Limitations of two-dimensional treatment planning programs

Some limitations of conventional two-dimensional computer programs used to plan radiation therapy are presented. These include: a lack of involvement in defining the clinical problem; deficiencies in the algorithms for computing dose; failure to compute dose throughout the volume of interest; an inability to handle treatments with noncoplanar beams; failure to provide estimates of error; lack of tools for comparing rival plans; inadequate definition of geometric coverage of anatomic structures by external beams; and failure to provide tools for specifying and verifying the accuracy of treatment delivery. Some suggestions are offered for improvements in some of these areas. In particular, subtraction of dose distributions is proposed as a tool for comparing plans, and displays which exhibit the results of error analyses are presented.