A simplified CT-based definition of the lymph node levels in the node negative neck

Introduction and purpose: Using three dimensional (3D) conformal radiothera py (CRT) techniques for elective neck irradiation (ENI) may allow for local disease control to be maintained while diminishing xerostomia by eliminati ng major salivary glands (or parts thereof) from the treatment portals. The standardization of CT based target volumes for the clinically negative (el ective) neck is a prerequisite for 3DCRT. The aim of the present study was to substantially modify an existing ('original') CT-based protocol for the delineation of the neck target volume, into a more practical ('simplified') protocol. This will allow for rapid contouring and the implementation of c onformal ENI in routine clinical procedures. Material and Methods: An earlier ('original') version of the CT-based defin ition for elective neck node regions 2-5 was re-evaluated, using 15 plannin g CT scans of previously treated patients. The contouring guidelines were s implified by (1) using a smaller number of easily identifiable soft tissue- and bony anatomical landmarks, which in turn had to be identified in only a limited number of CT slices, and (2) by subsequently interpolating the co ntoured lymph node regions. The adequacy of target coverage and the sparing using both 'original' and 'simplified' delineation protocols was evaluated by DVH analysis after contouring the primary tumor, the neck and the major salivary glands in a patient with supraglottic laryngeal (SGL) carcinoma w ho was treated using a 3DCRT technique. Results: The BEV projections of the 'original' and the 'simplified' version s of the 3D elective neck target showed good agreement and were found to be reproducible. The DVH's of the target and parotid glands were not signific antly different using both contouring protocols. Conclusions: The 'simplified' protocol for the delineation of the 3D electi ve neck target produced both comparable target coverage and sparing of the major salivary glands. When used together with an interpolation program, this 'simplified' protoco l substantial reduced the contouring time and makes ENI with sparing of the major salivary glands a practical and achievable goal. (C) 1999 Elsevier S cience Ireland Ltd. All rights reserved.