Abstract : during the last decade, the field of radiotherapy has benefited from major technological innovations and continuously improving treatment efficacy, comfort and safety of patients. This mainly concerns the imaging techniques that allow 4d ct scan recording the respiratory phases, on-board imaging on linear accelerators that ensure perfect positioning of the patient for treatment and irradiation techniques that reduce very significantly the duration of treatment sessions without compromising quality of the treatment plan, including imrt (intensity modulated radiation therapy) and vmat (volumetric modulated arc therapy). In this context of rapid technological change, it is the responsibility of medical physicists to regularly and precisely monitor the perfect functioning of new techniques to ensure patient safety. This requires the use of specific quality control equipment best suited to these new techniques. We will briefly describe the measurement system delta4® used to control individualized treatment plan for each patient treated with vmat technology.