Sticking volumes

i have neck and chest ct for same patient but in different series , is it possible to stitch the two ?

As long as two series line up correctly (one continues from where the other left), one way to achieve merging:

  1. Use CropVolume to create a new volume that will encompass the full size of the combined volumes by defining a new ROI (you will probably have to go back and forth between your two series to make sure ROI spans the entire size)
  2. Then use the Add Volumes module, to combine two series and specify the output volume as the volume from step 1.

I am sure there are other ways too.

Unfortunately there is overlap between two volumes

You can still use the method @muratmaga suggested, just add a step to use CropVolume to cut off the overlapping part from one or the other series.