[Quality control of equipment used for radiotherapy]

Due to the modifications of components, to unexpected breakage of elements or to electronic dysfunctions, the performance of radiotherapy machines may decrease with age. Quality Assurance procedures and maintenance program are necessary to guarantee the performances. For linear accelerators, modus operandi of control tests and their frequency are based on regulations and recommendations widely published, that are presented here. Concerning accessories, especially those recently developed (multileaf collimators, dynamic wedges, ...), recommendations remains to be defined. Simple tests are proposed. Concerning numerical imaging systems, widely used for three dimensional dosimetry, image quality and geometry controls must be performed with phantom tests. For portal imaging, a quality assurance program is proposed. A strict and complete Quality Assurance program is essential to guarantee quality and safety of the treatment. A regular control of linear accelerator is one of the important component of this program. It suppose the implementation of permanent tests procedures, periodically modified following technological progresses and treatment techniques. Measurements must be sensible to variations below the tolerance level defined during the installation process. The analysis of the variations of measurements with time are an objective criterion of quality.