Patent Number: 
Section: abstract

An investigative X-ray apparatus comprises a source of X-rays emitting a cone beam centred on a beam axis, a collimator to limit the extent of the beam, and a two-dimensional detector, the apparatus being mounted on a support which is rotatable about a rotation axis, the collimator having a first state in which the collimated beam is directed towards the rotation axis and the second state in which the collimated beam is offset from the rotation axis, the two-dimensional detector being movable accordingly, the beam axis being offset from the rotation axis by a lesser amount than the collimated beam in the second state. The X-ray source is no longer directed towards the isocentre as would normally be the case; the X-ray source is not orthogonal to the collimators. This is advantageous in that the entire field of the X-ray tube can be utilised. As a result, a lesser field is required of the X-ray tube and the choice of tube designs and capacities can be widened so as to optimise the performance of the X-ray tube in other aspects.