Centre for the Developing Brain, School of Biomedical Engineering & Imaging Sciences, King''s College London, UK.
Centre for the Developing Brain, School of Biomedical Engineering & Imaging Sciences, King''s College London, UK; Sackler Institute for Translational Neurodevelopment, Department of Forensic and Neurodelopmental Science, Institute of Psychiatry, Psychology & Neuroscience, King''s College London, UK.
Neuroimage Clin. 2019;23:101820. doi: 10.1016/j.nicl.2019.101820. Epub 2019 Apr 10.
Diffusion MRI (dMRI) studies using the tensor model have identified abnormal white matter development associated with perinatal risk factors in preterm infants studied at term equivalent age (TEA). However, this model is an oversimplification of the underlying neuroanatomy. Fixel-based analysis (FBA) is a novel quantitative framework, which identifies microstructural and macrostructural changes in individual fibre populations within voxels containing crossing fibres. The aim of this study was to apply FBA to investigate the relationship between fixel-based measures of apparent fibre density (FD), fibre bundle cross-section (FC), and fibre density and cross-section (FDC) and perinatal risk factors in preterm infants at TEA. We studied 50 infants (28 male) born at 24.0-32.9 (median 30.4) weeks gestational age (GA) and imaged at 38.6-47.1 (median 42.1) weeks postmenstrual age (PMA). dMRI data were acquired in non-collinear directions with b-value 2500 s/mm on a 3 Tesla system sited on the neonatal intensive care unit. FBA was performed to assess the relationship between FD, FC, FDC and PMA at scan, GA at birth, days on mechanical ventilation, days on total parenteral nutrition (TPN), birthweight z-score, and sex. FBA reveals fibre population-specific alterations in FD, FC and FDC associated with clinical risk factors. FD was positively correlated with GA at birth and was negatively correlated with number of days requiring ventilation. FC was positively correlated with GA at birth, birthweight z-scores and was higher in males. FC was negatively correlated with number of days on ventilation and days on TPN. FDC was positively correlated with GA at birth and birthweight z-scores, negatively correlated with days on ventilation and days on TPN and higher in males. We demonstrate that these relationships are fibre-specific even within regions of crossing fibres. These results show that aberrant white matter development involves both microstructural changes and macrostructural alterations.
弥散磁共振成像（dMRI）研究使用张量模型已经确定了与早产儿在胎龄相当的年龄（TEA）研究中围产期风险因素相关的异常白质发育。然而，该模型是对潜在神经解剖结构的过度简化。基于固定点的分析（FBA）是一种新的定量框架，它可以识别包含交叉纤维的体素中单个纤维群的微观结构和宏观结构变化。本研究的目的是应用 FBA 研究在 TEA 时的早产儿中，基于固定点的表观纤维密度（FD）、纤维束横截面积（FC）和纤维密度与横截面积（FDC）的测量值与围产期风险因素之间的关系。我们研究了 50 名婴儿（男 28 名），胎龄为 24.0-32.9 周（中位数 30.4 周），出生后在 38.6-47.1 周（中位数 42.1 周）进行了 MRI 检查。在新生儿重症监护病房的 3T 系统上，以非共线方向采集 b 值为 2500 s/mm 的 dMRI 数据。FBA 用于评估 FD、FC、FDC 与扫描时的 PMA、出生时的 GA、机械通气天数、全胃肠外营养（TPN）天数、出生体重 z 评分和性别之间的关系。FBA 揭示了与临床风险因素相关的 FD、FC 和 FDC 中纤维群特有的改变。FD 与出生时的 GA 呈正相关，与需要通气的天数呈负相关。FC 与出生时的 GA、出生体重 z 评分呈正相关，在男性中较高。FC 与通气天数和 TPN 天数呈负相关。FDC 与出生时的 GA 和出生体重 z 评分呈正相关，与通气天数和 TPN 天数呈负相关，在男性中较高。我们证明，即使在交叉纤维区域内，这些关系也是纤维特异性的。这些结果表明，异常的白质发育既涉及微观结构变化，也涉及宏观结构改变。
