Structural and Functional Magnetic Resonance Imaging of the Cerebellum: Considerations for Assessing Cerebellar Ataxias
Structural and Functional Magnetic Resonance Imaging of the Cerebellum: Considerations for Assessing Cerebellar Ataxias
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DOI：
10.1007/s12311-015-0738-9
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发表时间：
2016-02-01
期刊：
影响因子：
3.5
通讯作者：
Timmann, Dagmar
中科院分区：
文献类型：
--
作者：
Deistung, Andreas;Stefanescu, Maria R.;Timmann, Dagmar
大脑的磁共振成像（MRI）对于诊断和理解退行性共济失调具有很高的意义。在这里，我们提出了最先进的MRI方法来表征小脑的结构变化，并介绍了初步的实验，以显示小脑核异常。临床上，T-1加权MR图像用于评估小脑皮质、脑干和脊髓的萎缩，而T-2加权和PD加权图像通常用于描述可能与某些类型共济失调相关的潜在白色病变。最近，注意力也集中在表征小脑核，这是可辨别的空间高分辨铁敏感的MR图像，由于其相对较高的铁含量，包括T-2* 加权图像，磁敏感性加权图像（SWI），有效横向弛豫率（R-2*）地图，和定量磁化率地图（QSM）。在这些铁敏感技术中，QSM揭示了小脑核与其周围环境之间的最佳对比。特别是，即使在临床上广泛使用的3 T场强下，齿状核的回旋也被显著描绘。磁化率和局部铁含量之间的线性关系允许非侵入性地测定小脑核中的铁沉积。超高场MRI（B-0 >= 7 T）信噪比的提高和空间归一化方法的进步使功能性MRI（fMRI）能够在小脑皮质和小脑核水平上进行。来自最初的fMRI研究的数据以三种常见形式的遗传性共济失调（弗里德赖希共济失调、脊髓小脑共济失调3型和脊髓小脑共济失调6型）呈现。功能性磁共振成像信号的特征变化进行了讨论，根据组织病理学数据和目前的知识，在小脑的功能性磁共振成像信号的基本生理。
Magnetic resonance imaging (MRI) of the brain is of high interest for diagnosing and understanding degenerative ataxias. Here, we present state-of-the-art MRI methods to characterize structural alterations of the cerebellum and introduce initial experiments to show abnormalities in the cerebellar nuclei. Clinically, T-1-weighted MR images are used to assess atrophy of the cerebellar cortex, the brainstem, and the spinal cord, whereas T-2-weighted and PD-weighted images are typically employed to depict potential white matter lesions that may be associated with certain types of ataxias. More recently, attention has also focused on the characterization of the cerebellar nuclei, which are discernible on spatially highly resolved iron-sensitive MR images due to their relatively high iron content, including T-2*-weighted images, susceptibility-weighted images (SWI), effective transverse relaxation rate (R-2*) maps, and quantitative susceptibility maps (QSM). Among these iron-sensitive techniques, QSM reveals the best contrast between cerebellar nuclei and their surroundings. In particular, the gyrification of the dentate nuclei is prominently depicted, even at the clinically widely available field strength of 3 T. The linear relationship between magnetic susceptibility and local iron content allows for determination of iron deposition in cerebellar nuclei non-invasively. The increased signal-to-noise ratio of ultrahighfield MRI (B-0 >= 7 T) and advances in spatial normalization methods enable functional MRI (fMRI) at the level of the cerebellar cortex and cerebellar nuclei. Data from initial fMRI studies are presented in three common forms of hereditary ataxias (Friedreich's ataxia, spinocerebellar ataxia type 3, and spinocerebellar ataxia type 6). Characteristic changes in the fMRI signal are discussed in the light of histopathological data and current knowledge of the underlying physiology of the fMRI signal in the cerebellum.