Reconstruction of a time‐averaged midposition CT scan for radiotherapy planning of lung cancer patients using deformable registrationa)

Purpose: lower lobe lung tumors move with amplitudes of up to due to respiration. To reduce respiration imaging artifacts in planning CT scans, 4D imaging techniques are used. Currently, we use a single (midventilation) frame of the 4D data set for clinical delineation of structures and radiotherapy planning. A single frame, however, often contains artifacts due to breathing irregularities, and is noisier than a conventional CT scan since the...