Autodesk Inventor supports export to plenty of other 3D modeling / CAD formats, including Parasolid models (.x_t file). This means the easiest and most reliably way to convert idw to x_t would be to use the original tool. Some viable alternative would be to use some other, 3rd party 3D modeling or CAD tool with support of Inventor's formats.
Updated: October 4, 2022