Serena Psoroulas with the experimental setup in Gantry 1, with which she is testing the new FLASH technology. If successful, it will help advance proton therapy. Photo credit: Paul Scherrer Institute / Mahir Dzambegovic
For the first time, researchers at the Center for Proton Therapy at the Paul Scherrer Institute PSI in Switzerland have tested ultra-fast high-dose irradiation with protons. This new, experimental FLASH technology could revolutionize radiation therapy for cancer and save patients many weeks of treatment.
In nature, lightning strikes with a short, strong flash of light and an energy-rich discharge. In radiation medicine, FLASH also stands for ultra-short, high-dose, one-time radiation and could save patients many weeks of treatment in the future. At the CPT Center for Proton Therapy, PSI researchers are testing whether FLASH is also suitable for proton irradiation using the spot scanning technology developed at PSI. For their experiments, CPT boss and chief physician Damien Weber and his team at PSI work together with the Center Hospitalier Universitaire Vaudois (CHUV) in Lausanne. There, with the approval of the Swiss Academy of Medical Sciences (SAMS), the only patient in the world to date has been irradiated with the FLASH technique to heal a malignant tumor in the skin. Unlike at PSI, the researchers at CHUV use electron beams. These are only suitable for very superficial tumors. In contrast to this, the protons used at PSI also reach tumors deep in the body and can be stopped precisely at the point in the body where they should have their maximum effect on the cancer cells.
Short and intense
"If we can achieve the high precision and good results of proton therapy with FLASH radiation without damaging healthy tissue, this would be a big step forward," says Damien Weber. Treatments could be much shorter and less stressful for patients. "If the principle works, the patients would only have to come for radiation treatment a few times, ideally only one to five times. The resulting treatment appointments would be available to other cancer patients." Due to the extremely short radiation, it is even possible to use the FLASH technique to treat tissue in the lungs that changes its position with every breath. However, before the method is technically mature enough to be routinely used on patients, it will take many years of technical development and very many tests. With FLASH, a radiation dose of up to 1,000 gray per second is applied. That is a radiation dose per second that is about a hundred times higher than with conventional treatments. This destroys the tumor cells very effectively. "But first and foremost, we need evidence that the proton irradiation with the FLASH technology does not damage healthy body tissue," says Weber.
In their experiments, the PSI researchers therefore want to use the maximum possible intensity of the beam and direct it without loss onto biological tissue that is less than a millimeter thick. For this purpose, particle physicist Serena Psoroulas and her team have optimized the beam guidance settings in a former treatment station for proton therapy at PSI, known as Gantry 1. "The older colleagues here at PSI in particular have a lot of experience due to their development and built and tested the devices themselves," says Psoroulas. "You have set up the monitoring and security systems and written the program code for the radiation." The PSI researchers have now used this know-how, which includes high-performance technology, medical expertise and physics, to carry out the world's first experiments on FLASH irradiation with the spot-scanning technology developed at PSI.
The study shows that full irradiation is possible in less than a second
Paul Scherrer Institute
New technology for ultrafast tumor therapy (2020, September 29)
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