3 terms

Steps for Taking a Lateral Cephalometric Radiograph

film placement
cassette is perpendicular to the floor, long axis of cassette is positioned horizontally
head position
left side of the patients head is adjacent to the cassette, midsagittal plane is perpendicular to the floor and parallel to the cassette, frankfort plane is parallel with the floor, head is centered over the cassette
beam alignment
central ray is directed through the center of the cassette and is perpendicular to the cassette