Disk Encryption with TrueCrypt and Backups

Most companies these days are using disk encryption on their laptops. I
am planning to use TrueCrypt for my laptop. The question I have now is
about backups and the system restore procedures.

I do my backups to an external disk and am assuming that the complete
system backup is also going to be an encrypted image. My main concern
is about the restore session. If I do have to restore my laptop from
the backup, then how does the disk encryption crypto tools such as
TrueCrypt work?

Thank you in advance for any information.