B. Intensity Modulation and Radiotherapy Guidelines Anatomical data that is required for the planning process is acquired using a Philip's AcQSim CT simulation system. The immobilized patient is squared up relative to the bore of the Picker PQ2000S CT scanner using the ceiling and side lasers of the system. A scout view is obtained so that the superior and inferior borders of the volume study can be determined. Forty seconds prior to the commencement of image data acquisition contrast media (125 cc of Ultravist 300) is power injected at the rate of 1.3-2.0 cc/sec using a Liebel-Flarsheim device. The CT data set is acquired with 3 mm slice thickness and spacing using the spiral mode of the scanner. While the patient is on the table, the images are transferred to the VoxelQ work station that is running AcQSim software version 4.1.1. Before the patient is released a reference isocenter is established and recorded in the AcQSim system and marked on the face mask using the isocenter locating lasers of the CT simulator, if not already indicated by radio-opaque fiducials.