Impact of FDG-PET/CT Fused Imaging on Tumor Volume Assessment of Head-and-Neck Squamous Cell Carcinoma: Intermethod and Interobserver Variations

Background: Although gross tumor volume (GTV) at the primary site can predict local control of head-and-neck squamous cell carcinoma (SCC) in patients who are treated with organ-preservation therapy, GTV assessment does not eliminate substantial interobserver variation.Purpose: To evaluate whether F-18-fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography (CT) fused imaging provides additional information for GTV assessment.Material and Methods: We obtained FDG-PET/CT fused images on 20 patients with head-and-neck SCC. All had undergone preoperative conventional workup, including contrast-enhanced CT and magnetic resonance imaging (MRI). The GTV of the primary tumors was designed by two independent observers who used routine clinical data. Observer A was a radiologist and observer B a radiation oncologist. GTV1 and GTV2 were designed without and with FDG-PET/CT, respectively. For geometric interobserver comparison, we calculated the concordance rate as the ratio of the intersection...