Lurker's post in How to Delete Common Roads (Polylines) from Shapefile was marked as the answer
so those identity are identical? you can use selection by location, IMHO
Lurker's post in removing unwanted background from dem in direction hydrology process was marked as the answer
is it on arcgis?
after you finish your analysis, with your boundary you can crop your image to match with the boundary only
dont forget to check on "Use input features for clipping geometry (optional)"