-- ctsim: Added tips to be displayed at startup and via the help menu.
-- ctsim: Added center-detector concept. Allow for detector array
to be any arbitrary distance from center of scanner. As a result,
-- ctsim: Added tips to be displayed at startup and via the help menu.
-- ctsim: Added center-detector concept. Allow for detector array
to be any arbitrary distance from center of scanner. As a result,