anyone know how to burn a .mdf image whit Nero 7 Ultra Edition ???

when i try to open the image (.mdf or .mds) whit Nero Burning ROM or Nero Express the program say "Unexpected file format"

and i dont wanna convert it to another file format like ISO or CUE/BIN etc i want to know who i burn a image whit nero 7 in (.MDF/.MDS) format