The objective evaluation of alternative treatment plans: I. Images of regret

An innovative approach to treatment planning is described in which a planned dose distribution is evaluated in terms of prescribed limits of acceptability, and any discrepancies (referred to as "regions of regret") are displayed in the form of a contour diagram in which colors are used to represent different types and degrees of regret. A commercial treatment planning system has been modified to display images of regret in addition to conventional isodose plots, and is used for the comparison of alternative plans in terms of adequate target coverage and minimal irradiation of sensitive organs. Required tumor dose levels and organ-specific tolerance doses are prepared in advance by the clinician for each site and stored in a prescription file for use in the planning process. The method is found to expedite the optimization procedure, is objective and reproducible, and provides clear documentation of the selection process.