It is not possible to add ecw raster image in arcmap window as well as manage it trough arc catalog.
it is about ArcDesktop 10.6
See this post: https://community.esri.com/groups/whats-new-in-arcgis/blog/2018/01/18/arcmap-106-doesnt-support-ecw-... no solution available as far as I can tell. Still waiting for Hexagon.
