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A High Angular Resolution Diffusion Imaging (HARDI) Template of the Human Brain
Title
A High Angular Resolution Diffusion Imaging (HARDI) Template of the Human Brain
Creator
Varentsova, Anna
Date
2011-05-01, 2011-05-08
Description
High Angular Resolution Diffusion Imaging (HARDI) is a powerful extension of Diffusion Tensor Imaging (DTI) capable of resolving intravoxel...
Show moreHigh Angular Resolution Diffusion Imaging (HARDI) is a powerful extension of Diffusion Tensor Imaging (DTI) capable of resolving intravoxel heterogeneity of fiber orientations which is important for brain connectivity studies. The purpose of this study was to produce a human brain HARDI template by combining information from artifact-free low angular resolution datasets collected on 67 subjects.
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Development of MIITRA T1w, DTI and FOD templates of the older adult brain in a common space
Title
Development of MIITRA T1w, DTI and FOD templates of the older adult brain in a common space
Creator
Wu, Yingjuan
Date
2022
Description
Human brain atlases play an important role in neuroimaging studies and are commonly used as references for spatial normalization, tissue...
Show moreHuman brain atlases play an important role in neuroimaging studies and are commonly used as references for spatial normalization, tissue segmentation, automated brain parcellation, seed selection for functional connectivity analyses and fiber-tracking, or standards for algorithm evaluation. A brain atlas typically consists of brain templates of different imaging modalities in a common space and semantic labels that delineate brain regions according to the characteristics of the underlying tissue.High-quality T1-weighted (T1w) and diffusion tensor imaging (DTI) brain templates that are representative of the individuals under study enhance the accuracy of template-based neuroimaging investigations, and when they are also located in a common space they facilitate optimal integration of information on brain morphometry and diffusion characteristics. However, such multimodal templates have not been constructed for the brain of older adults. This thesis introduced an iterative method for construction of multimodal T1w and DTI templates that aims at maximizing the quality of each template separately as well as the spatial matching between templates. The performance of the proposed method was evaluated across iterations and was compared to the performance of state-of-the-art multimodal template construction approaches based on multichannel registration. Using the proposed method, along with other recently developed techniques, high-quality T1w and DTI templates of the older adult brain were developed in a common space at 0.5mm resolution for the MIITRA atlas. In this thesis, the new templates were compared to other available templates in terms of the image quality, inter-subject and inter-modality spatial normalization accuracy achieved when used as a reference, and the representativeness of the older adult brain. Furthermore, as fiber orientation distribution (FOD) model is capable of resolving intravoxel heterogeneity, which overcomes the limitations of the DTI model especially in regions with complex neuronal microarchitecture, FOD template is in high demand to facilitate FOD-based, fixel-based analyses, white matter connectivity studies and white matter parcellations. In this thesis, several FOD template construction methods were compared and a FOD template was developed at 0.5mm resolution for the MIITRA atlas. Overall, the present work brought new insights into multimodal template construction, conducted a thorough, quantitative evaluation of available multimodal template construction methods, and generated much-needed high quality T1w, DTI and FOD templates of the older adult brain in a common space with 0.5mm resolution.
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