A miniature X-ray source device connected to a distal end of a guiding wire for insertion towards a desired location within an animal body for effecting radiation thereby. The X-ray source device at least includes a vacuum tube containing a cathode and an anode spaced apart at a distance from each other; an emitter for emitting free electrons from the cathode; an electric field generator for applying a high-voltage electric field between the cathode and the anode for accelerating the emitted free electrons towards the anode; and a getter material located in a high-voltage electric field free region in the vacuum tube. The vacuum tube is at least partly transparent to X-ray radiation emitted by the anode.