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Age-specific DTI templates for human brain from 28 days to children1Radiology, the First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China, Xi'an, China, 2MR Research China, GE Healthcare, Bei Jing, China
Synopsis
The human brain develops rapidly from 28 days to children,there are distinct developmental trends at different ages.This period is important and difficult to acquire the images because of motion artifacts.Diffusion Tensor Imaging(DTI)was used to study brain structure.When analyzing DTI images of different individuals,a common standard space is needed to ensure the tissue diffusion information used for different individual images corresponds to the same spatial location.To understand how the human brain develops between 28 days and children,it is essential to make age-specific DTI templates for human brain.We built DTI templates for human brain of six periods from 28 days to children.
Introduction
Diffusion Tensor Imaging (DTI) can provide information on the microstructure of brain tissues by detecting the three-dimensional displacement distribution of water molecules1,2. DTI brain templates are indispensable neuroimaging tools which represent the brain microstructures to a certain extent and are important for comparing the structural integrity of neurons and the brain connectivity between populations3,4. The human brain develops rapidly from 28 days to children, and there are distinct developmental trends at different ages. Due to motion artifacts, images of this period are not easy to obtain. It's important to focus on the development of children during this period. Our study aimed to build DTI brain templates for Chinese people in six age groups from 28 days to children based on a large amount of data. The six age groups are 28 days to 6 months,6 months to 1 year old, 1 to 2 years old, 2 to 3 years old, 3 to 6 years old, 6 to 15 years old. These templates can help us to understand the normal development of children during this period and to compare them with diseases. From the template, we can intuitively see that the maturation of white matter fiber bundles increases with age.Methods
This study was approved by the local Internal Review Board and all parents of participants had signed the informed consents.Inclusion criterion was human aged 28 days to 15 years with normal imaging findings. Subjects wth developmental abnormalities, metabolic diseases, history of central nervous system infection,clinical diagnosis of epilepsy, and clinical diagnosis of related brain injury diseases were excluded.According to the above criteria, 120 subjects were included in this study. The demographic information is shown in Table 1.Single-shot echo-planar DTI were performed on a 3T scanner (Signa HDXT; GE Healthcare, Milwaukee,Wisconsin) with an 8-channel head coil. The other parameters for DTI were the following: 35 gradient directions; b-values =0 and 1000 s/mm2; TR/TE= 5500/95–105 ms; section thickness=4mm without a gap; FOV=180 × 180 mm2; matrix size =128 × 128; and voxel size= 1.41 × 1.41 × 4 mm3.
Data preprocessing: DTI data were processed by using the FMRIB software library (FSL; http://www.fmrib.ox.ac.uk/fsl)5. First, the eddy current correction was performed. Then, brain regions were extracted by using the FSL Brain Extraction Tool (http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/BET). To exclude the influence of artifacts, we rejected artifact-corrupted volumes (directions) automatically before the tensor estimation6. The number of rejected volumes varied across subjects (median =2; range, 011). DTI metrics of fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) were calculated by using the FMRIB Diffusion Toolbox(http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FDT).
Brain templates construction: all individual FA images were transformed to align AC-PC lines. The first average FA image was obtained by averaging the FA image among the subjects. Using the first average FA image as the registration target image, the individual FA image was registered with the registration target image. With the second average FA image as the target image, the individual FA image was registered with the target image. The deformational displacement fraction of the individual FA image was calculated during the registration process. The individual FA image corresponding to the minimum deformational displacement fraction was selected as the final target image. The target image was the individual brain template.Every subject's FA image was registered to the target image selected in the last step to realize the standardization of group data, and the final average FA image was obtained by average operation between subjects. The average FA image was the average brain template.
Result
Brain templates are the basis of image registration and parameter measurement. In our study, DTI parameters were selected to construct brain templates for human from 28 days to 15 years old. We built 6 templates according to different age groups. The six age groups are 28 days to 6 months,6 months to 1 year old, 1 to 2 years old, 2 to 3 years old, 3 to 6 years old, 6 to 15years old. As shown in Figure 1, the template is labeled with false colors. By observing the images of FA and white matter fiber bundles, we can find that the most obvious changes are in the first year of life (compared with the templates of 28 days to 6 months, 6 months to 1 year and 1 to 2 years old). Compared with the templates under 3 years old, the range of change between the 3-year-old and the 14-year-old templates is smaller. These findings are closely related to the development of white matter in the brain.Discussion
DTI brain templates are indispensable neuroimaging tools.We built DTI templates for human brain of six periods from 28 days to children. These templates can help us to understand the normal development of children during this period and to compare them with diseases. The most obvious changes are in the first year of life.Conclusion
We have buit DTI brain templates for Chinese people in six age groups from 28 days to adolescence based on a large amount of data.Acknowledgements
This study was supported by the National Key Research and Development Program of China (2016YFC0100300), National Natural Science Foundation of China (81471631 , 81771810 and 81171317), the 2011 New Century Excellent Talent Support Plan of the Ministry of Education, China (NCET-11-0438), the Fundamental Research Funds for the Central Universities (xjj2018265), the Fundamental Research Funds of the First Affiliated Hospital of Xi'an Jiaotong University (2017QN-09) .References
1. Makris N, Worth A J, Sorensen A G, et al. Morphometry of in vivo human white matter association pathways with diffusion-weighted magnetic resonance imaging. Ann Neurol 2010;42(6): 951-962.
2. Basser P J, Pierpaoli C, et al. Microstructural and physiological features of tissues elucidated by quantitative-diffusion-tensor MRI. J Magn Reson 2011;213(2): 560-570.
3. Zhang S, Arfanakis K, et al. Evaluation of Standardized and Study-Specific Diffusion Tensor Imaging Templates of the Adult Human Brain: Template Characteristics, Spatial Normalization Accuracy, and Detection of Small Inter-Group FA Differences. Neuroimage 2018 ;172:40-50.
4. Jiang F,Wang Y, et al. BrainTemplate Construction of Diffusion Tensor Imaging. Chinese J Magn Reson 2018;35(4): 520-530.
5. Smith SM, Jenkinson M,Woolrich MW, et al. Advances in functional and structural MR image analysis and implementation as FSL. Neuroimage 2004;23(suppl 1):S208–19.
6. Li X, Yang J, Gao J, et al. A robust post-processing workflow for datasets with motion artifacts in diffusion kurtosis imaging. PLoS One 2014;9:e94592.
Figures
Table 1.demographics.
a Age values are medians (ranges).
Figure 1.The templates for human brain from 28 days to 15y.
The red is darker, the white matter is more mature.