Figure 2.

Example DCHs for CTV D₉₈ and OAR D₅₀ in the current optimization iteration. The DCH gives the probability that, in an individual treatment course, the realized value of the dose metric (CTV D₉₈ or OAR D₅₀) will exceed the dose on the x-axis. In this example the OAR DCH passes through the point (OD,0.05), where OD is the OAR dose, ensuring Pr[D₅₀≤OD]=95%. The CTV DCH passes to the left of the point (TD, 0.95), where TD is the target dose. The desired coverage criterion is: Pr[D₉₈≥TD]≥95%. The figure shows a strategy for meeting this criterion. At each iteration, one uses the current DCH to find the DAPC. In this example, the prescription coverage is 0.95. The objective function sums contributions from all voxels with doses d such that DAPC≤d≤TD. This causes the optimizer to increase dose to these voxels, pushing the current DCH toward the desired DCH.