Verification and recording of radiotherapy treatments using a small computer

A small computer has been interfaced to a linear accelerator used for routine radiotherapy. The objectives are to assess the rate and magnitude of some of the mistakes which may occur, to prevent these where possible and to assist radiographers with record keeping. In this paper we describe our approach to the problem, the apparatus used, the computer program, and the results of several years of operating experience while the system was continually being developed. On one linear accelerator, we estimate that an error has been prevented roughly once in every 500 field parameters set. The most common error is in setting the diaphragms and a detailed analysis is given of possible reasons. Doses in monitor units are recorded automatically and a running total of cumulative dose is maintained; plans for the printing of the dose in rads at selected points are discussed.