Figure 1.

Overall framework of our proposed approach. Deformable image registration (DIR) was used to register end of exhalation (EE) CT to deep inspiration breath hold (DIBH) CT. The resultant deformation vector field (DVF) was then used to map the CT numbers from the EE CT to the DIBH CT space, resulting in deformed EE CT v1. At the same time, Jacobian was calculated from the DVF and used to correct the CT numbers inside the lung for the deformed EE CT v1, resulting in deformed EE CT v2, which improved the accuracy of the CT numbers. [Color figure can be viewed at wileyonlinelibrary.com]