IEEE Trans Med Imaging. 2019 Sep;38(9):2028-2036. doi: 10.1109/TMI.2019.2904762. Epub 2019 Mar 15.
The brain is cleaned from waste by glymphatic clearance serving a similar purpose as the lymphatic system in the rest of the body. Impairment of the glymphatic brain clearance precedes protein accumulation and reduced cognitive function in Alzheimer's disease (AD). Cardiovascular pulsations are a primary driving force of the glymphatic brain clearance. We developed a method to quantify cardiovascular pulse propagation in the human brain with magnetic resonance encephalography (MREG). We extended a standard optical flow estimation method to three spatial dimensions, with a multi-resolution processing scheme. We added application-specific criteria for discarding inaccurate results. With the proposed method, it is now possible to estimate the propagation of cardiovascular pulse wavefronts from the whole brain MREG data sampled at 10 Hz. The results show that on average the cardiovascular pulse propagates from major arteries via cerebral spinal fluid spaces into all tissue compartments in the brain. We present an example, that cardiovascular pulsations are significantly altered in AD: coefficient of variation and sample entropy of the pulse propagation speed in the lateral ventricles change in AD. These changes are in line with the theory of glymphatic clearance impairment in AD. The proposed non-invasive method can assess a performance indicator related to the glymphatic clearance in the human brain.
大脑通过支持类似身体其他部位淋巴系统功能的“类淋巴系统”清除废物。在阿尔茨海默病（AD）中，类淋巴系统脑清除功能障碍先于蛋白质积累和认知功能下降。心血管搏动是类淋巴系统脑清除的主要驱动力。我们开发了一种利用磁共振脑成像（MREG）定量人脑心血管搏动传播的方法。我们将标准光流估计方法扩展到三维，并采用多分辨率处理方案。我们添加了特定于应用的标准，以丢弃不准确的结果。通过提出的方法，现在可以从以 10 Hz 采样的全脑 MREG 数据中估计心血管脉冲波前的传播。结果表明，心血管脉冲平均从主要动脉通过脑脊液空间传播到大脑的所有组织隔室。我们提出了一个例子，即 AD 中心血管搏动明显改变：AD 患者侧脑室脉搏传播速度的变异系数和样本熵发生变化。这些变化与 AD 中类淋巴系统清除功能障碍的理论一致。该非侵入性方法可以评估与人类大脑中类淋巴系统清除相关的性能指标。
