Dose-volume population histogram: a new tool for evaluating plans whilst considering geometrical uncertainties

We present a method to incorporate geometrical uncertainties into dose-volume histogram evaluation: the dose-volume population histogram (DVPH). For each dose-volume point, the probability of the plan DVH meeting the constraint is calculated. The use of DVPH for the target shows that the minimum dose to the PTV might not be representative of the minimum dose to the CTV considering geometrical uncertainties when the PTV extends into the build-up region. For OARs, the DVH obtained from DVPH with 90% confidence level is found to be different to the planning organ at risk volume (PRV) DVH recommended by ICRU 62, especially for parallel organs.