A quality assurance program for monitor unit calculators.

A quality assurance protocol has been developed to assess the relative accuracy of computerized monitor unit calculations. Results from this testing reveal that errors (defined as the difference between the computer results and those obtained using a standard formula with manual calculation) in monitor unit calculators are possible when they are tested over a wide range of clinically relevant field sizes (including blocked fields), source-to-surface distances, and depths. It is suggested that computerized monitor unit calculators be checked against hand calculations and that this be permanently documented both at the time of initial implementation and following any subsequent changes in the program.