Michal,
You can use your cameras that have Twain drivers with LabVIEW. Although National Instruments does not directly have any tools for Twain drivers, you can make calls to the Twain API directly or you can use a toolkit which has done this for you.
Graftek has a Twain toolkit for this type of application. Also,
KB 16M8P2QH discusses this issue in more detail.
Regards,
JR A.
Application Engineer
National Instruments