Clark D P, Badea C T
Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Box 3302, Durham, NC 27710, USA.
Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Box 3302, Durham, NC 27710, USA.
Phys Med. 2014 Sep;30(6):619-34. doi: 10.1016/j.ejmp.2014.05.011. Epub 2014 Jun 26.
Micron-scale computed tomography (micro-CT) is an essential tool for phenotyping and for elucidating diseases and their therapies. This work is focused on preclinical micro-CT imaging, reviewing relevant principles, technologies, and applications. Commonly, micro-CT provides high-resolution anatomic information, either on its own or in conjunction with lower-resolution functional imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). More recently, however, advanced applications of micro-CT produce functional information by translating clinical applications to model systems (e.g., measuring cardiac functional metrics) and by pioneering new ones (e.g. measuring tumor vascular permeability with nanoparticle contrast agents). The primary limitations of micro-CT imaging are the associated radiation dose and relatively poor soft tissue contrast. We review several image reconstruction strategies based on iterative, statistical, and gradient sparsity regularization, demonstrating that high image quality is achievable with low radiation dose given ever more powerful computational resources. We also review two contrast mechanisms under intense development. The first is spectral contrast for quantitative material discrimination in combination with passive or actively targeted nanoparticle contrast agents. The second is phase contrast which measures refraction in biological tissues for improved contrast and potentially reduced radiation dose relative to standard absorption imaging. These technological advancements promise to develop micro-CT into a commonplace, functional and even molecular imaging modality.
微米级计算机断层扫描（显微CT）是用于表型分析以及阐明疾病及其治疗方法的重要工具。这项工作聚焦于临床前显微CT成像，回顾相关原理、技术及应用。通常，显微CT自身或与正电子发射断层扫描（PET）和单光子发射计算机断层扫描（SPECT）等低分辨率功能成像模态联合使用时，可提供高分辨率解剖信息。然而，最近显微CT的先进应用通过将临床应用转化到模型系统（如测量心脏功能指标）以及开拓新应用（如用纳米颗粒造影剂测量肿瘤血管通透性）来生成功能信息。显微CT成像的主要局限在于相关辐射剂量以及相对较差的软组织对比度。我们回顾了基于迭代、统计和梯度稀疏正则化的几种图像重建策略，表明随着计算资源日益强大，低辐射剂量下也可实现高图像质量。我们还回顾了两种正在大力发展的造影机制。第一种是结合被动或主动靶向纳米颗粒造影剂进行定量物质鉴别的光谱造影。第二种是相衬造影，它测量生物组织中的折射以改善对比度，并相对于标准吸收成像可能降低辐射剂量。这些技术进步有望将显微CT发展成为一种常见的、功能性甚至分子成像模态。
