... volume delineation in head -and- neck cancerusing CT and PET/CT fusion. Int J Radiat Oncol Biol Phys 2006, 65:726-732.31. Black QC, Grills IS, Kestin LL, Wong CY, Wong JW, Martinez AA: Defining aradiotherapy ... B,Cummings B, Dawson L, Keller A, Kim J, Ringash J, Yu E, Hendler A,Waldron J: Intraobserver and interobserver variability in GTV delineationon FDG-PET-CT images of head and neck cancers. Int ... determined whenusing 15% isodensity volumes (green line). CT-based GTV wasoutlined by red line.Figure 3 The BTV of the primary tumor was determined whenusing 20% isodensity volumes (pink line)....