Some DTI‐derived data, such as fractional anisotropy (FA) and the apparent diffusion coefficient (ADC), provide information on WM diffusion (Basser & Pierpaoli, 1996). FA is a composite measure of three eigenvalues (λ 1, λ 2, and λ 3). λ 1, the largest in three, which is called the axial diffusivity (AD), is the component parallel to, and λ 2 and λ 3, whose average is called the radial diffusivity (RD), are components perpendicular to the axonal fibers (Basser, 1995; Wozniak & Lim, 2006). We selected FA as a main index because it measures the degree of water diffusion anisotropy on a scale from zero to one and characterizes WM microstructural abnormalities (Basser & Pierpaoli, 1996). In addition, FA is the most widely used anisotropy measure (O'Donnell & Westin, 2011). We used Philips Extended Workspace (EWS, Release 2.6.3.1; Philips) to analyze DTI data. FA threshold for line tracking was set to 0.2. The maximum angle threshold was 50°. We performed tractography using the two‐regions‐of‐interest (ROIs) approach. In recent years, analyses have been carried out by segmenting CC fibers using a two‐ROIs
