Subject This field is automatically populated with the ID of the subject when you load a subject file.

Session This drop down menu is automatically populated with all of the sessions available for the current subject.

Configuration This drop down menu is automatically populated with all of the configurations available for the currently selected session.

Trial This drop down menu is automatically populated with all of the trials available for the currently selected configuration.

Object This list is automatically populated with all of the objects in the currently selected trial. Each object is enabled if it is trackable, meaning that it has a 3D image file associated with it, for generating DRRs.