1. In a computer implemented system for assisting in an interstitial radiation therapy treatment where the computer receives two-dimensional images of a three-dimensional treatment area and the computer system comprises a display for graphically displaying the two-dimensional images, and a processor for creating interstitial radiation therapy treatment plans, a method comprising the steps of: providing variation specific parameters; creating an original plan using variation specific parameters; creating a variation plan by manipulating variation specific parameters of the original plan; and displaying the original plan and the variation plan on the display, wherein the original plan and the variation plan are mutually accessible for comparison on the display.