File Vault 2 imaging

Hi,
For a MacBook Pro with FileVault 2 volume level encryption what are the options for imaging?? I have a login to the machine….
This is what I'm considering but haven't tested yet

1. Live image using FTKi CLI (not sure if I can image at the volume level with this tool or just the physical which won't be any good)
2. Decrypt the drive (not keen as I don't know what the process is going to do to the data)

Any help appreciated as my experience with Mac's is quite limited.
Thanks,
Karen