For tumors sitting in the middle of the lung and not near any other moving structures with similar Hounsfield units like mediastinum, larger vessels, chest wall, or diaphragm, then maximum intensity projection is a good place to start (verified with 4D video afterwards). If there is contact with oth...

Usually something different. A multiply-fused slow CT approach is functionally equivalent to "contour[ing] on each time phase of the 4DCT and boolean[ing] the results together to generate the ITV" (I've confirmed to my own satisfaction), but it doesn't require the technology necessary to measure res...