hdiutil convert -format UDRW -o ~/path/to/new.img ~/path/to/source.iso
sudo su root
dd if=/path/to/new.img of=/dev/rDISKNUMBER bs=1m
Where DISKNUMBER = disk1 or disk2 for example. Add that leading "r".
Back in Disk Utility, unmount/eject the disk.
Done!