Geometry calibration for x-ray equipment in radiation treatment devices

It is essential for radiological tumor treatment to position a patient very accurate in the treatment device. To avoid sub-millimetre misalignments for a patient in the treatment facility, X-ray images acquired from within the device can be compared to the planning CT. But as slight displacements of the treatment beam nozzle, the digital X-ray panels and the X-ray tubes may arise over time and with movements of the dynamic parts of the treatment device, the underlying geometry model for the patient set-up correction may become inaccurate. To solve this problem, an automatic calibration routine is proposed, which bases on the known geometry of a calibration phantom and X-ray images acquired during the calibration routine. The result from the registration of the X-ray projections of the phantom and its known geometry is used to update the geometric model of the respective beamlines to enable accurate alignment correction.