Project

Discipline

proton therapy; FLASH radiotherapy; pencil beam scanning; beam delivery systems; gantry

Lead
Ziel jeder Strahlentherapie ist es die richtige Dosis zielgenau im Tumorvolumen zu deponieren. In strahlenbiologischen Experimenten mit Elektronenstrahlen und deutlich erhöhten Dosisraten (sogenannte FLASH Bestrahlungen) konnte in den letzten Jahren eine bessere Schonung des gesunden Gewebes unter Beibehaltung der Wirkung auf den Tumor beobachtet werden. Ob der bisher noch nicht vollständig verstandene FLASH Effekt auch für Protonentherapie zutrifft, ist bisher unbeantwortet. Im Vergleich zur konventionellen Strahlentherapie ist konforme Protonentherapie mittels Spot-Scanning wesentlich komplexer und eine signifikante Erhöhung der Dosisrate erfordert neue technische Lösungen.
Lay summary
Inhalt und Ziel des Forschungsprojekts Unser Ziel ist es eine klinisch nicht mehr benutzte Protonen-Gantry für biologische FLASH Experimente aufzurüsten. Das eingesetzte Protonen-Zyklotron liefert bei maximaler Strahlenergie zwar einen hohen Protonenstrahlstrom, allerdings wird die Dosisrate durch die Energiemodulation stark reduziert. Daher wollen wir (i) den ungebremsten Protonenstrahl zum Bestrahlungsplatz transportieren und (ii) die Energieanpassung lokal auf der Anlage durchführen. Weiter wird untersucht, wie (iii) die Dosis im FLASH Regime präzise appliziert werden kann. Schlussendlich wird (iv) der Effekt der Dosisratenerhöhung auf die Strahlqualität untersucht. Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts Der FLASH Effekt hat das Potential die Strahlentherapie und die Tumorbehandlung zu revolutionieren. Mit unserem Forschungsprojekt schaffen wir die Grundlage für weitere Untersuchungen des FLASH Effekts in der Protonentherapie.

Direct link to Lay Summary

Last update: 16.12.2019

Active participation

Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

Tumour treatment with protons is a form of radiation therapy in which the better localization of the dose in the target volume (Bragg peak) is exploited. In comparison to conventional radiotherapy, this feature allows to better spare the healthy tissue. The current standard procedure to deliver proton therapy is the so-called pencil beam scanning (PBS), in which the tumour volume is irradiated sequentially with the Bragg peak at different positions and energies. It is only a few years since there has been experimental evidence that in addition to the dose level also the dose rate has a biological effect. So-called FLASH irradiations with similar dose but much high dose rates show the same tumour control in the target volume but a better preservation of the healthy tissue. At PTCOG58 in 2019, the most important conference for proton therapy, FLASH irradiation was among the most discussed topics with many contributions. The challenges from a technical point of view are the generation of high proton current and the application of FLASH using the PBS technique. We want to investigate these technical questions within the framework of this project. Thanks to a clinical proton irradiation room with a gantry that is no longer in operation since a few months, we have the unique prerequisites and opportunity in our organization to test and investigate these questions in practice. Since the system is an in-house development, we have great flexibility and can carry out modifications rather easily. In particular, the following questions will be examined in context of this project:•Can the high proton beam current of a cyclotron be exploited by means of local proton energy modulation as it is already available on the gantry?•How can the applied dose be precisely measured and controlled at massively higher dose rates?•What effects do local energy modulation and the FLASH regime have on the characteristics of proton beam?With the help of local energy modulation on the gantry, we expect to achieve dose rates up to one order of magnitude higher than the reported threshold for the FLASH regime. This will allow us to further experimentally investigate the FLASH effect for proton therapy in the future. This includes in-vitro experiments in radiation biology as well as in-vivo investigations with small animals. Ultimately, even a human application is not excluded. This opens up the possibility for Switzerland to play again a leading role in the development of proton therapy.Over the last years, a certain saturation has been observed in the development of radiation therapy. The FLASH effect could be the key initiator to further improve the effectiveness beyond what is now state-of-the-art.