[vtkusers] volume orientation

[John Hunter]

I am reading 3D CT data using vtkVolume16Reader, and then displaying
it with a vtkImagePlaneWidget.   

  reader = vtkVolume16Reader()
  reader.SetDataByteOrderToLittleEndian()
  reader.SetFilePrefix('.')
  reader.SetDataDimensions((512,512))
  reader.SetImageRange(155,183)  # slices 155 to 183

Like most CT data, the first slice is the bottom.  What is the best
way to inform vtkVolume16Reader, vtkImageReslice or
vtkImagePlaneWidget of the orientation of the data?  I haven't found
any methods that allow me to read the data in from last slice to first
slice.

I could write a transform (eg, reflect the data about the midpoint of
the slice axis), but figured there must be a better way since loading
CT data is such a common task.

Thanks,
John Hunter