Artifacts in Conventional Computed Tomography (CT) and Free Breathing Four-Dimensional CT Induce Uncertainty in Gross Tumor Volume Determination

In the present study, the choice of CT method significantly influenced the delineated GTV size, on average, leading to an increase in GTV size compared to the reference BHCT. The uncertainty caused by artifacts is estimated to be in the same magnitude as delineation uncertainty and should be considered in the design of margins for radiotherapy.