Fig. 4.

Phantom construction. (a) Circular phantom construction. Left: A subset of vertices of a 3-level subdivided icosahedron, 93 out of 642, were selected. Vectors pointing from the center of the sphere to these vertices constitute the normal vectors of the planes within which circular phantoms were realized. Right: Five representative unit circles with orientations corresponding to the vertices on the left of matching color. For example, the red circle falls within a plane that passes through the center of the sphere and has its normal vector pointing from the center of the sphere to the red point shown on the left. (b) Streamline-based phantom construction. A WM streamline constructed using tractography (shown in yellow) is randomly selected, a focal point along the streamline is randomly selected, and a diffused non-binary activation pattern is created around the focal point (shown in red). (c) Axial, coronal, and sagittal view of a representative streamline-based phantom with 100 streamline activations, overlaid on subject’s T1-weighted image.