Inter-Modality Variation in Gross Tumor Volume Delineation in 18FDG-PET Guided IMRT Treatment Planning for Lung Cancer

Rapid advances in 18FDG-PET/CT technology and novel co-registration algorithms have created a strong interest in 18 FDG-PET/CT's application in intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT). Accurate target volume delineation, particularly identification of pathologically positive lymph nodes, could translate into favorable treatment outcome. However, gross tumor volume (GTV) delineation on both CT and 18FDG-PET is very sensitive to observer variation. The objectives of the study were to investigate the inter-modality variation in gross tumor volume delineation defined by two imaging modalities for lung cancer: CT and 18FDG-PET/CT and its dosimetric implications in intensity modulated radiation therapy (IMRT)