McGarry Matthew, Sowinski Damian, Tan Likun, Weaver John, Zwanenburg Jacobus J M, Paulsen Keith
Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
Interface Focus. 2025 Apr 4;15(1):20240044. doi: 10.1098/rsfs.2024.0044.
Fluid movement in the interstitial space of the brain affects the clearance of waste products, which is an important factor in the pathophysiology of dementia. Estimating interstitial fluid (ISF) flow is critical to understanding these processes; yet, it has proven difficult to measure non-invasively. The pulsatile component of ISF flow may be particularly important for clearance, e.g. by facilitating fluid mixing. Directly measuring ISF flows is challenging due to the slow velocities and small volume fractions involved; however, pulsatile flows present a unique opportunity as their driving forces can be estimated from observations of pulsatile tissue motion. In this work, we present pressure gradient magnetic resonance imaging (pgMRI), which assimilates retrospectively gated pulsatile tissue deformations measured with a displacement encoding with stimulated echoes MRI sequence into a patient-specific poroelastic computational model by estimating the distribution of fluid sources. The new method is demonstrated to recover a spherical fluid source accurately from synthetic data with simulated noise of up to 20%, and to produce not previously reported brain fluid source images along with companion images of the three-dimensional stresses and pressure gradients which drive ISF movement. Repeated exams of four healthy volunteers demonstrated variability below 10% for pgMRI parameters in most cases.
脑间质空间中的液体流动会影响废物清除，而这是痴呆症病理生理学中的一个重要因素。估计间质液（ISF）流动对于理解这些过程至关重要；然而，事实证明非侵入性测量很困难。ISF流动的脉动成分对于清除可能特别重要，例如通过促进液体混合。由于涉及的速度慢和体积分数小，直接测量ISF流动具有挑战性；然而，脉动流动提供了一个独特的机会，因为可以根据脉动组织运动的观察结果来估计其驱动力。在这项工作中，我们提出了压力梯度磁共振成像（pgMRI），它通过估计流体源的分布，将用刺激回波MRI序列的位移编码测量的回顾性门控脉动组织变形纳入特定患者的多孔弹性计算模型中。新方法被证明能够从高达20%模拟噪声的合成数据中准确恢复球形流体源，并生成以前未报道过的脑流体源图像以及驱动ISF运动的三维应力和压力梯度的伴随图像。对四名健康志愿者的重复检查表明，在大多数情况下，pgMRI参数的变异性低于10%。
