Quality management of medical physics issues at the German heavy ion therapy project

For the commissioning and operation of the German Heavy Ion Therapy Project a quality assurance program was developed and successfully applied. The co mplete radiotherapy process using heavy ions was carefully analyzed and div ided into three areas related to beam delivery and control, safety-interloc k system and medical physics issues. In this paper, the medical physics iss ues are addressed. Since the irradiation with heavy ions is a nonstandard m odality, new concepts and ion specific tests were developed. As far as poss ible, national and international standard specifications for radiotherapy w ere adopted. For each aspect, a performance characteristic and a correspond ing acceptance test were introduced. In addition, test characteristics for the constancy tests were established. For all tests, intervention threshold s and test frequencies were specified. Using the described protocol of acce ptance tests, the commissioning was passed successfully. The heavy ion irra diation facility was approved by the governmental authorities on the basis of these test results. During clinical operation, constancy tests are perfo rmed at the beginning of each treatment period, in order to maintain the qu ality found during the acceptance tests. Up to now, 48 patients have been t reated within 6 treatment periods of 4 weeks each. The concepts used and th e tests developed for the quality assurance program may serve as an example of how to introduce systematically a quality assurance program for a new t reatment modality. (C) 2000 American Association of Physicists in Medicine.