Inter-observer Variation in Gross Tumor Delineation of Esophageal Cancer on MR, CT and PET CT

The aim of the study is to investigate inter-observer variation in gross tumor volume (GTV) delineation of oesophageal cancer on different imaging modalities - CT, PET CT and MR.Twenty-three consecutive patients with esophageal cancer treated with preoperative or curative chemoradiotherapy were selected. All patients had CT, PET CT and MR imaging in treatment position prior to radiotherapy.Five experienced observers from our institution will independently delineate GTV on CT alone, MR alone, PET CT alone, on co-registered CT and MR and co-registered PET CT and MR. Inter-observer agreement, expressed in generalized conformity index (CIgen) and mean volumes of GTV will be calculated per patient and imaging modality.