Mobile Mammography Unit means a mammography x-ray unit located in a vehicle (truck, van, etc.) that is driven from one location to another to perform mammography. These units may be fixed in a vehicle such as a van or a truck, or may be portable (i.e., can be wheeled-off the van and moved into a site). Mobile units usually go to locations where patients would not normally get mammograms. Note: many stationary facilities have mammography units that are equipped with wheels so they can be easily moved from one room to another. Such units are not considered mobile mammography units.