This figure illustrates the smart arc IMRT treatment method used to deliver the dose pattern illustrated in figure 1, with the left panel illustrating the concept of delivering the treatment from a full 360 degree arc that rotates around the patient, and the right panel illustrating a "beam's eye view" display of moving "leaves" within the head of the medical linear accelerator machine. These beam shaping "leaves" move continuously as the linear accelerator device rotates around the patient, creating a customized and very conformal radiotherapy pattern. This process represents the three dimensional "printing" of the prescribed radiation dose pattern every day, to fit each patient's exact prostate cancer target volume.