Coincident treatment and imaging source

摘要

An apparatus which can switch between a therapeutic beam and a beam-eye-view diagnostic beam, using a single source. Such a radiation source comprises an electron gun 102, a pair of targets 108 Interchangeably locatable In the path 146 of a beam produced by the electron gun, one target of the pair being of a material with a lower atomic number than the other, and an electron filter 118 insertable Into and withdrawable from the path of the beam. In a preferred form, the electron gun is within a vacuum chamber 100, and the pair of targets are located at a boundary of the vacuum chamber. The lower atomic number target can be Nickel and the higher atomic number target Copper and/or Tungsten. The electron filter can be Carbon, and can be located within the primary collimator 114, or within one of a plurality of primary collimators interchangeably locatable in the path of the beam. Such a radiation source can be included within a radiotherapy apparatus, to which the present invention further relates. A flat panel imaging device for this source can be optimised for low energy x-rays rather than high energy; Caesium Iodide-based panels are therefore suitable.