Diffusion tensor imaging and resting-state functional MRI-scanning in 5- and 6-year-old children: training protocol and motion assessment

Abstract

Advanced Magnetic Resonance Imaging (MRI) techniques such as Diffusion Tensor Imaging (DTI) and resting-state functional MRI (rfMRI) are widely used to study structural and functional neural connectivity. However, as these techniques are highly sensitive to motion artifacts and require a considerable amount of time for image acquisition, successful acquisition of these images can be challenging to complete with certain populations. This is especially true for young children. This paper describes a new approach termed the 'submarine protocol', designed to prepare 5- and 6-year-old children for advanced MRI scanning. The submarine protocol aims to ensure that successful scans can be acquired in a time- and resource-efficient manner, without the need for sedation. This manuscript outlines the protocol and details its outcomes, as measured through the number of children who completed the scanning procedure and analysis of the degree of motion present in the acquired images. Seventy-six children aged between 5.8 and 6.9 years were trained using the submarine protocol and subsequently underwent DTI and rfMRI scanning. After completing the submarine protocol, 75 of the 76 children (99%) completed their DTI-scan and 72 children (95%) completed the full 35-minute scan session. Results of diffusion data, acquired in 75 children, showed that the motion in 60 of the scans (80%) did not exceed the threshold for excessive motion. In the rfMRI scans, this was the case for 62 of the 71 scans (87%). When placed in the context of previous studies, the motion data of the 5- and 6-year-old children reported here were as good as, or better than those previously reported for groups of older children (i.e., 8-year-olds). Overall, this study shows that the submarine protocol can be used successfully to acquire DTI and rfMRI scans in 5 and 6-year-old children, without the need for sedation or lengthy training procedures.

Figure 1. Boxplots of the RMS_abs displacement over the time-series of the DTI scans.

Boxplots of the absolute root mean squared motion are shown for each of the 75 children that underwent DTI scanning. Continuous line  =  width of one voxel, dotted line  =  half a voxel's width.

Figure 2. Boxplots of the RMS_abs displacement over the time-series of the rfMRI scans.

Boxplots of the absolute root mean squared motion are shown for each of the 71 children that underwent rfMRI scanning. Continuous line  =  width of one voxel, dotted line  =  half a voxel's width.

Figure 3. RMS_rel rfMRI time-series of subject 11.

Subject 11 showed an obvious increase in motion during the second half of the rfMRI scan.