[Computed tomographic determination of the target volume of tumors in the pharyngeal and laryngeal areas].

Computed tomography plays an important role in radiotherapy, especially in the delimitation of a target volume. For the oncologist, tumor and lymph node regions form a therapeutic unity. A direct imaging of the normal lymph node regions is not possible by CT. A method is described which allows an indirect presentation of lymph nodes in the head and neck area and, consequently, a better delimitation of the target volume. A three-dimensional presentation of the target volume is obtained by a certain quantity of CT scans which show various irregular forms making evident that a two-dimensional consideration of a single scan is no longer justified. Therefore five to seven scans are required for a more precise, three-dimensional determination of a target volume in the head and neck area.