Construction of the MIITRA T1‐weighted and DTI templates of the older adult brain in a common space at 0.5mm resolution

Abstract Background High resolution multimodal MRI templates of the older adult brain have the potential to facilitate template‐based studies of aging. As part of the Multichannel Illinois Institute of Technology & Rush university Aging (MIITRA) atlas, the present work developed high quality 0.5mm isotropic resolution T1‐weighted (T1w) and diffusion tensor imaging (DTI) templates in common space using data from a large, diverse, community cohort of non‐demented older adults. Method Data T1w and DTI data were collected using two 3T MRI scanners on 400 non‐demented older adults (50% male;64.9‐98.9 yrs;54% white,43% black) (Bennett et al.,2018; Barnes et al.,2012). Template construction Step1: An unbiased initial T1w template was created by pairwise affine registration (Ridwan et al.,2021). Step2: Spatial normalization was driven by T1w and DTI data alternatively (Wu et al., 2019). All transformations were combined to minimize interpolations and applied to both modalities. A patch‐based tissue‐guided sparse‐representation approach was employed to compute the template (Ridwan et al.,2021). Step3: High spatial resolution templates were created based on principles of super‐resolution (Niaz et al.,2022) The resulting templates are referred to as MIITRA_0.5mm templates. Evaluation T1w and DTI data from 202 ADNI3 non‐demented older adults were used for evaluation. The MIITRA_0.5mm templates were compared to other high resolution templates and the templates including older adults in terms of image sharpness and spatial normalization accuracy of ADNI3 data when each template was used as a reference for normalization. Result MIITRA_0.5mm templates exhibited higher image sharpness (Fig.1,2). MIITRA_0.5mm templates allowed the highest inter‐subject spatial normalization accuracy across spatially normalized ADNI3 data and required less deformation than other high‐resolution templates (Fig.3,4). It should be noted that 1mm templates require on average less deformation than high‐resolution templates because larger voxels limit local deformations. Finally, the MIITRA_0.5mm templates allowed higher inter‐modality spatial matching of normalized older adult data (Fig.5). Conclusion This work developed high resolution T1w and DTI multimodal templates of the older adult brain for the MIITRA atlas. The new templates exhibited higher image quality, were more representative of the older adult brain, and allowed higher spatial normalization accuracy compared to other templates. The new templates will be available for download at www.nitrc.org/projects/miitra .