Abstract : the clinical development of ionizing irradiation, both in the fields of medical imaging and radiotherapy treatment, is the result of a comprehensive understanding of the basics of radiation physics. This has lead to major innovations in the field of radiotherapy. Those innovations aim at a better dose distribution i.e. Hitting the target while leaving healthy tissues as much as possible outside of the high-dose region. New techniques such as treatment with heavy ions are the reflections of the continuous evolution of science and knowledge in the field. At the boundaries of radiation physics, we are reaching the field of radiation biology. The combination of knowledge issued from both scientific fields does offer a unique opportunity for treatment optimization.