神经黑色素敏感MRI(NM-MRI)提供了一种非侵入性的神经黑色素(NM)含量测量,多巴胺代谢的产物,随着年龄的增长在黑质(SN)的多巴胺神经元中积累。NM-MRI已被验证为测量多巴胺神经元的损失,在神经退行性疾病中的应用,和多巴胺功能,在精神疾病中的应用。此外,一种体素分析方法已经被验证可以解决子结构,例如腹侧被盖区(VTA),在中脑多巴胺能核内被认为具有不同的解剖靶标和功能作用。因此,NM-MRI是一种有前途的工具,可以进行多种研究和临床应用,以在神经精神疾病中进行体内无创地询问多巴胺系统。尽管Langley等人进行了重测可靠性研究。使用最近报道的高可靠性的标准NM-MRI协议,尚未对各种采集参数和预处理方法的性能进行系统和全面的研究。特别是,以前的大多数研究使用相对较厚的MRI切片(~3毫米),与典型的平面内分辨率(~0.5毫米)和SN的高度(~15毫米)相比,为了克服特定吸收率和信噪比等技术限制,以部分体积效应为代价。这里,我们评估了各种采集和预处理参数对NM-MRI信号强度和重测可靠性的影响,以确定感兴趣区域(包括整个SN-VTA复合体和图谱定义的多巴胺能细胞核)和体素测量的优化方案.即,我们确定了优化NM-MRI信号的强度和可靠性的参数组合,包括采集时间,切片厚度,空间归一化软件,和空间平滑度。使用新开发的,详细的采集协议,平均间隔13天的两次扫描,我们获得了具有良好可靠性和高对比度的类内相关值,这可以通过一组不同的参数来实现,具体取决于感兴趣的度量和实验约束,例如采集时间。基于此,我们提供了详细的指南,涵盖了通过分析进行的采集,并为进行高质量和可重复性的NM-MRI实验提供了建议.这项工作为NM-MRI的优化和标准化提供了基础。一种有前途的MRI方法,在临床和基础神经科学中的应用越来越多。
Neuromelanin-sensitive MRI (NM-MRI) provides a noninvasive measure of the content of neuromelanin (NM), a product of dopamine metabolism that accumulates with age in dopamine neurons of the substantia nigra (SN). NM-MRI has been validated as a measure of both dopamine neuron loss, with applications in neurodegenerative disease, and dopamine function, with applications in psychiatric disease. Furthermore, a voxelwise-analysis approach has been validated to resolve substructures, such as the ventral tegmental area (VTA), within midbrain dopaminergic nuclei thought to have distinct anatomical targets and functional roles. NM-MRI is thus a promising tool that could have diverse research and clinical applications to noninvasively interrogate in vivo the dopamine system in neuropsychiatric illness. Although a test-retest reliability study by Langley et al. using the standard NM-MRI protocol recently reported high reliability, a systematic and comprehensive investigation of the performance of the method for various acquisition parameters and preprocessing methods has not been conducted. In particular, most previous studies used relatively thick MRI slices (~3 mm), compared to the typical in-plane resolution (~0.5 mm) and to the height of the SN (~15 mm), to overcome technical limitations such as specific absorption rate and signal-to-noise ratio, at the cost of partial-volume effects. Here, we evaluated the effect of various acquisition and preprocessing parameters on the strength and test-retest reliability of the NM-MRI signal to determine optimized protocols for both region-of-interest (including whole SN-VTA complex and atlas-defined dopaminergic nuclei) and voxelwise measures. Namely, we determined a combination of parameters that optimizes the strength and reliability of the NM-MRI signal, including acquisition time, slice-thickness, spatial-normalization software, and degree of spatial smoothing. Using a newly developed, detailed acquisition protocol, across two scans separated by 13 days on average, we obtained intra-class correlation values indicating excellent reliability and high contrast, which could be achieved with a different set of parameters depending on the measures of interest and experimental constraints such as acquisition time. Based on this, we provide detailed guidelines covering acquisition through analysis and recommendations for performing NM-MRI experiments with high quality and reproducibility. This work provides a foundation for the optimization and standardization of NM-MRI, a promising MRI approach with growing applications throughout clinical and basic neuroscience.