The design and testing of novel clinical parameters for dose comparison

Purpose: New multidimensional dose comparison parameters, normalized agreement test (NAT) values and the NAT index, are introduced and compared with an ideal dose comparison parameter. In this article, we analyze a clinically based two-dimensional (2D) quantitative dose comparison case using a wide range of new and old comparison tools. In doing so, we address the benefits and limitations of many common dose comparison tools. Methods and Materials: An in-house software program was developed using the MATLAB 6.5 programming language. Using this software, several 2D quantitative dose comparison, parameters were calculated for the computed and measured dose distributions in an intensity-modulated radiotherapy (IMRT) prostate cancer treatment. The experiences gained in the design and testing of this software program form the basis of the dose comparison tool analysis. Results: Each dose comparison tool has unique strengths and weaknesses. The underlying assumptions of the NAT values and NAT index lead to acceptable generalized behavior, but are not always valid. Conclusion: A thorough 2D quantitative dose comparison analysis can only be accomplished through the use of many dose comparison tools. The introduction of the NAT index allows a 2D dose comparison to be reduced to a single value, and is thus ideal for setting clinical acceptance criteria for IMRT verifications. (C) 2003 Elsevier Inc.