How does C-RAD Catalyst HD enable research into FLASH Radiotherapy?

Over the last 20 years, research done in the delivery of radiation therapy has shown that delivering higher doses of radiation in fewer treatments leads to better results with fewer side effects. The question is, “Can an even higher radiation dose lead to more effective treatments?”

FLASH Radiotherapy (FLASH-RT) is the delivery of radiation therapy at extremely high dose rates. While traditional radiation therapy is typically delivered at the rate of 6 Gy per minute to 20 Gy per minute, FLASH-RT is delivered well over 100 Gy per second and in many research settings much faster. While FLASH-RT is still new and is not widely available clinically, research has progressed to the treatment of animals and some clinical trials in humans. The first patient in the world was treated with FLASH-RT in 2019 at Lausanne University Hospital, and research is ongoing.

A critical component of a FLASH-RT research system is the ability to monitor the animal position and verify that the radiation is being delivered to the target.

The Skåne University hospital and Lund University, in Lund, Sweden, use C-RAD Catalyst HD as part of the facility’s animal research program in FLASH-RT. In close cooperation the scientists, medical physicists, engineers, oncologists, RTTs and veterinarians have converted an Elekta linac to deliver high-dose rates of electrons to test FLASH-RT on dogs. As a critical component to the research, Catalyst verifies that the animal is in the correct position immediately before each dose is triggered.

While Catalyst was not developed for the purpose of treating dogs, the team at Lund University has demonstrated that Catalyst meets the requirements to monitor a dog’s position prior to starting the delivery of a dose of treatment. The institution’s research not only demonstrates that the Catalyst system is effective for use in delivering FLASH-RT, but that the system is flexible enough to consider a dog’s body shape and fur color to deliver FLASH-RT in a research setting. Due to Catalyst´s large FOV sufficient surfaces could be created although the dogs were treated in a position far from isocenter. The data and results have been submitted for presentation at the 2021 ESTRO Congress in Madrid and will serve as a benchmark as other research programs look to develop their FLASH-RT programs.

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Left panel: The setup of a canine cancer patient (a), overlayed with the resulting surface image (b). Right panel: Position (mm) relative to reference surface over time (min); red bars indicate motion exceeding tolerance and the grey bar indicates the time for beam on.

Why is there an interest in FLASH-RT?

As stated earlier, if high doses of precise radiation can target tumors effectively, while reducing side effects, could higher doses produce even better results in fewer treatments?

Take for example, delivering radiation therapy to a lung tumor. The standard radiobiological model used to predict the effectiveness and toxicities of a radiation therapy course of treatment tells us that the cumulative effective dose of the treatment determines the effect on the tumor while an increasing number of individual treatment fractions reduces the toxic effects of radiation – mostly due to radiation delivered to normal tissue.

As technology has improved – giving us the ability to deliver higher doses of radiation, more accurately, and with greater precision while reducing the dose to normal tissue – clinicians have been confident that they could achieve the same clinical results in fewer treatments.

The early research that has been done to date shows that FLASH-RT could lead to an improvement in the effectiveness of radiation therapy. It appears that delivering radiation therapy at extremely high dose rates in fewer treatments with FLASH-RT actually delivers better results with better local control of the tumor and reduced toxic side effects. More research is underway and precise positioning with animal models (and humans) with a system like Catalyst is critical in the effort to ensure accurate and safe radiation delivery, especially with these high doses.

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Parts of the research team at Lund University and Skåne University Hospital, Lund, Sweden inside the bunker with the linac used for the FLASH studies. From left: Annika Mannerberg, Sofie Ceberg, Michael Lempart, Kristoffer Petersson, Tommy Knöös, Elise Konradsson, Börje Blad, Gabriel Adrian and Crister Ceberg.

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PhD-students within the Surface guided FLASH RT project. From left: Annika Mannerberg, Elise Konradsson and Malin Kügele.

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