Kvm booting from partition-image instead of disk-image?

hi!

Is it possible to boot kvm with a image-file from a partition (e.g. dd of /dev/sda1). I’m able to boot it from a disk-image (dd of /dev/sda), but not from a partition.
??
If not, is it possible to “convert” a partition file to a disk-image??
thanks for help!

regards
chris