It is my understanding that the ecm format is for psx games only. The ecm format is designed to remove a lot of information from the psx image because of how the anti- piracy was baked into the disc and bios. Sony write the disc with errors that way when you tried to copy it your drive (at the time) would try to correct them automatically...the psx bios sees a "fixed disc" and thus will not boot the disc.
Thus doing this makes it smaller..and then compressing it makes it even smaller.
Anyway what I am saying is that you may have a psx image NOT a sega cd image. I could be wrong. HurruicaneFan is correct though. it is all over the web out how to do this. When you get it unpacked and have a clean bin file and if it still will not load try it as a psx game and see it it loads..I'm thinking it will.