NTFS support in part-image is experimental ( I've never used
it) ... dd doesn't care, it takes copies of the PHYSICAL structure
of the HDD and doesn't give an owls hoot about the fs on it.
dd if=/dev/hda1 of=my_part.img
You'd need to make sure (in that scenario) that the target
space is ideally the same size as the original partition.
Forgot to mention