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MRI scan quantity and quality in childhood
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Introduction
In the first decade of life, extensive changes occur in the structure and function of the brain (Gilmore et al., 2018). With the introduction of Magnetic Resonance Imaging (MRI), these changes in brain characteristics can be studied in vivo, and a growing body of literature has provided insight in the developing brain. Although MRI research is non-invasive, the scanner itself - in particular its noise level and narrow space- and the surrounding procedures are rather imposing and can induce anxiety in children (Tyc et al., 1995; Durston et al., 2009). Such scanner related distress makes it less likely for children to successfully finish an MRI scan, resulting in reduced scan quantity compared to older samples. Moreover, the quality of the scans heavily depends on the amount of (head) motion, which is specifically troublesome in developmental samples, as head movement during MRI is strongly correlated with age (Poldrack et al., 2002; Satterthwaite et al., 2013). Several prior developmental neuroimaging findings have been called into question after studies showed that these findings were largely influenced by age-related differences in head motion (Power et al., 2012; Van Dijk et al., 2012; Savalia et al., 2017), highlighting the need for an in-depth investigation of factors that can influence scan quality in children. In the current study we therefore provide an overview of MRI scan quantity and quality in a large developmental twin sample (N=512, 256 twin pairs, aged 7-9), and investigated the genetic and environmental influences on MRI data quantity and quality.
Scan quality is not only influenced by head motion but can also be influenced by additional sources of noise such as scanner drift and respiratory signals (Kotsoni et al., 2006; Liu, 2017; Power, 2017). However, as excessive head motion is especially pronounced in developmental samples (Satterthwaite et al., 2013), the current study focused on head motion as measure of scan quality. In the last couple of years, the topic of MRI motion artifacts has received increasing attention, and several methods to correct for motion during MRI analyses have been developed (Power et al., 2015; Fassbender et al., 2017b; Power, 2017). Much less research has focused on specific factors that contribute to MR scan quality in children. Recent studies have pointed towards genetics as a possible factor influencing scan quality, with findings suggesting that head motion in adults is a stable and heritable phenotype (Van Dijk et al., 2012; Couvy-Duchesne et al., 2014), with heritability estimates ranging from 37-51% in adults. Exploratory twin-analyses on pediatric MRI data also showed familial similarities in children (Engelhardt et al., 2017), although the small sample size hindered direct estimations of heritability. In the current study we provide direct estimates of heritability by conducting behavioral genetic analyses on a large childhood twin sample.
In addition to trait-like, genetic influences on scan quality, we also investigated the influence of environmentally affected factors, such as emotional
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