Figure 3.

Mean implemented shifts for prostate displacement sequentially over the phases of treatment: from cone beam computed tomography (CBCT) to planar imaging just prior to initiation of arc 1, and between each of the partial arcs incorporating the displacement detected on the image pair obtained subsequent to the corresponding arc. Depicted mean shifts are relative to the immediate predecessor intra-fractional displacement and are based on an institutional threshold of implementing shifts with displacement ≥1 mm. Arc 4 is not included, as there is no IGRT performed after completion of the fourth arc delivery.