Optimizing QSM-T1w Neuroimaging Templates: Exploring the Impact of the Number of Subjects on Template Quality

Motivation: Previously, automated delineation of deep gray matter (DGM) regions predominantly relied on T1-weighted (T1w) brain images with limited iron-rich DGM contrast. Multi-contrast atlases incorporating quantitative susceptibility mapping (QSM) have been introduced to overcome this issue and are increasingly being used in multi-atlas segmentation methods. Goal(s): To determine a generalizable minimum number of subjects to be used for generating high quality QSM-T1w templates. Approach: We quantitatively investigated the effect of increasing (factor=2) the number of subjects (N=10-160) used for template construction on resulting template quality. Results: In highly heterogeneous cohorts, more than 40 subjects result in a diminishing return for QSM-T1w template generation. Impact: Using a small number of subjects for template generation ensures economic use of resources and facilitates the creation of more sub-group templates from the same cohort, to be used in advanced multi-atlas techniques.