CRUK RADNet: FLASH Radiation

Recent preclinical studies have shown that FLASH irradiation, which is radiation delivered in a fraction of a second, reduces incidence and severity of radiation side effects compared to conventional irradiation used in clinical practice. However, the treatment effect on tumours is not reduced. This is called the “FLASH” effect. The benefit of FLASH radiotherapy has been further shown in veterinarian clinical studies and in the first treatment of a human. FLASH radiotherapy uses irradiators with a high radiation output that allows for the treatment to be delivered in fractions of a second, compared to several minutes for conventional treatments. The short treatment times used in FLASH radiotherapy, often less than 0.1s, have the added value of minimising treatment delivery uncertainties caused by patient motion during delivery, for example a reduced risk of missing a lung tumour due to the breathing motion. Carefully implemented, this would allow for smaller volumes of normal tissue being unnecessarily irradiated. Given both the radiobiological advantageous FLASH effect and its potential to “freeze” physiological motion, FLASH radiotherapy has the potential to be an important (r)evolutionary step in cancer treatment. However, we do not yet understand the biology underpinning the FLASH effect.

Through funding from CRUK – RadNet, we have been able to set up and support a FLASH Radiation core at OIRO. We have a dedicated linac for our preclinical FLASH experiments, dedicated dosimetry, setups in our experimental station for various mice and cell (2D and 3D) irradiation, a room adjacent to the linac bunker for temporary mice holding and anaesthesia, as well as an in-vitro lab area and state-of-the-art dedicated hypoxia equipment (Hypoxylab and Oxylite, Oxford Optronix). The funding also supports two postdoctoral researchers and a technician (80%), to assist with all FLASH in-vivo and in-vitro research projects.

Figure 1: One of the setups used for irradiating cells with FLASH irradiation, using our dedicated linear accelerator. The radiation beam comes out of the circular opening in the upper left corner. The beam spreads out as it travels towards the flask and is collimated (shaped) by the brass plate in the aluminium casing with a circular aperture, just prior to hitting the flask containing our monolayer of cells (attached to the inside surface of the flask closest to the brass collimator).