Proton flash - Biotech Spain

The Institute of Instrumentation for Molecular Imaging (i3M), a joint centre of the Spanish National Research Council (CSIC) and the Universitat Politècnica de València (UPV) is leading a multidisciplinary project to pave the way for an effective and controlled therapeutic model of proton flash radiotherapy, a new type of cancer therapy. The Pulsed Laser Centre of Salamanca (CLPU) is hosting the first experiment in Spain to generate high doses of ultrafast radiation in less than a second, using laser-accelerated protons to hit living cells. The aim is to understand the mechanisms between the different dose rates.

Conventional radiotherapy uses a continuous beam of particles. In recent years, however, it has been observed that the adverse effects of radiation on healthy tissue are significantly reduced when the clinical dose of radiation (of about 40 Gray) is delivered in short bursts of less than one second. In other words, the effects of radiotherapy depend not only on the dose delivered but also on the rate at which that dose is delivered.

Laser accelerators are suitable tools to achieve ultra-fast, high-intensity doses because they can concentrate protons, the particles that, together with the neutron, form the nucleus of the atom, in very short pulses and at very high instantaneous doses. The CLPU has VEGA, the only laser system in Spain capable of reaching a peak power of one petawatt with a repetition rate of one hertz, which allows each sample to be irradiated in a few minutes.

The experiment led by Michael Seimetz, CSIC Research Assistant at the i3M, aims to understand the mechanisms that occur in the organism between different radiation dose rates. Commercial cell cultures of human adenocarcinoma, a type of lung cancer, will be used as a model. Research Assistants at the Institute of Functional Biology and Genomics in Salamanca, led by Olga Calvo, prepare the samples, transport them to the laboratory and keep them under control until they are returned to their facilities, where they are subsequently analysed.

Next objective: increasing the instantaneous dose

For this experiment, the IGFAE has developed a target (the laser interaction medium used to generate the protons) that allows up to 800 shots fired in a few hours. This high-vacuum particle source has been complemented by an energy selector, built by the i3M, to reduce the proton spectrum’s width and guide the protons through a thin window, a necessary condition for irradiating biological samples kept at atmospheric pressure.

For Michael Seimetz, the next step in the experiment will be to increase the instantaneous dose: "We could do this by focusing the proton beam behind the target because this will increase the flux of accelerated protons. And we will be delighted to come back to this facility. The CLPU is a unique scientific and technological infrastructure of the Ministry of Science and Innovation, the Junta de Castilla y León and the University of Salamanca, co-financed by the European Regional Development Funds (ERDF).