Effects of variability in manually contoured spinal cord masks on fMRI co-registration and interpretation.
Effects of variability in manually contoured spinal cord masks on fMRI co-registration and interpretation.
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DOI：
10.3389/fneur.2022.907581
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发表时间：
2022
影响因子：
3.4
通讯作者：
中科院分区：
文献类型：
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人脊髓(SC)的功能磁共振成像(FMRI)是一种独特的非侵入性方法，用于表征神经血管对刺激的反应。SC fMRI数据的分组分析涉及将受试者级别的数据共同配准到标准空间，这需要手动掩蔽脊髓，并可能导致组级别SC fMRI结果的偏差。为了测试这一点，我们检查了从21名健康参与者的fMRI数据中提取的SC面具的可变性，该数据来自一项已完成的研究，该研究绘制了C7皮肤刀对感觉刺激的反应。8名具有不同程度神经成像经验的评分者在时间平均功能图像上绘制了面具，原始研究的评分者作为参考。使用Dice相似性系数来衡量评分者和参考模板之间的空间一致性，并使用方差分析来检验评分者和数据集之间的影响。每个评分者的面具被用来将功能数据登记到PAM50模板。用记录的功能数据的灰质-白质信号对比度来评估评分者的空间归一化精度。对于每个评分者的共同登记数据，进行了在左侧和右侧感觉刺激期间的受试者和组水平的激活分析。与参考SC掩码的一致性与评分者(F(7,140)=32.12，P<；2×10−16，η2=0.2 9)和数据集(F(20,140)=2 0.5 8，P<；2×10−16，η2=0.5 3)相关。数据集差异可能反映图像质量指标：脊髓体素信号强度与周围脑脊液信号强度的比率与数字减影扫描结果相关(p<；0.001)。正如预测的那样，人工绘制掩模的可变性影响了空间归一化，注册数据中的GM：WM对比度显示了评分者和数据集的显著影响(评分者：F(8,160)=23.57，P<；2×10−16，η2=0.24；数据集：F(20,160)=22.00，P<；2×10−16，η2=0.56)。登记差异被传播到受试者水平的激活图中，这表明依赖于评分者的激活图与参考一致。尽管不同评分者的群体水平激活图不同，但没有发现系统性偏见。脊髓fMRI数据人工轮廓一致性的提高改善了激活映射中的共同配准和评价者之间的一致性，然而我们的结果表明，图像采集和后处理的改进也是解决问题的关键。
Functional magnetic resonance imaging (fMRI) of the human spinal cord (SC) is a unique non-invasive method for characterizing neurovascular responses to stimuli. Group-analysis of SC fMRI data involves co-registration of subject-level data to standard space, which requires manual masking of the cord and may result in bias of group-level SC fMRI results. To test this, we examined variability in SC masks drawn in fMRI data from 21 healthy participants from a completed study mapping responses to sensory stimuli of the C7 dermatome. Masks were drawn on temporal mean functional image by eight raters with varying levels of neuroimaging experience, and the rater from the original study acted as a reference. Spatial agreement between rater and reference masks was measured using the Dice Similarity Coefficient, and the influence of rater and dataset was examined using ANOVA. Each rater's masks were used to register functional data to the PAM50 template. Gray matter-white matter signal contrast of registered functional data was used to evaluate the spatial normalization accuracy across raters. Subject- and group-level analyses of activation during left- and right-sided sensory stimuli were performed for each rater's co-registered data. Agreement with the reference SC mask was associated with both rater (F(7, 140) = 32.12, P < 2 × 10−16, η2 = 0.29) and dataset (F(20, 140) = 20.58, P < 2 × 10−16, η2 = 0.53). Dataset variations may reflect image quality metrics: the ratio between the signal intensity of spinal cord voxels and surrounding cerebrospinal fluid was correlated with DSC results (p < 0.001). As predicted, variability in the manually-drawn masks influenced spatial normalization, and GM:WM contrast in the registered data showed significant effects of rater and dataset (rater: F(8, 160) = 23.57, P < 2 × 10−16, η2 = 0.24; dataset: F(20, 160) = 22.00, P < 2 × 10−16, η2 = 0.56). Registration differences propagated into subject-level activation maps which showed rater-dependent agreement with the reference. Although group-level activation maps differed between raters, no systematic bias was identified. Increasing consistency in manual contouring of spinal cord fMRI data improved co-registration and inter-rater agreement in activation mapping, however our results suggest that improvements in image acquisition and post-processing are also critical to address.
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