in the following areas: (a) further progress in the use of the Python and TCL scripting interfaces and the addition of extensive documentation; (b) the first realistic picture of the dynamical nature of DNA in solution has been obtained by combining information from NMR and Solution X-ray scattering techniques; (c) it is now possible to refine molecular structures directly against solution X-ray scattering and small-angle neutron scattering data. (2) The Imaging Sciences Laboratory has a commitment to providing computational and engineering expertise to a variety of clinical and biomedical activities at NIH. Specifically, PET, ultrasound, CT, MRI, EPR, microscopy, imaging in cancer research, and imaging related to neural dysfunction have been supported in a number of ways. To support scientific in the NIH intramural program, CIT has developed and continues to enhance a sophisticated platform-independent, n-dimensional, extensible image processing and visualization application. The MIPAV (Medical Image Processing Analysis and Visualization) is an application that enables quantitative analysis and visualization of biomedical imaging modalities (from micro to macro) and is used by researchers at NIH and around the world. At NIH, MIPAV has been used to analyze anatomical structures in CT datasets, assist in pretreatment analysis (registration and segmentation) of image datasets associated with radio frequency ablation (RFA) procedures, analysis of MRI datasets for NIMH, and has been used by NCI for the analysis of 2D and 3D microscopic samples. We also continue to support the NEI with research of diseases of the eye and support analysis of image data from the Osteoarthritis Initiative, a nationwide research study sponsored by the National Institutes of Health, that will help us better understand how to prevent and treat knee osteoarthritis. In addition, we manage and develop major components of the National Database for Autism Research (NDAR) project which is a collaborative biomedical informatics system created by the National Institutes of Health to provide a national resource to support and accelerate research in autism. NDAR is a collection of information systems supporting the full range of autism research activities, including genomic, imaging, laboratory, clinical, and behavioral data sources. It will provide the core technology for a data warehouse, a data-entry system, and a centralized source for common measures and their documentation. It will support large-scale, multi-site projects as well as pilot studies and basic science investigations.