Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
Faculty of Health Data Science, Juntendo University, Chiba, Japan.
J Magn Reson Imaging. 2024 May;59(5):1476-1493. doi: 10.1002/jmri.28977. Epub 2023 Sep 1.
The comprehension of the glymphatic system, a postulated mechanism responsible for the removal of interstitial solutes within the central nervous system (CNS), has witnessed substantial progress recently. While direct measurement techniques involving fluorescence and contrast agent tracers have demonstrated success in animal studies, their application in humans is invasive and presents challenges. Hence, exploring alternative noninvasive approaches that enable glymphatic research in humans is imperative. This review primarily focuses on several noninvasive magnetic resonance imaging (MRI) techniques, encompassing perivascular space (PVS) imaging, diffusion tensor image analysis along the PVS, arterial spin labeling, chemical exchange saturation transfer, and intravoxel incoherent motion. These methodologies provide valuable insights into the dynamics of interstitial fluid, water permeability across the blood-brain barrier, and cerebrospinal fluid flow within the cerebral parenchyma. Furthermore, the review elucidates the underlying concept and clinical applications of these noninvasive MRI techniques, highlighting their strengths and limitations. It addresses concerns about the relationship between glymphatic system activity and pathological alterations, emphasizing the necessity for further studies to establish correlations between noninvasive MRI measurements and pathological findings. Additionally, the challenges associated with conducting multisite studies, such as variability in MRI systems and acquisition parameters, are addressed, with a suggestion for the use of harmonization methods, such as the combined association test (COMBAT), to enhance standardization and statistical power. Current research gaps and future directions in noninvasive MRI techniques for assessing the glymphatic system are discussed, emphasizing the need for larger sample sizes, harmonization studies, and combined approaches. In conclusion, this review provides invaluable insights into the application of noninvasive MRI methods for monitoring glymphatic system activity in the CNS. It highlights their potential in advancing our understanding of the glymphatic system, facilitating clinical applications, and paving the way for future research endeavors in this field. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 5.
近年来，人们对被假定为负责中枢神经系统（CNS）内间质溶质清除的液-脑淋巴系统（glymphatic system）的理解取得了重大进展。虽然涉及荧光和对比剂示踪剂的直接测量技术在动物研究中取得了成功，但它们在人体中的应用具有侵入性，且存在挑战。因此，探索能够在人体中进行液-脑淋巴研究的替代非侵入性方法势在必行。本综述主要关注几种非侵入性磁共振成像（MRI）技术，包括血管周围空间（PVS）成像、沿 PVS 的扩散张量图像分析、动脉自旋标记、化学交换饱和传递和体素内不相干运动。这些方法为间质液动力学、血脑屏障跨膜水通透性以及脑实质内脑脊液流动提供了有价值的见解。此外，该综述阐明了这些非侵入性 MRI 技术的基本概念和临床应用，强调了它们的优势和局限性。它还讨论了液-脑淋巴系统活性与病理改变之间的关系问题，强调需要进一步的研究来建立非侵入性 MRI 测量值与病理发现之间的相关性。此外，还讨论了在多中心研究中存在的与 MRI 系统和采集参数的变异性相关的挑战，并建议使用协调方法（如联合关联检验（COMBAT））来增强标准化和统计功效。本综述还讨论了评估液-脑淋巴系统的非侵入性 MRI 技术的当前研究空白和未来方向，强调需要更大的样本量、协调研究和联合方法。总之，本综述为使用非侵入性 MRI 方法监测 CNS 中液-脑淋巴系统活性提供了宝贵的见解。它强调了这些方法在推进我们对液-脑淋巴系统的理解、促进临床应用以及为该领域的未来研究努力铺平道路方面的潜力。证据水平：3 技术功效：5 级。
