Treatment planning computer tomography of carcinoma in situ. Planning CT shows the position of the Visicoil radiographic marker in transversal, sagittal and coronal sections with respect to the right upper lobe main bronchus and demonstrates the ellipsoidal PTV with respect to the Visicoil radiographic marker and the left upper lobe main bronchus in transversal, sagittal and coronal slices. Upper row: fast helical scan of planning CT; lower row: slow helical high resolution scan acquired during verification procedure. Whereas in fast scanning mode almost no motion of radiographic marker can be seen, breathing motion becomes apparent in slow helical scanning mode. For verification of correct treatment position therefore the latter scanning mode was chosen. Radiographic marker movement center was found by means of a 3D-cursor (cross).