Delgorio Peyton L, Hiscox Lucy V, Daugherty Ana M, Sanjana Faria, Pohlig Ryan T, Ellison James M, Martens Christopher R, Schwarb Hillary, McGarry Matthew D J, Johnson Curtis L
Department of Biomedical Engineering, University of Delaware, Newark, DE 19716, USA.
Department of Psychology, Institute of Gerontology, Wayne State University, Detroit, MI 48202, USA.
Cereb Cortex. 2021 May 10;31(6):2799-2811. doi: 10.1093/cercor/bhaa388.
Age-related memory impairments have been linked to differences in structural brain parameters, including the integrity of the hippocampus (HC) and its distinct hippocampal subfields (HCsf). Imaging methods sensitive to the underlying tissue microstructure are valuable in characterizing age-related HCsf structural changes that may relate to cognitive function. Magnetic resonance elastography (MRE) is a noninvasive MRI technique that can quantify tissue viscoelasticity and may provide additional information about aging effects on HCsf health. Here, we report a high-resolution MRE protocol to quantify HCsf viscoelasticity through shear stiffness, μ, and damping ratio, ξ, which reflect the integrity of tissue composition and organization. HCsf exhibit distinct mechanical properties-the subiculum had the lowest μ and both subiculum and entorhinal cortex had the lowest ξ. Both measures correlated with age: HCsf μ was lower with age (P < 0.001) whereas ξ was higher (P = 0.002). The magnitude of age-related differences in ξ varied across HCsf (P = 0.011), suggesting differential patterns of brain aging. This study demonstrates the feasibility of using MRE to assess HCsf microstructural integrity and suggests incorporation of these metrics to evaluate HC health in neurocognitive disorders.
与年龄相关的记忆障碍与大脑结构参数的差异有关，包括海马体（HC）及其不同的海马亚区（HCsf）的完整性。对潜在组织微观结构敏感的成像方法对于表征可能与认知功能相关的年龄相关的HCsf结构变化很有价值。磁共振弹性成像（MRE）是一种非侵入性MRI技术，可以量化组织粘弹性，并可能提供有关衰老对HCsf健康影响的额外信息。在这里，我们报告了一种高分辨率MRE方案，通过剪切刚度μ和阻尼比ξ来量化HCsf的粘弹性，这两个参数反映了组织组成和组织的完整性。HCsf表现出不同的力学特性——下托的μ最低，下托和内嗅皮层的ξ最低。这两个指标都与年龄相关：HCsf的μ随年龄增长而降低（P < 0.001），而ξ则升高（P = 0.002）。与年龄相关的ξ差异幅度在不同的HCsf中有所不同（P = 0.011），表明大脑衰老的模式不同。这项研究证明了使用MRE评估HCsf微观结构完整性的可行性，并建议纳入这些指标以评估神经认知障碍中的HC健康状况。
