Figures & data
Figure 1. Schematic of workflow for dose painting with clinical treatment planning systems. From a fused PET/CT image, PET uptake within the target volume is transformed to a voxel-based prescription via a linear redistribution of dose (prescription function). The prescription is discretized into equi-spaced dose levels (e.g. 5 levels), which form the basis for target substructures (dose discretization). Each substructure is prescribed the mean dose representative of the underlying voxel doses, with a DVH objective given by the fractional volume receiving this mean dose or higher. A clinically deliverable treatment plan is generated from IMRT optimization to substructure objectives, yielding a planned dose that can be compared back to the prescribed dose at every voxel.
Table I. Dose conformity for permutations of plan parameters. Plans were generated from permutations of physical objectives for each prescription sub-volume modifying various plan parameters. Bolded values represent default plan parameters. Pitches equivalent to 0.860 divided by an integer were used in this study to minimize the thread effect [Citation17].
Figure 2. Axial planned dose distributions and QVH plots for varying prescription dose levels and permutations in physical delivery parameters in a head and neck cancer patient. Variations in plan conformity are quantified by QVH plots. Note that with increasing dose level, increasing modulation factors (MF) up to 2.0, and decreasing jaw width, plan conformity increases. Plan conformity is invariant to changes in pitch.
