A mobile radiation imaging apparatus includes a radiation generation means, such as an x-ray tube 1, a cart or trolley unit 6, supporting members 2, 3, 4, 5 formed on the cart and for holding the radiation generation means in a movable manner with respect to the cart. A detector 100, which can be a contact sensor, detects whether the radiation generating means is in a non imaging position by determining whether there is contact between a beam 3 and cart 6 for example. A control unit 101 limits the motion of the supporting member, for example using brakes or a dead-man lock type member, according to the position of the radiation generating means as determined by the detector. This allows the chance of a collision between the radiation generation means and other parts of the apparatus to be reduced. It may also include a display 9 or protruding means (304, figure 3) which can be made of rubber or the like, to act as a buffer. A load sensor can also be included, if the load sensor detects a load greater than a particular threshold value, the control unit 101 can disable the motion limitation to allow movement.
