Advantage 4d workstation

All patients underwent a respiration‐correlated 4D CT scan using the Varian Real Time Position Management Respiratory Gating System, version 1.7 (Varian Medical Systems) and a Discovery CT750HD CT Scanner (General Electric Medical Systems, Waukesha, WI) with a slice thickness of 2.5 mm in the axial cine mode.
Then, the 4D CT slices and respiratory motion data were transferred to an Advantage 4D Workstation (General Electric Medical Systems, San Francisco, CA), where maximum intensity projection (MIP) and averaged intensity projection (AIP) images were obtained after a phase binning of the 4D CT in 10 equally spaced phase bins. The dataset was imported to the Eclipse (Varian Medical Systems) for treatment planning using 6 MV photon beams. ITV was delineated on the AIP image with references to the MIP image. PTVs were created by adding 5‐mm margins to the ITVs in all directions.⁽¹⁹⁾ A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the PTV D95%. The isocenter was always inside the PTV. Dose calculation was done with the default dose‐to‐medium reporting mode of the AXB (version 11.0.31) with a grid size of 2.5×2.5×2.5 mm3. Recalculation was subsequently done with the AXB−Dw and AAA (version 11.0.31) using identical beam setup.