COMMISSIONING AND QUALITY ASSURANCE OF TREATMENT PLANNING COMPUTERS

The process of radiation therapy is complex and involves many steps. A t each step, comprehensive quality assurance procedures are required t o ensure the safe and accurate delivery of a prescribed radiation dose . This report deals with a comprehensive commissioning and ongoing qua lity assurance program specifically for treatment planning computers. Detailed guidelines are provided under the following topics: (a) compu ter program and system documentation and user training, (b) sources of uncertainties and suggested tolerances, (c) initial system checks, (d ) repeated system-checks, (e) quality assurance through manual procedu res, and in vivo dosimetry, and (f) some additional considerations inc luding administration and manpower requirements. In the context of com mercial computerized treatment planning systems, uncertainty estimates and achievable criteria of acceptability are presented for: (a) exter nal photon beams, (b) electron beams, (c) brachytherapy, and (d) treat ment machine setting calculations. Although these criteria of acceptab ility appear large, they approach the limit achievable with most of to day's treatment planning systems. However, developers of new or improv ed dose calculation algorithms should strive for the goal recommended by the International Commission of Radiation Units and Measurements of 2% in relative dose accuracy in low dose gradients or 2 mm spatial ac curacy in regions with high dose gradients. For brachytherapy, the aim should be 3% accuracy in dose at distances of 0.5 cm or more at any p oint for any radiation source. Details are provided for initial commis sioning tests and follow-up reproducibility tests. The final quality a ssurance for each patient is to perform an independent manual check of at least one point in the dose distributions, as well as the machine setting calculation. As a check of the overall treatment planning proc ess, in vivo dosimetry should be performed on a select number of patie nts.