FreeView is comprised of a number of drawing and visualizing tools that are intended to help the user manually segment, or outline, brain structures.
The Freehand tool is used to outline structures that must be drawn by hand by adding or deleting individual voxels. This tool is generally used for structures that have similar intensity values as bordering tissue. It is helpful to manually draw the outline of a structure using this tool, and then fill it in the outline using the Fill button.
The Intensity Contour tool is used to estimate borders between areas of varying intensity. It is most useful for drawing borders between tissue types with high contrast, such as grey or white matter and cerebrospinal fluid. Specifically, this tool works well to highlight the exterior border of the cerebral hemispheres and lateral ventricles. To use the tool, click on the “intensity contour” button in the drawing toolbox, and then drag the mouse while holding down the “Ctrl” and “Alt” buttons until you reach the best fit outline of your structure of interest. Then, edit the outline using shift + right click to add voxels, or right click to delete. Make sure that you outline the entire structure and fill in any holes. Finally, fill it in with the appropriate label by holding down “Ctrl” while left-clicking. Turn the intensity contour on and off by clicking “Alt” + “H”.