Structural brain white matter (WM) changes such as axonal caliber, density, myelination, and orientation, along with WM-dependent structural connectivity, may be impacted early in Parkinson disease (PD). Diffusion magnetic resonance imaging (dMRI) has been used extensively to understand such pathological WM changes, and the focus of this systematic review is to understand both the methods utilized and their corresponding results in the context of early-stage PD. Diffusion tensor imaging (DTI) is the most commonly utilized method to probe WM pathological changes. Previous studies have suggested that DTI metrics are sensitive in capturing early disease-associated WM changes in preclinical symptomatic regions such as olfactory regions and the substantia nigra, which is considered to be a hallmark of PD pathology and progression. Postprocessing analytic approaches include region of interest-based analysis, voxel-based analysis, skeletonized approaches, and connectome analysis, each with unique advantages and challenges. While DTI has been used extensively to study WM disorganization in early-stage PD, it has several limitations, including an inability to resolve multiple fiber orientations within each voxel and sensitivity to partial volume effects. Given the subtle changes associated with early-stage PD, these limitations result in inaccuracies that severely impact the reliability of DTI-based metrics as potential biomarkers. To overcome these limitations, advanced dMRI acquisition and analysis methods have been employed, including diffusion kurtosis imaging and q-space diffeomorphic reconstruction. The combination of improved acquisition and analysis in DTI may yield novel and accurate information related to WM-associated changes in early-stage PD. In the current article, we present a systematic and critical review of dMRI studies in early-stage PD, with a focus on recent advances in DTI methodology. Yielding novel metrics, these advanced methods have been shown to detect diffuse WM changes in early-stage PD. These findings support the notion of early axonal damage in PD and suggest that WM pathology may go unrecognized until symptoms appear. Finally, the advantages and disadvantages of different dMRI techniques, analysis methods, and software employed are discussed in the context of PD-related pathology.

中文翻译：

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使用扩散 MRI 评估早期帕金森病的白质病理学：系统评价。


结构性脑白质 (WM) 变化，例如轴突直径、密度、髓鞘形成和方向，以及 WM 依赖性结构连接，可能会在帕金森病 (PD) 早期受到影响。扩散磁共振成像 (dMRI) 已被广泛用于了解此类病理性 WM 变化，本系统综述的重点是了解早期 PD 背景下所使用的方法及其相应结果。弥散张量成像（DTI）是探测 WM 病理变化最常用的方法。先前的研究表明，DTI 指标对于捕获临床前症状区域（例如嗅觉区域和黑质）中与早期疾病相关的 WM 变化非常敏感，这被认为是 PD 病理学和进展的标志。后处理分析方法包括基于兴趣区域的分析、基于体素的分析、骨架化方法和连接组分析，每种方法都有独特的优势和挑战。虽然 DTI 已广泛用于研究早期 PD 中的 WM 紊乱，但它有一些局限性，包括无法解析每个体素内的多个纤维方向以及对部分体积效应的敏感性。鉴于与早期 PD 相关的微妙变化，这些限制会导致不准确，严重影响基于 DTI 的指标作为潜在生物标志物的可靠性。为了克服这些限制，采用了先进的 dMRI 采集和分析方法，包括扩散峰度成像和 q 空间微分同胚重建。 DTI 中改进的采集和分析相结合可能会产生与早期 PD 中与 WM 相关的变化相关的新颖且准确的信息。 在本文中，我们对早期 PD 的 dMRI 研究进行了系统和批判性的回顾，重点关注 DTI 方法的最新进展。这些先进的方法产生了新颖的指标，已被证明可以检测早期 PD 的弥漫性 WM 变化。这些发现支持 PD 早期轴突损伤的观点，并表明 WM 病理可能在症状出现之前未被识别。最后，在 PD 相关病理学的背景下讨论了不同 dMRI 技术、分析方法和所使用软件的优缺点。