Construction of lung dose-related organ features
The lung dose-related organ feature was constructed by estimating the volume of the lung in the tangential beams. For each slice, the two detected lead wire markers were used to determine the margin of the exposed lung region. Then, the margin was moved 5.0 mm inward according to the PTV outline. The segmented area of the ipsilateral lung region outside the exposed margin was calculated, and the sum of the calculated areas for each slice was then divided by the total ipsilateral lung region a and used as the proposed organ feature. Figure 