The prescription for the target(s) defines the dose goal for the treatment, the minimal acceptable dose and percent volume that can be under dosed and the maximum acceptable dose. The prescription for radio sensitive structures sets the nominally allowed dose, the percent volume that can be overdosed, the maximum tolerable dose and the minimum dose below which no radiation damage can be observed. These specifications, for various targets and critical structures, translate into defining three points on a dose volume histogram (DVH) curve for each tissue type. The Corvus system computes the optimal beam intensity maps using a simulated annealing algorithm whereas the ADAC system uses a sequential quadratic search method to minimize a quadratic objective function, which is constructed from a set of dose-based or dose-volume-based objectives for individual regions of interest. Delivery of the dose as prescribed by the idealized maps is accomplished by using step and shoot IMRT at both institutions. In this method the beam direction incident on the patient along with field size and collimator angle is determined by the treatment planner before the software designs the IMRT intensity maps. Therefore it is important to choose beam geometries carefully so as to maximize exposure to the target and minimize exposure to critical structures as visualized in the beam's eye view. The IMRT beams are created by utilizing a standard 80 cm leaf MLC on an Elekta Sli linear accelerator.