Supplementary Material for: A Neuroimaging Strategy for the Three-Dimensional in vivo Anatomical Visualization and Characterization of Insular Gyri

Background: Interest in the anatomy of the insula is driven by its multifunctionality and the need for accurate visualization for surgical purposes. Few in vivo studies of human insular anatomy have been conducted due to methodological and anatomical challenges. Objective: We used brain cortical morphometry tools to accurately reconstruct insular topology and permit a detailed visualization of its gyri in 3 dimensions. Methods: Sixty healthy subjects (33 females; 37.8 ± 12.8 years) underwent 3-tesla MRI scans. The strategy for characterizing the insula was: (1) create 3-dimensional (3-D) insula representations for visual analysis; (2) rate topological features using a gyral conspicuity index; (3) identify individual variations across subjects/between groups; (4) compare to prior findings. Results: Insular reconstruction was achieved in 113/120 cases. The anterior short, posterior short, anterior long gyri and central sulcus were easily identified. In contrast, middle short (MSG), posterior long (PLG) and accessory gyri (AG) were highly variable. The MSG, but not the PLG or AG, was clearer in males and in the left hemisphere, suggesting sex- and laterality-related differences. Conclusions: A noninvasive in vivo 3-D visualization strategy revealed anatomical variations of the insula in a healthy cohort. This methodological approach can be adopted for broad clinical and/or research purposes.