Fig. 2.

For patient 4 (with a 16 MeV electron beam), Dose Volume Histograms for the CTV and PTV obtained using reference data and lower and upper variations (a). Mean percent difference in dose and gamma values between upper variation and reference data as a function of dose threshold for computation is shown in (b). An axial slice displays calculated isodose lines for the upper variation (black) and reference data (red) in (c). A wax compensator overlaid on the skin to shape the isodoses to the target is also shown. The PTV (in blue) and percent dose difference (color bar legend) are included for reference. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)