Page 203 - Like me, or else... - Michelle Achterberg

MRI scan quantity and quality in childhood
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Scanner related distress
To get an estimate of the children’s scanner related distress we asked the children to indicate how they felt about the scanner by using a visual analogue scale, based on Durston et al. (2009). Children’s feelings of stress and excitement were assessed at three different moments: before the MRI simulation, before the MRI scan, and after the MRI scan. Participants were asked to indicate how tensed and how excited they felt about the scan session, by pointing to the cartoon smiley that best represented their feelings (Figure 1a). Since children tend to underreport their tension or anxiety (Durston et al., 2009), the child’s emotional state was consecutively also estimated by the researcher and the parent. It should be noted that both the child’s and the researcher’s estimates were written on the same form with the child reporting first, making them not independent. The parents estimated scanner related distress separately from the child and therefore these estimates were independent. Therefore, multi-informant ratings were based on child and parent reports. Parents, however, did not estimate the children’s emotional state after the MRI scan, as they were not present during the MRI scan (being involved in parent-child interaction tasks with the other twin sibling). Therefore, the scores after the MRI scan were based on child report only.
MRI data acquisition
MRI scans were acquired with a standard whole-head coil on a Philips Ingenia 3.0 Tesla MRI system. To prevent head motion, foam inserts surrounded the children’s heads. The fMRI tasks and the movie were projected on a screen that was visible through a mirror on the head coil. Functional runs of the fMRI tasks (first task: SNAT (Achterberg et al., 2018b); second task: PCG (van der Meulen et al., 2018)) were acquired using a T2*-weighted echo-planar imaging (EPI). The first two (dummy) volumes were discarded to allow for equilibration of T1 saturation effects. The SNAT consisted of 3 runs in total with 148 volumes (5.43 min), 142 volumes (5.21 min), and 141 volumes (5.17 min) respectively. The PCG consisted of 2 runs in total. The number of volumes was dependent on the reaction time of the participant, with a maximum of 175 volumes. On average, 136 volumes (4.99 min) were acquired for each PCG run. Volumes covered the whole brain with a field of view (FOV) in mm = 220 (ap) x 220 (rl) x 111.65 (fh) mm; repetition time (TR) of 2.2 seconds; echo time (TE) = 30 ms; flip angle (FA) = 80°; sequential acquisition, 37 slices; and voxel size = 2.75 x 2.75 x 2.75 mm. Subsequently, a high-resolution 3D T1scan was obtained as anatomical reference (FOV= 224 (ap) x 177 (rl) x 168 (fh); TR = 9.72 ms; TE = 4.95 ms; FA = 8°; 140 slices; voxel size 0.875 x 0.875 x 0.875 mm). In addition, a high-resolution EPI scan was obtained for RS-fMRI registration purposes (TR = 2.2 sec; TE = 30 ms, flip angle = 80°, FOV= 220.000 (rl) x 220.00 (ap) x 168.00 (fh), 84 slices). Next, two transverse Diffusion Weighted Imaging (DWI) scans were obtained with the following parameter settings (similar to Achterberg et al. (2016a)): 30 diffusion-weighted volumes with
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