A method and apparatus for holding multiple x-ray cassettes for imaging a target including multiple layers of x-ray cassettes wherein the x-ray cassettes in successive layers are positioned in partial overlapping relationship such that when the target and x-ray cassettes are exposed to x-rays, a continuous image of the target is obtained. A concealing unit conceals the predetermined region detected by the detector using decoded data. In one embodiment, the piping system is configured without a horizontal flow path section of piping. The rover is moved to a plurality of locations and images are acquired of the one or more targets of the station andor the rover. This prevents activation of an opaque surface over the vehicle glass while the vehicle is in operation. The probe sets are moveable along with the holders.