Figure 1.

An example of a 4-dimensional computed tomography (4DCT)–ventilation image with a functional lung contour for a patient enrolled on the trial. The bright colors in the 4DCT-ventilation image represent functional portions of the lung, whereas the darker colors represent ventilation defect regions. A functional lung contour (outlined in light blue) that represented higher-functioning portions of the lung was created to assist in treatment planning using a threshold of a 15% or greater function on the 4DCT-ventilation image. The purpose of functional avoidance radiation therapy is to preferentially spare the higher-functioning portions of the lung using treatment-planning techniques, which for this patient included portions of the right lower lobe and left lung.