Mikulis David J, Roberts Timothy P L
Department of Medical Imaging, The University Health Network, The Toronto Western Hospital, Toronto, ON, Canada.
J Magn Reson Imaging. 2007 Oct;26(4):838-47. doi: 10.1002/jmri.21041.
Clinical MRI depends on a symbiosis between MR physics and clinical requirements. The imaging solutions are based on a balance between the "palette" of available image contrasts derived from nuclear spin physics and tissue biophysics, and clinical determinants such as the anticipated pathology and efficient use of imaging time. Imaging is therefore optimized to maximize diagnostic sensitivity and specificity through the development of protocols organized along the lines of major disease categories. In the other part of this two-part review, the primary determinants of image contrast, including T1, T2, and T2*, were highlighted. The development of pulse sequences designed to optimize each of these image contrasts was discussed and the impact of technological innovation (parallel imaging and high-field systems) on the manner in which these sequences could be modified to improve clinical efficacy was further emphasized. The scope of that discussion was broadened to include the application of: 1) water diffusion imaging used primarily for detection of pathologies that restrict the free movement of water in the tissues and for defining fiber tracts in the brain; 2) the intravenous administration of exogenous contrast agents (gadolinium-diethylene triamine pentaacetic acid [GdDTPA]) for assessment of blood-brain-barrier (BBB) defects and brain blood flow; and 3) MR spectroscopy (MRS) for assessment of brain metabolites. The goal of this part is to discuss how these acquisitions are combined into specific protocols that can effectively detect and characterize, or in keeping with our artistic analogy, "paint" each of the major diseases affecting the central nervous system (CNS). This work concludes with a discussion of image artifacts and pitfalls in image interpretation, which, in spite our best efforts to minimize or eliminate them, continue to occur. Much of the ensuing discussion is based on our own institutional experience. Protocols, therefore, do not necessarily match those from other institutions due to variability in clinical emphasis, MR instruments, and available software. An attempt was made to focus on basic clinical sequences that are available on most modern MR systems, with protocols employing generally accepted clinical imaging philosophies.
临床磁共振成像（MRI）依赖于磁共振物理与临床需求之间的共生关系。成像解决方案基于源自核自旋物理和组织生物物理的可用图像对比度“调色板”与临床决定因素（如预期的病理情况和成像时间的有效利用）之间的平衡。因此，通过制定按照主要疾病类别组织的方案，成像得以优化，以最大限度地提高诊断敏感性和特异性。在这篇分为两部分的综述的另一部分中，重点介绍了图像对比度的主要决定因素，包括T1、T2和T2*。讨论了旨在优化每种这些图像对比度的脉冲序列的发展，并进一步强调了技术创新（并行成像和高场系统）对修改这些序列以提高临床疗效的方式的影响。该讨论的范围扩大到包括以下应用：1）水扩散成像，主要用于检测限制组织中水分子自由移动的病变以及定义脑内纤维束；2）静脉注射外源性造影剂（钆 - 二乙烯三胺五乙酸[GdDTPA]）以评估血脑屏障（BBB）缺陷和脑血流量；3）磁共振波谱（MRS）用于评估脑代谢物。本部分的目标是讨论如何将这些采集方法组合成特定的方案，这些方案能够有效地检测和表征，或者按照我们的艺术类比，“描绘”影响中枢神经系统（CNS）的每种主要疾病。本文最后讨论了图像伪影和图像解读中的陷阱，尽管我们尽最大努力将它们最小化或消除，但它们仍然会出现。随后的许多讨论基于我们自己机构的经验。因此，由于临床重点、磁共振仪器和可用软件的差异，方案不一定与其他机构的方案相匹配。我们试图专注于大多数现代磁共振系统上可用的基本临床序列，其方案采用普遍接受的临床成像理念。
