Extract iso from resulting files of livecd-iso-to-pxeboot

[hai wu]

Does anyone know how to extract iso file from initrd.img file generated from
command 'livecd-creator'/'livecd-iso-to-pxeboot'? This livecd tools embed
the ISO file in initrd.img and hide it there, and there is not tool so far
to extract ISO file out of initrd.img file ..