Chapter 8 contains a description of the radiation techniques used at the department of Radiation Oncology of the University Medical Center Groningen, with emphasis on whether the position in head and neck cancer patients and pituitary adenoma patients during radiation therapy could be determined from portal images of the oblique radiation beams. Currently applied additional anterior posterior (AP) and lateral verification beams could then be abandoned. Seven hundred and fifty-one portal images from 18 different patients were analyzed, of which 9 were pituitary adenoma patients. These patients were irradiated with the tetrahydron technique, in which 4 radiation beams are used with equidistant angles of 109 degrees with the isocenter located in the pituitary fossa. The results showed that the position in pituitary adenoma patients treated with the tetrahedron technique could not be reliably verified using portal images of the oblique radiation beams themselves, but that additional AP and lateral verification beams are required for verification and correction of the position of the treatment fields.