Thesis title: Electron Linacs for Flash Radiotherapy
Radiation Therapy (RT) is nowadays the most common methodology to treat cancer cells. The goal of the treatment is to destroy the tumor and to minimize the damage of the healthy tissues as well as any side effect. The Flash radiotherapy has been shown a reduction in normal tissue toxicity but the same efficiency of the conventional treatment to inhibit tumor growth. This innovative technique delivers very high dose rates (> 60 Gy/s), several orders of magnitude greater than in conventional radiotherapy, in very short time of irradiation (< 200 ms). The protective role of Flash therapy in normal tissues, called FLASH effect, has been demonstrated from several study but the underlying biological mechanisms remain to be fully elucidated. For this purpose, we have developed a dedicated S-band (2.998 GHz) linear accelerator for FLASH radiotherapy, that is optimized for a nominal energy of 7 MeV and a pulsed electron beam current of > 100 mA, currently installed at Curie Institute in Orsay (France). In order to have a very compact machine a new C-band (5.712 GHz) linear accelerator was developed with nominal energy of 12 MeV and pulsed electron beam current of 50 mA. Here, we will discuss the genesis of the Flash methodology, we will summarize the current evidence of the FLASH effect and its implementation based on electron linear accelerators. We will show the RF and beam dynamics design of the S-band and C-band linacs as well as the commissioning and power RF tests. Finally, challenges associated with clinical translation of FLASH-RT and its future prospects are discussed.