ABSTRACT
Objective To study the variation of gross tumor volume (GTV) and clinical target volume (CTV) definition for lung cancer between different doctors.Methods Ten lung cancer patients with PET-CT simulation were selected from January 2008 to December 2009.GTV and CTV of these patients were defined by four professors or associate professors of radiotherapy independently.Results The mean ratios of largest to smallest GTV and CTV were 1.66 and 1.65, respectively.The mean coefficients of variation for GTV and CTV were 0.20 and 0.17, respectively.System errors of CTV definition in three dimension were less than 5 mm, which was the largest in inferior and superior (0.48 cm,0.37 cm,0.32 cm;F=0.40,0.60,0.15,P=0.755,0.618,0.928).Conclusions The variation of GTV and CTV definition for lung cancer between different doctors exist.The mean ratios of largest to smallest GTV and CTV were less than 1.7.The variation was in hilar and mediastinum lymphanode regions.System error of CTV definition was the largest (<5 mm) in cranio-caudal direction.