 In radiotherapy and radiosurgical systems, fiducial points are landmarks in the tumour to facilitate correct targets for treatment.In neuronavigation, a "fiducial spatial coordinate system" is used as a reference, for use in neurosurgery, to describe the position of specific structures within the head or elsewhere in the body.Such fiducial points or landmarks are often created in magnetic resonance imaging and computed tomography images by using the N-localizer.