Add a rectifier to correct CT volumes for gantry tilt.
Implement "Reverse" in vtkDICOMCTRectifier.
Use sinc interpolation to rectify gantry-tilted CT.
Include the required vtkVersion header file.
Add method GetGantryDetectorTilt to the rectifier.
Use the CT rectifier in the conversion tools.

A NIfTI file format does not really support non-rectangular volumes,
so it is best to rectify a tilted-gantry volume before conversion.