Rapid proton irradiation is a more effective and less invasive cancer treatment than x-rays. However, modern proton therapy requires large particle gas pedals, which has led experts to investigate alternative gas pedal concepts, such as laser systems to accelerate protons. Such systems are deployed in preclinical studies to pave the way for optimal radiation therapy. A research group led by Helmholtz-Zentrum dresden - rosssendorf (HZDR) has now successfully tested laser proton irradiation in animals for the first time, with the group's report published in the journal Nature Physics.
Radiation therapy is one of the main cancer treatments. It usually utilizes intense, focused x-rays. Protons - the nuclei of hydrogen atoms - accelerated to high energies and bundled into small, precisely targeted beams are another option. They can penetrate deep into the tumor tissue, where they store most of their energy, destroying the cancer while leaving the surrounding tissue largely intact. This makes the method more effective and less invasive than x-ray therapy, explains Dr. Elke Beyreuther, a researcher at HZDR: "This method is particularly suitable for irradiating tumors at the base of the skull, in the brain and in the central nervous system. It is also used in pediatric cancer patients to minimize possible long-term effects."
However, this method is much more complex than x-ray therapy because it requires sophisticated gas pedal equipment to generate fast protons and transmit them to the patient. This is why there are only a few proton therapy centers in Germany. Experts are now steadily improving this method to make it suitable for patients. Laser-based proton gas pedals can make a decisive contribution in this regard.
Customized laser scintillation
Dr. Florian Kroll, a physicist at HZDR, explains, "This method is based on the generation of strong and very short light pulses by a high-power laser, which is fired onto a thin layer of plastic or metal foil." The intensity of these flashes knocks electrons out of the foil, creating a powerful electric field that can beam protons into pulses and accelerate them to high energies. Interestingly, the scale of the process is very small:the acceleration path is only a few micrometers long.
"We've been working on this project for 15 years, but so far the protons haven't gotten enough energy to irradiate." Beyreuther says, "In addition, the pulse intensity varies too much, so we can't be sure we're delivering the right dose." In the past few years, scientists have finally made key advances, especially due to a better understanding of the interaction between the laser flash and the foil. "Most importantly, the precise shape of the laser flashes is particularly important, and we can now tune them to produce proton pulses with sufficient energy and sufficient stability." The researchers explained.
Gas pedal readiness and beam delivery stability.
New research needs
The parameters were optimized allowing the HZDR team to initiate a series of key experiments: the first controlled irradiation of mouse tumors using laser-accelerated protons. These experiments were conducted in collaboration with experts at Dresden University Hospital in oncoray - the National Center for Radiation Research in Oncology - and were benchmarked against comparative experiments at conventional proton therapy facilities. "We found that the laser-driven proton source could produce biologically valuable data, which laid the groundwork for further research and allowed us to test and optimize our approach."
Another characteristic of laser-accelerated proton pulses is their enormous intensity. Whereas in conventional proton therapy the radiation dose is delivered in a matter of minutes, the laser-based process can be completed in a millionth of a second," explains Elke Beyreuther: "There are indications that such a fast dose administration helps to protect the surrounding healthy tissue even better than before. We want to follow up these indications with our experimental device and conduct preclinical studies to investigate when and how this rapid irradiation method can be used to gain advantages in cancer treatment."
